HomeMy WebLinkAboutChapel by the Lake Biomass Pre-Feasability Study 09-16-2014-BIOPRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 2 | 32 Final Report
Development Corporation 16 Sept 2014
Chapel
by
the
Lake
Biomass
Pre-‐Feasibility
Study
Submitted
to
CBTL
and
AWEDTG
Greg
Koontz,
PE
and
Bill
Wall,
PhD
of
Alaska
Wood
Energy
Associates
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 3 | 32 Final Report
Development Corporation 16 Sept 2014
Table
of
Contents
1
EXECUTIVE
SUMMARY ......................................................................................................4
1.1
Acknowledgements ................................................................................................................4
1.2
Objective ................................................................................................................................4
1.3
Sources ...................................................................................................................................5
1.4
Scope ......................................................................................................................................5
1.5
Financial
Metrics.....................................................................................................................6
1.6
Resource
Assumptions ............................................................................................................7
1.7
Summary
of
Findings ..............................................................................................................9
1.8
Next
steps ............................................................................................................................13
2
TECHNICAL
SUMMARY ....................................................................................................14
2.1
Existing
Conditions ...............................................................................................................14
2.2
Wood
Fuels
/
Wood
Fired
Heating
Equipment ......................................................................15
2.3
Proposed
Conditions.............................................................................................................15
Scenario
1 ...........................................................................................................................................16
Scenario
2 ...........................................................................................................................................16
2.4
Cost
Estimate ........................................................................................................................16
2.5
Energy
Savings ......................................................................................................................19
Appendix
1.
INTERCONNECTIONS ....................................................................................21
Interconnections
and
the
Impact
on
Construction
Cost ..................................................................21
Thermal
Storage.............................................................................................................................24
Appendix
2.
Photos
and
site
map .........................................................................................26
Appendix
3.
Brochure
for
MES
OkuFen
Pellet
Boilers ...........................................................29
Appendix
4.
Portion
of
Tech
Brochure
for
PEX
Piping ...........................................................31
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 4 | 32 Final Report
Development Corporation 16 Sept 2014
1
EXECUTIVE
SUMMARY
1.1
Acknowledgements
This feasibility study was supported by the Alaska Wood Energy Development Task Group and
administered by the Fairbanks Economic Development Corporation.
1.2
Objective
The objective of this report is to document the results of a pre-feasibility study performed for the
Chapel by the Lake (CBTL) complex in Juneau, Alaska. The target buildings are the Chapel itself
(composed of three phases, the Sanctuary, the Ed Wing, and Smith Hall), the Old Chapel, and the
Parsonage, a house located on the property.
The buildings in the CBTL complex are currently heated with oil, one oil boiler per building.
The primary subject of the study is the feasibility of constructing a wood-fired heating plant to serve all
three buildings in the complex. A secondary objective is to evaluate the installation of a wood-fired
boiler solely for the CBTL itself.
Although the Juneau area has a fairly extensive road system covering the municipality and
surrounds, the system does connect to the rest of the state, so everything comes in by air or sea. However,
because of the large population and large volume of shipping, oil is basically as inexpensive as it would
be in a City or Village on the road system. For that reason, we did not evaluate the two smaller buildings
for individual boilers – they do not have the scale to be economical with the local oil prices.
Because there are no wood chips available in the area currently, and the CBTL is not interested in
stick-fired boilers, this study evaluates only pellet fired boilers.
Feasibility studies are often classified as Level 1 (L1), Level 2 (L2), or Level 3 (L3). Level 1
study consists of very rough calculations on a small number of important metrics (unit fuel costs, etc).
Some refer to L1 studies as “back-of-the-envelope” calculations.
At the other end, L3 studies are commonly called “investment grade studies”; the level of detail
and calculation is so high that one could use the results of an L3 study to get an outside entity to fund the
implementation of the project.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 5 | 32 Final Report
Development Corporation 16 Sept 2014
Level 2, then, is the bridge between L1 and L3; it is a screening study done to determine if it is
worth the time and expense to initiate an L3 study. Level 3 studies are generally quite expensive and thus
not entered into lightly. The L2 study helps decision makers determine which aspects, if any, of a
proposed project are worth the expense of an L3 study.
A L1 study can be done remotely; a L2 study requires at least a minimum amount of site
observation of existing conditions, conversations with the affected parties, and research with second-order
parties (local foresters, vendors, local contractors, etc). This is a Level 2 study.
Sustainability, Inc (SI) and efour, PLLC (efour) cooperate and do business as Alaska Wood
Energy Associates to perform L2 and L3 studies across the state of Alaska, from cities to small villages in
off road system areas. We use the same performance and economic models for each type of study; for us,
the primary difference between the two studies is the quality of the inputs, which is generally a function
of how much time has been spent gathering information and the depth of that information that is
available.
1.3
Sources
The primary sources of information that inform this study are data collected on site by SI and data
provided by the Fairbanks Economic Development Corporation (FEDC). Data collected on site by SI
include existing site conditions, equipment name plate data, current energy cost data, and equally
important, information gathered by talking to the local church administrator.
In addition to the site knowledge gathered by SI, additional biomass boiler performance and cost
data have been accumulated over the past several years from working with local engineers and
contractors, and from performing multiple L2 and L3 wood-fired feasibility studies. Hourly weather data
for the performance model was extracted from data collected and reported by the Juneau Airport.
1.4
Scope
The original scope of this report is limited to the CBTL complex made up of three interconnected
buildings; one boiler, located in the basement, serves the three phases of the Chapel. AWEA expanded
that scope to include the original log structure chapel and the parsonage, each serviced by its own boiler.
No individual building data was obtained for the amount of fuel used by the log chapel or the parsonage,
so this was estimated through square footage and expected domestic water usage in the parsonage.
Biomass heating systems can be expensive to install; the economics generally work better for
larger buildings, or where two or more smaller buildings can be grouped together and served by a single
biomass boiler, using buried piping between the buildings to distribute the heat. A significant part of the
cost of a district heating plant (DH Plant) are the interconnections to the individual boilers; in this case,
we only have to make three interconnections, which helps contain costs.. Interconnections are discussed
in detail in Appendix 1.
Although the three-building cluster is the only grouping of buildings we modeled for a DH plant,
we modeled two different variations of that Plant (each configuration is called a Scenario, abbreviated as
Sc 1 or Sc 2). The thermal performance is nearly identical; the primary difference is the implementation
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 6 | 32 Final Report
Development Corporation 16 Sept 2014
cost. In Scenario 1, the DH Plant is built into the basement adjacent to the existing CBTL boiler. This
assumes that all the equipment fits through the doors, which we believe to be true or can be brought in
through a framed opening into the basement under a walk way. However, as a back-up, we modeled
Scenario 2 in which the DH Plant is built into a shipping container, which would then be placed on a
purpose-built concrete slab just outside the building.
In addition to costing more, Scenario 2 has fewer savings, because an external boiler “plant” (the
shipping container) must be heated, as must the boiler combustion air. The existing basement is already
heated, so Scenario 1 does not pay this thermal “penalty”. As a third comparison we analyzed just
heating the primary building with a single pellet boiler and not developing a district heating system,
which was the original requested scope by the Chapel. This boiler was placed in the current boiler room
and integrated with the current oil boiler.
The basis of most biomass projects in Alaska is the large differential in the unit cost of oil versus
wood, measured in dollars per million BTUs ($/mmBTU). This is shown in subsection 1.6 below. The
result based on the cost of pellets and the cost of oil and electricity is that we must limit implementation
costs as much as possible, and not provide more equipment and “technology” than the project requires in
order to be financially successful.
1.5
Financial
Metrics
There are many 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).
At Level 2, we use two financial metrics. Net simple payback (NSP) does not require any
assumptions about interest rates or escalation rates – it is simply: the project implementation cost divided
by the year one savings, and the units are “years”. It demonstrates how long it takes to pay for a project
out of the cost saving incurred by the project.
The Benefit / Cost ratio (B/C), on the other hand, requires assumptions on both interest rates and
fuel escalation rates. The B/C is defined in detail below:
The Benefit to cost ratio is an attempt to capture the value of the project over the lifetime of the
project; a lifetime of 20 years is commonly used. The output of the calculations included is
actually two numbers, the actual benefit/cost ratio, and the net present value (NPV) benefit of the
project.
The project cost is a one-time event, but the savings accrue over the life of the project.
Depending on the assumed inflation rate of the various fuel sources, the savings may actually
increase each year (if, for instance, oil rises faster than biomass). On the other hand, a dollar
saved in year 20 is not worth a dollar today; it is worth the NPV of one dollar at the assumed
discount rate. The discount rate is the rate of return one assumes the Client could make if that
dollar were invested in some other fashion – in a bank account, or on another project. The
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 7 | 32 Final Report
Development Corporation 16 Sept 2014
combination of one time and recurring costs, plus inflation and discounting means that it would
be very useful if the lifetime benefits, divided by the lifetimes costs, could be boiled down to one
number; the benefit to cost ratio.
The current year is always year zero for the calculation, and it is generally assumed that
construction would be completed in year one (or, for a long process or project, year two). The
NPV of the project cost for a project completed in year one is almost, but not quite the same as
the project cost; it has only been discounted one year. This is the COST part of the ratio. The
BENEFIT is the NPV of the cash stream of savings (fuel savings, in this case) that the project
generates over the 20-year lifetime. Divide the Benefit (in dollars) by the Cost (in dollars), and
you get the dimensionless Benefit to Cost ratio; generally, any value over 1.00 is considered
good, but different agencies have different target values.
The NPV benefit is simply the NPV of the combined (savings minus cost) Cost and Savings cash
flow over 20 years. In the year the project is constructed, the “savings stream” is negative,
because the discounted project cost is much greater than the yearly savings – all other years, the
savings are positive. Take the NPV of that cash stream, and that is the NPV benefit of the project.
Unlike the B/C ratio, this value only really tells one something useful when compared to another
variant of the same project, or another project that would use the same initial cash input. The
project with the higher NPV benefit (n dollars) is generally better.
The client discount rate and escalation assumptions used in the B/C and NPV Benefit calculations
are shown in Figure 1.1 below. All Building Level and DH Plant summaries indicate the NSP, B/C and
NPV Benefit values for that opportunity. These nominal rates reflect recent escalation rates in SE Alaska
as provided by input from a USFS representative. Note again that while the escalation rates do not affect
NSP, they strongly affect the Benefit to Cost Ratio, which is based on 20 years of energy costs inflated at
the rates shown below. These numbers primarily affect the B/C ratio and show the potential escalated
value of the project.
Figure 1.1
1.6
Resource
Assumptions
As noted above, the only form of biomass modeled in this report is wood pellets. Figure 1.2
below shows the assumptions that have been made for the existing fuels in Juneau (oil and electrical
energy), in the units in which they are sold:
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 8 | 32 Final Report
Development Corporation 16 Sept 2014
Figure 1.2
There is a large question as to the short and long-term cost of pellets. The study assumes $300 per
ton for the basic study, which is based on the cost of purchasing 40# bags of pellets locally from Home
Depot, but we also evaluated the results at $330 per ton, which is based on a quote for delivered costs
from a supplier and from the regional mill in Ketchikan. Both sets of result are presented below. In
addition, there is a sensitivity analysis performed for up to $360 per ton for each scenario. The more
pellet projects that come on line in Southeast Alaska, the more stable a future cost of pellets will become.
Because each form of fuel has a differing heat content and is sold in differing units, direct
comparisons between the costs of fuels are difficult. To make the comparison simple, all these energy
sources are converted to a common unit, one million BTU (1 mmBTU).
To make the comparison even more relevant, the conversion efficiency of each source has been
factored in. In this case, the conversion efficiency for each fuel is the boiler efficiency (electricity has an
efficiency of 1.00). It is different for each fuel – using drier wood results in better boiler efficiency, and
the oil boilers have their own efficiencies as well. In Figure 1.3 below, therefore, the $/mmBTU values
are those coming out of the boiler into the space, not the gross heat content of the fuel going into the
boiler.
Figure 1.3
As Fig 1.3 shows, electrical energy is actually less expensive than No. 1 oil (a rare result in
Alaska), which in turn is about 1.75 times more expensive than wood pellets. The wood pellets are
assumed to contain 8,200 BTU/lb. as per published data from the US Forest Service Wood Products Lab.
But in reality, this number varies based on actual quality, species and moisture content of the pellet.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 9 | 32 Final Report
Development Corporation 16 Sept 2014
1.7
Summary
of
Findings
The following Figures summarize the performance and economic modeling that AWEA
performed. We have based the model on a pellet cost of $300 per ton and $330 per ton. For that reason,
we show the summary results twice one at $300 per ton and one at $330 per ton. Since there is some
uncertainty about the price of pellets, there is a graph included, which shows the sensitivity of net simple
payback to pellet cost up to $360 per ton. We used $300 per ton because pellets can be purchased locally
at $293 per ton in 40# bags in one-ton lots from Home Depot. All prices on pellets are subject to change.
The church members could then load the bins by hand for the cost savings, if that was a choice that
members wanted. However, the amount of pellets required for heating the primary chapel alone is
approximately 68 tons so this would be quite a bit of work over a heating season. Otherwise, pellets can
be delivered in bulk to the bin at $330 per ton based on a recent quote. So the analysis shows both.
Figure 1.4 below shows the overall economic summary with pellets at $300/ton (the analysis is
set up to allow up to four Scenarios – in this case, only Scenario 1 (Sc1) and Scenario 2 (Sc2) are used).
This is the same in Figure 1.5 as well. Recall that Scenario 1 (Sc1) is with the boilers placed in the current
boiler room and Scenario 2 (Sc2) is the boilers placed in a container outside the boiler room and thus
higher implementation costs.
Figure 1.4
Note that in both Scenarios, pellets displace 99.99 percent of the base oil consumption. In both
Scenarios, the DH Plant consisted of two (2) Maine Energy Systems PES 56 boilers. The table in Figure
1.4 demonstrates an estimated cost for placing the boilers in the current boiler room of $151,351 in
Scenario 1 compared to an estimated cost of $186,069 for placing the boiler in a container. The
difference in actual annual savings labeled “total savings” is minor but the net simple payback of Scenario
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 10 | 32 Final Report
Development Corporation 16 Sept 2014
1 is approximately three years less than Scenario 2. The B/C ratios is quite a bit higher in Scenario 1.
Thus it makes sense if at all possible to place the boilers in the current boiler room and develop a system
for feeding pellets to the boiler either through an outside bin or through a shoot leading to an inside bin.
Figure 1.5 shows the same metrics with pellets at $330/ton with similar comparative financial
results between the two Scenarios. However, one can see the difference between $300 per ton and $330
per ton pellets quickly by comparing the NSP. In Figure 1.4 NSP for Scenario 1 is 9.6 years and in
Figure 1.5 the NSP for Scenario 1 is 11.5 years.
Figure 1.5
As footnote (3) indicates in Figure 1.4, we have not estimated any increase in annual maintenance
with the installation of the pellet-fired boiler. This is because the fuel consistency is so high, the material
handling so smooth, and the pellet boilers so reliable that in essence it is as close to being as automatic as
an oil fired boiler. We would expect that whoever currently cares for the oil boilers will also take care of
the pellet boilers, and that no significant additional time or parts expenses will be incurred. Experience
has shown that pellet boilers are reliable enough to be used in residences; this would not be the case if
there was significant maintenance and expense required.
Using the escalation factors from Figure 1.1 above results in the following 20-year cash flows for
the $300/ton analysis only in Figure 1.6. With these escalation factors, the savings increase by nearly
seven times over 20 years; the project becomes increasingly more valuable with time. This demonstrates
that the project is not only financially doable now but becomes much better through time. Figure 1.6
shows a total savings over the life of the boiler of $1,032,819 for Scenario 1 with the pellet boilers in the
current boiler room and only approximately $16,000 less if the boilers are placed in a standalone room
outside the building. Of course as the assumed price of pellets increases the total amount of 20 years
savings decreases, but as demonstrated by the difference between $300 and $330 per ton the total savings
is still quite impressive.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 11 | 32 Final Report
Development Corporation 16 Sept 2014
Figure 1.6
Of course, a primary variable in the financial analysis is the cost of pellets. For that reason, as
noted above, we include a Figure 1.7 that shows the effect of pellet cost on net simple payback. In
Scenario 1 the payback escalates from 9.6 years to a little less than 14 years at $360 per ton.
Figure 1.7
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 12 | 32 Final Report
Development Corporation 16 Sept 2014
When one considers a 20-year project flow of savings as demonstrated in Figure 1.6, even at this price
savings are significant over the life of the project.
Finally, Figure 1.8 below shows a financial performance summary for the Chapel by the Lake as
an individual building without connecting to the Parsonage and the Log Chapel. This was the original
request by the Chapel. When we evaluate individual buildings, we use the same cost factors, but a
different reporting format. This is because many elements that go into a DH Plant do not apply when
looking at a single boiler / single boiler configuration. The soft costs are reduced and it is assumed that
no additional study is done. We assume the contractor is largely competent enough to design the
interconnects within the system. Some construction oversight is assumed, but at a lower level. The
contingency is reduced to five percent, as well.
There are three columns in the Figure 1.8, and a Summary section at the bottom. The first sets of
values are the current and proposed oil values and costs (note that the proposed boiler would displace 97.3
percent of the base oil). The second column of values shows the value and costs of the added biomass
fuel and electrical energy required. The final column is a summary of the implementation costs. In the
Summary section at the bottom, it can be seen that the NSP is 4.1 years, and the B/C ratio a very
impressive 10.3. Finally, at the upper right, it can be seen the selected boiler is a single Maine Energy
Systems PES 56.
In this case, only a single pellet boiler is required, and since the boiler is assumed to be located in
the basement next to the existing boiler, project costs are very low. So despite the relatively low base oil
cost, the Chapel has a very attractive net simple payback of 4.1 years. It is believed that the project costs
could be significantly lower, so this should be considered a “worst case”. A minimal amount of field
work is all that would be required to refine this implementation cost. This single building project will
displace 97.3% of the current amount of oil used in the main Chapel.
Figure 1.8
As demonstrated in Figure 1.8 a stand-alone project, the Chapel itself shows very attractive
financial metrics at $300 per ton pellets. Although not shown as a stand-alone project at $330 per ton
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 13 | 32 Final Report
Development Corporation 16 Sept 2014
would also show very good financial metrics with a payback. If the CBTL management should decide
not to go for a DH system to heat all of their buildings then just heating the main building would be a
really strong financial payback on investment. Another way to look at the overall project is in phases
with the primary opportunity for the greatest savings at the lowest cost would be to start with one boiler in
the boiler room of the main Chapel as depicted above. Then at a later time one could add another boiler
and connect the other two buildings.
1.8
Next
steps
The Owners of the Chapel by the Lake complex must of course evaluate these results using their
own investment metrics and criteria. However, it appears based on the findings of this report, that if
CBTL can lock down favorable pellet prices and form a team of the right professionals and contractors,
and design a lean delivery method that minimizes soft costs, this DH is certainly a viable project,
financially.
As noted above the next step would be to try to tie down fuel sources and prices, and to spend a
minimal amount of time to ensure that the DH Plant can be built in the basement, the piping can be run
through the building, and that the interconnections to the existing boiler are simple. All of which the
authors of this study believe is the case.
At the same time, the viability of the individual Chapel boiler could be confirmed and those
project prices sharpened. This would likely be considered an extremely strong fallback project, if the
main DH Plant cannot meet the investment criteria of the CBTL.
In addition to financial performance, AWEA believes that wood energy projects generate benefits
to the owners of the project beyond the obvious monetary ones; we call these VBECS (value beyond
energy cost savings), a term borrowed from the Rocky Mountain Institute. VBECS are different
depending on the location and circumstances of the project. The value of VBECS can only be determined
locally and by the owners of the project. Some of the potential VBECS for this project located in Juneau
are:
• Use of renewable resources
• Reliance on local or regional, rather than remote energy sources if pellets come from Alaska
• Reduced carbon footprint
• Reduced secondary emissions (NOx, S, CO, etc)
• Potential increased fuel price stability (for future budget planning)
There are no doubt others as well. As was noted above, a Level 2 study is a screening study,
meant to provide enough information to the stakeholders to A) determine how to proceed next, B)
determine whether to proceed, or C) halt the project until conditions improve. This study provides the
information needed for the CBTL owners and other stakeholders to make these decisions.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 14 | 32 Final Report
Development Corporation 16 Sept 2014
2
TECHNICAL
SUMMARY
2.1
Existing
Conditions
The following statistics in Figure 2.1 summarize the existing conditions in the CBTL complex:
Figure 2.1
The primary boiler in the main Chapel is 28 years old, but it has recently been retrofitted with a
new burner. The boiler in the parsonage is fairly new and in good condition but the exact date is
unknown. The boiler in the log chapel has been well maintained but is likely as old or older than the main
boiler in the chapel. The AWEA was not able to obtain exact numbers on fuel usage of the Log Chapel or
the Parsonage so used modeled estimates to determine fuel usage. It was estimated that the Parsonage
used 960 gallons and the Log Chapel used 1344 gallons per year.
The proposed pellet-fired DH Plant would displace over 99 percent of the current fuel oil
consumption; however, the existing boilers would remain in place as back up in all Scenarios analyzed.
As a cost-savings measure, no additional back up was included in the DH Plant.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 15 | 32 Final Report
Development Corporation 16 Sept 2014
2.2
Wood
Fuels
/
Wood
Fired
Heating
Equipment
Figure 2.2 below shows the properties of the pellets that were used in this study:
Figure 2.2
The most pertinent value in the Figure 2.2 is the net useable heat content, 8,200 BTU/lb. Because
of the low moisture content (4 percent), pellets are by far the most energy-dense form of wood fuel
locally available.
There are a number of manufacturers of pellet boilers; the basis of design boilers used in this
study are the PES series of boilers made by Maine Energy Systems (MES). We used these because there
are other installations in the area and they are a good quality boiler. There are eight sizes in the PES
series, ranging from 41 kBTU/h to 191 kBTU/h (output). This project uses two Model PES 56 pellet
boilers for the District Heating Scenarios and one for the Scenario that heats only the primary Chapel.
The basic system components include:
• A pellet bin, which holds bulk amounts of wood pellets.
o This bin is kept filled by periodic deliveries to the Chapel by truck from the docks or is
filled by members from bags purchased from the low cost supplier home Depot
• A means getting the pellets from the bin into the boiler (material handling)
o For MES, this is a vacuum system; the bin may be up to 66 ft away from the boiler
• The boiler
o The boiler uses onboard controls to modulate the firing rate to meet heating demand
o Will remain on and operating as long as the bin is kept filled, and no fuel fouling occurs
o Is a “hands-off” unit
• A vent or boiler stack
o This vents the products of combustion and boiler emissions into the air through an
elevated stack or vent pipe
o May or may not include additional emissions control equipment
A brochure of the MES boilers and accessories are included in Appendix 2.
2.3
Proposed
Conditions
As noted above, the thermal performance of both Scenarios is relatively similar – Scenario 2
simply has a few more parasitic losses since it is located in a separate building. What changes from
between these two Scenarios is the implementation cost. Some of the details of the expected conditions
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 16 | 32 Final Report
Development Corporation 16 Sept 2014
in the development of Scenario 1 are listed below under Scenario 1 and the differences between the two
are listed in Scenario 2 below.
Scenario
1
Some of the features of Scenario 1 include the following:
• Two new 8 x 34 pellet boilers, located in the basement close to the existing Chapel boiler
• The DH Plant appurtenances includes new primary piping to connect the two boilers, an
expansion tanks, ash container(s), individual boiler controls and a Plant controllers, and all
required electrical lighting and wiring
• A primary / secondary heat exchanger and variable speed secondary pumps, and secondary
loop expansion tank
• Distribution piping from the DH Plant to the Chapel boiler, and to the other two buildings as
described above.
• Connection from the distribution piping to each of the 3 boilers (see Section 3)
• DDC controls as required to control the Plant and interconnections
• The new piping will be tied into the existing systems in such a way that it will always take the
“wood heat” before taking oil heat (Figure 3.2 below)
• Distribution piping from the slab to each building
• However, if for any reason the wood fired system cannot meet load, the existing boilers will
automatically start and fire as required to meet load
• Full design and construction administration/management services, with 7.5 percent
contingency
Scenario
2
Scenario 2 varies from Scenario 1 in the following ways:
• A new 8 x 34 containerized pellet boiler plant, piped and wired at the manufacturer, and
delivered to the site
• The container includes primary piping, two boilers, expansion tanks, ash container, controls
as specified, lights, and all electrical lighting and wiring – plus room for variable speed
secondary pumps, secondary pumps and a secondary heat exchanger and expansion tank
• A new slab constructed to house the container, with pipe and wiring routed to slab
• A primary / secondary heat exchanger and variable speed secondary pumps, and secondary
loop expansion tank
• Once the secondary pipe is in the basement, Sc 2 becomes just like Sc 1
2.4
Cost
Estimate
The detailed construction cost estimate is provided below in Figure 2.3. These are what are
commonly referred to as the “hard costs” of the project. The remaining soft costs, fees, permits,
engineering, are detailed in Figure 2.4 below.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 17 | 32 Final Report
Development Corporation 16 Sept 2014
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 18 | 32 Final Report
Development Corporation 16 Sept 2014
Figure 2.3
There are two notes that must be amended to Figure 2.3:
1. In Scenario 1, the DH plant is in the basement, next to the existing boiler. Much of the piping
runs through the building, to the SE corner. From there, it runs in an insolated soffit in the
overhead walkway to the Old Chapel. Between the SE corner and the Parsonage, the PEX
piping is direct buried.
2. In Scenario 2, the DH Plant is containerized, and located at grade just outside the building
(near the oil tank for the existing boiler). A new slab is to be poured for the container, with
electrical and piping from the basement to the slab. All other aspects of the two Scenarios are
the same.
The DH Plant has reasonable financial performance, if A) fuel can be obtained for $330/ton or
under, and B) the plant can be built in the basement of the Chapel (Scenario 1). The first priority of any
further work on this Plant would be to confirm those two items.
Figure 2.4 below is a summary of the cost estimate, showing the soft costs of the project. These
are developed and based on industry standards if grant funding is used from the Alaska Energy Authority.
In some cases, if private funds are used, these costs can be reduced. A more detailed construction
estimate is contained in Section 2 of the report.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 19 | 32 Final Report
Development Corporation 16 Sept 2014
Figure 2.4
2.5
Energy
Savings
Figure 2.5 below summarizes the Scenario 1 energy consumption, existing and proposed, on a
monthly basis. The top two rows of the table are the estimated total gallons of oil and cost used under the
current conditions of the three oil boilers in the three buildings. The middle three rows are the estimated
gallons of oil used, the tons of pellets consumed and the amount of additional electricity used in scenario
1. These are based on estimated air temperature and thus demand for heat and on the estimated amount of
domestic hot water used each month. The next four rows convert the amount of oil, pellets, and
electricity used per month into dollar amounts. And finally the bottom row shows the monthly and
annual savings for scenario 1 compared to the amount of oil currently used. These energy and cash flows
are for the optimistic cost of $300 per ton for pellets. The total annual 1st year savings for scenario 1at
$330 per ton is $13,141 about $2500 less than at $300 per ton.
Figure 2.5
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 20 | 32 Final Report
Development Corporation 16 Sept 2014
Figure 2.6 shows the exact same data for Scenario 2 at $300 per ton for pellets. At $330 per ton
this scenario would have a 1st year annual savings of $12,447 compared to the below value of $15,163.
Figure 2.6
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 21 | 32 Final Report
Development Corporation 16 Sept 2014
Appendix
1.
INTERCONNECTIONS
Interconnections
and
the
Impact
on
Construction
Cost
One of the most important features of a District Heating system is the interconnection between
the DH system and the existing buildings systems. These interconnections can range from complex (and
expensive), to very simple, often with one or more variations in between. The simpler the
interconnections get, the less they cost. However, even the least expensive connections constitute a
significant amount of money. The goal, therefore, is to first minimize the number of connections, and
then apply the lowest appropriate level of technology for each connection, minimizing overall
construction cost.
One thing that all possible interconnections should have in common is that no operator
intervention should be required in the event that the DH Plant fails, or that the biomass boilers cannot
meet the peak loads in very cold weather. At the same time, in periods of the very high heating load, the
system should ideally use 100 percent of the capacity from the biomass boilers first, and use the “back-
up” oil only to cover the peaks.
The following is a summary of some of the things all interconnections should have in common:
• In all systems, we prefer to install a heat exchanger between the distribution piping and the
building piping. Many building systems use glycol, while the DH distribution systems use
100 percent water. The heat exchanger provides a physical barrier between the two systems
to prevent cross-contamination, while allowing heat to cross over. A control valve is used on
the distribution return line to control the hot water return water temperature on the building
side of the exchanger.
• The interconnect is always made in such a way that it heats the building hot water return
before it gets to the building boiler(s). The basic premise is that the temperature setpoint for
the building return water coming off the heat exchanger is 5 deg F (for example) hotter than
the setpoint of the boiler itself. The result is simple; if the biomass system heats the building
return water to a temperature at or above that of the boiler setpoint, the boiler will not come
on, HOWEVER,
• If for any reason, the biomass system cannot heat the building return water all the way to
boiler setpoint (failure or very cold weather), the return water temperature will begin to fall,
and when it falls below the boiler setpoint, the boiler will automatically add enough heat to
make its setpoint.
• This ensures that 100 percent of the available biomass heating capacity is utilized before any
back-up fuel is used. Once the load drops to the point where the heat exchanger can heat the
return water to above the boiler setpoint, the building boiler will stop firing.
• In order to prevent “drafting losses” when the biomass boiler is providing the heat (the hot
boiler would pull room air through the fan and this air rises up the stack, cooling the boiler), a
draft damper can be installed in the boiler stacks. This would be hard-wired to the boiler;
when the burner is ON, the damper is open and when the burner is OFF, the damper is closed.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 22 | 32 Final Report
Development Corporation 16 Sept 2014
Given the list above, for any given site, there can be many possible variations in the way
buildings are connected. In general, the size of the DH Plant, the number and nature of the end-users, and
the sophistication of the individual building controls also factor into the decisions on how to interconnect
the buildings.
• For large DH Plants with extensive piping systems, the cost of the pumping energy required
to distribute the heat through the pipes is significant. For that reason, we almost always use
variable speed secondary hot water pumps. At any load less than 100 percent, variable speed
pumps cut the pumping energy by 1/4th to 1/8th of the energy of constant volume system at
the same flow. In these situations, the preference is to use a good quality motor-actuated
control valve to control the flow at each building (actually, at each connection – so there may
be more than one per building).
• A motor-actuated valve generally pre-supposes that the building has a pneumatic or DDC
control system to control all of the HVAC systems. Larger, more sophisticated buildings
tend to have such control systems; smaller buildings use only local controls.
• For a DH Plant that serves multiple buildings with multiple owners, a metering system is
installed. This allows the DH Plant to charge the end-users for the exact amount of heat the
use.
The situation at the CBTL complex is relatively simple; one boiler per building, and no need to
sub-meter the heat. Figure 3.1 below shows a relatively common “typical” building, with two boilers
(we have only one boiler per building, but the concepts are the same)
Figure 3.1
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 23 | 32 Final Report
Development Corporation 16 Sept 2014
Figure 3.2 shows the typical connection detail we would use for a large, extended DH Plant with
multiple owners; this diagram assumes a minimum level of control in the each building as well (in this
example, B-1 and B-2 have different owners, and must therefore be individually served and metered).
Figure 3.2
Figure 3.2 represents just about the most expensive means of interconnecting to an existing
boiler. This detail assumes that 1) each boiler must be connected separately, 2) that each end-user must
be sub-metered, 3) an external control system exists in each building, and 4) the secondary pumping is
variable speed.
As noted above, the system is configured to heat the building hot water return before it gets to the
boiler. The 2-position valve directly below the pump would be closed, and the other two 2-position
valves open; building hot water return flows to the heat exchanger. The building HWR would be heated,
and return to the boiler loop just above the point it enters the boiler. Because the HWR is now hotter than
the setpoint for the boiler, the boiler never fires. The modulating valves at the HX control the building
HWR temperature, and the flow meters at each HX allow the DH Plant operator to measure the exact
amount of heat consumed by each residence within the multi-plex.
This is clearly over-kill for the situation at the Chapel. First, the amount of flow in the system is
so small that the secondary pumps are less than one horsepower. Thus, while electricity is still expensive,
there is no need to use expensive control valves at each HX. Second, there are no building control
systems to control all the valves shown above. Third, there is no reason to individually meter the heat to
each building.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 24 | 32 Final Report
Development Corporation 16 Sept 2014
Instead, for CBTL, we priced an interconnect much like that shown in Figure 3.3, except that, as
noted, there is only one boiler per building. We would have one HX, and one self-contained valve at each
boiler. The isolation valves are manual, not 2-position.
Figure 3.3
The final interconnect detail will be determined during the next steps phase – a brief
discovery/design/documentation phase.
Thermal
Storage
When referring to a hot water heating system, thermal storage simply refers to a hot water tank, which
stores hot water (thus thermal storage). The importance of using thermal storage in a biomass-fired
heating plant varies depending on the form the wood.
Stick fired boilers are batch fed, with an operator adding batches of fuel as needed. In this case, thermal
storage is almost a requirement. This is because once the fuel starts burning, it is impossible to modulate
the rate of burn to match the heat load. Instead, the amount of fuel added is sized to heat the thermal
storage, while the pumping/piping system extracts heat from the thermal storage as needed to match the
load. The thermal storage “de-couples” the rate of burn from the variations in heating load.
Chip fired boilers are automatically fed, and can modulate to meet load. It would seem then that they
would not need thermal storage, and in fact many chip systems are installed without storage. Where
storage really provides value in a chip system is when the heating load varies over a very large range, as
they do in Alaska. The boiler can only turn down to about 25 percent of full load capacity – below that
heating demand, the boiler will cycle off until hot water temperature drops a set amount, and then restart.
A good chip boiler will auto-restart, but they still will not cycle On and Off like an oil boiler, for instance.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 25 | 32 Final Report
Development Corporation 16 Sept 2014
Once the fuel is in a solid fuel burner, it will burn whether the heat is needed or not. They take a long
time to cool down, and an equally long time to heat back up. Finally, if the fuel is very wet, the auto-start
may take a long time, or in extreme cases, fail. A storage tank help limit the cycling – the boiler now
modulates to keep the tank at setpoint, and as above, the system extracts heat from the tank as needed.
The thermal storage can keep the boiler running at very low levels rather than cycling.
The performance of pellet boilers is as close to an oil-fired boiler as is possible with wood. The fuel is
very dry, and easy to re-start. The boilers are generally much smaller than chip boilers, so there is not
much fuel in the unit at any given time. They are as heavy, so they heat up much quicker. While a
thermal storage tank would again limit cycling at low loads, pellet boilers generally do not need a tank to
modulate and follow loads. However, all good pellet boilers have an auto-cleaning feature, where they
clean the tubes, generally once a day. Many models cannot do this while the boiler is actually running, so
they shut down. Such boilers generally use thermal storage to “bridge over” the time they are off. The
Okofen boilers sold by Maine Energy Systems do not shut down while cleaning, and so while one can add
thermal storage to the MES boilers, we determine whether to add storage based on the application.
In a district heating application, one is likely to have two, or even three boilers. If each boiler has a 4:1
turndown, then a plant with two boilers can turn down 8:1, and a three-boiler plant can turn down 12:1.
The buried piping provides a small but constant load, and even on warm days in AK, nights can be cold.
So in this DH situation, we do not add thermal storage – the combined turndown of the boilers is
sufficient to minimize cycling.
In a small single building or residential application, we would likely add a small (50 – 90 gallon) tank
even for an MES boiler, space and money permitting.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 26 | 32 Final Report
Development Corporation 16 Sept 2014
Appendix
2.
Photos
and
site
map
Figure
1.
Photo
of
Parsonage
residence
added
to
the
heating
analysis.
Figure
2.
Log
chapel
added
to
the
heat
analysis.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 27 | 32 Final Report
Development Corporation 16 Sept 2014
Figure
3.
Boiler
room
just
under
stack
and
is
accessible
through
a
small
roof
under
the
walkway
if
needed.
Pellet
storage
will
either
be
in
an
outside
bin
or
through
a
shoot
leading
to
a
bin
in
the
boiler
room.
Figure
4.
Site
layout.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 28 | 32 Final Report
Development Corporation 16 Sept 2014
Figure
5.
Boiler
label
for
boiler
in
main
building.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 29 | 32 Final Report
Development Corporation 16 Sept 2014
Appendix
3.
Brochure
for
MES
OkuFen
Pellet
Boilers
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 30 | 32 Final Report
Development Corporation 16 Sept 2014
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 31 | 32 Final Report
Development Corporation 16 Sept 2014
Appendix
4.
Portion
of
Tech
Brochure
for
PEX
Piping
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS
Chapel by the Lake, Juneau, Alaska Alaska Wood Energy Associates
Fairbanks Economic 32 | 32 Final Report
Development Corporation 16 Sept 2014