HomeMy WebLinkAboutUpper Kobuk Region Biomass Project Study - Sep 2010 - REF Grant 7050840Prepared for.- Alaska Wood Energy Associates
by
Forest & Land Management, Inc.
P.O. Box 110149
Anchorage, Alaska 99511-0149
September 2010
Table of Contents
EXECUTIVE SUMMARY............................................................................................................ 2
SETTING........................................................................................................................................ 3
PURPOSE.......................................................................................................................................
3
METHODOLOGY.........................................................................................................................
3
DISCUSSION AND RESULTS..................................................................................................... 4
Trees, Volumes, and Suitability for Biomass............................................................................. 4
Forest Succession and implications for future management....................................................... 5
Potential Wood Supply Characteristics of Ambler, Shungnak, and Kobuk .............................
10
Ambler: .................................................................................................................................
10
Shungnak:.............................................................................................................................
12
Kobuk: ...................................................................................................................................
12
Considerations for harvesting...................................................................................................
14
Planning Harvest Areas and Managing For Regeneration: ...................................................
14
Ownership Of Trees and Logs: .............................................................................................
14
Log delivery, handling, and storage: .....................................................................................
14
Forest Practices Regulations: ................................................................................................
15
Harvesting and Transport Equipment: ..................................................................................
15
Personnel: ..............................................................................................................................
15
FEASIBILITY ASSUMPTIONS: ................................................................................................
16
CONCLUSION.............................................................................................................................
16
REFERENCES.............................................................................................................................
17
ACKNOWLEGEMENTS.............................................................................................................
17
1
Upper Kobuk Valllley Wood Biomass Study
EXECUTIVE SUMMARY
The remote location of Ambler, Shungnak, and Kobuk results in a high cost for diesel oil and
gasoline, which must often be flown in by air tanker. These communities rely on diesel oil for
electrical power generation and heating of community buildings. Firewood is used in many
homes to supplement diesel oil for heating. The extreme climatic conditions dictate the need for
reliable electric power and heat.
Three species of hardwood (balsam poplar, aspen, and birch) and two species of conifer (white
spruce and black spruce) are indigenous to the region, and are available for use as wood biomass
fuel for electrical power generation and heating. The implementation of wood biomass power
projects in this area must be: 1) accomplished at an appropriate scale, preferably with an imtial
�r1 of project, an su sect to detailea management and accountability from the first step o
harvestOng through the process of managing and maintaining the electrical generation and
cheating facilities.
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Feasibility Study
A Comparison of Automated and Hand -fed
Boiler Systems
For Upper Kobuk Valley Villages
Prepared by Alaska Wood Energy Associates
E4 Engineering
For
WHPac�fic
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Table of Contents
EXECUTIVESUMMARY..................................................................................................................................................................4
MajorFindings.........................................................................................................................................................4
INTRODUCTION.............................................. ....... ... ... ..... ...... ............... .................................................................................... I..... 5
Goalsand Objectives..............................................................................................................................................5
ProjectScale..............................................................................................................................................................5
ResourceAssumptions..........................................................................................................................................8
LEVEL 2 SUMMARY - DESCRIPTION OF OUTPUTS............................................................................................11
StickBoiler Modeling.........................................................................................................................................11
AmblerModel Outputs.......................................................................................................................................11
KobukModel Outputs.........................................................................................................................................13
ShungnakModel Outputs.................................................................................................................................14
OtherConsiderations..........................................................................................................................................15
SECTION 2: HEAT, DISTRIBUTION, AND INTEGRATION............................................................................................16
General......................................................................................................................................................................16
Recovered Heat (Ambler and Shungnak only).......................................................................................16
WoodHeat (all villages)...................................................................................................................................17
SupplementalHeat..............................................................................................................................................20
HEATDISTRIBUTION............................................................................................................................................23
Piping.........................................................................................................................................................................
23
Pumping...................................................................................................................................................................
25
Integration of Recovered Heat (DH plants only)...................................................................................26
Building Integration (chip or stick -fired, DH plant or single building applications) ...........
26
DESIGN CONSIDERATIONS FOR THE USE OF CHIP -FIRED AND STICK FIRED BOILERS...............................29
Stickred Boilers.................................................................................................................................................29
Sizing, Boiler Control, and Utilization Rate.............................................................................................29
End -user Issues......................................................................................................................................................
31
MaterialHandling...............................................................................................................................................33
Emissions Controls/Efficiency........................................................................................................................34
Maintenance...........................................................................................................................................................
34
SitingIssues............................................................................................................................................................35
CHIP -FIRED BOILERS............................................................................................................................................35
Sizing, Boiler Control, and Utilization Rate.............................................................................................36
End -user Issues......................................................................................................................................................
39
MaterialHandling...............................................................................................................................................39
EmissionsControls/Efficiency........................................................................................................................40
Maintenance........................................................................................................................................................... 41
SitingIssues............................................................................................................................................................42
SECTION3: SYSTEM ANALYSIS.............................................................................................................................................
42
Limits.........................................................................................................................................................................
42
METHODOLOGY......................................................................................................................................................4
3
EnergySavings......................................................................................................................................................
43
RecoveredHeat.....................................................................................................................................................46
CostEstimates.......................................................................................................................................................
47
Results.......................................................................................................................................................................
47
SECTION 4: FINANCIAL METRICS........................................................................................................................................ 47
Alaska Wood Energy Associates 2
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
FinancialMetrics..................................................................
APPENDICES................................................................................
Level 2 Study
IYA
.............................................................................. 49
APPENDIXA: AMBLER MODEL OUTPUT............................................................................................................................ 49
Ambler Inputs, DH Summary, Chip Summary, and Stick Wood Summary................................49
Amber District Heat Layout: Conceptual.................................................................................................. 50
Scenario1................................................................................................................................................................51
Scenario2................................................................................................................................................................ 52
Scenario3................................................................................................................................................................ 53
Individual Building Chip and Stick -fired Boiler Summaries............................................................54
APPENDIX B: KOBUK MODEL OUTPUT............................................................................................................................... 55
Kobuk Inputs, DH Summary, Chip Summary, and Stick Wood Summary .................................. 55
Kobuk District Heat Layout: Conceptual.................................................................................................. 56
Scenario1...........................................................................................................................................................—.57
Scenario2................................................................................................................................................................ 58
Scenario3................................................................................................................................................................ 59
Scenario4................................................................................................................................................................ 60
Individual Building Chip and Stick -fired Boiler Summaries............................................................ 61
APPENDIX C SHUNGNAK MODEL OUTPUT....................................................................................................................... 62
Shungnak Inputs, DH Summary, Chip Summary, and Stick Wood Summary .......................... 62
Shungnak District Heat Layout. Conceptual........................................................................................... 63
Scenario1................................................................................................................................................................ 64
Scenario2................................................................................................................................................................ 65
Scenario4................................................................................................................................................................ 67
Individual Building Chip and Stick fired Boiler Summaries............................................................68
APPENDIX D
District Heating Plant/Recovered Heat Integration: Sample Sequence of Operations...... 69
APPENDIXE.................................................................................................................................................................................... 70
SampleCalculations........................................................................................................................................... 70
Alaska Wood Energy Associates 3
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Executive Summary
Level 2 Study
Alaska Wood Energy Associates has developed and applied a unique modeling approach
for project feasibility in each village. The model simultaneously tests individual
commercial buildings, selected neighborhoods and various district heating systems for
both stick -fired boilers and automated chip -fired boilers. Multiple scenarios for district
heating systems have been displayed from the modeling process for this report based on
key assumptions and financial feasibility. The feasibility modeling process is dynamic
and with additional information, or with additional questions, new solutions can be
produced.
Major Findings
/11�1. Model results demonstrated that using wood energy, as a substitute for fuel
oil, is ecologically sustainable for wood production and economically feasible
for each of the villages. Either cord wood systems or chip systems can be
utilized. Pros and cons of each are discussed.
�2. If the project goal is to displace a maximum amount of fuel oil in each of the
villages and to create a sustainable heat utility, then a chip -fired automated
system is the most effective approach. However, many of the scenarios for
stick -fired systems are economically feasible if sma er sca e approac es are
preferred.
3. Only residences that are somewhat close together are economically feasible
to connect with a district heating system; thus, Shungnak has 43 houses
connected, Ambler has 10 houses and Kobuk has 9 houses. Connecting
additional houses to the primary district heating system is not considered
financially feasible at this time, primarily due to piping costs and heat loss.
However, additional small stick -fired systems may be feasible, once the
larger systems are installed, through economies of scale for wood supply and
operations.
4. Key metrics for the largest modeled chip systems in each of the villages are
as follows:
Village
Cost
Millions
NSP
Years
NVP
Millions
Gallons
Displaced
Tons of
Biomass
Ambler
$2.6
11.1
$4.04
67,616
773
Shungnak
$3.4
12.5
$4.8
77,833
885
Kobuk
$2.2
14.1
$2.7
44,441
630
Ambler and Shungnak assume that waste heat from the generators will be utilized
and increases the financials over Ro uk—fli as e hea o u i ize.
r
Alaska Wood Energy Associates 4
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Introduction
Goals and Objectives
The objective of this Level 2 Cost and Feasibility Study report is to document the
progress and findings at the feasibility stage of the project. The scope of the project
is to provide enough analysis to allow the villages and potential funders involved to
determine if the project or projects included should proceed to investment grade
studies, design, and eventual implementation. The Level 2 Study looks at both small
district heating (DH) plants as well as individual building -level biomass boiler
applications. It compares the costs and net simple paybacks of both stick -fired
boilers and automated chip -fired systems.
Some of the examples are taken from a similar analysis performed for Fort Yukon,
which is currently 90 percent completed, with an investment grade study, and more
than 35 percent complete with design.
A team of professionals, Alaska Wood Energy Associates, is doing the work on this
project. This team consists of people from a number of different companies,
representing various skill and knowledge sets. Greg Koontz of efour, PLLC, Seattle,
WA, is performing the boiler modeling and feasibility study. Greg Koontz will also
provide design services specific to the boilers and any DH plant.
A primary concern for any biomass -fired plant is availability of the wood resources.
Assessing availability is the responsibility of Bill Wall, PhD of Sustainability, Inc. The
means and methods of procuring the wood and processing it will be documented
elsewhere. For that reason, this report does not address supply, only (to a small
degree) storage and material handling.
The objective for the team and the villages is to use the study to choose a path
forward into final design and construction, or, failing that, to determine under what
conditions the projects would move forward. This report documents the financial
feasibility study.
Project Scale
In order to be successful, a DH plant must achieve a certain economy of scale. The
capital costs involved are quite large, so the savings to the village must be on the
same scale in order to make economic sense.
In the villages of Ambler, Kobuk, and Shungnak, the number and size of (relatively)
adjacent public buildings are towards the lower end of the range of economic
feasibility for a DH plant; nevertheless, in each of the villages, at least one variation
Alaska Wood Energy Associates 5
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
of a DH plant may be feasible, depending on the resource assumptions made and the
village's financial targets (see Section 1.4 below).
DH plants can be defined in this report as being any "large" plant connected by
distributed piping to two or more buildings and utilizing a chip -fired boiler. At the
same time, each building in each village was analyzed to determine the feasibility of
a dedicated boiler, both a chip -fired and stick wood -fired boiler. Finally, the study
looks at smaller groups of buildings (usually no more than three, generally very
close together) that may be served by a dedicated boiler (either chip or stick wood,
in this case). These could technically be called district heating plant, but are so
small that they are basically considered a "large building" that happens to need
more piping and more building connections than a one boiler/one building
application would. Each DH plant is labeled in the model and in the tables as a
"Scenario", which is often abbreviated as "Sc" - Sc 1 indicates Scenario 1, for
instance. Dedicated building boilers or small boilers serving two to three buildings
are simply labeled by the name(s) of the building(s) served.
Compared to Kobuk, Ambler and Shungnak have the potential advantage of having a
village power plant. Ideally, any DH plant would be co -located with the power plant
and would utilize the "waste" heat from the generators as the "first stage" of DH
heat. The models assume that the DH plants in Ambler and Shungnak are utilizing
this recovered heat. It is recognized that AVEC owns the power plants and an
agreement will be required with them to capture the heat, and a price agreed upon
to do so. In Ambler, three variations of a DH plant were studied, shown in Figure 1.1
below. The largest is Scenario 3 that includes the subdivision of nine houses and
the city hall and city building. The smallest, Scenario 1, excludes the subdivision and
the city buildings. Although feasible to heat, these are the least efficient extensions
on this particular loop.
BUILDING SELECTION by SCENARIO
Res
ID No. ? Sc 1
Sc 2
Sc 3 Sc 4
max
load to
space
kBTU/h
Base
oil
gallons
1
1
school complex
1
1
1
602.0
27,000
3
1
water treatment
1
1
1
42.3
3,500
4
1
city building
1
18.3
750
5
1
city hall
1
18.3
750
6
1
health clinic
1
1
1
36.6
1,642
7
1
tribal office
1
1
1
21.4
880
S
1
NANA office
1
1
1
313.8
13,000
9
1
sewer line trace
1
1
1
151.1
12,500
10
10
N subdiv, single 1
1
1
19.4
8,000
11
Figure 1.1, Ambler DH Plant Buildings included in study
Alaska Wood Energy Associates 6
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
In Kobuk, the smaller buildings and lack of recovered heat adversely affects the
economics of a DH plant; nevertheless, four Scenarios were developed for Kobuk.
However, this is slightly misleading. It was indicated that the school might be
expanded in Kobuk. Until it is constructed it is best to look at the proposed DH both
ways - with the existing school, and with the proposed "future" school (with
correspondingly higher oil consumption). In the table below Sc 1 is the same as Sc
2, except the "school" is selected in Sc 1, while the "future school" is selected for Sc 2.
Likewise, Sc 3 and Sc 4, which include the residential buildings, are the same, except
for differences in which "school" is selected. So, in essence, only two groups of
buildings are being evaluated. The column labeled "No." shows how many buildings
there are. The column labeled "Res ?" simply indicates that a building is either a
residence (blue 1), or not (blank); this is used only for cost estimating.
BUILDING SELECTION by SCENARIO
max
ID
No.
Res
?
Sc 1
Sc 2
Sc 3
Sc 4
load to
space
kBTU/h
Base
oil
gallons
1
1
school
1
1
209.5
9,000
2
1
clinic
1
1
1
1
33.9
1,455
1
city office
1
1
1
1
43.9
1,800
4
1
water treatment
1
1
1
1
72.0
4,200
5
1
NANA office
1
1
1
1
309.4
13,000
6
9
9 house subdiv 1
1
1
175.4
7,200
8 1 teacher housing 1 1 1 1 36.6 1,500
9 1 future school 1 1 372.4 16,000
'10
Figure 1.Z Kobuk Buildings included in study
The four streets listed in the table are meant to include all the houses that could be
reached by a pipe running down each respective street for a total of 43 residences.
The more buildings included in a DH plant, the more likely it is to be economically
feasible; the exception to this is when the cost of the additional distance of piping
needed to connect a building, and the additional heat loss and pumping energy
associated with that pipe exceed the value of displacing the oil associated with the
building. In Shungnak, four DH plants were evaluated.
Alaska Wood Energy Associates
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
BUILDING SELECTION by SCENARIO
max
Level 2 Study
ID
No.
Res
?
Sc 1
Sc 2
Sc 3
Sc 4
load to
space
kBTU/h
Base
oil
gallons
1
1
school
1
1
1
1
535.3
23,000
1
clinic
1
1
1
1
62.7
2,692
3
1
water treatment
1
1
1
1
60.0
3,500
4
1
city office
1
1
1
1
24.4
1,000
5
1
NANA
1
1
1
1
309.4
13,000
6
4
Back street
1
1
1
1
78.0
3,200
7
11
Andy Lane
1
1
1
214.5
8,800
8
14
Alley
1
1
1
273.0
11,200
0
14
Jim street
1
1
300.3
12,320
10
Figure 1.3, Shungnak DH Plant Buildings included in study
Resource Assumptions
In order to compare all the DH plants and individual boilers on an equal basis, some
base level assumptions about these costs had to be made and used in the
performance financial model. The assumptions shown in Figure 1.4 are based on
current estimates of recent fuel costs in the villages, plus projections of the cost of
obtaining wood chips and stick wood.
The primary resources of concern in this study are the various energy sources,
current and proposed. Because the systems involved are closed piping loops, water
and sewer use is almost zero on an annual cost basis. Aside from filling and/or
flushing the system, there is no water use, and thus no sewer use.
The fuels of concern are No. 1 oil and electrical energy (current costs), and wood
chips or stick wood (proposed costs). As will be seen in the following sections, even
if this project is implemented, oil and electrical energy will still be required for the
new plant as well as the parts of the village unaffected by the proposed plant.
One of the key assumptions that will govern the economics of these projects is the
cost of "bulk oil" in the villages. Based on recent data, the reported cost of oil in each
of the three villages appeared to be about $8.50 per gallon. However, in each case
the information provided indicated that the power plant (where applicable) and the
school received "bulk oil" at the rate of $3.75 per gallon. If this is correct, and the
bulk rate remains at this level, it will seriously affect the economics of many of the
proposed projects. The school is generally the first or second largest user of oil in
any village, so if it receives inexpensive oil it becomes more difficult to justify
switching to another fuel.
Alaska Wood Energy Associates
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Oil / Elec Data
Level 2 Study
Ambler
Kobuk
Shungnak
heating oil heat content
134.0
134.0
134.0
kBTIJ gal
heating oil density
7.1
7.1
7.1
lb/gal
sulfur content
500.0
500.0
500.0
pprn
sulfur emissions
0.0010
0.0010
0.0010
lh/gal
CO2 emissions
22.013
22.013
22.013
Ib/gaI
low cost (school, etc)
$3.750
$3.750
$3.750
pergal
unit cost to power plant
$3.500
$3.750
$3.500
per gal
high cost (to village)
$8.500
$8.500
$8.500
per gal
oil to H plant
$8.500
$8.500
$8.500
per gal
unit cost of recovered heat
$0.016
$0.016
per kBTU
electrical energy
$0.550
$0.550
$0.550
per kWh
NOx. and CO emissions are a function of the boiler
Figure 1.4, Base Level Oil / Electrical Assumptions, each village
Figure 1.4 lists four oil prices. This model is used in a number of villages, and needs
to be flexible. The "low cost" is used when some buildings in the village get better
prices than others (such as the schools). The "high cost" is what everyone else pays.
The other two are the cost of oil to the DH plant (in case it is different still), and the
cost to the power plant (in case they also get a different price). In this modeling
exercise only two values are used, $3.75/gal and $8.50/gal.
The corresponding values for biomass are shown in Figure 1.5 and are the same for
all three villages. These numbers are based partially on current price in the villages
and a very conservative modeled cost of producing chips with proposed equipment.
Cost of Fuel
wood chips $175 per green ton
pellets $300 per ton
stick wood $250 per cord
wood chips $14.97
per mmBTU
stick wood $13.49
per mmBTU
recovered heat $15.86
per mmBTU
low oil $27.99
per mmBTU
high oil $63.43
per mmBTLI
Figure 1.5, Base Level Wood Assumptions, all villages
Note that in Ambler and Shungnak, the cost of recovered heat is greater than the
gross cost of chips or stick wood. This price is a key variable for the villages.
Currently, the price for recovered heat appears to be about one-fourth the cost of
the same amount of oil heat based on cost projections from proposed heat sales
agreements. For comparison, if the cost of wood is considered, recovered heat
should not be utilized. However the recovered heat is displacing oil, not wood. This
is because chip -fired biomass boilers have a minimum "turndown"; a level below
which they cannot operate, which is usually about 30 percent of maximum capacity.
Alaska Wood Energy Associates 9
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
Until the load rises to this level, a DH plant either has to use oil, or recovered heat.
In the Ambler and Shungnak models, it is assumed recovered heat is used. In
Kobuk, this low load period must be served with oil; as a result, the Kobuk DH plant
paybacks are longer than in the other two villages.
Even in Ambler and Shungnak, the recovered heat has less value to a DH plant than
it does to an individual building that must otherwise utilize oil heat. Normally,
when recovered heat is available, it is always used to the fullest extent, until load
exceeds the available heat.
Finally, Figures 1.6 and 1.7 show the properties of the chip and stick wood that were
used in the model. These tables show the mix of species to be harvested in the area
and the expected moisture contents; this input is used to calculate the composite
wood properties. There is one table for chips, and one for stick -wood and they are
essentially the same for all three villages as the forests are very similar and the
project management strategies for the forest are similar.
moisture content at:
% by
INPUTS,
chips
burn
store
cut
weight
1
: Cottonwood, logs
0.25
0.35
0.50
0.100
2
: Birch, logs
0.25
0.25
0.50
0.200
3
: Aspen, logs
0.25
0.30
0.50
0.200
4
: B Spruce, logs
0.25
0.25
0.50
0.300
5
: W Spruce, logs
0.25
0.30
0.50
0.200
checksum 1.nnn
other variables
avg fuel storage temp 46.0 deg F
avg absolute humidity 36.0 gr/Ib
avg excess 02 0.10
avg air specific volume 12.9 cf/lb
avg stack temp 320 deg F
Composite Chip Properties
net useable heat
5,845
BTU/Ib at burn MC
weight at storage MC
1.044
Ib/lb at burn MC
weight at cut MC
1.500
Ib/lb at burn tvlC
density as stacked logs
21.866
Ib/cf at storage NIC
density as chips
21.787
Ib/cf at storage MC
combustion air req
5.246
Ib/wet Ib at burn MC
combustion air req
67.669
cf/wet Ib at burn RAC
CO2 formed
1.425
Ih/wet Ib at burn I IC
SOx formed
0.000
Ib/wet Ib at burn A,IC
ash
0.017
Ib/wet Ib at burn IVIC
ash specific volume
0.003
cf/wet Ib at burn PAC
available harvest rate
17.300
tons/acre wet
note: NOx, CC, VOC:. and FM emissions are a function of the boiler
Figure 1.6, Chip wood assumptions, all villages
moisture content at:
% by
INPUTS, chips
burn
store
cut
weight
1
: Cottonwood, logs
0.25
0.35
0.50
0.100
2
: Birch, logs
0.25
0.25
0.50
0.200
3
: Aspen, logs
0.25
0.30
0.50
0.200
4
: B Spruce, logs
0.25
0.25
0.50
0.300
5
: W Spruce, logs
0.25
0.30
0.50
0.200
checksum 1.nnn
other variables
avg fuel storage temp 46.0 deg F
avg absolute humidity 36.0 gr/Ib
avg excess 02 0.10
avg air specific volume 12.9 d/Ib
avg stack temp 320 deg F
Composite Chip Properties
net useable heat
5,845
BTU/Ib at burn MC
weight at storage MC
1.044
Ib/lb at burn NIC
weight at cut MC
1.500
Ib/Ib at bum MC
density as stacked logs
21.866
Ib/cf at storage MC
density as chips
21.787
Ib/cf at storage NIC
combustion air req
5.246
Ib/wet Ib at burn MC
combustion air req
67.669
cf/wet Ib at burn KIC
CO2 formed
1.425
Ih/wet Ib at burn MC
SOx formed 0.000 Ib/wet Ib at burn MC
ash 0.017 Ih/wet Ib at burn RAC
ash specific volume 0.003 cfhvet Ib at burn NIC
available harvest rate 17.300 tons/acre wet
note: NOx. CC'), VOC and PM emissions are a function of the hoiler
Figure 1.7, Stick -wood assumptions, all villages
Alaska Wood Energy Associates 10
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Summary — Description of outputs
Level 2 Study
Three mathematical models were constructed to model the performance of the
various DH plants and individual boilers in the three villages, and to compare their
financial performance. These models are discussed in detail in Section 3, and a
sample of the calculations is shown in Appendix E. To date it is not known how this
project would be financed, so the financial model does not include the cost, but
makes the assumption that the projects will be funded through grants.
Stick Boiler Modeling
There is a disparity in the capacities of the stick -fired and chip boilers used as the
basis of design in this study. The smallest Garn (stick) is much smaller than the
smallest Wiessmann (chip), and conversely, the largest Wiessmann is much larger
than the largest Garn. Many of the building loads are so small that even the smallest
Garn is too large - when this happens the net simple payback (NSP) gets very large.
Stick -fired boilers are also cheaper to install and operate than chip -fired boilers. For
that reason, in most cases, the stick -fired boiler has better economics than the chip -
fired boiler at the building scale. The model is flexible enough to compare building -
by -building installations, however in these three villages the only individual
building installations worth reviewing are with stick -fired boilers.
The only time the chip -fired boiler scores better is when the load is large as in a
district heating system. The largest Wiessmann boiler has more capacity than three
of the largest Garn boilers (actually equals about five of the large Garn). Installing
three Garn boilers, even if they are less expensive individually, results in a more
expensive installation than a single Wiessmann boiler. Note that for many buildings,
the chip -fired NSP is blank - in this case, the load was so small that it is below the
minimum firing rate of the smallest Wiessman.
Theoretically, if one were willing to put in enough stick -fired boilers, and feed them
nearly continuously, one could make do with fewer of them. Practically speaking,
this would be an incredible amount of labor. For this study, we limit the number of
stick -fired boilers per installation to three, and the number of firings per day to four.
At this point the key financial metric is net simple payback (NSP) at current costs.
Figures 1.8, 1.9 and 1.10 show abbreviated summaries of the results of the model
using the Base Level resource assumptions for each of the three villages (Ambler,
Kobuk, and Shungnak), respectively. The complete overall Summary sheets and cost
estimates can be found in Appendices A, B and C for Ambler, Kobuk and Shungnak.
Ambler Model Outputs
All of the Chip -fired districts heating system Scenarios 1-3 are fully financially
feasible and range in payback from 10.5 -11.1 years at current oil prices. The
Scenarios range in fuel displacement from 58,000-67,000 gallons of fuel annually at
Alaska Wood Energy Associates 11
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
99% displacement. This will require from 47 - 61 acres to be harvested annually.
Although the stick -fired scenario on a smaller scale described above has a quicker
payback, the overall benefits to the community in heat cost stabilization is much
less. Chip -fired systems are larger and present complexities for management;
however, the benefits of job development and development of management
capacities far exceeds the smaller systems. This is the crux of the decision process
that must be made by each of the villages and their regional support organizations
and is described in greater detail in the harvest assessment report.
The combined "small plants" studied in Ambler are: Sc 1) City Bldg + City Hall, Sc 2)
School + water treatment, and Sc 3) School + water treatment + sewer heating.
Small plants two and three are quite feasible and if the goal is to have a smaller
system that is not automated, then these certainly are worth considering with
project paybacks of 7.7 and 4.3 years sequentially.
Economy of scale is also what can make DH plants attractive. In Ambler, the data
shows that combining the same six buildings into a single DH plant (Sc 1, Ambler)
results in essentially the same payback as the six individual boilers combined. This
is about the minimum size required to gain the economy of scale needed for a chip -
fired plant. Note that with higher bulk oil prices, the chip -fired plant becomes more
economical than six individual boilers. If the bulk oil discount disappeared in
Ambler (i.e. everyone paid the same price) the DH plant payback would drop to 6.2
years, while the combined payback of the six individual boilers would drop only to 7
years. In such a case, the economy of scale of using a single boiler with distributed
piping overcomes the added cost of the distribution piping and the added heat and
pumping losses associated with the DH plant.
DH Plant Project Cost / Financials / Summary Ambler
Sc 1 Sc 2 Sc 3 Sc 4
project cost
$2,052,839
$2,459,244
$2,584,145
savings
$195,541
$228,108
$232,224
NSP
10.5 yrs
10.8 yrs
11.1 yrs
NPV (20 yr)
$3,376,002
$3,963,102
$4,040,569
oil displaced, gal 58,127 66,346 67,616
oil displaced 99.33% 99.74% 99.40%
harvest req, acre/yr 47.0 59.4 61.6
biomass boiler model 390 390 390
oil boiler model 80-380 80-480 80-480
Nc,tt: biomass b,_Jler m'fa is iNiessrnann. evil boiler info is Weil McLain
Alaska Wood Energy Associates 12
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Individual Building Boiler Summary
Stick Wood
base oil
oil
fuel
project
NSP
oil
fuel
project
NSP
bldg Building gal/yr
displaced
cost
cost
yrs
displaced
cost
cost
yrs
school complex 27,000
0.864
$60,159
$346,904
8.4
0.974
$55,245
$417,111
9.1
water treatment
3,500
1.000
$7,748
$244,971
11.1
4
city building
750
1.000
$2,512
$244,971
63.4
city hall
750
1.000
$2,512
$244,971
63.4
c
health clinic
1,642
1.000
$4,210
$244,971
25.1
tribal office
880
1.000
$2,760
$244,971
51.9
NANA office
13,000
0.943
$31,852
$262,793
3.3
9
sewer line trace
12,500
1.000
$24,519
$244,971
3.0
10
N subdiv, single
800
1.000
$2,607
$244,971
58.4
11
N subdiv plant
8,000
1.000
$16,594
$535,411
10.4
1
$32,445 $364,180
$9,070 $364,180
$9,070 $364,180
$16,652 $364,180
$10,175 $364,180
0.946 $32,490 $364,180 4.7
1.000 $25,998 $364,180 4.5
$9,495 $364,180
0.636 $12,181 $631,574 11.3
13 city bldg+ city hall 1,500 1.000 $3,940 $244,971 27.8 $15,445 $364,180
14 school+water treat 30,500 0.993 $62,236 $528,398 7.7 0.951 $70,274 $447,402 7.4
1 school/treat/sewer 43,000 0.926 $106,061 $559,390 4.3 0.994 $87,364 $542,178 3.6
16
Figure 1.8, Abbreviated Financial Summaries, Ambler
Kobuk Model Outputs
All of the Chip -fired districts, Scenarios 2-4, are marginally feasible and range in
payback from 15.9-14.1 years. The first scenario is not feasible as it has a 20+years
payback. The Scenarios range in fuel displacement from 35,000-44,500 gallons of
fuel annually 94-98% displacement of fuel oil use. This will require from 35-50
acres to be harvested annually. This lower payback is due to economies of scale and
the fact that there is no heat recovery from diesel engines.
In the Kobuk building -by -building model there are a number of combined small
plants. Because of space in the spreadsheet, a number of abbreviations had to be
used. These plants are in numeric order (using the numbers from the "bldg" column
in Figure 1.9): 11) School, Teacher Housing, City Office, and water treatment; 12)
Same as 11, except the "future school" is used; 13) School, Teacher Housing, City
Office, water treatment, and the proposed new NANA offices; 14) School, Teacher
Housing, City Office, water treatment, the proposed new NANA offices, and the
clinic; 15) same as 13, except with the "future school"; and 16) same as 14 except
with the future school. All six of the small plant scenarios are financially viable and
are in ascending order as to size.
In this case it makes sense to take a close look at the business model of sharing
harvest equipment between Kobuk and Shungnak, and whether stick -fired boilers
make more sense. It could be decided that if Shungnak went with chips then so
should Kobuk, even though the payback is lower. Management of the two processes
in the two communities will ultimately be the deciding factor in selection of boiler
types.
Alaska Wood Energy Associates 13
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Project Cost / Financials / Summary Kobuk
Sc 1 Sc 2 Se 3 Sc 4
project cost
$1,777,539
$1,780,383
$2,151,461
$2,149,367
savings
$85,591
$111,640
$140,723
$152,640
NSP
20.8 yrs
15.9 yrs
15.3 yrs
14.1 yrs
NPV (20 yr)
$1,525,316
$1,989,047
$2,482,034
$2,708,361
oil displaced, gal 26,048 35,835 37,101 44,441
oil displaced 84.15% 94.41% 97.24% 98.42%
harvest req, acre/yr 29.4 38.2 43.5 50.2
biomass boiler model 390 390 390 390
oil boiler model 80-480 80-480 80-480 80-380
Nnte: biomass_ hailer mfg is Wie: smann. nil boiler rrifg is Weil McLain
Individual Building Boiler Summary
Level 2 Study
bldg
Building
base oil
gal/yr
Stick Wood
oil fuel
displaced cost
project
cost
NSP
yrs
Chips
oil
displaced
fuel
cost
project
cost
NSP
yrs
1
school
9,000
0.968
$18,751
$246,796
16.5
0.701
$24,547
$366,004
39.8
clinic
1,455
1.000
$3,854
$246,796
29.0
$15,062
$366,004
3
4
C.
city office
water treatment
NANA office
1,800
4,200
13,000
1.000
1.000
0.951
$4,511
$9,081
$30,275
$246,796
$246,796
$264,617
22.9
9.3
3.3
0.901
$17,995
$38,395
$35,494
$366,004
$366,004
$366,004
4.9
6
9 house subdiv
7,200
1.000
$15,070
$512,557
11.1
0.530
$38,575
$609,301
26.9
a
teacher housing
future school
1,500
16,000
1.000
0.999
$3,940
$32,481
$246,796
$348,728
28.0
12.7
0.977
$15,445
$33,211
$366,004
$366,004
13.7
10
11
sch, TH, off, WT
16,500
1.000
$33,441
$441,706
6.9
0.982
$35,411
$457,240
7.4
12
13
fut sch, TH, off, WT
opt 11, NANA
23,500
29,500
0.930
0.814
$57,572
$94,404
$441,706
$472,699
6.7
4.2
0.986
0.948
$49,545
$68,832
$511,913
$542,906
6.9
3.9
14
opt 11, NANA, clinic
30,955
0.789
$104,027
$503,691
4.3
0.931
$75,386
$573,898
4.0
15
opt 12, NANA
36,500
0.937
$87,513
$621,375
4.2
0.829
$120,303
$917,914
8.1
16
opt 12, NANA, clinic
37,955
0.922
$94,679
$652,368
4.3
0.849
$119,530
$950,648
7.5
Figure 1.9, Abbreviated Financial Summaries, Kobuk
Shungnak Model Outputs
All of the chip -fired districts, Scenarios 1-4, are fully feasible and range in payback
from 12.5-14.4 years. The Scenarios range in fuel displacement from 42,000-77,000
gallons of fuel annually at 98-99% displacement. This will require from 23 - 70
acres to be harvested annually. Although several of the stick -fired scenarios on a
smaller scale described above have a quicker payback, the overall benefits to the
community in heat cost stabilization are much less. The results of this modeling
process demonstrates that the best fit for Shungnak is a chip -fired district heating
system, especially since there are 43 residences to be served in the largest district
heating system.
Alaska Wood Energy Associates 14
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Project Cost / Financials / Summary
Sc 1 Sc 2
Sc 3
Shungnak
Sc 4
project cost
$1,844,767
$1,980,869
$2,764,297
$3,440,215
savings
$128,522
$145,487
$235,729
$274,786
NSP
14.4 yrs
13.6 yrs
11.7 yrs
12.5 yrs
NPV (20 yr)
$2,178,798
$2,464,510
$4,032,822
$4,768,198
oil displaced, gal
42,887
46,266
65,945
77,833
oil displaced
99.29%
99.73%
99.33%
98.88%
harvest req, acre/yr
23.5
26.2
49.8
70.5
biomass boiler model
390
390
390
530
oil boiler model
80-380
80-380
80-580
80-380
Note: biornass bailer mfg is VViessmann. oil boiler mfg is Weil McLain
Individual Building Boiler Summary
Level 2 Study
bldg
Building
base oil
gal/yr
Stick Wood
oil fuel
displaced cost
project
cost
NSP
yrs
Chips
oil
displaced
fuel
cost
project
cost
NSP
yrs
I
school
23,000
0.926
$48,883
$348,728
9.3
0.882
$50,704
$366,004
10.3
2
3
clinic
water treatment
2,692
3,500
1.000
1.000
$6,210
$7,748
$246,796
$246,796
14.8
11.2
$25,577
$32,445
$366,004
$366,004
4
city office
1,000
1.000
$2,988
$246,796
44.8
$11,195
$366,004
6
NANA
Back street
13,000
3,200
0.951
1.000
$30,275
$7,177
$264,617
$339,773
3.3
17.0
0.901
$35,494
$29,895
$366,004
$457,240
4.9
-
Andy Lane
8,800
1.000
$18,116
$574,542
10.1
0.704
$36,365
$670,125
17.4
8
Alley
11,200
1.000
$23,310
$751,631
10.5
0.826
$36,481
$761,361
13.0
9
Jim street
12,320
1.000
$25,443
$751,631
9.5
0.866
$36,596
$761,361
11.2
10
11 Back street, clinic 5,892 1.000 $12,303 $370,766 9.8 0.222 $44,101 $487,652 81.5
12 Andy L, water tr 12,300 0.978 $26,646 $605,535 7.8 0.916 $32,458 $700,537 9.7
13
14
1
16
Figure 1.9, Abbreviated Financial Summaries, Shungnak
Other Considerations
One conclusion is that each village biomass project is extremely sensitive to the cost
of oil displaced, and less so to the cost of wood and electrical energy. As mentioned
before, a key issue is whether the schools can continue to get oil at the bulk rate in
the future. Economy of scale is important to make these projects feasible, so if the
largest end -user is getting inexpensive oil, it reduces the economics of using
biomass within the whole village.
Alaska Wood Energy Associates 15
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Section 2: Heat, Distribution, and Integration
General
There are two general configurations of boiler plants examined in this study, 1)
single building applications or very small groups of adjacent buildings and, 2)
district heating (DH) plants. Likewise, two wood burning technologies are included;
stick -fired and chip -fired. The characteristics of these boiler types are described in
detail below.
In general, stick -fired boiler systems are smaller, less automated, require less
associated equipment, and their lower heat output range makes them appropriate
for smaller scale installations (single building or small group applications). They
are simple and robust but their simplicity means that they are more labor-intensive
to operate than chip -fired boilers.
Chip -fired boilers require significantly more support equipment, and as such, they
require a greater scope of project to justify the higher up -front costs. Once installed,
they are highly automated and require almost no labor input. They are also robust,
but their larger capacity ranges mean that they are economical in a single -building
applications for only the largest village buildings and they are most cost effective in
multi -building DH applications.
This study includes the larger public buildings in each of the three villages; Ambler,
Kobuk, and Shungnak. Each building is evaluated for a stand-alone application
biomass boiler, and where the proximity of the buildings allows, adjacent buildings
are grouped into DH plants for evaluation as well. The selected buildings in each
village are indicated in Section 1, and detailed summaries of the results are to be
found in the Appendices.
The study considers three sources of heat: 1) heat recovered from village power
generators, 2) heat from wood, and 3) heat from oil.
Recovered Heat (Ambler and Shungnak only)
Heat recovered from an engine generator and used in a boiler system or DH Plant is
"free" in the sense that there is no marginal cost increase to reject that heat to a
heating loop compared to rejecting it to the atmosphere. The heat comes primarily
from the cooling jacket of the engine and must be carried away from the unit to
prevent it from overheating. In the absence of a co -located heating plant the heat is
normally carried to a radiator, which cools the jacket water by rejecting the heat to
the atmosphere (a fan blows air over a radiator coil).
Engine generators producing prime power are an ideal source of heat for any
heating plant. They run continuously, and the quality (temperature) of the heat
Alaska Wood Energy Associates 16
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
rejected is almost identical to the heat required by the boiler or plant. Generally,
recovered heat is the lowest cost form of input energy to the heating system, thus it
is normally selected first and used to the fullest.
However, since AVEC owns the generators in Ambler and Shungnak the "waste" heat
is "free" for them to provide, but not free to the end -user. Recovered heat costs have
been modeled at 25 percent of the avoided costs of heat generated by oil boilers. As
Section 1 notes, even at 25 percent this cost is currently slightly more expensive
than the gross energy from wood. It may be that these rates can be renegotiated as
a part of this process. As the individual village designs progress the proposed
operations will be continually examined to see if more recovered heat can be used in
place of wood or oil heat.
The below section on recovered heat describes how it will be integrated into the DH
Plant; Appendix D provides a general one -line diagram detail drawing and sequence
of operations for an integrated heat recovery / biomass boiler plant.
Wood Heat (all villages)
When available, recovered heat is considered the primary heat source because it is
generally used first to meet the needs of the DH Plant. Wood heat is thus considered
the secondary heat source. As with recovered heat, wood heat will always be used
to the extent possible before using the tertiary heat source (oil, in this case). The
villages own significant amounts of wood resources in the surrounding lands, and
the team believes it can be produced in a usable form (wood chips and/or stock
wood) at a price significantly below that of oil, on a BTU basis.
Wood fuel boilers require more infrastructure than oil -fired boilers. They require
space for wood storage and processing. Chip -fired systems require mechanical
material handling equipment to get the chips into the boiler. Stick -fired boilers
require space to cut to length and split wood to meet the boiler specifications.
Given the remoteness of the upper Kobuk Valley any equipment installed must be
reliable and well tested. It is also desirable that any boilers used be standard units,
or "off the shelf' so to speak. The use of proprietary or customized equipment
increases the chance that if equipment failure occurs, it will be expensive and/or
time consuming to get it fixed.
For applications where chip -fired boilers make sense, the team proposes to use a
German line of boilers and material handling equipment. Wiessmann (formerly
Kob) equipment has been deployed in hundreds of installations all over Europe, and
now is starting to be used in the US. The North American headquarters of
Wiessmann is in Vancouver, BC. The units have been modified to meet UL and
ASME standards, and can thus be approved by local authorities for use in the US.
They also enjoy a blanket exemption to the Buy America Act. The Wiessmann
Alaska Wood Energy Associates 17
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
boilers are standard products, which come in set sizes, and offer a range of options
specifically designed for each boiler in the range. The model range proposed for the
upper Kobuk is the Pyrtec line. Figure 2.1 below shows a Pyrtec boiler.
.M KO ;
Figure 2.1, Pyrtec Boiler
The Pyrtec range has a relatively wide range of capacities, from 1.3 mmBTU/h to 4.3
mmBTU/h. The boiler can be equipped with automatic start, automatic de-ashing, a
cyclone to remove particulate, and soot blowers to keep the tubes clean, as well as a
number of other options. All of this equipment is purpose-built for the boiler, and is
off -the -shelf equipment. Figure 2.2 below shows the range of Pyrtec boilers
available.
output
capacity
Pyrotec model kBTU/h
Wiessmann model 390 1,331
Wiessmann model 530
1,808
Wiessmann model 720
2,457
Wiessmann model 950
3,241
Wiessmann model 1250
4,265
Figure 2.1, Output Range of Wiessmann Boilers
Wiessmann also offers a smaller range of boilers, the Pyrot line. Because they have
lower capacities these smaller boilers would expand the number of applications in
which chips could be used. However, the maximum moisture content (MC) of the
chips that can be used in a Pyrot is much lower than that of the Pyrtec (35% v 50%,
respectively). The 35 percent MC limit would probably not be a limitation much of
Alaska Wood Energy Associates 18
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
the time, depending on harvest methodology. However, in the event that the chip
storage was depleted and a village needed to cut, chip, and burn wood in a very
short period the resulting green chips would have moisture content far in excess of
35 percent. Air -drying the chips to 35 percent MC could take three months or more
- an unacceptable limitation on the DH plant. Thus, the team is not proposing to use
the Pyrot line of boilers in the interior of Alaska at this time.
Wiessmann also offers a variety of material handling equipment to get the chips into
the boiler. When actual plant and wood yard sites are chosen in the three villages,
the details of the material handling will be finalized.
For stick -fired boilers, the team proposes the use of Garn boilers. Dectra
Corporation, located in St Anthony, owns Garn Minnesota. A number of Garn Boilers
are already installed in Alaska. Figure 2.3 is an example of a Garn boilers.
Figure 2.3, Garn Boiler
Note that a Garn boiler can also burn clean construction waste, slab wood, and
densified wood products (briquettes, etc). However, neither construction waste nor
slab wood was considered to be a reliable resource at the sites considered.
Densified wood products are not available in the interior; in fact, one of the primary
reasons to consider a stick -fired boiler is to minimize the processing required for
the fuel.
As Figure 2.3 shows, the Garn boiler consists of a burn chamber (the chamber hatch -
style door can be seen in 2.3) surrounded by a hot water storage tank. For that
reason the Garn boilers are much larger than the Wiessmann boilers for a given
output. It also means that Garn boilers have two output ratings: 1) burn rate, and 2)
storage capacity. The burn rate is the rate at which heat is released when the
chamber is loaded with stick wood per directions and fired. The storage capacity is
how much heat the tank can hold.
Alaska Wood Energy Associates 19
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
In order for the storage capacity to have any meaning, the maximum and minimum
storage temperatures must be specified. For the Garn, the tank is fully charged
when the tank water is 200 deg F. It is depleted when the tank temperature is 120
deg F.
Heating a building is a continuous process so heat is continually withdrawn from the
tank by a pump and transferred to a building. Heating the storage tank is a batch
process. A discrete amount of wood is burned in each "batch". No more fuel is
added until the previous burn is complete. The storage tank allows the Garn to
bridge the gap between the batch process of burning a load of wood and the
continuous process of heating a building. Below is a detailed comparison of the
implications of using both stick -fired and chip -fired boilers. Figure 2.4 below shows
the ratings of the Garn boilers available.
Garn
model
output
storage
kBTU/h
kBTU
WHS 1500
350.0
920.0
WHS 2000
425.0
1,272.0
WHS 3200
950.0
2,064.0
Figure 2.4, Garn Boiler Characteristics
The material handling associated with stick -fired boilers is much simpler than that
associated with chip -fired boilers. In essence, the wood should be cut to length, and
should fall within an acceptable range of diameters. Larger diameter lengths may
have to be split. Ash must be removed from the burn chamber manually, and tube
cleaning is manual as well.
The boilers must be fed manually regardless of how the wood is processed, but the
actual processing is a trade-off between simplicity and availability of equipment
(and thus more manual labor) versus less manual labor (and thus more expensive,
specialized equipment). If chainsaws and splitters are the primary material
handling equipment then a great deal of manual labor is required to process the
wood and feed the boilers. The up -side is that this equipment is cheap, easy to fix,
and abundant in the villages. If specialized harvesters and/or cutters are used much
of the manual labor is removed. However, this equipment is expensive, cannot
easily be replaced and there is likely only one of each per village - so a failure means
the operation is down until it is repaired. Each village in which a Garn is installed
will need to consider the associated material handling carefully in cooperation with
the team to determine the best solution for the village.
Supplemental Heat
There are two conditions under which the combination of recovered heat and wood
heat might not be able to meet the DH plant load. Chip -fired biomass boilers cannot
Alaska Wood Energy Associates 20
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
turn down much below 30 - 35 percent of their full load capacity (the study
assumed 35 percent). This "middle" range of temperature conditions is fairly
narrow, but it does exist. The second condition is if the sum of the biomass boiler
output and the recovered heat is too low to meet the total load on extremely cold
days. For both of these situations, any DH Plant would be equipped with a small oil-
fired boiler. The study assumes an oil -fired supplemental boiler for each DH plant,
but not for individual chip or stick -fired boilers serving a single building. This is
because each building already has oil -fired heat that can serve as a back up for a
single building.
Either one of these "oil" ranges can be eliminated through boiler sizing, but
generally not both because one occurs at minimum boiler load and the other at
maximum. Making the biomass boiler bigger eliminates the use of oil at the high
end of the load, but widens the gap between the recovered heat and the minimum
boiler load. Choosing a smaller boiler can eliminate this "middle" gap, but at the
expense of more oil required in very cold conditions. The goal is to choose the
boiler that has the highest utilization rate, and thus displaces the most oil. Figure
2.13 below shows graphically the effect of boiler sizing on boiler utilization rate.
As a result, choosing the biomass boiler is a balancing act. Using the model, one can
immediately see the effect of boiler size on heat source. Choosing a bigger boiler
reduces or eliminates oil consumption in the cold months, while increasing it in the
shoulder months. A smaller boiler has the opposite effects. Using two boilers can
eliminate or nearly eliminate oil use altogether; however, it adds significant initial
capital costs. None of the application studied in the upper Kobuk Valley were large
enough to justify two chip -fired boilers
It could be argued that no oil boiler need be included in the biomass fired DH plant
(with or without recovered heat). The means in which the DH plant connects to the
buildings allows the end -user to extract all the available heat possible from the DH
loop and still use their existing oil boilers to top up the heat if need be. This could be
a viable proposition; the DH plant could simply notify all the customers to enable
their existing heating equipment when the temperature dropped below a given
level. However, this relies on every end user to keep their oil tank full and their
equipment in operating condition; once end users get used to district heat, they are
less likely to keep their equipment in full operating condition. This study assumes a
supplemental boiler for all chip -fired DH plants.
Even if the building boilers were assumed to cover the peak loads during very cold
conditions, it would not be nearly as convenient to cover the "middle" gap in heating
that occurs when the load exceeds the recovered heat, but is too small to allow a
biomass boiler to be fired. As noted in Section 3 the model predicts electrical
demand (and thus available recovered heat) on an average basis. These profile
curves predict monthly consumption accurately using average demand data, but
Alaska Wood Energy Associates 21
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
have little or nothing to say about the demand (and thus heat) at a given time on a
given day. Thus the DH plant would always be in danger not meeting load in parts
of the shoulder season, and further, could not accurately predict when it might
happen.
If the DH plant operator cannot predict these events, they cannot warn their end -
users to have their equipment available and ready. The potential for the DH plant
under -supplying heat is significant.
Again, one could argue that selecting smaller biomass boilers for the DH plant could
mitigate this. However, that in essence shifts a significant (and unpredictable)
amount of the annual cost of heating back onto the end -user. In essence, this implies
building a plant that cannot meet the known loads, knowing that it will shift the
burden of heating in very cold weather to the end -user - again, not a very viable
proposition.
Because this would occur only in very cold periods, the consequences of a failed
"handover" (from the DH heat to the end user's heat) would be significant. This,
plus the unpredictability inherent in such an operating scheme (operationally and
financially) has led the team to recommend that the DH plant be able to deliver heat
throughout the entire range of expected load; in order to do this smoothly, a
supplemental oil -fired boiler is required.
Because an oil -fired boiler can start and stop very quickly, without human
intervention and with high reliability, it is ideal for the supplemental heat needed.
Oil heat will always be added last, only when the other two sources cannot be used
to maintain Load. See Appendix D for details of how the proposed oil -fired boiler
fits into the operating sequence.
NOTE: This section applies primarily to chip -fired boilers. The reason supplemental
heat is not usually included in stick -fired applications is the storage tank that is
integral to the stick -fired boiler. As long as the tank heat is replenished by periodic
"burns", any amount of heat can be extracted from the tank, from 1 BTU/h up to the
rated capacity of the burn chamber. Thus there are no "gaps" in output, whether the
Garn is used by itself, or in conjunction with recovered heat. There is a practical
limit to the output, however.
In Figure 2.4 above, the rated burn capacity of the Garn model 3200 is listed as 905
KBTU/h (905,000 BTU/h). The only way it could maintain 905 kBTU/h, however,
would be for an operator to continually refill and fire the boiler the minute each
successive burn was complete - not a practical mode of operation. The point of the
storage tank (other than to decouple a batch process from a continuous process) is
to store enough heat to prolong the time between burns. In this study, the team
assumed no more than four burns per day (i.e., six hours between burns). If a
Alaska Wood Energy Associates 22
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
building or DH plant required more than four burns per day to keep the tank(s)
charged the model adds a second (or third) Garn boiler to the plant. In only a few
cases was a supplemental boiler assumed when using stick -fired boilers.
In some instances, a single Garn may be adequate on all but the coldest days. In
such a case, a small oil fired boiler would be much cheaper than adding another
Garn (and less labor to operate). Having a back-up oil boiler could also relieve the
operator from having to manually feed and de -ash the boiler(s) in -50 deg F weather
- in such conditions, a full-sized back up boiler could operate. This can be seen in
the Summary sheets when the fraction of oil displaced by a stick -fired boiler is less
than 1.000.
There are many variations in plant configuration, and this will need to be
determined for each village as the studies get more detailed and the full design
begins.
Heat Distribution
Piping
The heat generated at the DH plant must be distributed to the various end -users.
This is accomplished by pumping hot water through distribution pipes to each
building. Traditionally the piping used in this part of Alaska is a rigid system of pre -
insulated piping. A carrier pipe carries the fluid; this is standard steel piping. Rigid
foam insulation surrounds the carrier, and an outer spiral -wound metal jacket in
turn protects insulation. See Figure 2.5 below
Figure 2.5, traditional "arctic pipe"
This system provides superior heat loss characteristics (i.e. very low losses), but it is
expensive, and installation must be very well planned. It is expensive primarily
because the whole piping system is rigid. It must therefore be installed below the
permafrost or frost heave will snap the pipe. In many areas of interior Alaska this
means burying the pipe 18 to 20 feet deep. The required trenching is expensive,
requires large equipment, and takes time.
Alaska Wood Energy Associates 23
BIOMASS HEATING FEASIBILITY
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Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
Installation must be well planned out because it is difficult to modify in the field.
Cutting a piece to length means cutting through all three layers; it is difficult to get a
clean cut and subsequent clean connection to the next piece. For that reason the
system is typically laid out in great detail in the plans, and each piece and fitting
made for a specific spot in the system. Thus any mistakes in fabrication or any
damage to a piece in the field can take a long time to repair.
If the boiler installations and plants proposed herein had to rely on this traditional
piping system, the payback would be significantly extended. Instead the basis of
design is a flexible, pre -insulated system that uses a plastic carrier pipe. The carrier
piping is constructed of cross -linked polyester, or PEX. The piping comes on rolls
that are dozens or hundreds of feet long. Standard easy to install fittings are used
anywhere in the piping to connect end -to -end, tee, or elbow as required. The piping
can be obtained as a single pipe within a pipe (outer layer), or even supply and
return in one common outer layer pipe. Figure 2.6 shows an example of PEX.
Figure 2.6, Pex piping
Because the system is flexible it can be installed in the active layer of the soil. For
example, in the heat capture plant installed in McGrath pipe was placed at 48 to 60
inches deep. Further investigation will be needed to determine the appropriate
depth in Ambler, Kobuk, and Shungnak. Pipe connections are simple so the layout
does not need to be planned in great detail. Because it comes in rolls, hundred of
feet of piping can be laid out in very little time. Trenches are shallow and simpler to
construct, generally using equipment that may already exist in the villages.
The most significant negative aspect of the PEX system as opposed to the traditional
system is that the insulation is not as effective. Heat losses are greater with the PEX
system, and piping losses can have a significant effect on ongoing operating costs.
However, the heat losses are built into the feasibility models used in this report.
Piping heat loss is a variable that limits the length of any specific district heating
system. PEX piping systems are being used more and more in rural Alaska;
thousands of feet of this type of piping were recently installed in McGrath in less
than one week.
Alaska Wood Energy Associates 24
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
Pumping
Individual boiler applications can use the existing building boiler pumps for the
biomass boiler; no additional pumps need to be added. The remainder of this
section references only DH plant applications.
Proposed DH plants include a primary and a secondary pumping system. This
means that within the DH plant is a small piping loop that includes all of the heat
sources, as well as some thermal storage. The secondary loop is the distribution
loop that includes all the buried piping, and the connections to the end -user
buildings. The primary loop piping is shown in detail in Appendix D, and a sample
sequence of operations for the Plant is also contained in Appendix D.
The heat sources are connected to the primary loop in the order the heat is
preferentially taken - the heat exchanger from the engine cooling loop is first, the
biomass boiler(s) second, and the oil -fired boiler last. Thus the biomass boiler adds
heat only when the recovered heat cannot maintain set point, and the oil boiler in
turn adds heat only if either/both of the other two sources cannot maintain set
point.
The thermal storage is added to primary loop because the volume of water in the
loop is quite small. Thus it reacts to added heat very quickly. A biomass boiler does
not react to temperature changes quickly, the way a gas or oil fired boiler can. Thus
the thermal storage slows down the response time of the primary loop, allowing the
biomass boiler to operate more smoothly. Three sensors in the tank at different
elevations give an advance notice of the trend that the temperature loop is taking.
The primary loop contains two small pumps, each constant volume and each sized
for 100 percent of the pumping load.
The secondary loop contains two much larger pumps, each variable speed (to save
energy) and each sized for 100 percent of the pumping load. These pumps must
pump all the way out to the farthest building and back. This system volume is quite
large, and has no heat sources connected, so no thermal storage is used. A heat
exchanger is placed between the primary and secondary loops and transfers heat
between the loops, but keeps them physically separate.
At the building connection(s), two way control valves are used to control the
transfer of heat to the end -users. As the loads decrease, the valves close. This raises
the differential pressure between the supply and return piping in the distribution
loop. As this happens, the control system reduces the speed of the secondary pumps
(using the associated variable frequency drives), driving the system differential
back down to its set point. An increase in load likewise results in the pumps
speeding up. Varying the speed of these large pumps in response to load creates
significant energy savings compared to constant speed pumps. In order to cover
Alaska Wood Energy Associates 25
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
such large piping systems, three differential pressure sensors are used at different
locations - the system uses the lowest of the three signals to modulate the pump
speed, ensuring that all parts of the system get adequate flow.
Integration of Recovered Heat (DH plants only)
Diagrammatically, the integration of recovered heat into a DH Plant is covered in
detail in Appendix D. The concept is very simple. Water in the cooling loop from the
operating engine(s) producing power in the power plant is routed first to the DH
Plant.
In the DH Plant, the heated cooling water flows through a heat exchanger. A three-
way control valve on the cooling loop side of the exchanger controls how much heat
is rejected to the primary DH loop. If the valve is wide open, all the flow goes
through the heat exchanger.
A temperature sensor in the primary loop compares the supply temperature to the
set point. If the supply temperature is below set point, the three-way valve will be
wide open, extracting as much heat as possible from the cooling loop. If this is not
enough heat to meet the load, additional wood or oil heat will be added to the
primary loop as required. If the load is less than the available recovered heat, the
three-way valve will modulate as required to maintain the heating loop at set point.
On the generator cooling loop side, the water leaving the DH plant, having flowed
either through the heat exchanger or through the valve bypass, will return to the
power plant cooler than it left. It will then flow to the engine radiators. If it is
already cooler than the radiator set point temperature, then the radiator fans will
not come on - the water continues back to the engine jacket to start the cycle over.
If the water from the DH Plant is warmer than the radiator set point, the fans will
come on as needed to cool the water, and send it back to the jacket.
Building Integration (chip or stick -fired, DH plant or single building applications)
Once in the building mechanical room, the new hot water distribution piping will be
tied into the existing hot water supply and return lines that feed the existing boilers.
Typically, four 2-position, 2-way automatic isolation valves will be installed in the
piping, as shown in Figures 2.7, 2.8, and 2.9 below. The position of these valves will
determine whether the heat comes from the building oil -fired boiler, the DH plant or
building biomass boiler, or both. The existing building pumps will continue to serve
the building -heating load.
The valves that control the origin of the heat will be controlled by the existing
building controls where they exist, or by a small -dedicated control panel if needed.
If this proves too costly for very small installations, the switchover can always be
done with manual valves, but this relies on an operator.
Alaska Wood Energy Associates 26
BIOMASS HEATING FEASIBILITY Level 2 Study
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Ambler, Kobuk, and Shungnak, Alaska
Figure 2.7 shows a typical installation for two oil -fired boilers. In this scenario, each
boiler is sized for 100 percent of the load; the boilers are manually alternated so
that they get roughly equal run time. In all cases (figures 2.7, 2.8, and 2.9), light
solid lines indicate existing equipment and piping, dark solid lines depict new
equipment and piping, and light dashed lines show the water flow through the
system. For convenience, it is assumed in all cases that Oil Fired Boiler - 1 is the
active boiler, and boiler 2 would be isolated using the associated manual isolation
valve. HWS is hot water supply to the building; HWR is hot water return from the
building.
D
HWR
i
�
I
3:
I
= a
3
ISO
VALVE
(TYP)
o I
❑
�w
�w
i�
om
om
Figure 2.7, oil -fired heating plant
Figure 2.8 shows the initial configuration of the combined oil and biomass heat, with
the biomass (plant or individual boiler) providing all the heat. In Figures 2.8 and
2.9, the "wood -fired boiler" represents hot water heat from a single boiler or DH
plant. Closed "auto" valves are solid, open valves are not "blacked in".
Alaska Wood Energy Associates 27
BIOMASS HEATING FEASIBILITY
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Ambler, Kobuk, and Shungnak, Alaska
®IMI
J---► rv�r— HWR
® HWR M
AU TO w
VALVE O
(TYP) M
-----------------------
ISO
VALVE
D'
TYP
Uj 0 0 �pw
WW '� �W _V 0 Li _ Oe'J
w E�w O
omFD om7m
Level 2 Study
Figure 2.8, combined oil and biomass heat, all heat from Biomass
In the event that the biomass heat cannot meet the building set point for any reason,
the two systems can operate in series. The lack of adequate heat from the biomass
boiler or DH plant could range from small to total (a plant failure), but the operation
would remain the same - the oil -fired boiler would simply add enough heat to
maintain set point, whether this is 1 percent or 100 percent of Load. This is shown
in Figure 2.9.
_J
HWR
AUTO W
VALVE
(TYP)
U) .- I
a
= a
3
0
w
LL_w
J
Om
,"
-------- - rJ M CD
IPF
i
ISO
VALVE
o (TYP)
w
2� of
w�
Om I
Figure 2.9, combined oil and biomass heat, boiler heat in series with biomass heat
Alaska Wood Energy Associates 28
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Design Considerations for the use of Chip fired and Stick fired Boilers
Some of the material below has also been presented above. The intent is for this
section to be a stand-alone comparison of the two system types without reference to
the remainder of the report.
Stick -fired -Boilers
As the name implies, stick -fired boilers burn round or split wood in relatively
straight pieces. The wood is minimally processed, being selected for a range of
diameters and trimmed only for length. If the diameter of the wood is too large, the
wood may be split. Although the processing is minimal (compared to chipping), it is
generally all done manually (some splitting may be done with a machine).
Nevertheless, at the assumed unit costs, stick -wood is the cheapest energy source
available to the villages for generating thermal energy.
However, utilizing stick -wood means that much of the available biomass cannot be
used. Wood that is too large or too small, smaller tops and limbs that are bent
and/or tangled, or tops that contain leaves, cones, or needles are generally too
difficult to handle in a stick -fired boiler. The burn chamber of the boilers (see figure
2.11 below) is designed for straight stick -wood of a given length. The wood used is
generally air-dried, not mechanically dried; mechanical drying would be very
expensive on such small scales.
The stick -fired boilers used as the basis of evaluation for this study are the following
models manufactured by Garn. Dectra Corporation, located in St Anthony,
Minnesota owns Garn. A number of Garn Boilers are already installed in Alaska.
Figure 2.10 is summary of the models that were included in this study.
Garn
model
output
storage
kBTUih
kBTU
WHS 1500
350.0
920.0
WHS 2000
425.0
1,272.0
WHS 3200
950.0
2,064.0
Figure 2.10, Garn Boiler characteristics
Sizing, Boiler Control, and Utilization Rate
A primary feature of the Garn boiler is the built-in thermal storage. Physically, this
is a large hot water tank that surrounds the combustion chamber. Functionally, the
tank "decouples" the burn rate of the boiler from the actual heat load requirements.
In essence, the process of combustion heats the tank and the tank serves the load
(through pumps and a piping system), but not at the same rate. This is illustrated in
figure 2.10 above. In the WHS 3200, for instance, the process of combustion
Alaska Wood Energy Associates 29
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
generates up to 950 KBTU/h. The storage tank can hold 2,064 KBTU. So, if the
"burn" lasts a little over two hours, it will completely charge the tank. If the heating
load is 500 KBTU/h, however, it will take a little over four hours to deplete the tank
- thus the rate of combustion is decoupled from the heat load by the storage tank.
Heating a building is a continuous process, heating the tank in a Garn is a "batch"
process. The thermal storage tank bridges the gap between the continuous process
of heating and the batch process of burning. A batch process is one in which an
event takes place at intervals - for instance, every eight hours, one fills the Garn
with a "batch" of wood, and burns it.
This decoupling effect eliminates the need for sophisticated combustion controls
that would allow the boiler to track the load; that is, to match the burn rate to the
load. The boiler is manually fed, and manual started. This results in a very simple
boiler, which holds down first cost. The primary control function of the Garn is
combustion control - simply ensuring that the combustion air is controlled such
that the wood burns hot and clean.
The decoupling effect also means that sizing is less of an issue than it is with a chip -
fired boiler. If more capacity is needed to meet load, the operator can simply
conduct more "burns" per day. When less capacity is needed, fewer burns are
performed.
There are limits to this, of course. An operator would not want to have to feed the
boiler once every three hours round the clock, especially in the -50 deg F
temperatures that can occur in the interior of Alaska. In this study, the assumption
was that if more than four burns per day were required to meet peak heating load,
another boiler would be added to the installation. Four burns per day imply a
minimum of six hours between burns. Adding another boiler increases the time
between burns, but it adds significant cost as well.
In addition, the number of stick -fired boilers per installation was limited to three.
Beyond this limit, it was felt, the installations got too large and too expensive.
Because of the thermal storage, the boilers are quite large, and they require at a
minimum a covered roof and flat slab floor; ideally they would be completely
enclosed. Equally important, the utilization rate of the equipment drops as the
number of boilers increases. If one boiler is adequate in "warm" weather, two
required for "cool" weather, and all three for "cold" weather, then the overall
utilization rate of the plant is probably no more than about one half (50 percent).
Installing equipment in the interior of Alaska is expensive; the higher the utilization
rate, the more cost-effective the installation.
In the summer, heat loss from the tank may become a significant factor. The
seasonal range of heating loads in the interior of Alaska is the highest in the country.
Alaska Wood Energy Associates 30
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
The heat load at -60 deg F is 20 times higher (or more) than the load at 80 deg F
(when the load is probably only domestic hot water). So a burn that only lasts six
hours at peak theoretically lasts 120 hours in the summer. Obviously, in 120 hours,
more heat is going to be lost through the tank insulation than is going to be actually
used. It might therefore be more practical to run the existing oil -fired boilers when
the load drops too low. However, for the purposes of this study, although insulation
losses were accounted for, it was assumed that the Garn boilers met 100 percent of
the load - no oil was used, even in summer.
End -user Issues
All of the facilities included in this study already exist, thus any installation of a
wood -fired boiler would by necessity be a retrofit to an existing heating system.
The intent is that the boilers be installed in such a way as to be transparent to the
end -user. That is, the occupants cannot tell whether the heat is coming from the
existing oil -fired equipment or from the proposed wood -fired equipment.
Moreover, the mechanical heating system must operate the same way regardless of
heat source; manually switching from one source to the other must be as simple as
opening and closing valves. Finally, the systems will be installed in such a way that
a failure of a wood -fired boiler automatically starts the oil -fired back-up, and ideally,
notifies the operator of the failure.
The Garn boilers do have one major limitation in terms of end -user transparency;
they cannot control the hot water supply throughout the burn cycle. When a burn
finishes, the storage tank is at design temperature (200 deg F is the design
temperature for Garn). However, as the hot water is pumped through the heating
system, it gives up heat to the space. As a result, when it gets back to the tank it is
colder than when it left - the difference between supply and return temperature,
called the delta T (or change in T) depends on the type of heating equipment (air
handling unit, baseboard heat, radiator, etc) and the heating load.
The cooler return water immediately begins to dilute the 200 deg F water, cooling it.
Once the burn is done, no more heat is being added to the tank, but heat is
continuously being removed to heat the space - thus the tank temperature falls
throughout the tank's "draw -down" cycle. Garn considers the tank to be "depleted"
when it reaches 120 deg F. The basis of the heat storage capacities listed in figure
2.10 is the assumption that the tank is heated to 200 deg F, and then heat is
extracted until it reaches 120 deg F, at which time, another burn is initiated.
However, in a retrofit situation, 120 deg F hot water may not be suitable. Many hot
water heating systems are designed to use hot water at 180 deg F or more when at
peak load. For instance, the heating coil in an air handling unit may have been sized
to provide the required peak heating output using 180 deg F supply water (180 deg
F is a very common coil temperature). In such a case, with the heating load at or
near peak, the Garn boiler will be able to meet load as long as the storage tank
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Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
temperature equals or exceeds 180 deg F, but as it falls below that value, the air
handling unit may no longer be able to meet the load. By the time the supply
temperature falls to 120 deg F, the air -handling unit will be operating significantly
below design capacity.
As a specific example, assume an air handling unit that requires 180 deg F supply
water at peak load (i.e., there was no spare capacity in the coil at peak load), then in
effect the storage capacity of the Garn boiler would be reduced by 3/4: 1 - [(200 -
180) / (200 - 120)] = 0.75. The WHS 3200 that has been used as an example above
would have a storage capacity of only 516 kBTU, rather than 2,064 kBTU. At the
same time, the time between burns would also be cut to 1/4 of the calculated time,
although each "burn" would be much shorter, since the burn only had to raise the
temperature of the tank by 20 deg F.
In load conditions less than peak, air handling units can try to compensate for
dropping supply temperatures by increasing the hot water flow rate through the
coil. However, some heating systems do not have such automatic compensation.
For these types of systems, the varying supply temperature may also present
problems for the end -user. For example, some hot water radiators or baseboard
heating units are locally controlled - the user manually opens and closes a valve at
the unit to control space temperature. Obviously, a supply temperature that varies
from 200 deg F to 120 deg F several times a day presents a challenge to anyone
trying to control space temperature manually. Below about 140 deg F, a true
radiator (which is different than a baseboard heater, although they look
superficially the same) will not even work - there is not enough difference between
the room temperature and the radiator surface temperature for the radiant effect to
work efficiently.
The point is that in a retrofit situation, the effective storage capacity may be less
than the specified capacity, and thus the time between burns may be shorter than
desired.
Practically speaking, most heating systems use hot water in the 140 deg F - 200 deg
F range. Only radiant floor systems typically use hot water as low as 120 deg F.
Thus, in almost all cases, the storage capacity of the Garn units may have to be Be-
rated if the systems were not over -sized. This study did not de -rate capacity of the
Garn for three reasons: 1) there was not sufficient time to survey all the existing
equipment, and related drawings and specs, to determine the design supply
temperatures, and 2) In all cases, at load conditions not at or close to peak, 120 deg
F water may suffice - thus the number of hours per year when the de -rate would be
applied may be quite small (however, this is when the weather is coldest, and the
most labor is required to maintain the fuel supply and burn rate), and 3) direct
observations of system in Alaska have shown that many are so over -sized that they
operate even with low hot water supply temperatures. It was therefore assumed
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Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
that the specified storage capacity could be used in full; before any installation
design is finalized, however, this assumption should be confirmed.
Material Handling
As noted above, the Garn boilers are manually fed. For each burn, the operator must
load the combustion chamber with new stick -wood and manually start the fire. Ash
is cleaned out by hand as well, but this occurs after several burns and not at each
firing. Once the fire is lit, the chamber door is shut, and the fire burns until all the
fuel is consumed.
However, as noted above, it would take a little over two hours of burn to fully heat
the storage tank (using the WS 3200 as an example again). A single load of wood
will not burn for two hours, meaning that each burn must consist of more than one
load of wood. In addition, during that time that the burn is taking place, heat is
being extracted from tank to meet the heating load. So although a "burn" is treated
as a single event in this study, it is important to note that at or near peak load, a
burn could take as long as three hours to complete, and require two to three
"reloads" of the combustion chamber. (A complete burn is defined herein as
burning enough fuel to raise the storage tank from 120 deg F to 200 deg F, even as
heat is being extracted from the tank for ongoing heating.) Thus although the
number of burns is limited (in this study) to no more than four a day, this could still
imply roughly 9 - 10 hours a day of loading and cleaning the combustion chamber.
As with any stick -fired appliance, the fuel should be kept dry, and should be located
close to the point of use. Therefore, any building or structure constructed to house
the boiler should have sufficient space to stack cord wood. The amount of wood to
be stored within the building (as opposed to in a wood yard) depends on the site
conditions. In harsh conditions, it may be desirable to store several days' worth of
cordwood (at peak load consumption rate) in the boiler building, in case weather
keeps the operator from being able to re -stock the building from the wood yard. On
the other hand, in all cases the existing oil -fired system is assumed to be left in place
as back up, so this may limit how much wood the operator chooses to store in the
boiler building.
Regardless of how much wood is stored in the boiler building, considerable manual
labor would be required to get the sticks from the wood yard to the building; labor
to load, unload, and stack the wood. Because no equipment is required once the
stick -wood reaches the yard, the material handling, though labor intensive, is not
subject to equipment breakdowns.
There are a number of options for discarding the ash. It is likely the ash would be
collected in a small bin or dumpster, and emptied only as this gets full.
Alaska Wood Energy Associates 33
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Level 2 Study
Emissions Controls/Efficiency
Garn boilers have no active emissions controls. The boiler uses an induced draft
(ID) fan to ensure that enough air is present to provide complete combustion. This
alone helps eliminate or mitigate many emissions. It helps prevents the formation
of carbon monoxide (CO), which forms as a result of incomplete combustion. It
minimizes smoke and particulates (but cannot extract any particulate formed and
emitted), by burning clean and hot thus leaving very little behind but incombustible
ash.
Using more air than is strictly necessary simplifies the control, and makes for a clean
burn, but it also reduces efficiency. Excess air-cools the boiler down as it enters and
brings additional moisture with it, both of which require excess heat to bring them
up to combustion temperature.
The Garn does provide good transfer from the stack gas to the hot water storage
tank. The stack gas essentially passes through the tank five times (a five -pass heat
exchanger). There are four horizontal passes and one vertical pass. Overall, the
efficiency of the Garn is quite good - the study assumed about 78 percent of the
useable heat content of the wood was transferred into the tank.
Maintenance
There is very little maintenance required on a Garn boiler, and in fact, there is not
much that an operator could do. Figure 2.11 below shows a cross section of a Garn
boiler. The wood is burned in the primary combustion chamber, "E". In the
secondary combustion chamber, " P, only gases are burned. As long is the ash is
removed from "E" as needed, there is not much to maintain. The ID fan ("H") must
be repaired or replaced if it fails.
Figure 2.2 also shows the "tubes" that transfer heat to the storage tank. The tubes
(from the end of 7" through the end of "I"), must be cleaned; if not, then any scaling
or fouling of the tubes is not removed, and these will gradually erode the efficiency
of the boiler (or even cause the tubes to fail). Running a wire brush through them
can generally clean the tubes. The frequency of cleaning depends in part on how
clean the wood is; clean forest wood should have no inclusions, while scrap and
construction debris often do. If these inclusions (adhesives, preservatives, etc) do
not burn completely, they often plate out on the tubes, degrading performance.
Between cleanings, efficiency will slowly degrade as deposits accumulate, until the
next cleaning. Figure 2.11 also shows that the boiler has two vertical tubes sections
- these are more difficult to clean. All feeding, de-ashing, and cleaning is manual.
The timing of the feeding is manual, although that could be automated (i.e., a control
system could alert the operator when the tank is nearly depleted).
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Figure 2.11, cross section through a Garn boiler
Siting Issues
Level 2 Study
As noted above, the Garn boilers are quite large as a consequence of the storage
tank. The WHS 3200, the largest Garn boiler considered in this study, is 14' - 3"
long, 7' -2" wide, and 7' - 9" high. Each unit (full of water) weighs 34,500 lb. The
largest Garn plant considered in this study includes three WHS 3200 units. Not
including interior wood storage (but including clearance around each unit), this
would require a minimum of 678 square feet (20' - 3" long by 33' - 6" wide) with an
average floor loading of 153 lb/sf. This floor loading will likely require a relatively
thick reinforced concrete slab to prevent differential settlement.
Assuming that the storage tank is not de -rated, and the minimum time between
burns is 6 hours, such a plant could produce 1,032,000 BTU/h.
Chip fired Boilers
These boilers burn chipped wood, which can come from virtually any size of tree, or
any part of the tree, although there are sometimes limits on the amount of needles
and leaves. The fuel is more highly processed than stick -wood in order to achieve
uniform chip size, and thus more slightly expensive on a unit basis. Generally it is
only cost effective to dry the chips if they need to be transported significant
distances - drying reduces weight as the water is driven off. The flip side of the
higher cost of processing is that a much higher fraction of the available biomass
(tops and limbs) can generally be used in a chip -fired boiler; this is important in an
area where biomass yields are low.
The basis of calculations for the chip -fired boilers evaluated is the Pyrtec boiler line,
manufactured by Kob (now Wiessmann) of Austria. The North American office of
Wiessmann is located in Vancouver, BC, Canada. Wiessmann was chosen for this
study because: A) it comes in a wide range of sizes (see figure 2.12, below), 2)
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because the line has many useful features and has proven to be very reliable, 3)
because they have recently gotten the required ASME and UL certification for these
boilers, which means they can now be installed in the US, and 4) they have a blanket
exemption to the "Buy America" act. Figure 2.12 below shows the characteristics of
the boilers line included in the study.
output
capacity
Pyrotec model kBTU/h
Wiessmann model 390 1,331
Wiessmann model 530 1,808
Wiessmann model 720 2,457
Wiessmann model 950 3,241
Wiessmann model 1250 4,265
Figure 2.12, Wiessmann Boiler characteristics
Note that the largest Wiessmann, the model 1250, can output over four times as
much heat as a "three-Garn" plant.
Sizing, Boiler Control, and Utilization Rate
Chip -fired boilers are fed mechanically; as long as the fuel bin is kept loaded, and the
feed mechanism maintained, a boiler will continue to operate until an operator
shuts it down. The firing rate can be matched to the load, within limits. The
Wiessmann boilers can generally turn down about 3:1- that is, the minimum firing
rate is 1/3 of the maximum rate. With biomass boilers, thermal storage is often
useful; it serves at least three purposes.
First, it helps even out the boiler operation when the load is very close to the
minimum boiler load. Second, it helps maintain smooth temperature control. A
series of temperature sensors at different elevations in a tank gives a boiler advance
warning that load is increasing and smoothes out fluctuations in supply
temperatures. Third, when the boiler shuts down, the capacity of the tank is enough
to absorb the heat of the fuel in the boiler - once fuel enters a solid fuel boiler and is
ignited, it cannot be "turned off'; it will eventually burn and a properly sized storage
tank can absorb this residual heat.
While thermal storage is often used with a chip -fired boiler, it is not integral to the
boiler. In this study, a separate thermal storage tank was assumed. This slightly
decouples the load from the firing rate (as with the Garn), but because the storage is
so small, this is mainly an advantage at very low loads. Over most of the firing
range, the firing rate of the boiler is not decoupled from the load, and must
modulate (within the 3:1 range) output to meet load. When it cannot meet load on
the low end (and the storage cannot carry over the low load), it must shut down; on
the high end, it needs supplemental heat from a back-up source.
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As noted above, a high utilization rate is critical to creating a cost-effective
installation. At the same time, the firing range of the boiler is limited by the 3:1
turndown ratio. For these reasons, sizing a chip -fired boiler is critical. Space
heating loads peak in the winter, and tail off to little or nothing in the summer (if
domestic hot water is generated using the boilers, the summer load increases
slightly); thus the boiler sizing is a compromise.
The intent is to keep the boiler on as many hours as possible per year, thus
displacing the maximum amount of oil. For that reason, the boiler is generally sized
below the peak -heating load. Even so, the summer load is generally too small to fit
within the 3:1 turndown. For that reason, supplemental heat from existing oil -fired
boilers is generally needed in winter (to meet peak loads) and in summer (to meet
the very small loads). A good measure of the effectiveness of the boiler sizing is
what fraction of the annual oil use it would displace. Figure 2.13 below shows some
examples of the effect of boiler sizing on utilization rate.
Load v Outside Air Temp Pyrtec 540 Load v Outside Air Temp Pyrtec 720 Load v Outside Air Temp Pyrtec 950
kBTU/h fraction of oil displaced 0.855 kBTU/h fraction of oil displaced 0.907 kBTU/h fraction of oil displaced 0.866
4,000
red = load. blue = catpaciiy
3,000 —
2,000
1,000
0
deg F (60) (25) 10 45 80
4,000
3,000
2,000
1,0on —
0
deg F (60) (25) 10 45 80
Figure 2.13, effects of boiler sizing on utilization rate
4,000
3,000
2,000
1,000
0
deg F (60) (25) 10 45 80
Three boiler sizes are shown; the middle graph shows the model best suited for the
application (in this case, the village school in Fort Yukon). In this example, the
Pyrtec 720 can displace 90.7 percent of the oil currently required on an annual
basis. There are a minimal number of hours at peak load and at summer load when
the heating load falls outside the range of the 720.
A selection is always checked by trying one smaller and one larger model. The
graph on the left is the next smaller model, the Pyrtec 530. The smaller boiler can
operate at higher outside air temperatures (i.e., lower loads) than the 720, but this
gain is offset by the loss of capacity on the top end. The top end is when the existing
system is using oil the fastest, so displacing an hour of load at -55 deg F is worth
much more than displacing an hour of load at 55 deg F. Still, the 540 displace 85.5
percent of the annual oil consumption, not a bad utilization rate. On the right is the
next larger model, the Pyrtec 950. In this case, the boiler capacity is actually larger
than the peak load - so the existing oil -fired boiler would not have to run at all in the
winter. However, this also means that there is some capacity that is never used at
all. Sometimes this works out as the best solution, but in this case, the 950 displaces
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Level 2 Study
86.6 percent of the annual oil, confirming the 720 as the best selection for a single -
boiler application.
In order to displace a larger fraction of the required oil, a second chip -fired boiler
can sometimes be added. In these cases, the second boiler is generally smaller than
the first, or main boiler. This allows it to add heat in winter to help manage the
peaks, and extend the amount of time the plant can run in summer before the load
falls below the 3:1 limit. A well designed boiler plant with two boilers can often
displace nearly all of the oil an existing oil -fired plant uses in a year. However, some
combinations of boilers and loads do not allow much further optimization. If the
top -end capacity of the small boiler and the low -end capacity of the large boiler do
not overlap, then an oil -fired boiler is required to cover the capacity gap. In this
case, a single well -selected boiler is often the most cost effective solution.
In terms of control, the combustion and firing rate controls of the Wiessmann
boilers are much more sophisticated than those of stick -fired boilers. Primarily, this
is because the heat output must be matched to the load. This requires that the
boiler be able to control the rate at which fuel is added, as well as the rate at which
combustion air is added.
Controlling the speed of feed system, based on load, controls the fuel rate. The
control of the combustion air is based on monitoring the amount of oxygen left in
the stack gas - ambient air is about 21 percent 02 by volume (23.2 percent by
weight). Ideally, the amount of air added would be exactly that needed to
completely combust all the fuel; in such a case, the amount of excess 02 would be 0.0
percent. In practice, trying to achieve 0.0 percent excess 02 is dangerous; if there is
too little air, the result is incomplete combustion, which generates carbon monoxide
(CO), and may even cause explosions when sufficient air eventually reaches the fuel.
So the combustion controls build in a certain amount of excess air - often a function
of the moisture content. The usual range for chip -fired boilers with good control is
8 - 10 percent excess 02.
Combustion air must be heated to the stack temperature, and it brings water vapor
into the boiler (which must also be heated), both of which detract from the fuel's net
useable heat. Thus, minimizing the amount of excess air (measured by excess 02)
ensures that efficiency is kept as high as possible.
The Wiessmann boilers combine an auto -start feature with the controls noted
above; this means that the boiler plant can be started remotely (by a signal from a
control system, for instance), and will then continue to run and meet load until 1)
the fuel runs out, or 2) the load falls below the minimum turndown of the boiler.
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End -user Issues
As with the stick -fired boilers, the chip -fired boilers must be installed in such a way
as to be transparent to the end -user and the mechanical system. In addition to
starting the oil -fired back-up in the event of a boiler failure, the chip -fired boiler
must also be able to start the oil -fired back-up when: A) load exceeds the maximum
capacity of the chip -fired boiler, or 13) load falls below the minimum output of the
chip -fired boiler.
With regard to the end -user heating systems in the buildings, the Wiessmann boilers
are completely transparent; they can produce hot water at any constant
temperature up to 210 deg F. Further, they can automatically reset the supply
temperature as load decreases. An air -handling unit that requires 200 deg F water
in winter may be able to meet load with 140 deg F water in spring and fall. Using
the boiler controls, the hot water supply temperature can be reset based on outside
air temperature, or any other parameter that can be measured. This is important
because the lower the supply temperature, the more efficient the boiler.
Material Handling
A boiler that is intended to run for long periods with no supervision is dependent on
its material handling systems. Fuel must be introduced into the boiler
automatically, and the ash removed. Wiessmann can provide the systems needed to
fuel and de -ash the boilers, but the trade-off for this automation is additional
maintenance, and more potential failure points.
In order to make chip -fired boilers feasible in the interior of Alaska, it will be
important to minimize the length of the material handling "chain", as well as the
number of moving parts. Ideally, a single auger would pull fuel out of a fuel bin,
which would be manually filled periodically (manual here implies a person running
a front loader or similar machine). The chips would slide by gravity to the auger
inlet, minimizing failure points. In practice, the feed process can be fully automated,
but this is not feasible on the scale of boiler plants considered in this study, and it
presents too many potential points of failure. This section of the study also does not
deal with the chipping equipment itself.
The design of the material handling systems will be key to successful
implementation of chip -fired boilers. Figure 2.14 below shows some of the material
handling elements integral to the boiler. On the right of the picture is the fuel inlet -
the chips must be augured to this point; from here the boiler modulates the flow
into the boiler. On the left is the de-ashing auger. This automatically removes ashes
from the boiler and deposits them in the bin shown. The Wiessman Pyrot boiler line
(shown) is not currently being considered for interior of Alaska, because it requires
chips with a moisture content of less than 35 percent; however, this picture shows
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Level 2 Study
the boiler -mounted elements of the material handling system common to all
Wiessmann boilers.
Figure 2.14, Wiessmann Pyrot boiler
Emissions Controls/Efficiency
As noted above, the Wiessmann boiler controls the combustion airflow to minimize
excess air. As with the Garn, this provides complete combustion, which helps to
minimize both CO and particulate. In addition, however, the Wiessmann can be
installed with flue gas recirculation (FGR). By injecting a fraction of the flue gas
back into the combustion chamber, the combustion temperature is lowered,
reducing the formation of oxides of nitrogen. Commonly labeled as NOx, these
oxides are major air pollutant, and they contribute to acid rain. Finally, a cyclone
(supplied by Wiessmann) can be installed to mitigate particulates. A cyclone, as the
name implies, causes the stack gas to spin as it enters the unit. This throws the
solids (the particulates) to the sides of the unit, where they fall to the bottom of the
unit. The gas exits up the center of the unit and out the flue to the atmosphere.
Combustion efficiency is a function of the difference between the temperature of
combustion air entering the boiler and the stack gas leaving the boiler - the cooler
the stack gas is, the more efficient the boiler. This difference in temperature is itself
a function of how hot the hot water return temperature is (the cooler the better, as
noted above), and the efficiency of the heat transfer from stack gas to hot water
(how clean the tubes are).
The Wiessmann boiler addresses both of these issues. Using the boiler controls
intelligently, the hot water supply temperature can be automatically reset down as
load decreases. In addition, the Wiessmann can be equipped with soot -blowers.
These are nozzles that direct high-pressure compressed air onto the tubes at regular
intervals to keep them clean. The material blown off the tubes is removed by the de-
ashing system. Using soot blowers does require a small air compressor, but it more
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Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
than pays for itself by keeping boiler efficiency high. Figure 2.15 below shows the
soot -blower array on a Wiessmann Pyrtec boiler.
Figure 2.15, Wiessmann Pyrtec boiler showing soot blowers
The soot blowers are the twelve black nozzles on the front of the boiler. On the left
is the fuel in -feed system. Note that in the Wiessmann boilers, the tubes are all
straight - they run from front to back. This makes them easier to manually clean
than the bent tubes in the Garn. However, with the soot blowers in place, the tubes
would only need to be manually brushed out every three months or so.
As result of good design, good control, and automatic tube cleaning, the efficiency of
the Wiessmann boilers approaches 84 percent (83 percent was used in the model).
Maintenance
There are obviously quite a few more moving parts on the Wiessmann boilers.
However, these boilers have been in service for many years in Europe. They are
designed to start up at the end of summer, and to run continuously until the next
summer. Most maintenance is performed once a year, generally during the summer
downtime. The only cleaning that is expected to occur more often that once a year is
the brushing out of the tubes.
One of the first Wiessmann boilers currently installed in the US is in Oregon; it has
been running for almost three years at the time of this report. The operator reports
that he looks in at the boiler once a day, and that he brushes out the tubes every two
to three months.
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A key will be minimizing the complexity of the material (fuel) handling systems;
these typically require more maintenance than the boilers. This material handling
will be evaluated on a site -to -site basis for the best solution.
Siting Issues
Because the chip -fired boilers do not incorporate an integral storage tank, they are
much smaller than the stick -fired units. The Pyrtec series boilers are too tall for a
standard shipping container, but there may be options for pre-packaging these
boilers. Being able to in essence build the boiler plant in a fabrication shop rather
than in the field in the interior of Alaska will lower costs, reduce construction time,
and result in a better quality product.
In addition to the advantage of being able to pre-package chip -fired boilers, they
have a much higher energy density than the stick -fired boilers. Above, it was noted
that it required a 678 sq.ft. building to house a stick -fired plant that could produce
just over 1 million BTU/h in heat output. The largest Wiessmann boiler, the Pyrtec
1250, produces 4.3 million BTU/h. The boiler itself is 14' - 4' long and 5' - 3" wide.
The building required to enclose the boiler and its support equipment would be
about 20' - 0" long by 15' - 0" wide (300 sq.ft.); that is over four times the BTU
output in less than half the space required for the stick -fired boiler plant.
In both cases, however, the fuel storage is an issue. It should be covered, and in the
case of wood chips, it would be ideal if a truck could dump into a covered bin with a
floor that sloped to the auger inlet. This will require more extensive construction
than a flat covered space suitable for stacking cordwood. For either type of boiler,
fuel storage will require considerable thought, and will need to be adapted to the
specific site conditions.
Section 3: System Analysis
Limits
As with any performance evaluations, the quality and validity of the outputs and
subsequent conclusions depends on the quality of the inputs and the methodology.
Methodology is discussed in Section 3.2 below. The input data gathered for used in
the analyses performed as a part of this study include:
➢ Building specific data
➢ Historical village PCE (electrical consumption) data
➢ Proposed DH Plant equipment data
➢ Annual oil consumption, by building
➢ Annualized weather data (bin data) from the Ambler airport
➢ Village maps and plans
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➢ Interviews with Civil Engineers, contractors, and consultants with significant
experience in the interior of Alaska
➢ Pricing data from boiler manufacturers, piping suppliers and other AK
vendors
➢ Performance data from Wiessmann and Garn
➢ Input from other Alaska Wood Energy Associate team members
What was not performed a part of this analysis was detailed measurements of
building heat loads and existing equipment performance. A building heating load
profile is central to predicting annual fuel consumption. Ideally, this would be
generated by directly measuring heating load throughout the year. At the same
time, the actual operating efficiency of the existing boilers and distribution system
would be measured. This would provide a highly detailed profile of heating load
and the energy required to meet that load, for any condition throughout the year.
In practical terms, however, the required measurements are difficult to perform,
and not cost-effective. The equipment needed to make these measurements is not
present at any of the installations in the villages, and would have to be flown in and
installed. The measurements would need to continue from winter to summer, to
generate a complete load profile. The resulting incremental increase in the accuracy
of the load profile cannot justify that level of cost. Even without the measurements,
the data that were collected limit the load profiles to within a narrow range of
values.
Also missing from this analysis is a detailed analysis of electrical load profiles (and
thus available recovered heat). The only data available was monthly. Ideally, at
least some hourly or daily data will be included in any Level 3 analysis.
Methodology
Energy Savings
The performance of the existing and proposed heating systems was modeled using
spreadsheets; the type of model used is known as a "bin model". The bins are
ranges of outside air temperatures (OATs). Temperature bins are used because
heating load is very closely correlated to OAT. Each "bin" of OAT is 2 deg F wide -
for instance, 40 - 42 deg F is a bin, with the midpoint temperature of 41 deg F. For
each OAT bin, the heating load profile assigns a heating load to that temperature bin.
The actual "bin data" is the number of hours per year that the outside air
temperature falls into each specific bin.
Bin weather data is published for numerous sites, including many in Alaska.
However, none of the villages in this study have published bin data. Therefore,
actual hourly temperature data from the Ambler airport was used to construct a bin
table for all sites. The weather data came from calendar years 2008 and 2009. The
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Level 2 Study
data were combined to come up the average number of hours per year that the OAT
in the upper Kobuk Valley falls into each bin. This was done a on a monthly basis -
for instance, the data in Figure 3.1 show the spread of temperatures in three
different bins; 80 to 82 deg F, 40 to 42 deg F, and -20 to -22 deg F.
hours per bin, Ambler Airport, 2008 - 2009 average
mid
pt hours per bin
deg F jan feb mar apr may Jun jul aug sep Oct nov dec
81 13.8
41 7.2 43.3 7.2 4.3 18.8 34.0 6.2
(21) 25.2 12.8 4.8 5.7 25.5
Figure 3.1, Ambler Airport bin data
In the calculations performed within the model, individual calculations are
completed in a series of tables that have the same format at the original bin
temperature data (see Appendix E for sample calculations). Figure 3.2 below shows
a portion of a calculation used in this study (in this case, the calculations involved
with the School in Shungnak).
OAT
mid
pt
85
17.20
School
output
: kBTU/h
61.1
3,200
2,064
950
80
HWS
deg F
120.0
model
kBTU
kBTU/h
deg F
de -rated
capacity
1.0000
Garn
store
bum
dT (store)
storage
(each)
kBTU
2,064
6.0
3
0.005
1,032
? No.
1 1
max burn intervals
max units
losses
max cap, KBTU/h
total
losses load
kBTU/h kBTU/h
10.3 71.5
2,064
3
324
Garn oil
cords/h gph
0.006
83
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
81
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
79
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
77
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
75
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
73
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
71
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
69
61.1
120.0
1.0000
2,064
1 1
10.3
71.5
0.006
67
191.7
120.0
1.0000
2,064
1 1
10.3
202.1
0.016
65
203.7
120.0
1.0000
2,064
1 1
10.3
214.1
0.017
Figure 3.2 Example calculations - partial bin model
Subsequent calculations are done to determine how much oil/wood/recovered heat
is required to meet that load - one table for each energy source (complex rules
determine which source is the primary, secondary, or tertiary source in each load
condition). Once the required oil (for instance) is calculated for each spot in the
table, the SUMPRODUCT function sums up all the oil required for each month. This
is the basic format of the calculations.
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The basis of all calculations is the heating load profiles for each building included in
the study. These load profiles reflect all the information available about the
building, such as heating equipment capacity, operating data, historical oil
consumption data, size and type of building, etc. As noted above, it is difficult to
measure heat load directly, but simple to measure oil consumption. So the first
profiles generated are oil consumption profiles. These profiles assign a specific oil
consumption rate to each OAT bin. Using the calculation format above, the model
calculates the amount of oil required to heat each building, and then compares that
to known consumption - obviously, the model must be able to back -predict known
consumption if it is to be used to predict future consumption.
Once the oil consumption profiles are verified, the oil consumption profile is
converted to a space heating load profile by multiplying BTU of input heat (oil)
times the efficiency of the boiler/furnace to arrive at the actual heat to the space.
Once these space load profiles are generated, they are fixed. An example of oil
consumption versus OAT load profile is shown in Figure 3.3 below.
Ft Yukon School Oil Consumption Load Profile (gal/hr vs OAT in deg F)
gaUhr
10.0
8.0
6.0
4.0
2.0
0.0
(60) (40) (20) 0 20 40 60 80
Figure 3.3, Example of Oil Consumption versus OAT for Fort Yukon School
No matter what heat source is used or how great any parasitic or piping losses are,
any proposed DH plant or biomass boiler must deliver that same amount of BTUs to
the space as the current oil -fired appliances do. Once the space load profiles are
established, the spreadsheet models the various DH plants and boilers to determine
how much energy they would consume to provide this required space heat. As
noted above, in addition to producing a set amount of BTU for space heat, a DH plant
must produce enough BTUs to heat the plant itself (parasitic loss) and to overcome
the heat lost from the distribution piping into the ground (piping losses). Finally,
the model must calculate how much pumping (electrical) energy must be used to get
the heat to the buildings. Once inside the buildings, the electrical energy used for
pumping is the same for the existing systems as it would be with a DH Plant in place,
so this energy is not calculated or accounted for in the model.
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Additional key load profile assumptions:
➢ Space heating load varies linearly with OAT (a 10 deg F drop in OAT results
in twice the increase in load that a 5 deg F drop causes)
➢ There is an OAT at which space heating stops - the OAT combined with the
internal loads in the building (people, lights, equipment) are such that no
additional heat is required; beyond this temperature, the only load is DHW.
This value can be set individually for each building.
➢ However, there is heating required above 60 deg F, for heating domestic hot
water in some of the buildings. This DHW heating value can also be set
individually for each building.
Recovered Heat
A "recovered heat" profile is generated similar to heating loads. This profile assigns
a specific village power requirement to each temperature bin. This is less
straightforward than assigning heat loads versus OAT, because the correlation
between village power and OAT is not as strong - there is also a time -of -day
component to power output. Bin models predicts long-term average performance
not hour -by -hour performance. A bin model that predicts consumption accurately
on a monthly basis is generally as specific as is required - most utilities bill and/or
report consumption on a monthly basis For each village (except Kobuk, which does
not generate its own power) a temperature versus power curve was developed
which accurately predicts monthly consumption.
The following is the list of other calculations made in order to predict performance.
Other than the calculations relating to the DH plant piping (flow rates, distance, pipe
size, etc), all of these calculation took the form of bin tables as described above
(again, sample calculations can be found in Appendix E):
➢ Proposed routing of DH pipe and associated lengths
➢ Peak flow rate required by each building
➢ Size of piping run -out to each building
➢ Size of each segment of the piping mains (any pipe that serves more than one
building)
➢ Minimum and maximum heat loss in each segment and run -out and bin
profile
➢ DH Plant parasitic heating load profile
➢ DH Plant heating load (building profile plus parasitic profile plus piping loss
profile)
➢ Useable recovered heat profile and bin calculation (month by month)
➢ Wood energy input profile and bin calculation (month by month)
➢ Oil energy input profile and bin calculation (month by month)
➢ Pumping energy input profile and bin calculation (month by month)
Alaska Wood Energy Associates 46
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Cost Estimates
The other component required to calculate the payback of any given scenario is the
project cost. One estimate was prepared for each proposed DH plant and individual
boiler installation (see Appendices A, B, and C for a copy of the cost estimates). The
current cost estimates contains the best knowledge of the team members regarding
construction in rural Alaska. As the study level proceeds, these costs estimates will
be constantly updated to reflect the current design. Ultimately, actual vendor
quotes and contractor's estimates or bids will be used for the final cost estimates.
Results
Financial results are provided in Appendices A, B and C for Ambler, Kobuk and
Shungnak respectively. They are summarized in Section 1 of this report with
recommendations.
Section 4: Financial Metrics
Financial Metrics
There are any numbers of financial metrics that can be employed to evaluate a
project. Many of these require that the source and means of financing the project be
known. Many require knowing the expected interest rate that money could be
borrowed at, and even the rate of return the client would expect to achieve if they
invested the capital elsewhere (not in the project).
In the case of projects in the villages of Ambler, Kobuk, and Shungnak, much of this
information is not known at this time. The exact funding mechanisms are not
known. The in -kind participation of the village, if any, is not defined, and therefore
the value of it cannot yet be determined. Finally, forward -looking interest rates are
not very predictable at this point in time.
At the same time, this study is a feasibility study. As such, it does not seem justified
to make assumptions about all of the relevant financial variables. For all these
reasons, this study has used a single financial metric to evaluate each potential
heating plant - both as a stand-alone investment and as a way to compare different
technologies and combinations of buildings.
Net simple payback (NSP) as used herein is defined simply as the implementation
cost of the project divided by the annual year energy savings. Year one savings are
specified; it is assumed that resource rates will change year to year (or faster).
All financial summaries used in this study use NSP as the sole financial metric for
evaluating each option. There are a number of factors that do not factor into the
Alaska Wood Energy Associates 47
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
NSP as defined herein; perhaps the two most relevant here are the labor cost and
the maintenance cost.
It is not known how the plants would be manned. The chip -fired boilers require
very little labor. The fuel bin must be filled, the ashbin emptied, and in the event a
failure, the material handling elements must be fixed. In a district -heating scenario,
two to four people could operate a plant that supplied 10 buildings or more (plant
only - does not count wood harvesting and processing).
The stick -fired boilers, on the other hand, require up to 12 loads of wood per day,
manually fed, at peak load. However, in such cold weather, the operator(s) may
choose to simply feed the boiler during the day, and let the oil -fired boilers take over
at night.
This kind of variation in amount of labor that would actually be applied to each
plant makes estimating labor costs difficult at best. In addition, there is the question
of what the labor would cost. An organization might simply assign someone already
employed in the building to load the boiler(s) and count the cost as zero. They
might equally well hire an outside contractor. If a District Heating plant were
installed, that would in likelihood imply the existence of a company specially formed
to implement and operate the plant.
Similarly, judging the maintenance costs of the boiler plants in the harsh climate of
the interior of Alaska presents an issue. The Garn boilers are very simple, with not
much to break. The Wiessmann boilers, originally built in Austria (now Germany),
are deployed throughout Europe, including Scandinavia - an area with harsh winter
climates as well. Nevertheless, they have more moving parts to maintain, and
possibly fail.
Labor and maintenance costs are annual, and thus deduct directly from the energy
savings (lengthening the NSP). The point being made above is simply that the range
of possible values for annual labor and maintenance costs is so wide that they
should not be used to make financial decisions as a part of this study. Instead, as the
project is developed in each village, the decisions on boiler technology and plant size
should go hand -in -hand with discussions of how the boilers will be operated and
maintained so that the true cost can be determined prior to making the investment.
Alaska Wood Energy Associates 48
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Appendices
Appendix A: Ambler Model Output
Ambler Inputs, DH Summary, Chip Summary, and Stick Wood Summary
INPUTS, chips
moisture content at: % by
bum store cut weight
1 : Cottonwood, logs
0.25
0.35
0.50 0.100
2 : Birch, logs
0.25
0.25
0.50 0.200
3 : Aspen, logs
0.25
0.30
0.50 0.200
4 : B Spruce, logs
0.25
0.25
0.50 0.300
5 : W Spruce, logs
0.25
0.30
0.50 0.200
other variables
checksum 1.000
avg fuel storage temp
46.0
deg F
avg absolute humidity
36.0
cir/lb
avg excess 02
0.10
avg air specific volume
12.9
cf/lb
avg stack temp
320
deg F
INPUTS, stick wood
moisture content at: % by
bum store cut weight
1 : Cottonwood, logs
0.35
0.35
0.50 0.500
2 : Birch, logs
0.25
0.25
0.50 0.500
other variables
checksum 1.000
avg fuel storage temp
46.0
deg F
avg absolute humidity
36.0
gr/lb
avg excess 02
0.20
avg air specific volume
12.9
cf/lb
avg stack temp
375
deq F
Oil Data
Composite Chip Properties
net useable heat
5,845
B-fl_I!Ib at burn Llu
weight at storage MC
1.044
Ih'It; at burn MC
weight at cut MC
1.500
Ib/Ib at burn MC
density as stacked logs
21.866
Ib/cf at storage MC
density as chips
21.787
Ib/cf at storage MC
combustion air req
5.246
Ib/v✓et lb at bum MC
combustion air req
67.669
cf/v✓et lb at burn ld(G
CO2 formed
1.425
lb/wet Ib at burn MC
SOx formed
0.000
lb/wet lb at burn MC
ash
0.017
It,/hvet lb at burn h✓IC
ash specific volume
0.003
cf/wet lb at burn MC
available harvest rate
17.300 tons/acre wet
note: NC-x.. CO. VOC, and PM emissions are a function of the boiler
Composite Stick Wood Properties
net useable heat
5,103
BTU/lb at burn MC
net useable heat
18,533
kBTU/cord
weight at storage MC
1.000
lb/lb at burn MC
weight at cut MC
1.400
lb/lb at burn MC
density as stacked logs
24.319
Ih/cf at storage MC
density as cord wood
28.372
Ib/cf at storage MC
combustion air req
5.146
lb/wet lb at burn K1C
combustion air req
66.379
cf/wet lb at burn NtC
CO2 formed
1.313
Ib/wet lb at burn 1,40
SOx formed
0.000
lb/wet lb at burn MC
ash
0.005
lb/wet lb at burn Mc
ash specific volume
0.001
cf/wet lb at burn [,,AC
available harvest rate
15.500
tons/acre wet
note: NCix, CO. VOC, and FM emissions are a function of the boilei
heating oil heat content
134.0
kBTU/gal
heating oil density
7.1
lb/gal
sulfur content
500.0
ppm
sulfur emissions
0.0010
lb/gal
CO2 emissions
22.013
lb/gal
low cost (school, etc)
$3.750
per gal
unit cost to power plant
$3.500
per gal
high cost (to village)
$8.500
per gal
oil to H plant
$8.500
per gal
unit cost of recovered heat
$0.016
per kBTU
NOx and CO emissions are a function of the boiler
Cost of Fuel
wood chips $175 per preen ton
pellets $300 per ton
stick wood $250 per cord
Alaska Wood Energy Associates 49
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Amber District Heat Layout: Conceptual
District Plant location is rectangle with rectangle inside.
Level 2 Study
Alaska Wood Energy Associates 50
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 1
Village Buildings
incl
No.
1 school complex
1
1
2
water treatment
1
1
4 city building
1
5 city hall
1
6 health clinic
1
1
7 tribal office
1
1
8 NANA office
1
1
9 sewer line trace
1
1
10 N subdiv, single
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant
(1 thru 3: wood, 4: oil) 280 sf
ID make model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann 390
334.4
1330.7
4 Weil McLain 80-380 278.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
$369.2
$173.6
$195.5
$195.5
est construction
$1,702,051
2
$380.3
$176.8
$203.5
$203.5
3
$391.7
$180.0
$211.7
$211.7
final design/study
$110,633
4
$403.4
$183.3
$220.1
$220.1
bid assistance
$8,510
5
$415.5
$186.7
$228.9
$228.9
Cons Admin
$129,621
6
$428.0
$190.1
$237.9
$237.9
Cx/start up
$17,021
7
$440.8
$193.7
$247.2
$247.2
contingency
$85,103
8
$454.1
$197.3
$256.8
$256.8
soft costs
$350,787
9
$467.7
$201.0
$266.7
$266.7
tax
10
$481.7
$204.8
$276.9
$276.9
11
$496.2
$208.7
$287.5
$287.5
project cost
$2,052,839
12
$511.0
$212.6
$298.4
$298.4
NSP
10.5 yrs
13
$526.4
$216.7
$309.7
$309.7
14
$542.2
$220.9
$321.3
$321.3
grants/rebates
$2,052,839
15
$558.4
$225.2
$333.3
$333.3
donated
16
$575.2
$229.5
$345.6
$345.6
amount financed
17
$592.4
$234.0
$358.4
$358.4
interest
5.000 %
18
$610.2
$238.6
$371.6
$371.6
term
15.0 yrs
19
$628.5
$243.3
$385.2
$385.2
payments/yr
1
20
$647.4
$248.2
$399.2
$399.2
discount rate
5.000 %
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source
%from
Base
Sc
delta
NPV
$3,376,002
rec ht
0.2517
CO2
644.1
845.3
201.1
escalation, rec ht
3.000%
wood
0.7427
CO
971.6
2,617.6
1,646.0
escalation, oil
3.000%
oil
0.0056
SOx
58.6
534.5
475.9
escalation, wood
1.000%
total
1.0000
NOx
666.6
756.8
90.2
escalation, elec
3.000%
sink
%to
end -use
0.7913
PM
513.5
oil displaced, gal
58,127
piping
0.1395
VOC
80.2
oil displaced
99.33%
plant
0.0692
ash
19,970
utilize rec heat
1
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc =
This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 6,493
5,700
5,917
5,105
4,240
3,283
3,097
3,722
4,038
5,204
5,845
5,878 58,522
B cost 39,850
35,077
36,636
31,990
27,282
21.825
20,908
24,390
26,035
32,658
36,118
36,419 $369,187
Sc rec heat, mmBTtJ 208.9 182.3 186.6 157.6 135.2 150.5 157.2 146.4 133.2 158.9 185.2 185.1 1,987
Sc biomass, tons 70.0 61.2 63.0 53.4 41.9 26.4 22.5 33.0 39.3 54.4 62.4 62.5 590
Sc oil, gal 14 107 197 57 19 395
Sc added elec, kWh 6,199 5,517 5,909 5,480 5.292 4,492 4,230 5,043 5,094 5,626 5,774 5,898 64,553
Sc
rec heat, cost
3,313
2,892
2,959
2,499
2,144
2,387
2,492
2,322
2,113
2.520
2,937
2,935
$31,514
Sc
biomass, cost
12,246
10,714
11,032
9,349
7,329
4,623
3,944
5,773
6,882
9,525
10,917
10,940
$103,274
Sc
oil, cost
121
911
1,671
486
166
$3,354
Sc
added elec, cost
3,409
3,034
3,250
3,014
2,911
2,471
2,326
2,774
2,801
3,094
3,176
3,244
$35,504
cost of inputs
18,969
16,640
17,241
14,862
12,504
10,392
10,434
11,355
11,962
15,139
17,030
17,119
$173,646
savings
20,881
18,437
19,395
17,128
14,778
11,433
10,474
13,035
14,073
17,519
19,088
19,300
$195,541
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
May
Jun
Jul
Auo
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.42
0.37
0.38
0.32
0.25
0.16
0.14
0.20
0.24
0.33
0.37
0.38
3.54
2
Birch, logs
1.17
1.02
1.05
0.89
0.70
0.44
0.38
0.55
0.66
0.91
1.04
1.04
9.84
3
Aspen, logs
0.84
0.73
0.76
0.64
0.50
0.32
0.27
0.40
0.47
0.65
0.75
0.75
7.08
4
B Spruce, logs
2.10
1.84
1.89
1.60
1.26
0.79
0.68
0.99
1.18
1.63
1.87
1.88
17.70
5
W Spruce, logs
1.05
0.92
0.95
0.80
0.63
0.40
0.34
0.49_._
_ 0.59
0.82
0.94
_0.94_
_ _8.85
totals
5.57
4.88
5.02
4.26
3.34
2.10
1.80
2.63
3.13
4.34
4.97
4.98
47.01
Alaska Wood) Energy Assoouates 51
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Village Buildings
incl
No.
school complex
1
1
2
3 water treatment
1
1
4 city building
1
5 city hall
1
6 health clinic
1
1
7 tribal office
1
1
8 NANA office
1
1
9 sewer line trace
1
1
10 N subdiv, single
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant
(1 thru 3: wood, 4: oil) 280 sf
ID make model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann 390
334.4
1330.7
5 Weil McLain 80-480 396.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
1
$437.2
$209.1
$228.1
$228.1
est construction
$2,051,968
2
$450.3
$212.7
$237.6
$237.6
3
$463.8
$216.5
$247.3
$247.3
final design/study
$133,378
4
$477.7
$220.3
$257.4
$257.4
bid assistance
$10,260
5
$492.1
$224.2
$267.8
$267.8
Cons Admin
$140,520
6
$506.8
$228.2
$278.6
$278.6
Cx/start up
$20,520
7
$522.0
$232.3
$289.7
$289.7
contingency
$102,598
8
$537.7
$236.5
$301.1
$301.1
soft costs
$407,276
9
$553.8
$240.8
$313.0
$313.0
AK state tax
10
$570.4
$245.2
$325.2
$325.2
11
$587.5
$249.7
$337.8
$337.8
project cost
$2,459,244
12
$605.2
$254.3
$350.8
$350.8
NSP
10.8 yrs
13
$623.3
$259.1
$364.3
$364.3
14
$642.0
$263.9
$378.1
$378.1
grants/rebates
$2,459,244
15
$661.3
$268.8
$392.4
$392.4
donated
16
$681.1
$273.9
$407.2
$407.2
amount financed
17
$701.6
$279.1
$422.6
$422.5
interest
5.000%
18
$722.6
$284.4
$438.2
$438.2
term
15.0 yrs
19
$744.3
$289.8
$454.4
$454.4
payments/yr
1
20
$766.6
$295.4
$471.2
$471.2
discount rate
5.000 %
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source %from
Base
Sc
delta
NPV
$3,963,102
rec ht
0.2038
CO2
732.2
1,065.0
332.9
escalation, rec ht
3.000%
wood
0.7941
CO 1,127.0
3,307.7
2,180.7
escalation, oil
3.000%
oil
0.0021
SOx
66.6
675.4
608.8
escalation, wood
1.000%
total
1.0000
NOx
768.4
954.6
186.2
escalation, elec
3.000%
sink
% to
end -use
0.7598
PM
649.2
oil displaced, gal
66,346
piping
0.1716
VOC
101.4
oil displaced
99.74%
plant
0.0686
ash
25,247
utilize rec heal
1
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario. all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
- Nov
Dec
B oil, gal 7,497
6,571
6,795
5,819
4,755
3,626
3,404
4,137
4,523
5,926
6,721
6,748 66,522
B cost 48,390
42,483
44,101
38,055
31,657
24,745
23,513
27,916
30,162
38,793
43,563
43,811 $437,187
Sc rec heal, mmBTU 208.9 182.3 186.6 157.6 132.5 124.2 116.2 136.2 129.4 158.9 185.2 185.1 1,903
Sc biomass, tons 86.2 76.0 78.6 66.2 51.8 37.2 35.4 42.6 49.0 67.4 77.8 77.9 746
Sc oil, gal 124 46 3 3 176
Sc added elec, kWh 8,821 7,739 8,010 7,057 6.341 5,855 6,037 6,102 6,117 7,201 7,907 7,979 85,165
Sc
rec heat, cost
3,313
2,892
2.959
2,499
2,102
1,969
1,843
2,160
2,053
2,520
2,937
2,935
$30,182
Sc
biomass, cost
15.084
13,306
13,760
11,584
9,069
6,508
6,187
7,461
8,567
11,787
13,620
13,630
$130,562
Sc
oil, cost
1,056
388
28
22
$1,494
Sc
added elec, cost
4,852
4,256
4.405
3,881
3,488
3,220
3,321
3,356
3,364
3,961
4,349
4,388
$46,841
cost of inputs
24,305
20,841
21,124
17,964
14,659
11,697
11,350
12,977
13,984
18,268
20,934
20,976
$209,079
savings
24,085
21,641
22,976
20,091
16,998
13,047
12,163
14,938
16,178
20,525
22,630
22,835
$228,108
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar -
Apr
May
Jun
Jul
Auo
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.52
0.46
0.47
0.40
0.31
0.22
0.21
0.26
0.29
0.40
0.47
0.47
4.48
2
Birch, logs
1.44
1.27
1.31
1.10
0.86
0.62
0.59
0.71
0.82
1.12
1.30
1.30
12.43
3
Aspen, logs
1.03
0.91
0.94
0.79
0.62
0.45
0.42
0.51
0.59
0.81
0.93
0.93
8.95
4
B Spruce, logs
2.59
2.28
2.36
1.99
1.55
1.12
1.06
1.28
1.47
2.02
2.33
2.34
22.38
5
W Spruce, logs
1.29
1.14
1.18
0.99
0.78
0.56
0.53
0.64
0.73
1.01
1.17
1.17
11.19
totals
6.87
6.06
6.26
5.27
4.13
2.96
2.82
3.40
3.90
5.37
6.20
6.20
59.44
Alaska Wood Energy Associates 52
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Village Buildings
incl
No.
school complex
1
1
water treatment
1
1
city building
1
1
5 city hall
1
1
6 health clinic
1
1
7 tribal office
1
1
8 NANA office
1
1
sewer line trace
1
1
10 N subdiv, single
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant
(1 thru 3: wood, 4: oil) 280 sf
ID make model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann 390
334.4
1330.7
5 Weil McLain 80-480 396.0
Level 2 Study
Case Flow, 1,000s
yr Base
Sc
savings
debt
net
Project Cost / Financials
1
$449.9
$217.7
$232.2
$232.2
est construction
$2,161,530
2
$463.4
$221.5
$241.9
$241.9
3
$477.3
$225.4
$251.9
$251.9
final design/study
$140,499
4
$491.7
$229.5
$262.2
$262.2
bid assistance
$10,808
5
$506.4
$233.5
$272.9
$272.9
Cons Admin
$141,615
6
$521.6
$237.7
$283.9
$283.9
Cx/start up
$21,615
7
$537.2
$242.0
$295.2
$295.2
contingency
$108,077
8
$553.4
$246.4
$307.0
$307.0
soft costs
$422,614
9
$570.0
$250.9
$319.1
$319.1
AK state tax
10
$587.1
$255.5
$331.6
$331.6
11
$604.7
$260.2
$344.5
$344.5
project cost
$2,584,145
12
$622.8
$265.0
$357.8
$357.8
NSP
11.1 yrs
13
$641.5
$269.9
$371.6
$371.6
14
$660.7
$275.0
$385.8
$385.8
grants/rebates
$2,584,145
15
$680.6
$280.2
$400.4
$400.4
donated
16
$701.0
$285.5
$415.5
$415.5
amount financed
17
$722.0
$290.9
$431.1
$431.1
interest
5.000%
18
$743.7
$296.4
$447.2
$447.2
term
15.0 yrs
19
$766.0
$302.1
$463.9
$463.9
payments/yr
1
20
$789.0
$307.9
$481.0
$481.0
discount rate
5.000%
Sc Source/Sink
source %from
rec ht 0.1980
Emissions
Base
CO2 748.7
metric
Sc
1,106.5
delta
357.8
pay at begin
sum of debt
ratio
NPV
escalation, rec ht
1
$4,040,569
3.000%
wood
0.7974
CO
1,156.2
3,429.8
2,273.6
escalation, oil
3.000%
oil
0.0047
SOx
68.1
700.4
632.2
escalation, wood
1.000%
total
1.0000
NOx
787.5
991.0
203.5
escalation, elec
3.000%
sink
%to
end -use
0.7525
PM
673.0
oil displaced, gal
67,616
piping
0.1790
VOC
105.1
oil displaced
99.40%
plant
total
0.0685
1.0000
ash 26,171
include wood in CO2
CO2 in tons/yr, all else in Ib/yr
1
utilize rec heat
bias to wood
1
1
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op% 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 7,687
6,736
6,961
5,953
4,852
3,688
3.457
4,213
4,615
6,062
6,886
6,912 68,022
B cost 50,001
43,881
45,510
39,201
32,479
25,272
23,967
28,563
30,936
39,952
44,969
45,206 $449,937
Sc rec heat, mmBTU 208.9 182.3 186.6 157.6 132.7 125.6 118.5 136.9 129.7 158.9 185.2 185.1 1,908
Sc biomass, tons 88.7 78.4 81.9 68.9 53.8 38.5 36.5 44.3 50.8 70.1 80.7 80.9 773
Sc Oil, gal 230 119 1 38 18 406
Sc added elec, kWh 9,328 8,167 8,410 7,350 6,508 5,943 6,116 6,214 6,273 7,493 8,315 8,374 88,490
Sc
rec heat, cost
3,313
2,892
2,959
2,499
2,104
1,992
1,879
2,171
2,056
2,520
2,937
2,935
$30,258
Sc
biomass, cost
15,515
13,719
14,327
12,053
9,419
6,738
6,384
7,744
8,897
12,261
14,117
14,163
$135,339
Sc
oil, cost
1,958
1,014
7
319
149
$3,447
Sc
added elec, cost
5,130
4,492
4,625
4,042
3,579
3,268
3,364
3,418
3,450
4.121
4,573
4,606
$48,669
cost of inputs
25,917
22,116
21,919
18,594
15,103
11,999
11,628
13,332
14,404
18,903
21,946
21,853
$217,713
savings
24,084
21,765
23,591
20,606
17,377
13,273
12,339
15,231
16,533
21,049
23,023
23,353
$232,224
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.53
0.47
0.49
0.41
0.32
0.23
0.22
0.27
0.31
0.42
0.48
0.49
4.64
2
Birch, logs
1.48
1.31
1.36
1.15
0.90
0.64
0.61
0.74
0.85
1.17
1.34
1.35
12.89
3
Aspen, logs
1.06
0.94
0.98
0.83
0.65
0.46
0.44
0.53
0.61
0.84
0.97
0.97
9.28
4
B Spruce, logs
2.66
2.35
2.46
2.07
1.61
1.16
1.09
1.33
1.53
2.10
2.42
2.43
23.20
5
W Spruce, logs
1.33
1.18
1.23
1.03
0.81
0.58
0.55
0.66
0.76
1.05
1.21
1.21
11.60
totals
7.06
6.25
6.52
5.49
4.29
3.07
2.91
3.53
4.05
5.58
6.43
6.45
61.61
Alaska Wood) Energy Associates 53
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Individual Building Chip and Stick -fired Boiler Summaries
Individual Building Boiler Summary
bldg
Building
base oil
gal/yr
Stick Wood
oil fuel
displaced cost
project
cost
NSP
yrs
Chips
oil
displaced
fuel
cost
project NSP
cost yrs
school complex
27,000
0.864
$60,159
$346,904
8.4
0.974
$55,245
$417,111 9.1
2
3
water treatment
3,500
1.000
$7,748
$244,971
11.1
$32,445
$364,180
4
5
city building
city hall
750
750
1.000
1.000
$2,512
$2,512
$244,971
$244,971
63.4
63.4
$9,070
$9,070
$364,180
$364,180
6 health clinic 1,642
7
tribal office
8
NANA office
9
sewer line trace
10
N subdiv, single
11
N subdiv plant
12
13
city bldg+ city hall
14
school+water treat
15
school/treat/sewer
16
880
13,000
12,500
800
8,000
1.000
$4,210
$244,971
25.1
1.000
$2,760
$244,971
51.9
0.943
$31,852
$262,793
3.3
1.000
$24,519
$244,971
3.0
1.000
$2,607
$244,971
58.4
1.000
$16,594
$535,411
10.4
$16,652 $364,180
$10,175 $364,180
0.946 $32,490 $364,180 4.7
1,000 $25,998 $364,180 4.5
$9,495 $364,180
0.636 $12,181 $631,574 11.3
1,500 1.000 $3,940 $244,971 27.8 $15,445 $364,180
30,500 0.993 $62,236 $528,398 7.7 0.951 $70,274 $447,402 7.4
43,000 0.926 $106,061 $559,390 4.3 0.994 $87,364 $542,178 3.6
Alaska Wood Energy Associates
54
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Appendix B; Kobuk Model Output
Level 2 Study
Kobuk Inputs, DH Summary, Chip Summary, and Stick Wood Summary
moisture content at: % by
INPUTS, chips
bum
store
cut
weight
1 : Cottonwood, logs
0.25
0.35
0.50
0.100
2 : Birch, logs
0.25
0.25
0.50
0.200
3 : Aspen, logs
0.25
0.30
0.50
0.200
4 : B Spruce, logs
0.25
0.25
0.50
0.300
5 : W Spruce, logs
0.25
0.30
0.50
0.200
other variables
checl<sum
1.000
avg fuel storage temp
46.0
deg F
avg absolute humidity
36.0
gr/lb
avg excess 02
0.10
avg air specific volume
12.9
cf/lb
avg stack temp
320 deg F
moisture content at:
% by
INPUTS, stick wood
bum store cut
weight
1 : Cottonwood, logs
0.35 0.35 0.50
0.500
2 : Birch, logs
0.25 0.25 0.50
0.500
checksum 1.000
other variables
avg fuel storage temp
46.0
deg F
avg absolute humidity
36.0
gr/lb
avg excess 02
0.20
avg air specific volume
12.9
cf/lb
avg stack temp
375
deg F
Comoosite Chip Properties
net useable heat
5,845
BTU/Ib at burn MC
weight at storage MC
1.044
lb/lb at burn MC
weight at cut MC
1.500
lb/lb at burn MC
density as stacked logs
21.866
Ib/cf at siorace MC
density as chips
21.787
Ib/cf at storage MC
combustion air req
5.246
lb/wet lb at burn MC
combustion air req
67.669
cf/wet lb at burn MC
CO2 formed
1.425
lb/wet lb at burn MC
SOx formed
0.000
lb/wet lb at burn MC
ash
0.017
lb/wet lb at burn MC
ash specific volume
0.003 cf/wet lb at burn MC
available harvest rate
17.300
tons/acre wet
note: NOx, CO, VOC, and PM emissions are a function of the boiler
Composite Stick Wood Properties
net useable heat
5,103
BTU/Ib at burn MC
net useable heat
18,533
kBTU/cord
weight at storage MC
1.000
lb/lb at burn MC
weight at cut MC
1.400
lb/lb at burn MC
density as stacked logs
24.319
Ib/cf at storage MC
density as cord wood
28.372
Ib/cf at storage MC
combustion air req
5.146
lb/wet lb at burn MC
combustion air req
66.379 cf/wet Ib at burn MC
CO2 formed
1.313
lb/wet lb at burn MC
SOx formed
0.000
lb/wet lb at burn MC
ash
0.005
lb/wet lb at burn MC
ash specific volume
0.001
cf/wet lb at burn MC
available harvest rate
15.500
tons/acre wet
note: PJOx. CO, VOC, and PM emissions are a function of the boiler
Oil Data
heating oil heat content
134.0
kBTU/gal
heating oil density
7.1
lb/gal
sulfur content
500.0
ppm
sulfur emissions
0.0010
lb/gal
CO2 emissions
22.013
lb/gal
low cost (school, etc)
$3.750
per gal
unit cost to power plant
$3.500
per gal
high cost (to village)
$8.500
per gal
oil to H plant
$8.500
per gal
unit cost of recovered heat
$0.016
per kBTU
NOx and CO emissions are a function of the boiler
Cost of Fuel
wood chips $175 per green ton
pellets $300 per ton
stick wood $250 per cord
Alaska blood Energy Associates 55
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Kobuk District Heat Layout: Conceptual
Level 2 Study
The red rectangle within the rectangle is the general location of the boiler plant.
Alaska Wood Energy Associates 56
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 1
Village Buildings
ind
No.
school
1
1
2 clinic
1
1
3 city office
1
1
4 water treatment
1
1
5 NANA office
1
1
6 9 house subdiv
9
7
8 teacher housing
1
1
9 future school
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers I Buildings plant
(1 thru 3: wood, 4: oil) 280 sf
ID make model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann 390
334.4
1330.7
5 Well McLain 80-480
396.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
1
$220.4
$134.8
$85.6
$85.6
est construction
$1.480,297
2
$227.0
$137.5
$89.4
$89.4
3
$233.8
$140.4
$93.4
$93.4
final design/study
$96.219
4
$240.8
$143.2
$97.6
$97.6
bid assistance
$7.401
5
$248.0
$146.2
$101.8
$101.8
Cons Admin
$104,803
6
$255.5
$149.3
$106.2
$106.2
Cx/start up
$14.803
7
$263.1
$152.4
$110.8
$110.8
contingency
$74.015
8
$271.0
$155.6
$115.4
$115.4
soft costs
$297,242
9
$279.2
$158.9
$120.3
$120.3
tax
10
$287.5
$162.2
$125.3
$125.3
11
$296.2
$165.7
$130.5
$130.5
project cost
$1,777,539
12
$305.0
$169.2
$135.8
$135.8
NSP
20.8 yrs
13
$314.2
$172.9
$141.3
$141.3
14
$323.6
$176.6
$147.0
$147.0
grants/rebates
$1,777,539
15
$333.3
$180.4
$152.9
$152.9
donated
16
$343.3
$184.4
$159.0
$159.0
amount financed
17
$353.6
$188.4
$165.2
$165.2
interest
5.000 %
18
$364.2
$192.5
$171.7
$171.7
term
15.0 yrs
19
$375.2
$196.8
$178.4
$178.4
payments/yr
1
20
$386.4
$201.1
$185.3
$185.3
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source
% from
Base
Sc
delta
NPV
$1,525,316
rec ht
CO2
340.7
579.5
238.8
escalation, rec ht
3.000 %
wood
0.8704
CO
601.5
1,658.2
1,056.8
escalation, oil
3.000 %
all
0.1296
SOx
31.0
338.7
307.7
escalation, wood
1.000%
total
1.0000
NOx
394.1
502.9
108.8
escalation, elec
3.000%
sink
% to
end -use
0.7783
PM
320.9
oil displaced, gal
26,048
piping
0.1439
VOC
50.1
oil displaced
84.15%
plant 0.0778
ash
12,479
utilize rec heat
total
1.0000
include wood in CO2
1
bias to wood
1
702 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 3,746
3,262
3.319
2,751
2,080
1,443
1,300
1,710
1,966
2,790
3,300
3,290 30,955
B cost 26,598
23,163
23,582
19,570
14,840
10,346
9,336
12,231
14,033
19,849
23,443
23,378 $220,368
Sc rec heat, mmBTIJ
Sc
biomass, tons
52.2
45.3
45.8
37.0
23.3
4.2
2.4
9.3
20.6
37.9
45.6
45.3
369
Sc
oil, gal
41
392
1,370
1,382
1,214
507
4,907
Sc
added elec, kWh
5,548
4,967
5,390
5,042
4,426
2,023
1,820
2,744
4,021
5,266
5,245
5,386
51,879
Sc
rec heat, cost
Sc
biomass, cost
9,135
7,929
8,007
6,473
4,085
733
422
1,620
3,599
6,629
7,976
7,928
$64,536
Sc
oil, cost
344
3,335
11,647
11,751
10,319
4,311
$41,707
Sc
added elec, cost
3,052
2,732
2,964
2,773
2,434
1,113
1,001
1,509
2,211
2,896
2,885
2,962
$28,533
cost of inputs
savings
12,186
14,411
10,661
12,502
10,972
12,610
9,590
9,980
9,854
4,986
13,493
(3,147)
13,174
(3,838)
13,448
(1,217)
10,121
3,911
9,526
10,323
10,861
12,583
10,891
12,487
$134,776
$85,591
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.31
0.27
0.27
0.22
0.14
0.03
0.01
0.06
0.12
0.23
0.27
0.27
2.21
2
Birch, logs
0.87
0.76
0.76
0.62
0.39
0.07
0.04
0.15
0.34
0.63
0.76
0.76
6.15
3
Aspen, logs
0.63
0.54
0.55
0.44
0.28
0.05
0.03
0.11
0.25
0.45
0.55
0.54
4.43
4
B Spruce, logs
1.57
1.36
1.37
1.11
0.70
0.13
0.07
0.28
0.62
1.14
1.37
1.36
11.06
5
W Spruce, logs
0.78
0.68
0.69
0.55
0.35
0.06
0.04
0.14
0.31
0.57
0.68
0.68
5.53
totals
4.16
3.61
3.65
2.95
1.86
0.33
0.19
0.74
1.64
3.02
3.63
3.61
29.38
Alaska Wood Energy Associates 57
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 2
Village Buildings
incl
No.
1 school
1
2 clinic
1
1
3 city office
1
1
4 water treatment
1
1
5 NANA office
1
1
6 9 house subdiv
9
7
8 teacher housing
1
1
9 future school
1
1
10
11
12
13
14
15
16
17
18
19
20
21
22
Boilers / Buildings plant fuel process
(1 lhru 3: wood, 4: oil) 280 sf 148 sf 1,200 sf
ID make model min max
7 Wiessmann 390 334.4 1330.7
5 Weil McLain 80-480 396.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
i
$246.6
$135.0
$111.6
$111.6
est construction
$1,482,792
2
$254.0
$137.3
$116.7
$116.7
3
$261.6
$139.8
$121.9
$121.9
final design/study
$96,381
4
$269.5
$142.3
$127.2
$127.2
bid assistance
$7,414
5
$277.6
$144.8
$132.8
$132.8
Cons Admin
$104,828
6
$285.9
$147.4
$138.5
$138.5
Cx/start up
$14,828
7
$294.5
$150.0
$144.4
$144.4
contingency
$74,140
8
$303.3
$152.8
$150.6
$150.6
soft costs
$297,591
$312.4
$155.5
$156.9
$156.9
AK state tax
10
$321.8
$158.4
$163.4
$163.4
11
$331.4
$161.3
$170.1
$170.1
project cost
$1,780,383
12
$341.4
$164.3
$177.1
$177.1
NSP
15.9 yrs
13
$351.6
$167.3
$184.3
$184.3
14
$362.2
$170.5
$191.7
$191.7
grants/rebates
$1,780,383
15
$373.0
$173.7
$199.4
$199.4
donated
16
$384.2
$176.9
$207.3
$207.3
amount financed
17
$395.7
$180.3
$215.4
$215.4
interest
5.000 %
18
$407.6
$183.7
$223.9
$223.9
term
15.0 yrs
19
$419.8
$187.3
$232.6
$232.6
payments/yr
1
20
$432.4
$190.9
$241.6
$241.6
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source %from
Base
Sc
delta
NPV
$1,989,047
rec ht
CO2
417.7
707.2
289.4
escalation, rec ht
3.000%
wood
0.9529
CO
737.5
2,137.4
1,399.9
escalation, all
3.000%
oil
0.0471
SOx
38.0
436.5
398.5
escalation, wood
1.000 %
total
1.0000
NOx
483.2
627.0
143.8
escalation, elec
3.000%
sink
% to
end -use
0.8028
PM
417.6
oil displaced, gal
35,835
piping
0.1211
VOC
65.2
oil displaced
94.41 %
plant 0.0761
ash
16,240
utilize rec heat
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else
in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 4,605
4,008
4,076
3,375
2,544
1,758
1,580
2,087
2,405
3,422
4,054
4,041 37,955
B cost 29,818
25,964
26,423
21,911
16,582
11,527
10,386
13,645
15,677
22,221
26,271
26,193 $246,618
Sc rec heat, mmB I U
Sc biomass, tons 62.4 54.1 54.5 44.5 31.9 16.5 10.9 22.3 29.3 45.1 54.4 54.0 480
Sc oil, gal 4 82 572 890 412 159 2,120
Sc added elec, kWh 5,997 5,340 5,725 5,326 5,071 3,644 2,981 4.331 4,749 5,479 5,593 5,719 59,955
Sc
rec heat, cost
Sc
biomass, cost
10,914
9,467
9,544
7,787
5,586
2,891
1,914
3,907
5,123
7,885
9,513
9,452
$83,983
Sc
oil, cost
38
698
4,866
7,564
3,499
1,354
$18,019
Sc
added elec,cost
3,299
2,937
3,149
2,929
2,789
2,004
1,639
2,382
2,612
3,014
3,076
3,145
$32,975
cost of inputs
14,213
12,405
12,693
10,754
9,073
9,761
11,118
9,788
9,089
10,899
12,589
12,597
$134,978
savings
15,605
13,559
13,730
11,157
7,509
1,766
(732)
3,857
6,588
11,322
13,683
13,596
$111,640
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
Mav
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.37
0.32
0.33
0.27
0.19
0.10
0.07
0.13
0.18
0.27
0.33
0.32
2.88
2
Birch, logs
1.04
0.90
0.91
0.74
0.53
0.28
0.18
0.37
0.49
0.75
0.91
0.90
8.00
3
Aspen, logs
0.75
0.65
0.65
0.53
0.38
0.20
0.13
0.27
0.35
0.54
0.65
0.65
5.76
4
B Spruce, logs
1.87
1.62
1.64
1.33
0.96
0.50
0.33
0.67
0.88
1.35
1.63
1.62
14.40
5
W Spruce, logs
0.94
0.81
0.82
0.67
0.48
0.25
0.16
0.33
0.44
0.68
0.82
0.81
7.20
totals
4.97
4.31
4.34
3.54
2.54
1.32
0.87
1.78
2.33
3.59
4.33
4.30
38.23
Alaska Wood [Energy Associates 58
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Village Buildings
incl
No.
school
1
1
clinic
1
1
3 city office
1
1
4 water treatment
1
1
5 NANA office
1
1
6 9 house subdiv
1
9
7
8 leacher housing
1
1
9 future school
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant
(1 thru 3: wood, 4: oil) 280 sf
ID make model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann 390
334.4
1330.7
5 Weil McLain 80-480
396.0
Level 2 Study
Case Flow, 1,000s
Project Cost I Financials
yr
Base
Sc
savings
debt
net
I
$281.6
$140.8
$140.7
$140.7
est construction
$1,801,720
2
$290.0
$143.2
$146.9
$146.9
3
$298.7
$145.5
$153.2
$153.2
final design/study
$117,112
4
$307.7
$147.9
$159.7
$159.7
bid assistance
$9,009
5
$316.9
$150.4
$166.5
$166.5
Cons Admin
$115,517
6
$326.4
$152.9
$173.5
$173.5
Cx/start up
$18,017
7
$336.2
$155.5
$180.7
$180.7
contingency
$90,086
8
$346.3
$158.1
$188.2
$188.2
soft costs
$349,741
9
$356.7
$160.8
$195.9
$195.9
AK state tax
10
$367.4
$163.6
$203.8
$203.8
11
$378.4
$166.4
$212.0
$212.0
project cost
$2,151,461
12
$389.8
$169.3
$220.5
$220.5
NSP
15.3 yrs
13
$401.4
$172.2
$229.2
$229.2
14
$413.5
$175.2
$238.3
$238.3
grants/rebates
$2,151,461
15
$425.9
$178.3
$247.6
$247.6
donated
16
$438.7
$181.5
$257.2
$257.2
amount financed
17
$451.8
$184.7
$267.1
$267.1
interest
5.000%
18
$465.4
$188.0
$277.4
$277.4
term 15.0 yrs
19
$479.3
$191.4
$288.0
$288.0
payments/yr
1
20
$493.7
$194.8
$298.9
$298.9
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source
% from
Base
Sc
delta
NPV
$2,482,034
rec ht
CO2
419.9
790.3
370.4
escalation, rec ht
3.000%
wood
0.9789
CO
741.4
2,427.3
1,685.9
escalation, oil
3.000%
oil
0.0211
SOx
38.2
495.7
457.4
escalation, wood
1.000%
total
1.0000
NOx
485.7
705.2
219.5
escalation, elec;
3.000%
sink
% to
end -use
0.7281
PM
475.5
oil displaced, gal
37,101
piping
0.1972
VOC
74.3
oil displaced
97.24%
plant 0.0748
ash
18,493
utilize rec heat
total
1.0000
Include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 4,655
4,050
4,113
3,396
2,543
1,745
1,563
2,076
2,402
3,442
4,092
4,076 38,155
B cost 34,322
29,863
30,334
25,057
18,780
12,907
11,576
15,346
17,742
25,398
30,178
30,064 $281,568
Sc rec heat, mmBTU
Sc biomass, tons 68.5 59.5 60.2 49.3 36.2 22.6 18.4 28.3 33.9 49.9 60.0 59.6 546
Sc oil, gal 36 300 484 168 65 1,054
Sc added elec, kWh 6,599 5,845 6,190 5,661 5,322 4,310 3,941 4,913 5,080 5,803 6,069 6,178 65,911
5c
rec heat, cost
Sc
biomass, cost
11,993
10,417
10,541
8,632
6,333
3,947
3.223
4,958
5,933
8,734
10,491
10,432
$95,634
Sc
oil, cost
310
2,549
4,116
1,428
556
$8,960
Sc
added elec,cost
3,629
3,215
3,405
3,113
2,927
2,371
2,168
2.702
2,794
3,192
3,338
3,398
$36,251
cost of inputs
15,622
13,632
13.946
11,745
9,569
8,867
9,507
9,089
9,284
11,926
13,829
13,830
$140,845
savings
18,700
16,231
16,388
13,311
9,210
4,041
2,069
6,258
8,458
13,473
16,349
16,234
$140,723
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
Mav
Jun
Jul
Aup
Sep
Oct
Nov
Dec
1 Cottonwood, logs
0.41
0.36
0.36
0.30
0.22
0.14
0.11
0.17
0.20
0.30
0.36
0.36
3.28
2 Birch, logs
1.14
0.99
1.00
0.82
0.60
0.38
0.31
0.47
0.57
0.83
1.00
0.99
9.11
3 Aspen, logs
0.82
0.71
0.72
0.59
0.43
0.27
0.22
0.34
0.41
0.60
0.72
0.72
6.56
4 B Spruce, logs
2.06
1.79
1.81
1.48
1.09
0.68
0.55
0.85
1.02
1.50
1.80
1.79
16.39
5 W Spruce, logs
1.03
0.89
0.90
0.74
0.54
0.34
0.28
0.42
0.51
0.75
0.90
0.89
8.20
totals
5.46
4.74
4.80
3.93
2.88
1.80
1.47
2.26
2.70
3.98
4.78
4.75
43.54
Alaska Wood Energy Associates 59
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 4
Village Buildings
incl
No.
1 school
1
2 clinic
1
1
3 city office
1
1
4 water treatment
1
1
5 NANA office
1
1
6 9 house subdiv
1
9
7
8 teacher housing
1
1
9 future school
1
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant fuel process
(1 thru 3: wood, 4: oil) 280 sf 148 sf 1,200 sf
ID make model min max
7 Wiessmann 390 334.4 1330.7
4 Weil McLain 80-380 278.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
1
$307.8
$155.2
$152.6
$152.6
est construction
$1,799,884
2
$317.1
$157.6
$159.4
$159.4
3
$326.6
$160.1
$166.4
$166.4
final design/study
$116,992
4
$336.4
$162.7
$173.7
$173.7
bid assistance
$8,999
5
$346.5
$165.3
$181.2
$181.2
Cons Admin
$115,499
6
$356.8
$168.0
$188.9
$188.9
Cx/start up
$17.999
7
$367.6
$170.7
$196.9
$196.9
contingency
$89.994
8
$378.6
$173.5
$205.1
$205.1
soft costs
$349,484
9
$389.9
$176.3
$213.6
$213.6
AK state tax
10
$401.6
$179.2
$222.4
$222.4
11
$413.7
$182.2
$231.5
$231.5
project cost
$2,149,367
12
$426.1
$185.2
$240.9
$240.9
NSP
14.1 yrs
13
$438.9
$188.3
$250.6
$250.6
14
$452.0
$191.4
$260.6
$260.6
grants/rebates
$2,149,367
15
$465.6
$194.7
$270.9
$270.9
donated
16
$479.6
$198.0
$281.6
$281.6
amount financed
17
$494.0
$201.4
$292.6
$292.6
interest
5.000 %
18
$508.8
$204.8
$304.0
$304.0
term
15.0 yrs
19
$524.0
$208.3
$315.7
$315.7
payments/yr
1
20
$539.8
$212.0
$327.8
$327.8
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source %from
Base
Sc
delta
NPV
$2,708,361
rec ht
CO2
497.0
905.9
408.9
escalation, rec hl
3.000 %
wood
0.9875
CO
877.4
2,796.9
1,919.5
escalation, oil
3.000%
oil
0.0125
SOx
45.2
571.1
525.9
escalation, wood
1.000%
total
1.0000
NOx
574.8
810.1
235.2
escalation, elec
3.000 %
sink
%to
end -use
0.7537
PM
548.4
oil displaced, gal
44.441
piping
0.1725
VOC
85.7
oil displaced
98.42%
plant
0.0738
ash
21,327
utilize rec heat
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr.
all else in Ibfyr
Inputs and Costs
(B = Baseline, Sc =
This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Auo
Sep
Oct
Nov
Dec
B oil, gal 5,514
4,797
4,871
4,021
3,008
2,060
1,843
2,453
2,841
4,075
4,846
4,827 45,155
B cost 37,543
32,663
33,175
27,397
20,522
14,088
12,626
16,760
19,387
27,770
33,006
32,880 $307,818
Sc rec heat, mmBTU
Sc biomass, tons 78.5 68.3 69.0 56.4 41.4 27.0 23.1 33.3 39.1 57.1 68.7 68.3 630
Sc oil, gal 16 1 24 207 338 94 34 714
Sc added elec, kWh 7,406 6,507 6,757 6,018 5,445 4,455 4,181 5,044 5.221 6,150 6,663 6,739 70,586
Sc
rec heat, cost
Sc
biomass, cost
13,741
11,954
12,078
91875
7,251
4,723
4,036
5,819
6,839
9,990
12,028
11,956
$110,289
Sc
oil, cost
137
8
203
1,762
2,874
797
285
$6,066
Sc
added elec,cost
4,073
3,579
3,716
3,310
2,995
2,450
2,300
2,774
2,872
3,382
3,665
3,706
$38,822
cost of inputs
savings
17,951
19,592
15,540
17,123
15,795
17,380
13,185
14,212
10,448
10,073
8,936
5,152
9,210
3,416
9,390
7,370
9,995
9,392
13,372
14,398
15,693
17,313
15,662
17,218
$155,178
$152,640
Required Harvest, acres
Jan
Feb
Mar
Apr
May
Jun
Jul
Auo
Sep
Wet Storage Area Required
Oct Nov Dec
413 sf
1
Cottonwood, logs
0.47
0.41
0.41
0.34
0.25
0.16
0.14
0.20
0.23
0.34
0.41
0.41
3.78
2
Birch, logs
1.31
1.14
1.15
0.94
0.69
0.45
0.38
0.55
0.65
0.95
1.15
1.14
10.50
3
Aspen, logs
0.94
0.82
0.83
0.68
0.50
0.32
0.28
0.40
0.47
0.69
0.82
0.82
7.56
4
B Spruce, logs
2.36
2.05
2.07
1.69
1.24
0.81
0.69
1.00
1.17
1.71
2.06
2.05
18.91
5
W _Spruce, logs
1.18
1.02
1.04
0.85
0.62
0.40
0.35
0.50
0.59
0.86
1.03
1.02
9.45
totals
6.26
5.44
5.50
4.50
3.30
2.15
1.84
2.65
3.11
4.55
5.48
5.44
50.21
Alaska Wood Energy Associates 60
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Individual Building Chip and Stick -fired Boiler Summaries
Individual Building Boiler Summary
Stick Wood
Chips
base oil
oil
fuel
project
NSP
oil
fuel
project
NSP
bldg
Building
gal/yr
displaced
cost
cost
yrs
displaced
cost
cost
yrs
1
school
9,000
0.968
$18,751
$246,796
16.5
0.701
$24,547
$366,004
39.8
2
clinic
1,455
1.000
$3,854
$246,796
29.0
$15,062
$366,004
city office
1,800
1.000
$4,511
$246,796
22.9
$17,995
$366,004
4
water treatment
4,200
1.000
$9,081
$246,796
9.3
$38,395
$366,004
5
NANA office
13,000
0.951
$30,275
$264,617
3.3
0.901
$35,494
$366,004
4.9
6
9 house subdiv
7,200
1.000
$15,070
$512,557
11.1
0.530
$38,575
$609,301
26.9
8 teacher housing 1,500 1.000 $3,940 $246,796 28.0 $15,445 $366,004
9 future school 16,000 0.999 $32,481 $348,728 12.7 0.977 $33,211 $366,004 13.7
10
11
sch, TH, off, WT
16,500
1.000
$33,441
$441,706
6.9
0.982
$35,411
$457,240
7.4
12
fut sch, TH, off, WT
23,500
0.930
$57,572
$441,706
6.7
0.986
$49,545
$511,913
6.9
13
opt 11, NANA
29,500
0.814
$94,404
$472,699
4.2
0.948
$68,832
$542,906
3.9
14
opt 11, NANA, clinic
30,955
0.789
$104,027
$503,691
4.3
0.931
$75,386
$573,898
4.0
15
opt 12, NANA
36,500
0.937
$87,513
$621,375
4.2
0.829
$120,303
$917,914
8.1
16
opt 12, NANA, clinic
37,955
0.922
$94,679
$652,368
4.3
0.849
$119,530
$950,648
7.5
Alaska Wood Energy Associates 61
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Appendix C Shungnok Model Output
Shungnak Inputs, DH Summary, Chip Summary, and Stick Wood Summary
INPUTS, chips
moisture content at:
burn store cut
% by
weight
1
: Cottonwood, logs
0.25
0.35
0.50
0.100
2
: Birch, logs
0.25
0.25
0.50
0.200
3
: Aspen, logs
0.25
0.30
0.50
0.200
4
: B Spruce, logs
0.25
0.25
0.50
0.300
5
: W Spruce, logs
0.25
0.30
0.50
0.200
other variables
check^urn
1.Onp
avg fuel storage temp
46.0 deg F
avg absolute humidity
36.0
or/lb
avg excess 02
0.10
avg air specific volume
12.9
cf/Ib
avg stack temp
320
deg F
moisture content at:
% by
INPUTS, stick wood
bum store cut
weight
1 : Cottonwood, logs
0.35 0.35 0.50
0.500
2 : Birch, loqs
0.25 0.25 0.50
0.500
checksum 1.000
other variables
avg fuel storage temp 46.0 deg F
avg absolute humidity 36.0 or/lb
avg excess 02 0.20
avg air specific volume 12.9 cf/Ib
avg stack temp 375 deg F
Oil Data
Composite Chip Properties
net useable heat
5,845
FTU%Ib at burn [d(-
weight at storage MC
1.044
Ih/lb at burn MC:
weight at cut MC
1.500
lb/lb at burn MC;
density as stacked logs
21.866
Ib/cf at storage PAC
density as chips
21.787
Ib/cf at siu:'rage PAC:
combustion air req
5.246
Ibi"ViA II. at burn MC
combustion air req
67.669
cf/wei Ib at burn MC
CO2 formed
1.425
Ibh'vei lb at burn MC
SOx formed
0.000
Ibh'vei Ib at burn MC
ash
0.017
Ibhwei lb at burn MC
ash specific volume
0.003
cf/wet lb at burn MC.
available harvest rate
17.300 tons!acre wet
note Pd0>:, CO. VOC. and FISH emissions are a function of the boiler
Composite Stick Wood Properties
net useable heat
5,103
B-IU/Ib at burn f.,IC
net useable heat
18,533
kBTU/cord
weight at storage MC
1.000
IbAb at burn MC
weight at cut MC
1.400
lb/lb at burn MC:
density as stacked logs
24.319
Ib/cf at storage PAC
density as cord wood
28.372
Ib/cf at storage MC
combustion air req
5.146
Ibhvet lb at burn PAC
combustion air req
66.379
cf/vvet lb- at burn MG
CO2 formed
1.313
Ibhwet lb at burn MC
SOx formed
0.000
Ib/wet lb at burn MG
ash
0.005
Ib/wet Ib at burn MC
ash specific volume
0.001
cf/wet Ib at burn MC
available harvest rate
15.500
tons/acre ;wet
note: PJOx. CO. VOC, and PM emissions are a function of the boiler
heating oil heat content
134.0
kBTU/gal
heating oil density
7.1
lb/gal
sulfur content
500.0
ppm
sulfur emissions
0.0010
Ib/gal
CO2 emissions
22.013
lb/gal
low cost (school, etc)
$3.750
per gal
unit cost to power plant
$3.500
per gal
high cost (to village)
$8.500
per gal
oil to H plant
$8.500
per gal
unit cost of recovered heat
$0.016
per kBTU
NO- and CO emissions are a function of the hoiler
Cost of Fuel
wood chips $175 per green ton
pellets $300 per ion
stick wood $250 per cord
Alaska Wood Energy Associates 62
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Shungnak District Heat Layout: Conceptual
Level 2 Study
Alaska Wood Energy Associates 63
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 1
Village Buildings
incl
No.
1
school
1
1
2
clinic
1
1
3 water treatment
1
1
4
city office
1
1
5
NANA
1
1
6
Back street
4
7
Andy Lane
11
8
Alley
14
9
Jim street
14
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers I Buildings
( i thru 3: woad, 4: oil)
ID make
plant
280 sf
model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann
390
334.4
1330.7
4 Weil McLain 80-380 278.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
1
$257.9
$129.4
$128.5
$128.5
est construction
$1,519,533
2
$265.6
$132.2
$133.4
$133.4
3
$273.6
$135.1
$138.5
$138.5
final design/study
$98,770
4
$281.8
$138.1
$143.7
$143.7
bid assistance
$7,598
5
$290.2
$141.2
$149.0
$149.0
Cons Admin
$127,695
6
$299.0
$144.4
$154.6
$154.6
Cx/start up
$15,195
7
$307.9
$147.6
$160.3
$160.3
contingency
$75,977
8
$317.2
$151.0
$166.2
$166.2
soft costs
$325,235
9
$326.7
$154.4
$172.3
$172.3
tax
10
$336.5
$157.9
$178.6
$178.6
11
$346.6
$161.5
$185.1
$185.1
project cost
$1,844,767
12
$357.0
$165.2
$191.8
$191.8
NSP
14.4 yrs
13
$367.7
$169.0
$198.7
$198.7
14
$378.7
$172.9
$205.8
$205.8
grants/rebates
$1,844,767
15
$390.1
$176.9
$213.1
$213.1
donated
16
$401.8
$181.1
$220.7
$220.7
amount financed
17
$413.8
$185.3
$228.5
$228.5
interest
5.000%
18
$426.2
$189.6
$236.6
$236.6
term
15.0 yrs
19
$439.0
$194.1
$244.9
$244.9
payments/yr
1
20
$452.2
$198.7
$253.5
$253.5
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source
%from
Base
Sc
delta
NPV
$2,178,798
rec ht
0.4729
CO2
475.4
423.4
(52.0)
escalation, rec ht
3.000%
wood
0.5211
CO
839.2
1,307.9
468.7
escalation, all
3.000%
oil
0.0060
SOx
43.3
267.1
223.8
escalation, wood
1.000%
total
1.0000
NOx
549.8
378.7
(171.2)
escalation, elec
3.000%
sink
% to
end -use
0.8135
PM
256.5
oil displaced, gal
42.887
piping
0.1114
VOC
40.1
oil displaced
99.29%
plant
0.0751
ash
9,974
utilize rec heat
1
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 5,253
4,572
4,647
3,843
2,889
1,988
1,782
2,364
2,730
3,896
4,622
4,606 43,192
B cost 31,250
27,205
27,673
22,925
17,305
11,984
10,777
14,210
16,357
23,246
27,519
27,431 $257,882
Sc rec heat, mmBTU 391.6 337.3 347.5 246.1 117.0 62.1 60.5 73.6 106.3 237.4 347.5 331.1 2,658
Sc biomass, tons 30.9 27.0 26.4 25.3 24.9 18.4 15.5 22.1 23.8 26.7 26.2 27.5 295
Sc oil, gal 10 80 141 53 22 305
Sc added elec, kWh 5.700 5,082 5,462 5,140 5,083 4,153 3,779 4,741 4,851 5,286 5,330 5,458 60,063
Sc
rec heat, cost
6,210
5,349
5,511
3,903
1,855
984
959
1,167
1,686
3,765
5,511
5,251
$42,152
Sc
biomass, cost
5,402
4,724
4,621
4,427
4,358
3,219
2.720
3,865
4,171
4,679
4,588
4,806
$51,580
Sc
oil, cost
82
679
1,197
448
187
$2,594
Sc
added elec, cost
3,135
2,795
3,004
2,827
2,796
2,284
2,078
2,608
2,668
2,907
2,931
3,002
$33,035
cost of inputs
14,747
12,868
13,135
11,157
9,091
7,167
6,955
8,087
8,712
11,351
13,030
13,058
$129,360
savings
16,503
14,337
14,538
11,768
8,213
4,817
3,822
6,123
7,645
11,895
14,488
14,373
$128,522
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
Mav
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.19
0.16
0.16
0.15
0.15
0.11
0.09
0.13
0.14
0.16
0.16
0.16
1.77
2
Birch, logs
0.51
0.45
0.44
0.42
0.42
0.31
0.26
0.37
0.40
0.45
0.44
0.46
4.91
3
Aspen, logs
0.37
0.32
0.32
0.30
0.30
0.22
0.19
0.27
0.29
0.32
0.31
0.33
3.54
4
B Spruce, logs
0.93
0.81
0.79
0.76
0.75
0.55
0.47
0.66
0.71
0.80
0.79
0.82
8.84
5
W Spruce, logs
0.46
0.40
0.40
0.38
0.37
0.28
0.23
0.33
0.36
0.40
0.39
0.41
4.42
totals
2.46
2.15
2.10
2.02
1.98
1.47
1.24
1.76
1.90
2.13
2.09
2.19
23.48
Allaska Wood Energy Associates 64
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 2
Village Buildings
Intl
No.
1
school
1
1
2
clinic
1
1
3 water treatment
1
1
4
city office
1
1
NANA
1
1
Back street
1
4
7
Andy Lane
11
8
Alley
14
9
Jim street
14
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant fuel process
(1 thru 3: wood, 4: oil) 280 sf 148 sf 1,200 sf
ID make model min max
7 Wiessmann 390 334.4 1330.7
4 Weil McLain 80-380 278.0
Level 2 Study
Case Flow, 1,000s
Project Cost I Financials
yr
Base
Sc
savings
debt
net
$285.1
$139.6
$145.5
$145.5
est construction
$1,638,920
2
$293.6
$142.6
$151.0
$151.0
3
$302.4
$145.7
$156.7
$156.7
final design/study
$106,530
4
$311.5
$148.9
$162.6
$162.6
bid assistance
$8,195
5
$320.9
$152.2
$168.6
$168.6
Cons Admin
$128,889
6
$330.5
$155.6
$174.9
$174.9
Cx/start up
$16,389
7
$340.4
$159.0
$181.4
$181.4
contingency
$81,946
8
$350.6
$162.6
$188.0
$188.0
soft costs
$341,949
9
$361.1
$166.2
$194.9
$194.9
AK state tax
10
$372.0
$170.0
$202.0
$202.0
11
$383.1
$173.8
$209.3
$209.3
project cost
$1,980,869
12
$394.6
$177.8
$216.9
$216.9
NSP
13.6 yrs
13
$406.5
$181.8
$224.7
$224.7
14
$418.7
$186.0
$232.7
$232.7
grants/rebates
$1,980,869
15
$431.2
$190.2
$241.0
$241.0
donated
16
$444.1
$194.6
$249.5
$249.5
amount financed
17
$457.5
$199.1
$258.4
$258.4
interest
5.000%
18
$471.2
$203.7
$267.5
$267.5
term
15.0 yrs
19
$485.3
$208.5
$276.9
$276.9
payments/yr
1
20
$499.9
$213.4
$286.5
$286.5
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source
%from
Base
Sc
delta
NPV
$2,464,510
rec ht 0.4663
CO2
510.6
470.6
(40.0)
escalation, rec ht
3.000%
wood
0.5314
CO
901.4
1,460.0
558.6
escalation, oil
3.000%
oil
0.0023
SOx
46.5
298.1
251.7
escalation, wood
1.000%
total
1.0000
NOx
590.6
421.6
(168.9)
escalation, elec
3.000%
sink
%to
end -use
0.7977
PM
286.5
oil displaced, gal
46,266
piping
0.1280
VOC
44.8
oil displaced
99.73%
plant
0.0743
ash
11,142
utilize rec heat
1
total
1.0000
Include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 5,658
4,923
5,001
4,131
3,095
2,120
1,896
2,527
2,924
4,187
4,975
4,956 46,392
B cost 34,688
30,187
30,679
25,369
19,060
13,108
11,745
15,592
18,009
25,718
30,517
30,408 $285,082
Sc rec heat, mmBTLI 402.5 348.8 369.6 268.3 130.9 78.5 70.8 93.6 121.2 255.3 375.0 356.2 2,871
Sc biomass, tons 36.4 31.6 30.0 27.8 27.1 19.7 17.6 23.4 25.9 29.8 29.3 30.7 329
Sc oil, gal 3 35 70 13 5 126
Sc added elec, kWh 6,259 5,548 5,883 5,427 5,253 4,471 4,208 5,020 5,055 5,561 5,765 5,874 64,324
Sc
rec heat, cost
6,383
5,532
5,862
4,254
2,076
1,245
1,123
1,484
1,922
4,049
5,946
5,649
$45,526
Sc
biomass, cost
6,372
5.531
5,254
4,872
4,741
3,450
3,072
4,096
4,525
5,209
5,122
5,375
$57,620
Sc
oil, cost
29
295
594
112
40
$1,071
Sc
added elec, cost
3,443
3,051
3,236
2,985
2,889
2,459
2,314
2,761
2,780
3,059
3,171
3,231
$35,378
cost of inputs
16,197
14,114
14,351
12,112
9,735
7,449
7,104
8,453
9,268
12,317
14,240
14,255
$139,595
savings
18,491
16,074
16,328
13,257
9,325
5,659
4,641
7,139
8,741
13,401
16,278
16,154
$145,487
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
May
Jun
Jul
Auq
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.22
0.19
0.18
0.17
0.16
0.12
0.11
0.14
0.16
0.18
0.18
0.18
1.98
2
Birch, logs
0.61
0.53
0.50
0.46
0.45
0.33
0.29
0.39
0.43
0.50
0.49
0.51
5.49
3
Aspen, logs
0.44
0.38
0.36
0.33
0.33
0.24
0.21
0.28
0.31
0.36
0.35
0.37
3.95
4
B Spruce, logs
1.09
0.95
0.90
0.84
0.81
0.59
0.53
0.70
0.78
0.89
0.88
0.92
9.88
5
W Spruce, logs
0.55
0.47
0.45
0.42
0.41
0.30
0.26
0.35
0.39
0.45
0.44
0.46
4.94
totals
2.90
2.52
2.39
2.22
2.16
1.57
1.40
1.86
2.06
2.37
2.33
2.45
26.23
Alaska Wood Energy Associates 65
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 3
Village Buildings
incl
No.
1
school
1
1
2
clinic
1
1
3 water treatment
1
1
4
city office
1
1
5
NANA
1
1
6
Back street
1
4
7
Andy Lane
1
11
8
Alley
1
14
9
Jim street
14
10
11
t2
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings
(1 th,u 3: wood, 4: oil)
ID make
plant
280 sf
model
fuel
148 sf
min
process
1,200 sf
max
7 Wiessmann
390
334.4
1330.7
6 Weil McLain 80-580 515.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
1
$455.1
$219.4
$235.7
$235.7
est construction
$2,319,558
2
$468.7
$223.7
$245.0
$245.0
3
$482.8
$228.2
$254.6
$254.6
final design/study
$150,771
4
$497.3
$232.9
$264.4
$264.4
bid assistance
$11,598
5
$512.2
$237.6
$274.6
$274.6
Cons Admin
$143,196
6
$527.6
$242.4
$285.1
$285.1
Cx/startup
$23,196
7
$543.4
$247.4
$296.0
$296.0
contingency
$115,978
6
$559.7
$252.5
$307.2
$307.2
soft costs
$444,738
9
$576.5
$257.7
$318.7
$318.7
AK state tax
10
$593.8
$263.1
$330.7
$330.7
i1
$611.6
$268.6
$343.0
$343.0
project cost
$2,764,297
-
$629.9
$274.2
$355.7
$355.7
NSP
11.7 yrs
13
$648.8
$280.0
$368.8
$368.8
14
$668.3
$286.0
$382.3
$382.3
grants/rebates
$2,764,297
15
$688.4
$292.0
$396.3
$396.3
donated
16
$709.0
$298.3
$410.7
$410.7
amount financed
17
$730.3
$304.7
$425.6
$425.6
interest
5.000 %
18
$752.2
$311.3
$440.9
$440.9
tens
15.0 yrs
19
$774.7
$318.0
$456.7
$456.7
payments/yr
1
20
$798.0
$324.9
$473.1
$473.1
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source %from
Base
Sc
delta
NPV
$4,032,822
rec ht
0.3258
CO2
730.7
896.2
165.5
escalation, rec ht
3.000%
wood
0.6689
CO
1,290.0
2,774.6
1,484.6
escalation, oil
3.000%
oil
0.0053
SOx
66.5
566.6
500.1
escalation, wood
1.000%
total
1.0000
NOx
845.2
802.3
(42.9)
escalation, elec
3.000%
sink
% to
end -use
0.7563
PM
544.3
oil displaced, gal
65,945
piping
0.1721
VOC
85.0
oil displaced
99.33%
plant
0.0716
ash
21,167
utilize rec heat
1
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr.
ali else in Ib/yr
Inputs and Costs
(B = Baseline. Sc = This Scenario. all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 8,186
7,115
7,211
5,928
4,386
2,947
2,607
3,543
4,138
6,005
7,180
7.145 66,392
B cost 56,176
48,826
49,469
40,645
30,031
20,134
17,793
24,230
28,333
41,170
49,258
49,016 $455,082
Sc rec heat, mmBTU 405.0 354.0 376.9 277.7 139.3 107.8 103.6 119.7 132.8 261.9 383.7 365.0 3,027
Sc biomass, tons 75.2 65.1 63.7 54.9 46.6 29.9 25.4 37.0 43.9 57.4 62.6 63.8 625
Sc oil, gal 13 0 14 126 219 55 20 447
Sc added elec, kWh 12,810 11,026 10,871 8,973 7,116 5,595 5,302 6,331 6,806 9,068 10,892 10,820 105,610
Sc
rec heat, cost
6,423
5,613
5,977
4,404
2,209
1,710
1,644
1,898
2,106
4,153
6,084
5,788
$48,009
Sc
biomass, cost
13,160
11,394
11,145
9.606
8,152
5,228
4,450
6,472
7,674
10,048
10,961
11,172
$109,461
Sc
oil, cost
114
4
119
1,072
1,858
465
166
$3,798
Sc
added elec, cost
7,046
6,064
5,979
4,935
3.914
3,077
2,916
3,482
3,743
4,987
5,991
5,951
$58,085
cost of inputs
26,743
23,075
23,101
18,945
14,394
11,087
10,867
12,316
13,690
19,188
23,036
22,911
$219,353
savings
29,433
25,751
26,369
21,700
15,637
9,047
6,926
11,914
14,643
21,982
26,222
26,105
$236,729
Required Harvest, acres
Wet Storage Area Required
413 sf
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1 Cottonwood, logs
0.45
0.39
0.38
0.33
0.28
0.18
0.15
0.22
0.26
0.34
0.38
0.38
3.75
2 Birch, logs
1.25
1.09
1.06
0.91
0.78
0.50
0.42
0.62
0.73
0.96
1.04
1.06
10.42
3 Aspen, logs
0.90
0.78
0.76
0.66
0.56
0.36
0.31
0.44
0.53
0.69
0.75
0.77
7.51
4 B Spruce, logs
2.26
1.95
1.91
1.65
1.40
0.90
0.76
1.11
1.32
1.72
1.88
1.92
18.76
5 W Spruce, logs
1.13
0.98
0.96
0.82
0.70
0.45
0.38
0.55
0.66
0.86
0.94
0.96
9.38
totals
5.99
5.19
5.07
4.37
3.71
2.38
2.03
2.95
3.49
4.57
4.99
5.09
49.83
Alaska Wood Energy Associates 66
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Scenario 4
Village Buildings
Intl
No.
school
1
1
2
clinic
1
1
3
water treatment
1
1
4
city office
1
1
5
NANA
1
1
6
Back street
1
4
7
Andy Lane
1
11
8
Alley
1
14
9
Jim street
1
14
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Boilers / Buildings plant fuel process
(1 thru 3: wood, 4: oil) 308 sf 201 sf 1,200 sf
ID make model min max
8 Wiessmann 530 450.4 1808.4
4 Weil McLain 80-380 278.0
Level 2 Study
Case Flow, 1,000s
Project Cost / Financials
yr
Base
Sc
savings
debt
net
11
$559.8
$285.0
$274.8
$274.8
est construction
$2,912,470
2
$576.6
$290.5
$286.1
$286.1
3
$593.9
$296.1
$297.8
$297.8
final design/study
$189,311
4
$611.7
$301.8
$309.9
$309.9
bid assistance
$14,562
5
$630.1
$307.6
$322.4
$322.4
Cons Admin
$149,125
6
$649.0
$313.6
$335.3
$335.3
Cx/startup
$29,125
7
$668.4
$319.8
$348.6
$348.6
contingency
$145,623
8
$688.5
$326.1
$362.4
$362.4
soft costs
$527,746
9
$709.1
$332.6
$376.6
$376.6
AK state tax
10
$730.4
$339.2
$391.2
$391.2
11
$752.3
$346.0
$406.4
$406.4
project cost
$3,440,215
12
$774.9
$352.9
$422.0
$422.0
NSP
12.5 yrs
13
$798.1
$360.1
$438.1
$438.1
14
$822.1
$367.4
$454.7
$454.7
grants/rebates
$3,440,215
15
$846.8
$374.9
$471.9
$471.9
donated
16
$872.2
$382.6
$489.6
$489.6
amount financed
17
$898.3
$390.4
$507.9
$507.9
Interest
5.000 %
18
$925.3
$398.5
$526.8
$526.8
term
15.0 yrs
19
$953.0
$406.8
$546.2
$546.2
payments/yr
1
20
$981.6
$415.3
$566.3
$566.3
discount rate
5.000%
pay at begin
1
sum of debt
Sc Source/Sink
Emissions
metric
ratio
source
%from
Base
Sc
delta
NPV
$4,768,198
rec ht
0.2540
CO2
866.3
1,270.9
404.6
escalation, rec ht
3.000%
wood
0.7378
CO
1,529.4
3,927.4 2,398.0
escalation, oil
3.000%
oil
0.0082
SOx
78.9
802.0
723.1
escalation, wood
1.000%
total
1.0000
NOx
1,002.0
1,136.9
134.9
escalation, elec
3.000%
sink
%to
end -use
0.6990
PM
770.2
oil displaced, gal
77,833
piping
0.2303
VOC
120.3
oil displaced
98.88%
plant
0.0707
ash
29,952
utilize rec heat
1
total
1.0000
include wood in CO2
1
bias to wood
1
CO2 in tons/yr, all else in Ib/yr
Inputs and Costs
(B = Baseline, Sc = This Scenario, all Tables)
plant op % 1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
B oil, gal 9,743
8,466
8,573
7,035
5,181
3,456
3,046
4,169
4,887
7,125
8,538
8,494 78,712
B cost 69,412
60,307
61,044
50,055
36,790
24,462
21.519
29,551
34,692
50,688
60,802
60,478 $559,802
Sc rec heat, mmBTU 405.0 354.0 376.9 277.7 139.3 107.8 103.6 119.7 132.8 261.9 383.7 365.0 3,027
Sc biomass, tons 106.5 92.7 92.0 78.2 64.0 41.4 35.3 51.2 60.3 81.0 90.7 91.8 885
Sc oil, gal 46 5 28 244 409 108 39 0 879
Sc added elec, kWh 16,709 14,380 14,174 11,633 9,078 6,841 6.295 7,915 8,655 11,747 14,199 14,091 135,718
Sc
rec heat, cost
6,423
5,613
5,977
4,404
2,209
1,710
1,644
1,898
2,106
4.153
6,084
5,788
$48,009
Sc
biomass, cost
18.637
16,217
16,094
13,688
11,208
7,250
6,183
8,952
10,559
14,183
15,864
16,059
$154,893
Sc
oil, cost
391
45
234
2.070
3,481
919
329
1
$7,469
Sc
added elec,cost
9,190
7,909
7,796
6,398
4,993
3,762
3,462
4.353
4,760
6,461
7.810
7,750
$74,645
cost of inputs
34,641
29,785
29,866
24.491
18,644
14,792
14,770
16,122
17,754
24.796
29,759
29,597
$285,016
savings
34,772
30,522
31,178
25,565
18,145
9,670
6,750
13,429
16,938
25,892
31,043
30,881
$274,786
Required Harvest, acres
Wet Storage Area Required
561 sf
Jan
Feb
Mar
Apr
Mav
Jun
Jul
Auc
Sep
Oct
Nov
Dec
1
Cottonwood, logs
0.64
0.56
0.55
0.47
0.38
0.25
0.21
0.31
0.36
0.49
0.54
0.55
5.31
2
Birch, logs
1.77
1.54
1.53
1.30
1.07
0.69
0.59
0.85
1.01
1.35
1.51
1.53
14.75
3
Aspen, logs
1.28
1.11
1.10
0.94
0.77
0.50
0.42
0.61
0.72
0.97
1.09
1.10
10.62
4
B Spruce, logs
3.19
2.78
2.76
2.35
1.92
1.24
1.06
1.53
1.81
2.43
2.72
2.75
26.55
5
W Spruce, logs
1.60
1.39
1.38
1.17
0.96
0.62
0.53
0.77
0.91
1.22
1.36
1.38
13.28
totals
8.48
7.38
7.33
6.23
5.10
3.30
2.81
4.08
4.81
6.46
7.22
7.31
70.51
Alaska Wood Energy Associates 67
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Individual Building Chip and Stick -fired Boiler Summaries
Individual Building Boiler Summary
bldg
Building
base oil
gal/yr
Stick Wood
oil fuel
displaced cost
project
cost
NSP
yrs
Chips
oil
displaced
fuel
cost
project
cost
NSP
yrs
1
school
23,000
0.926
$48,883
$348,728
9.3
0.882
$50,704
$366,004
10.3
clinic
2,692
1.000
$6,210
$246,796
14.8
$25,577
$366,004
water treatment
3,500
1.000
$7,748
$246,796
11.2
$32,445
$366,004
city office
1,000
1.000
$2,988
$246,796
44.8
$11,195
$366,004
NANA
13,000
0.951
$30,275
$264,617
3.3
0.901
$35,494
$366,004
4.9
6
Back street
3,200
1.000
$7,177
$339,773
17.0
$29,895
$457,240
-
Andy Lane
8,800
1.000
$18,116
$574,542
10.1
0.704
$36,365
$670,125
17.4
E
Alley
11,200
1.000
$23,310
$751,631
10.5
0.826
$36,481
$761,361
13.0
Jim street
12,320
1.000
$25,443
$751,631
9.5
0.866
$36,596
$761,361
11.2
10
11 Back street, clinic 5,892 1.000 $12,303 $370,766 9.8 0.222 $44,101 $487,652 81.5
'12 Andy L, water tr 12,300 0.978 $26,546 $605,535 7.8 0.916 $32,458 $700,537 9.7
13
14
'I5
16
Alaska Wood Energy Associates
BIOMASS HEATING FEASIBILITY
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Level 2 Study
Appendix
District Heating Plant/Recovered Heat Integration: Sample Sequence of
Operations
[CV.dP.1]_ [dPT.PL.1
BYPASS �
OIL-
FIRED
BOILER
i
v L---
x
THERMAL
STORAGE
TANK
] dPT IF PLANT HAS (2) BIOMASS BOILERS
TO/FROPO M
PLANTw NA
I
U
All,
/ ! I �•77U �U
m m L
IBIOMASS� I '-� BIOMASS
BOILER i n BOILER
I GENERATOR
LOP HX C
[TT.PS.1 ]
---------------- -
L----------
PRIMARY
PUMPS
[CV.SL1] EXP TANK
AIR
SEPARATOR
PHWR
---[CV.PL.1]
CONTROL
\ VALVE (TYP),
y ACTUATORS
VARY
GCL:
I
PRIMARYSECONDA
FLOW
METER
TEMP
TRANSMITTER
(TYP)
GENERATOR
I
Y
()
TO/FROM
LOOP COOLING
I
HX
TT
DH LOOP
HWS:
N SHWR
SHWR
HOT WATER
SUPPLY
_
i
EXP TANK
[FM.SL1]
SHWS SHWS
I
u
[TT.SS.1]
-- ---
HOT WATER
RETURN
SECONDARY
[dPT.SL1]
DI STRIBUTION)
PUMPS
[dPT.SL.2]
HX:
'
[dPT.SL3]
HEAT
EXCHANGER
r- VFD
SHOWS CONTROL i
dPT dPT� dPT
P:
r- VFD
RELATIONSHIPS
(TYP)7
PRIMARY
1
L-----------------------
L --j------ L___-1
---- J
5:
SECONDARY
WH,rE�AT RECOVERY l DH PLANT INTERFACE
Alaska Wood Energy Associates
e
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
Appendix E
Sample Calculations
0.2 min
oil, act
23,000
1
boiler
61 / B2 / 133
3
1 boilers
4.7 max
oil, pied
23,000
307
max cap
stotaae
2,064
4
max burns/day
(0.03) a
oil boiler
2
102
min cap
eff
0.750
6
burn period
3.1 b
eff
0.790
0.850
losses
0.005
1.000
derafe
OAT :
school
mid
oil, gph
1
load
chips /
oil
216
2,721
stick
status
losses
total
%
_pt
heat
DHW
total
kBTU/h
Ib/hr
gph
tons
gal
derate
store
?
1 2
3 kBTU/h kBTU/h
load
85
0.4
0.4
37.3
0.4
1
1.000
2,064
1
1
10.3
47.7
0.14
83
0.4
0.4
37.3
0.4
1
1.000
2,064
1
1
10.3
47.7
0.14
81
0.4
0.4
37.3
0.4
5
1.000
2,064
1
1
10.3
47.7
0.14
79
0.4
0.4
37.3
0.4
6
1.000
2,064
1
1
10.3
47.7
0.14
77
0.4
0.4
37.3
0.4
3
1.000
2,064
1
1
10.3
47.7
0.14
75
0.4
0.4
37.3
0.4
11
1.000
2,064
1
1
10.3
47.7
0.14
73
0.4
0.4
37.3
0.4
10
1.000
2,064
1
1
10.3
47.7
0.14
71
0.4
0.4
37.3
0.4
12
1.000
2,064
1
1
10.3
47.7
0.14
69
0.4
0.4-:
37.3
0.4
32
1.000
2,064
1
1
10.3
47.7
0.14
67
0.4
0.4-:
37.3
0.4
34
1.000
2,064
1
1
10.3
47.7
0.14
65
0.4
0.4-:
37.3
0.4
48
1.000
2,064
1
1
10.3
47.7
0.14
63
1.0
0.4
1.3-:
141.1
28
2
1.000
2,064
1
1
10.3
151.4
0.44
61
1.0
0.4
1.4
148.3
30
2
1.000
2,064
1
1
10.3
158.6
0.46
59
1.1
0.4
1.5
155.4
31
1
1.000
2,064
1
1
10.3
165.7
0.48
57
1.2
0.4
1.5
162.6
33
3
1.000
2,064
1
1
10.3
172.9
0.50
55
1.3
0.4
1.6
169.8
34
4
1.000
2,064
1
1
10.3
180.1
0.52
53
1.3
0.4
1.7
176.9
36
4
1.000
2,064
1
1
10.3
187.2
0.54
51
1.4
0.4
1.7-:
184.1
37
7
1.000
2,064
1
1
10.3
194.4
0.57
49
1.5
0.4
1.8
191.3
38
5
1.000
2,064
1
1
10.3
201.6
0.59
47
1.5
0.4
1.9
198.4
40
5
1.000
2,064
1
1
10.3
208.7
0.61
45
1.6
0.4
1.9-:
205.6
41
5
1.000
2,064
1
1
10.3
215.9
0.63
43
1.7
0.4
2.0
212.8
43
5
1.000
2,064
1
1
10.3
223.1
0.65
41
1.7
0.4
2.1
219.9
44
3
1.000
2,064
1
1
10.3
230.2
0.67
39
1.8
0.4
2.1
227.1
46
5
1.000
2,064
1
1
10.3
237.4
0.69
37
1.9
0.4
2.2 :
234.3
47
5
1.000
2,064
1
1
10.3
244.6
0.71
35
1.9
0.4
2.3-:
241.4
49
5
1.000
2,064
1
1
10.3
251.7
0.73
33
2.0
0.4
2.3-:
248.6
50
7
1.000
2,064
1
1
10.3
258.9
0.75
31
2.1
0.4
2.4
255.8
51
3
1.000
2,064
1
1
10.3
266.1
0.77
29
2.1
0.4
2.5
262.9
53
3
1.000
2,064
1
1
10.3
273.2
0.79
27 :
2.2
0.4
2.6
270.1
54
4
1.000
2,064
1
1
10.3
280.4
0.82
25
2.3
0.4
2.6
277.3
56
5
1.000
2,064
1
1
10.3
287.6
0.84
23
2.3
0.4
2.7 :
284.4
57
3
1.000
2,064
1
1
10.3
294.7
0.86
21
2.4
0.4
2.8-:
291.6
59
5
1.000
2,064
1
1
10.3
301.9
0.88
19
2.5
0.4
2.8 :
298.8
60
6
1.000
2,064
1
1
10.3
309.1
0.90
17
2.5
0.4
2.9-:
305.9
62
6
1.000
2,064
1
1
10.3
316.3
0.92
15
2.6
0.4
3.0
313.1
62
0.1
9
16
1.000
2,064
1
1
10.3
323.4
0.94
13
2.7
0.4
3.0
320.3
62
0.1
6
23
1.000
2,064
1
1
10.3
330.6
0.96
11
2.7
0.4
3.1
327.4
62
0.2
8
48
1.000
2,064
1
1
10.3
337.8
0.98
9
2.8
0.4
3.2
334.6
62
0.3
7
59
1.000
2,064
1
1
10.3
344.9
1.00
7
2.9
0.4
3.2
341.8
62
0.3
8
82
1.000
2,064
1
1
10.3
352.1
1.00
5
2.9
0.4
3.3-:
348.9
62
0.4
4
46
1.000
2,064
1
10.3
359.3
1.00
3
3.0
0.4
3.4-:
356.1
62
0.5
7
106
1.000
2,064
1
10.3
366.4
1.00
1
3.1
0.4
3.4
363.3
62
0.5
7
121
1.000
2,064
1
10.3
373.6
1.00
(1)
3.1
0.4
3.5
370A
62
0.6
7
132
1.000
2,064
1
10.3
380.8
1.00
(3)
3.2
0.4
3.6-:
377.6
62
0.7
5
117
1.000
2,064
1
10.3
387.9
1.00
(5)
3.3
0.4
3.6-:
384.8
62
0.7
7
168
1.000
2,064
1
10.3
395.1
1.00
(7)
3.3
0.4
3.7 :
391.9
62
0.8
3
88
1.000
2,064
1
10.3
402.3
1.00
(9)
3.4
0.4
3.8-:
399.1
62
0.9
4
101
1.000
2,064
1
10.3
409.4
1.00
(11)
3.5
0.4
3.8-:
406.3
62
0.9
4
113
1.000
2,064
1
10.3
416.6
1.00
(13)
3.6
0.4
3.9
413.4
62
1.0
2
53
1.000
2,064
1
10.3
423.8
1.00
(15)
3.6
0.4
4.0
420.6
62
1.1
3
102
1.000
2,064
1
10.3
430.9
1.00
(17)
3.7
0.4
4.0
427.8
62
1.1
2
88
1.000
2,064
1
10.3
438.1
1.00
(19)
3.8
0.4
4.1
434.9
62
1.2
3
103
1.000
2,064
1
10.3
445.3
1.00
(21) :
3.8
0.4
4.2
442.1
62
1.3
2
94
1.000
2,064
1
10.3
452.4
1.00
(23) :
3.9
0.4
4.2 :
449.3
62
1.3
4
161
1.000
2,064
1
10.3
459.6
1.00
Alaska Wood Energy Associates 70
BIOMASS HEATING FEASIBILITY Level 2 Study
Upper Kobuk Valley
Ambler, Kobuk, and Shungnak, Alaska
OAT
mid
0.561 0.557 0.570 0.495 0.320
total mmBTU
391.6 337.3 347.5 246.1 117.0
Load picked up by Engine Heat Recovery, kBTUIh
0.245
62.1
0.262
60.5
0.246
73.6
0.308
106.3
0.472
237.4
0.572
347.5
0.548
331.1
_pt
85
jan
feb
mar
apr
may
jun
jul
75
aug
sep
Oct
nov
dec
83
80
81
85
79
90
77
95
95
75
100
100
73
105
105
71
110
110
69
115
115
115
115
115
67
120
120
120
120
120
65
125
125
125
125
125
63
131
131
131
131
131
61
3
3
3
3
3
59
18
18
18
18
18
18
57
34
34
34
34
34
34
55
49
49
49
49
49
49
53
65
65
65
65
65
65
51
81
81
81
81
81
81
49
97
97
97
97
97
97
47
112
112
112
112
112
112
112
45
129
129
129
129
129
129
129
43
145
145
145
145
145
145
145
41
161
161
161
161
161
161
161
39
178
178
178
178
178
178
178
178
37
194
194
194
194
194
194
194
194
194
35
202
202
202
202
202
202
202
202
202
33
207
207
207
207
207
207
207
207
207
207
207
31
212
212
212
212
212
212
212
212
212
29
217
217
217
217
217
217
217
217
217
27
222
222
222
222
222
222
222
222
25
227
227
227
227
227
227
227
227
23
232
232
232
232
232
232
232
232
232
21
237
237
237
237
237
237
237
237
237
19
347
347
347
347
347
347
347
347
347
17
365
365
365
365
365
365
365
365
15
382
382
382
382
382
382
382
382
13
400
400
400
400
400
400
400
11
417
417
417
417
417
417
417
9
435
435
435
435
435
435
435
7
453
453
453
453
453
453
453
5
471
471
471
471
471
471
471
3
489
489
489
489
489
489
489
1
507
507
507
507
507
507
507
(1) :
525
525
525
525
525
525
525
(3) :
544
544
544
544
544
544
544
(5):
551
551
551
551
551
551
551
(7) :
557
557
557
557
557
557
557
(9) :
562
562
562
562
562
562
562
(11) :
568
568
568
568
568
568
568
(13) :
573
573
573
573
573
573
573
(15) :
579
579
579
579
579
579
579
(17) :
584
584
584
584
584
584
(19) :
590
590
590
590
590
(21) :
596
596
596
596
596
(23) :
601
601
601
601
601
(25) :
607
607
607
607
607
(27) :
613
613
613
613
(29) :
619
619
619
619
(31) :
625
625
625
625
(33):
631
631
631
631
(35) :
638
638
638
(37) :
644
6"
644
(39) :
650
650
(41) :
657
657
(43) :
664
664
(45) :
671
(47) :
678
71