HomeMy WebLinkAboutRural Fuel & Energy Use in Alaska & Solid Fuel Stirling Engine Development revised 1984Kura] Tuel ¥ Energeye USe
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STATE OF ALASKA
DEPARTMENT OF COMMUNITY AND REGIONAL AFFAIRS
STIRLING ENGINE DEVELOPMENT PROJECT
ANALYSIS OF RURAL FUEL AND ENERGY USE IN ALASKA
AND
SOLID FUEL STIRLING ENGINE CRITERIA DEVELOPMENT
AUGUST 31, 1983
REVISED JANUARY 3, 1984
PROPERTY OF:
Alaska Power Authority
334 W. 5th Ave.
Anchorage, Alaska 99501
PREPARED BY:
MARENCO, INC. ALASKA ENERGY RESEARCH GROUP
MECHANICAL TECHNOLOGY, INC. TANANA CHIEFS CONFERENCE, INC.
Ne
Stirling Engine Development Project
TABLE OF CONTENTS
PART I
Analysis of Rural Fuel and Energy Use
Section
I Introduction
rT Summary
III Methodology
IV Residential Energy Use
vI
VALE
A) Anchorage Residences
B) Rural Residences
C) Remote Residences
1) Subsistance Lifestyle
2) Small, Intermittent Use Generator
3) Small Settlement
Free Piston Stirling Engine Total Energy System Use in Alaska
A) System Concept
B) Heating Systems
C) Energy Balances
1) Single Structure
2) Utility Energy Balance
D) Homeowner Use of FPSE/TES
E) Economics of FPSE/TES Use
F) Sensitivity Analysis
G) Comparison of FPSE/TES with Alternatives
Alaskan Market for Residential FPSE/TES
Mature System Considerations
A) Cogeneration
B) Commercial and Other Markets
C) Development of Other Fuels
D) Effect of Subsidies
E) Uniqueness of Alaska
F) Future use in Alaska
Page
13
LT
U7.
18
22
24
25
28
32
33
34
sy
41
43
50
50
52
52
53
53
54
PART II
Design Criteria Development
Page
I Introduction 56
II Methodology 56
III Criteria Specifications 58
A) Fuel Input 58
B) Electrical Output 60
C) Thermal Output 61
D) Exhaust 62
E) Other Factors 63
F) System Cost 65
IV Summary 66
Bibliography 67,68
List of Tables
Table No. Page
1 Electrical Consumption, Anchorage Residences 8
2 Gas vs. Electric Appliance Use 9
3 Appliance Saturation and Use 9
4 Energy Consumption, Costs, and Ratios for 10
Anchorage Homes
§ Heating Degree Days - Anchorage hi
6 July/January Consumption Ratios of Electricity ae
7 Gas Consumption of Anchorage Homes 12
8 Energy Ratios 12
9 Energy Consumption in Rural Homes 13
10 Annual Energy Consumption, Costs, and Ratios for
Rural Homes 16
11 3kw Diesel Generation Costs 20
12 FPSE costs 24
3 3kw FPSE/TES Itemized Generation Costs 36
14 FPSE/TES Total Annual Costs 37
a5 Alaskan FPSE/TES Residential Market Estimates 45-48
=f4=
List of Figures
Part I
Page
1 Energy Flow Diagram 29
Part II
1 FPSE/TES Schematic 57
2 Diesel Gen Set/Wood Furnace Schematic 57
-iii-
STIRLING ENGINE DEVELOPMENT PROJECT
PART 1
ANALYSIS OF RURAL FUEL AND ENERGY USE IN ALASKA
z INTRODUCTION
The State of Alaska entered into a contract with Marenco, Inc. of Anchorage, Alaska on July 7, 1983 to develop and demonstrate a solid fuel, free piston Stirling engine energy system for use in rural Alaskan villages. The cost of electricity and heat in these villages is very high in comparison with costs in other parts of Alaska, in part due to high transportation and storage costs and low efficiency
of generating and heating systems.
Mechanical Technology, Inc., and Alaska Energy Research Group
are involved with Marenco, Inc. in a team effort to develop a solid
fueled, free piston Stirling engine generator to demonstrate the
generation of electricity and heat for applications in small, rural
Alaskan homes.
The State of Alaska is committed to reducing energy costs for
rural Alaskan villages and is continually searching for the timely
implementation of more cost effective power generation and heating
technologies.
Historically, the State of Alaska has actively participated
in the development of power generation and heating systems through all
phases of idea development, research, engineering, construction, and
demonstrations. At present, the state of Alaska provides assistance
to rural electric consumers while new technologies and systems are
developed and applied.
Of the emerging power technologies, the Stirling engine
invented in 1816 by Robert Stirling, a Scottish clergyman, promises to
be a cost effective and practical solution to providing affordable
electricity and heat for Alaskan rural communities. The Stirling
engine comes closer to being thermodynamically perfect than any other
engine yet devised or developed. Mechanical Technology's free piston
Stirling engine is a self-contained unit capable of developing 1 to 5
kilowatts of continuous power and can produce enough waste heat to
heat a home and provide domestic hot water. The Stirling engine is
extremely quiet, burns a great variety of fuels and approaches an
overall system efficiency of 30 percent. In contrast, a small diesel
or gasoline engine generator requires special and expensive fuel,
discharges more pollutants, is noisy and requires frequent and expen-
sive maintenance.
The objective of this report is to determine the market
breadth, depth and requirements for the application of free piston
Stirling engine generators with waste heat utilization in rural and
urban Alaskan communities. The market requirements will in turn
determine the design criteria for a residential, solid fueled free
piston engine generator and the research plan steps necessary to suc-
cessfully develop and demonstrate the system in Alaska.
Sales
STIRLING ENGINE DEVELOPMENT PROJECT
PART 1
ANALYSIS OF RURAL FUEL AND ENERGY USE IN ALASKA
II SUMMARY
Data from statewide thermal and electric consumption indica-
tes that the use of electricity for appliances ranges from 2 to 16
percent of the total energy consumed on an annual basis. The electric
to total energy ratio in Anchorage varied from 8% in January to 12% in
July, indicating a relative insensitivity to seasonal fluctuations.
This ratio is an important factor for a home using a total
energy system, since it indicates the amount of energy wasted, if any,
for the generation of electricity. Since the efficiency of a FPSE, or
just about any prime mover, is well over this ratio, heat rejected by
the engine/generator will be needed for space or water heating,
greatly improving system economics.
FPSE annual costs were then compared to a representative
alternative for generation of comparable amounts of electricity and
heat. In all cases, costs of FPSE use were less than the defined
alternative.
Projected costs ranged from 37¢/kwh for an early, expensive,
short lived, high maintenance system burning oil with no waste heat
capture (vs. 55¢/kwh for a comparable diesel gen set) to a low value
of 2¢/kwh for an advanced FPSE/TES (Free Piston Stirling Engine/Total
Energy System) at full load factor using natural gas (vs. 5¢/kwh
urban electric rates). The greatest relative advantage of FPSE use is
seen in the case of a wood fired TES (with rates from 6-20¢/kwh
depending on FPSE assumptions) when compared to small intermittent use
diesels ($1.26/kwh and up), and this is the application targeted in
this project.
The FPSE alone has a projected retail cost of between $1015
and $1545 depending on production volume. Very compact gas or oil
burners designed for the FPSE are projected to cost $150-500 depending
on fuel and accessories. Installation is expected to average about
$200, equivalent to placement of a furnace. Total installed cost (in
urban areas) is projected at $1400-2200. Net cost is lower, if credit
for the: TES heating system is applied against the normal home furnace
cost. A wood combustor to power the FPSE is expected to be more
costly, about $2000, which is equivalent to many home wood furnaces.
Accessories might add another $500 to this price, for a net cost $500
more than an equivalent home furnace. Amortization of all capital
ea as
expenses was at 11% annual discount rate over the estimated component
Atte.
Compared to a 3kw diesel generator, all projections for
FPSE/TES showed lower capital cost and lower operating expense, often
significantly so. TES also was cheaper than most rural utilities with
pay back terms as low as 3 months for large usage and under 6 months
for typical home usage. Home usage of advanced gas fired systems had
a predicted payback of 3.5 years against present Anchorage rates.
When operating in the total energy system mode in a typical
residence the system cost and power factor were of major significance,
followed by assumptions of fuel cost and efficiency, controls, main-
tenance, and labor. For higher load factors fuel cost and labor
(using wood fuel) become more significant.
When compared to utility power, the FPSE/ TES may be signifi-
cantly less expensive, but may have diminished quality of power, i.e.,
3kw maximum power, 110v, single phase, and the necessity of running
the furnace to have power.
The market for the very early FPSE/TES was determined to be
24,000 units, which corresponds to essentially all residences faced
with actual electric rates of over 25¢/kwh (excluding Power Cost
Assistance) or the option of home generation. The availability of
mature and advanced systems will increase the market to 42,775 and
over 100,000 units. This market does not include any commercial or
cogeneration applications. A distinction between conventional markets
and rural Alaska was noted.
The largest impact of mature FPSE systems may be realized through
cogeneration, with great benefits to the utilities as well as the
FPSE/TES owner. The TES user receives lower cost power with greater
reliability, and the utility can purchase cheaper power during their
peak demand periods, while reducing capital expenditures for genera-
tion and distribution systems, and maximize overall system security.
Analysis of FPSE costs shows that larger users, such as commer-
cial or public buildings, will realize greater benefits. Initial
marketing to these users may be easier, consequently they are likely
to receive some of the first installations.
Alternative fuels, such as peat or wood chips, will likely be
more readily developed for a village relying predominately on FPSE
systems, since these fuels would be displacing more expensive diesel
used for electrical generation.
Existing subsidies for utilities were identified as well as those
that might apply to a FPSE/TES user. In the analysis of comparable
costs, no subsidies were assumed to benefit FPSE/TES while the utili-
ties' rates included all existing subsidies except Power Cost
Assistance, if applicable, since this subsidy is written to gradually
diminish in magnitude. It appears that the unsubsidized FPSE/TES can
compete with subsidized utilities, opening the possibility of removal
of these subsidies with no adverse affect on consumers. Prevalence
of various subsidies for electrification masks the relationship
between capital expenditure per consumer and economic capabilities of
the user, consequently the analysis dwelt on present means of
electrification and attendent costs.
Future conditions appear to favor FPSE/TES users even more than
at present. As fuel prices increase, the more efficient fuel utiliza-
tion of total energy systems becomes more important. Overall system
security is improved as FPSE systems can use diversified fuel types,
and are independent of blackouts caused by failure of a single com-
ponent such as a generator or major transmission line.
The economic advantages of a total energy system rely on three
external variables:
1) High cost of utility power
2) Concurrent demand for heat and electricity
3) Low cost of alternative fuel.
These conditions are more prevalent in rural Alaska than anywhere else
in the Nation, and coupled with the newness of the FPSE explain the
general lack of awarenes of the TES concept.
III METHODOLOGY
The concept of Total Energy System use in Alaska has been
mentioned several times but never seriously addressed, primarily
through lack of suitable hardware.
A Total Energy System (TES) provides all of a structure's
electrical and heating needs. A diesel gen set, if placed inside
a building, would both heat and electrify it. However, no one
wants to live next to a noisy, smelly diesel so the TES concept
remained essentially academic. This basic deficiency is further
exacerbated by the extreme maintenance costs and poor reliability
of small home sized diesels.
The engine being demonstrated by MTI has promise of successful
operation in Total Energy Systems. This research shall analyze
Alaskan energy use to determine the potential that a FPSE will
have, as the prime mover in a TES, and define the design criteria.
The analysis begins with examination of available information
on Alaskan residential energy use. Characterization of this data
in terms pertinent to Total Energy System analysis is the focus
of Section IV. Since TES simultaneously produces electricity and
heat (3kw electrity, 10 kw heat for the FPSE), the amount used,
time of use, cost of use, etc. are pertinent to economics of
operation. Separate data on electricity vs. simultaneous thermal
thermal use is only available in Anchorage on a system-wide basis.
A net electrical use, exclusive of water heating, space heating,
etc. was determined for Anchorage, and compared to thermal
requirements for various seasons. Ratios of usage were determined
for different seasons and housing types.
This same information was developed for the remainder of
Alaska and average consumptions of fuel and electricity, energy
ratios and costs determined, for both rural and remote homes.
Small diesel generation costs were investigated as a comparison.
Section V investigated factors affecting FPSE/TES economics
in the various regions identified in Section IV. Energy balances
of various structures/operations were determined, particular
assumptions on use were calculated and simplified formulas developed.
Sensitivity of FPSE/TES costs to various assumptions was discussed,
as well as relative comparison for new utility consumer install-
ations.
Section VI determines the potential market in Alaska for
residential FPSE/TES. In developing this estimate, the total
housing stock was first analyzed for utility consumers and cost,
then for heating fuel and cost, and using these two factors the
potential market of early, mature and advanced FPSE units was
estimated. Assumptions of FPSE/TES costs were projected.
Section VII discusses the concept of cogeneration, and the
adaption of FPSE to fit in the utility system, including technical
and safety considerations.
a=
Factors pertinent to system use in public/commerical buildings were
examined.
Development of other fuels as a result of FPSE/TES deployment is
discussed, as are effects of various electrical, fuel, and alternative
energy subsidies by local, state, and federal governments.
Finally, the economic limitations on future use of these systems are
investigated and projections made.
Iv RESIDENTIAL ENERGY USE
In this section, the energy used in Alaskan residences is analyzed with regards to type (electrical or thermal), quantity, cost, and source. The actual end use of this energy, and season of use is determined, to define the necessary outputs of the Free Piston Stirling Engine/Total Energy System.
Information on actual end use is not normally compiled by utilities, at least in the detail necessary for this study. The raw data exists only for Anchorage, and even then several sweeping assumptions must be made. After detailed energy use patterns are
derived for Anchorage homes, the analysis is taken to rural and
remote areas and similar use patterns derived for them. The use- ful result is a set of consumptions and costs which can be used
as a basis for projecting the usefulness of FPSE/TES.
A) Anchorage Residences
The relative wealth of data on Anchorage home energy
consumption makes this the logical area to begin analysis. Besides
acccurate and detailed consumption information provided by electric
and gas utilities, Anchorage is perhaps more similar to certain
stateside areas in appliance saturation and use than other areas
of Alaska. These usage patterns were used to derive final end use
of energy for heat and other appliances.
Table 1 lists electrical consumption for homes using gas and
for all-electric homes. The entire sample was broken into thirds
and the average taken for each group. This method compensates
for the fact that a small percentage of consumers use most of
the electricity, and the average consumption would be more than
that used by about 60% of the users.
TABLE 1 ELECTRICAL CONSUMPTION, ANCHORAGE RESIDENCES 4
Figures are averages for each group in kwh/month
A) Residences, System wide (a)
Jan April July Oct Ave/mo Ave/year
Lower 1/3 342 236 205 214 249 2988
Middle 2/3 749 590 492 519 587 7044
Upper 3/3 2242 1351 1034 1120 1437 17244
Total System
Average 1110 742 431 650 720 8645
B) All Electric Homes
Lower 1/3 1500 804 386 690 846 10152
Middle 2/3 2594 2446 1350 1912 2326 27912
Upper 3/3 7986 7684 4046 4968 6172 74064
All Electric Average 32214
(a) 3-4% of these residences are all-electric
End use analysis can proceed following these observations and assumptions:
1) Residences using gas heat have a certain proportion of electric
resistance heat for water heating, drying clothes, cooking and
miscellaneous space heat.
2) Electric and gas heated houses have the same electric consumption
for non-resistive uses, i.e. refrigeration, lights and small
appliances
Census data indicates numbers of homes with gas heating, water
heaters, and cookstoves. If all the gas water heaters and stoves are
in homes with gas space heaters then the number of electric appliances
for these uses in gas heated homes can be estimated:
Table 2 Gas vs. Electric Appliance Use
# of homes % gas % electricity
Homes heated with gas 43,244 100
Homes with gas water heaters 38, 251 88 12
Homes with gas stoves, 14,516 34 66
Homes with gas dryers 4,633 31 89
Table 3 Appliance Saturation and Use
Cons Sat Elec Cons Elec Cons Elec Cons
Appliance (kwh/y)? (8)? (8)? (kwh/y) (8) (kwh/y) (%) (Kwh/y)
Water Heater 3475 99 413 100 3440
"for Dishwasher 700 47 ja 1419 12 39 100 329
"for Clothes 1050 77 97 100 809
Dryer 1000 71 92 653 89 632 100 712
Range 1200 100 72 864 66 664 100 1200
Dishwasher 230 47 100 108 100 108 100 108
Clotheswasher 103 77 100 54 100 54 100 54
Television 400 148 100 592 100 592 100 592
Lights 1000 100 100 1010 100 1000 100 1000
Small Appliance 1010 100 100 1010 100 1000 100 1000
Refrigerator 1250 100 100 1250. 100. 1250 100 1250
Freezer 1350 46 100 621 100 621 100 621
Space Heat
Single Fam 32,000 52 3078 100 16640
Duplex 21,200 8.3 718.5 325 44 1020 100 1760
Multifamly 15,000 26.7 735 100 4005 Mobile Hm 23,900 13 375 — 100 3107
Total per Household 12,282 7490 36,625
Example:
Usage = (Consumption) (Appliance Saturation) (% Electric)
Dryer consumption in gas heated homes =
(1000 kwh/y) (.71) (.89) = 632 kwh/y
The largest end use of electricity is for thermal purposes. If low temperature uses (space heat, water heating, clothes drying) are to be provided by the home furnace, the average remaining
electrical consumption is 5489 kwh/yr for an average Anchorage home. If gas is used for cooking, the usage drops to 4625 Kwh/y. This yields an annual electric bill of $294 at 1983 prices.°
These figures are derived, from any category, by subtracting the
resistive consumptions from the total.
The average annual consumption of gas for Anchorage single-
family residences has been about 216 mcf over the last five years®
(approximately 216 x 106Btu/year gross). At an average efficiency
of 70%, the net thermal supply is 151 x 106Btu which includes water
heating and cooking. Average gas bill is $61l/year.
All-electric homes using a total of 36,625 kwh/year use 4625
kwh for small seph tires and 32,000 kwh for heat for a thermal
use of 109 x 10°Btu. Cost of this amount of electricity is $1,662.4
TABLE 4: Energy Consumption, Costs, and Ratios for Anchorage Homes
Homes _using gas = Al 1-Electric
Appliance consumption 4625 kwh/y 4625 kwh/y
Cost $294/y $294/y
Thermal consumption, net 151 x 106Btu 109 x 106Btu Cost $61l1/y $1662/y
Total energy consumption 167 x 106Btu 125 x 106Btu
Cost $905 $1956
Ratio Electrical/Total “ .094 126
Ratio Cost, Electrical/Total .32 okS
=10=
Available energy consumption data does not allow a direct
comparison of individual ratios of electrical/thermal loads and
costs for other than system averages. It is likely that the
energy ratios are similar for low consumers as well as high
consumers. That is, small homes will have both a small electrical
load and a small thermal load. Individual ratios, however, are
likely to experience substantial variations.
The seasonal variation in load ratios is dependent on house
quality: a well insulated home is less likely to experience wide
variations. The space heating load has often been assumed to
reflect seasonal variations in heating degree days.
TABLE 5: Heating Degree Days - Anchorage 8
Jan 1649 May 583 Sept 507
Feb 1322 June 312 Oct 936
Mar 1280 July 220 Nov E347
April 891 Aug 282 Dec 1612
Total 10911
Thus we might expect a July/Jan heating ratio of 220/1649
or .133. However upon examining consumption in Table 1 we find
much less drastic summer/winter ratios:
TABLE 6: July/January Consumption Ratios of Electricity
A) Gas Heated homes B) All-electric homes
Lower 1/3 0.60 0.25
Middle 1/3 0.66 05.52
Upper 1/3 0.50 0.51
The variation in consumption is less than the variation in
heating degree days for all cases, and for all-electric homes
with high consumption the ratio is the same as for gas heated
homes. The most logical explanation is that high consumption
(less seasonal fluctuation) is caused by higher use of electric
water heaters for both categories.
slo
6 TABLE 7 Gas Consumption of Anchorage Homes
1980 1981 1982 Ave 1980 1981 1982 ave
Jan 33MCF 33 31 32.3 July 8 7 8 7.7 Feb 28 24 31 20 aT Aug 7 8 7 te3 Mar 22 20 28 23.3 Sept 9 8 S 8.7 April 20 17 22 19.7 Oct 14 15 15 14.7 May 14 13 15 14.0 Nov 19 20 23 20.7 Jun a 9 11 10.3 Dec 28 25 _26 26.3_
Total 214 201 227 214
July/Jan = .24
The summer/winter consumption ratio follows more closely the
heating degree day variation. The average ratio of electrical to thermal loads can be estimated by comparing the net appliance usage
determined for gas heated homes to the average gas consumption for
a given month. The calculated non-heat consumption of 5489 kwh
represents 73% of the total 7490 kwh. If we assume that this
ratio is valid for individual months, then the electrical/total
energy ratios can be calculated.
TABLE 8 Energy Ratios
Year Jan April July Oct
Total Electrical (kwp) ° 8645 1110 742 431 650
Total Electrical (10 BEu) 29.5 3.8 2.5 1.5 Za2
Non-heat Electrical (10° Btu) 21.5 2.8 1.8 1.1 L6 Gas (10° Btu) 6 214 32.3 19.7 Tat 14.7 Total Energy (10° Btu) 243.5° 366% 2262 9.2 16.9
Non-heat Electrical/Total -09 -08 +i «32 -09
(a) From Table 1
(b) From Table 7
While large fluctuations occur in both the non-heat electrical load
as well as the gas heating load, they remain in phase over the
year.
While there is no assurance that Anchorage energy consumption
can be projected to any other area in Alaska, such a projection
is more preferable, at least for determinign electric/thermal
ratios, than relying on outside data.
-12=
B) Rural Residences
Data on rural residential energy use is very sketchy.
Individual totals of energy use are extremely varied and data on
monthly consumption of heat is not available. Several sources
provide data on total fuel consumption, and those based on actual
household interviews are in fair agreement.
In developing Table 9,
address electrical consumption and cost, APUC or APA reports. 5 24
TABLE 9
Study
10 11 iZ
if the study cited did not specifically
Energy Consumption in Rural Homes
Lime Vigil
RurALCAP
ISER NANA 14
Battellel3
ISER,
Misc
12
Location
Lime Vlg
Allakaket
Chalkyitk
Chefornak
Newtok
Nightmute
Nikolai
Shageluk
Degree Days@
14,500
16,000
16,000
13,200
13,200
13,200
14,500
14,500
Toksook By 13,200
Nthwest 14-16,000
N Slope 17-20,500
18 Vlgs 11-13,000
AVEC 48 Villages Barrowl3
9
Dillinghaml2
Southernl5 10,000
=S1o=
Wood oil (cords) (gal)
8.5 0
8.55 0
8.56 0
1034
45 798
1.79 589
9.2 0
9.15 0
798 89.7
2.9 1344
0 1784
1175
1083
Totalb 106
Btu
88
88.7
88.8
99.8
81.7
15.3
95.2
94.7
1885
60
172
114
90
182
105
939
that data was taken from
2642
4460
1500
349
L353
TABLE 9
Lime Vlg
Allakaket
Chalkyitk
Chefornak
Newtok
Nightmute
Nikolai
Shageluk
Toksook
ISER NANA
Battele
ISER
AVEC
Barrow
Dillingham
Southern
lbs
45
440
266
14
70
259
325
Continued
$
59
296
212
24
105
297
374
Blazo K
gal §
40.5 270
5.3 29
46 219
1982
41 197
17.5 111
13. 59
3 14
16 98
Kerosene Util Ele
gal $ Kwh §
31 143
4086 1351
1080
1761 881
3999 1935
3415 1653
2361 1143
5000 556
5112 1105
5000 1548
All figures are on an annual basis
15
-06
23
ell
-02-.13
c Total
$ 106 apeac See. f
6 329
10.2 325
15.5 574
16.3 1433
5.4 221
1296
13.2 1237
691 21.1 2323
13.6 1751
526
900
a) Heating degree days from nearest town with data - DEPpD8&
b) Oil @ 138,000 Btu/gal, 70% efficiency; wood @ 18.8 x 106Btu/cord,
55% efficiency
082
-086
-14
2
c) $100/cord assigned for wood gathered by homeowner unless local
prices were higher
da) For appliance usage of fuels,
and all consumption assumed within the home.
e) PCA (Power Cost Assistance) included when available
f) E = Electrical consumption, Btu/y.
Q = Heat consumption, Btu/y
-l]4-
100% thermal efficiency was used,
As expected, homes in the colder regions require more heating
fuel. However, within more relatively temperate regions, factors
other than weather become important, including housing size and
condition, family size, seasonal use patterns, water heating, and
cooking fuel. Unit cost of fuel may also be important, although
homes using wood do not use more fuel. In general, total heat
requirements of homes using 1983 estimates are less than earlier
estimates, perhaps reflecting results of conservation awareness
and programs or different estimating methods.
Contributing to the total heat supply are uses of electricity,
propane, blazo, and kerosene. While these are too expensive for
large scale space or water heating, their convenience and control-
lability make them desirable for cooking and lighting. In many
rural homes, substantial cooking is done on the space heater.
Consumption of blazo, propane, etc. varies drastically from village
to village. Housing developments in a single village tend to have
only one option for appliances, determining to a large degree the
fuel and usage required. Many households spend a portion of time
away from home, i.e. in a fish camp, and fuel use there may or may
not be included in the totals. Also, present housing stock or
electric utilities may be recently installed and steady energy
usage may not yet be reached.
The electricity to heat ratio of Table 9 is not exactly
parallel to the ratio calculated for Anchorage as there was no
way to separate out the water heating portion. The rural ratios
would decrease if adjusted for the resistance heat loads.
The seasonal fluctuations in use rates and ratios will vary
substantially throughout the bush. Interior locations with hot
summers will see wider swings in consumption than a coastal
location with cool summers and milder winters. A household
involved in subsistence food gathering may require additional
energy use for food processing during a particular period; i.e.
electricity for freezing or heat for canning.
The residential summer/winter use rate reported by AVEC is much flatter than for ML&P (.7 vs .4).9¢4 This might indicate more
variation in electrical/heat ratio than observed in Anchorage,
however this can't be determined without first subtracting
resistance heating as was done in the Anchorage analysis.
Despite the wide variations among individual homes and
villages, average rural home energy consumption and costs are
estimated for geographical areas in Table 10. Access to utility
power is assumed, with actual consumer cost of 25¢/kwh in all
areas. Fuel prices are approximately regional averages.
-15-
TABLE 10 Annual Energy Consumption, Costs, and
Rural Homes
Central
eil wood
Thermal consumption, 138 169 gross (106Btu)
Thermal consumption, 97 93 net (106Btu) Cost $/year 1500 900
Electrical consumption (kwh) 3600 3600
Cost $/year 900 900
Total energy consumption, net (106Btu) 109 105
Total energy consumption, gross (106) 150 181
Total Cost $/year 2400 1800
Ratio consumption, Elec/total eer}
Ratio costs, Electrical/thermal as 1.0
-16-
NW
oil
240
160
2650
5000
1250
S77)
257
4100
-10
472
4500
5000
1250
189
263
5750
-09
3
Ratios for
Southeast
gil wood
136. 165
91 91
1500 700
5000 5000
1250 1250
108 108
147; 177
2750 1950
SEL Gi erbO
eto rave.
C) Remote Homes
Remote homes are defined as those not accessible to an electric utility. Thermal sources and consumption are similar to homes in nearby villages, with some qualifications. Increased distance from bulk fuel storage will raise price and decrease consumption of fuel oil, and conversely wood availability and consumption will likely increase. The net result will probably be a decrease in cash expenditures for heating. Where wood is unavailable, heating costs
will increase with the additional fuel transportation expense.
Electrical consumption and costs are extremely difficult to estimate. Homes not on a utility grid have several options:
1) do without the electrical end use (i.e., lighting, refrigera-
tion
2) substitute a different fuel for the end use (lanterns,
propane refrigeration)
3) generate electricity
4) combination of any of these
Lifestyle variations are the major determinant for degree of
remote electrification; the closer the home to a non-cash,
subsistence lifestyle, the greater the tendency for no end use
electrical consumption.
Representative remote homes can be categorized as:
1) low cash subsistance - no generator
2) medium income household - small, intermittent use generator
3) small settlement - medium size generator
Each is analyzed separately:
1) Subsistence Lifestyle -
Energy costs and consumption can be characterized by those
villages in Table 9 that have no utility service. Cash costs for
cooking, lighting, etc. are usually under $1000/year, but much
more time is spent in providing for servies. Only rarely will a
household do completely without some form of electricity or at least
indirect use of generators. Dry cell batteries power radios, and
often 12v battery will be charged by a nearby generator and carried
home. This battery brigade can provide 1-l10kwh/month, depending
on accessibility to the charger, and is sufficient for radios and a fluorescent light.11
The largest single economic reason for a subsistence household
to desire electricity is for refrigeration of food. Up to one half
of all foods gathered spoil and become unfit for the table.
Consequently, the food gathering activities must be continous even
though most of the food may be available in only one month. The
primary means of preserving food without freezing is by air drying,
which requires substantial labor and can be ruined by rainy warm
-17-
weather. Access to freezing capabilities allows food to be gathered in its prime season with better resource management. Dependence on and use of expensive store bought goods is decreased and more healthy diets are affordable.
Although propane refrigerators are very reliable, they are
expensive and generally too small to use for food freezing,
especially long term storage.
2) Small, Intermittent Use Generator
While the very small, lightweight generators are fine for
portable power and augmenting the subsistence lifestyle, they are
not designed for the long term reliability to operate a household
freezer.
Selecting a generator set requires careful load analysis,
especially in regard to induction motors. Starting amperage
requirements can be 4-10 times that required for running. Usually
some means of load management is necessary to keep several induction
appliances from starting simultaneously. Also, shunt trips or other
motor protection devies are advisable to shield against low voltage
and early motor burnout.
The minimum recommended size gen set for running a domestic
freezer is 2 kw.16 Given adequate protection and load management,
other appliances can be run simultaneously as long as no larger
induction motors are used. However, reliability usually improves
in larger sizes. For the following analysis a 3kw diesel generator
will be investigated to derive an estimated electrical cost.
Two assumptions on usage are investigated, full use at 75%
load generating 19,710 kwh per year, and intermittent usage of
2190 hours generating 2000 kwh/yr.
a) Capital Costs:
3kw diesel gen sets cost in the order of $4000 depending on
brand and accessories included, such as high temperature/low oil
pressure shutoffs, water separator, or remote start.
Installation may include building a separate generator shack
if a detached building is not available. Freight charges depend
primarily on whether air transport is necessary.
Fuel storage requirements are determined by fuel transport;
i.e. if delivered in bulk, then usually large tanks are economical.
If the homeowner must transport fuel in drums, he often uses the
drums for storage as well.
Assuming that in many installations, the shed and storage
tanks will be multi-use, the average total of all these accessories
may be $1500, giving a total of $5500 if ground transport can be
used.
=18=
b) Fuel Costs:
Rated fuel consumption at full load lies between .34-.44
gal/hr. Load factor on small sets is very poor, usually well
under 30%. Consumption at this rating is usually between .14-.28
gal/hr. Fuel consumption is more dependent on generator hours and load factor than on kwh utilized. Average load factor for
2000 kwhr from 6 h/d running time is .3, which will consume about 450 gallons. At .75 load factor, consumption is about .35 gallons
per hour.
c) Repairs and maintenance:
This category often includes the greatest cost and disadvan-
tage of small scale generation. Manufacturers' schedules for
repairs and engine life are realized only with constant care,
protective devices, and some luck. Greater initial expense in
quality equipment, generator facilities, and clean fuel storage
often pays off quickly through reduced repair. Although some
small sets are still working after 100,000 hours, the majority
are scrapped well before their designed life of 50,000 hours and
often before two years (5000 hrs). A major factor in maintenance
is transportation - air freighting a dead engine to the machine
shop may be more than the salvage value, hence an engine is often
scrapped rather than rebuilt. Operator skill or accessibility of
service is likewise critical, since prompt diagnosis and repair of
minor problems will prevent major failures. The cost of calling a
mechanic from town, perhaps a two day trip, or sending the unit to
the shop, means that minor repairs have a major cost, hence many
repairs are attempted only after a failure has occurred.
Maintenance costs, listed in Table 1l are derived from
generator service representatives' recommendations.
An idealized operation of a generator will be assumed to
establish a basis; a minimum cost can then be derived.
Continuous operation at an average load factor of 75%,
maintenance as per manufacturer's recommendation, city prices for
labor and parts, no freight, no penalty for downtime, capital
costs as quoted and 11% discount rate are the idealized conditions.
Actual installations are considerably less than ideal and each
will incur different additional costs. For the assumed installation
using 2000 kwhr/yr, ground transport is assumed for initial hard-
ware and fuel, while some air transport will be required for
repairs. The owner is assumed to be capable of making all repairs
not requiring special tools. Every 1000 hours the valves and
injectors are checked and adjusted. Every 9000 hours a complete
overhaul is conducted, including replacement of rings, bearings,
injectors, and pumps as needed. Parts are ordered in advance,
so only a couple days' down time is needed. If at any time
-19-
machine work on the gen set is required, the long transport
time will prompt the owner to exchange his set for a new or
reconditioned one, assuming the salvage value exceeds the
transportation cost. This same process applies. to component
parts, i.e., the engine may wear out while the alternator is
still serviceable. Catastrophic failures are kept to a
minimum by regular maintenance and protective devices, yet the
total set is worn out in three years.
TABLE 11 3Kw Diesel Generation Costs
item Interval Unit Cost
Gen Set (a) 26,300 hrs $4000
Shed/fuel storage 10 year $2000
Fuel $2 gallon
Oil change 200 hr $2/qt
Oil filters 200 hr $5 each
Fuel filters 250 hr $4 each
Air filters 1000 hr $12 each
Minor overhaul 1000 hr $50 each
Major overhaul 9000 hr $1500
Total Cost
Total hours run/year
Energy used/year
Rate $/kwh
Continuous
$10784
8760
19,710 kwh
$.55 kwh
Intermittent
2000 kwh
$1.26 kwh
(a) Capital costs spread over life of component at 11% discount
rate.
-20-
The various components of operation in Table 11 can be
inspected to determine sensitivity to changes in the $1.26/kwh
price derived for intermittent generation:
Capital cost:
Fuel:
A less expensive diesel or gasoline system may be
installed for as little as $2000 if few accessories are
needed, but expected life is shorter and fuel and repairs
will increase. No net savings are likely. More
expensive systems are expected to offer savings in fuel
and repairs. Changing the discount rate on term will
have impact on the net cost; in general the more use made
of the component the less the interest paid.
Increase cost 25%, increase rate 6%.
This represents the largest single cash expense. The fuel
price used, $2/gal, probably represents an average for
those areas served by gen sets, although significantly
higher prices can be found. At $4 gallon, the rate
increases to $1.68/kwh. Fuel costs represent a larger
portion of total costs of continuous operation.
Small gen sets, being mostly air cooled and very noisy, do
not lend themselves to waste heat recapture, hence no
credit is given for space or water heating. A gen set
will keep the building warm where it's located, but such
a space is unsuitable for habitation.
Some gas driven gen sets have been fitted with waste heat
recapture equipment and sound attenuation and are suitable
for installation in close proximity to living space.1l7
None, however, are known in these small sizes.
If the homeowner heats with oil at $2/gallon, and 30% of
engine input energy is recaptured, the rate drops 9%. °
Operation and Maintenance:
No owner labor costs have been included for either
installation or routine maintenance but are included in
the major overhaul item. Regular operation also entails
considerably more work than merely turning on a switch.
Owner time spent on fueling, startup, shut down, changing
oil, monitoring, etc., depends on the system, but may
a2 te
range from 20-100 hours/year for intermittent usage. The ratio of labor to power generated decreases with greater
usage. While this labor does not need to be highly skilled, it must be attentive. There are many things that will destroy an engine, and most are innocuous, i.e. leaky
oil seal, water in fuel. Although protective devices
help, they can't replace vigilance.
There is also a very real risk of fire and personal injury
from gen sets. Carbon monoxide poisoning is more common
from improper use of portable gasoline gen sets. Gas and
noise pollution from all engines is a widely recognized
health hazard.
Addition of transportation costs for emergency repairs can
easily make O&M of these sets extremely expensive. At 40¢/
lb transport in a small plane, one way, a 3501b gen set
gets costly to fix. To allow more flexibility in repairs,
a small portable gen set becomes practical, although the
redundancy increases capital costs. This is the same
dilemma that all utilities face, i.e., providing emergency
backup power.
Including owner labor at $15/hour increases rate 12-60%.
Cost of fire risk, personal safety, environmental
degradation, etc. cannot be assessed.
Including one round trip plane fare to the machine shop for
$280 increases rate 11%. Bringing a mechanic from town for
about $600 increases rate 25%.
A failure to fix properly may shorten life to one year,
raising rate 26%.
3) Small settlement:
Several houses living in relative proximity often share
generation costs, with the motivation of reduced operating
expense and greater reliability of larger gen sets. A major
difference from a full fledged small utility is in the distri-
bution system. A small system uses only 115/230 volt rather
than high voltage lines, and is limited to rather short
distances.
-22-
Such a system can vary greatly in size and operating costs.
In the larger sizes, efficiency and reliability approach those
of the smaller diesel fired utilities and consumer cost can be
less since a large distribution system is avoided. In the
smaller sizes, costs are slightly better than for a single home.
In all cases, the considerable labor required for operation will
have to be assigned a cash value to keep the system economically
viable.
Often an installation is designed for a single consumer such
as a school or store, with off hours' power delivered to homes.
If the large consumer is shut down at times, availability of
power to homes is less than with separate generators. Costs of a
well run system lie between those of village scale utility
($.25-.50/kwh) and those of a single home generator ($1.00 and
up)
Summary:
Costs and patterms of residential energy use vary substan-
tially within Alaska, illustrated by analysis of Anchorage,
rural, and remote home consumption. Since a Total Energy
System produces limited amounts of heat and electricity, each
of these end uses must be characterized to predict the useful-
ness of any TES.
Analysis of energy end use in Anchorage homes, the only
region with sufficient data, revealed that the ratio of
electrical to total energy varied from .08 in January to .12 in
July. Annual ratios in other regions were also in this range,
where electricity is available at modest rates. This indicates
the minimum efficiency requirement of candidate thermal
machines before heat heat is wasted in supplying the necessary
electricity.
The costs of supplying energy are a function of distance
from population centers, with Anchorage having cheapest thermal
and electrical rates. While remote thermal costs are generally
modest the cost of electrical generation with small diesel sets
is exorbitant, usually over $1.26/kwh.
— 3
,
V FREE PISTON STIRLING ENGINE-TOTAL ENERGY SYSTEM USE IN ALASKA
A) System Concept: Manufacturers' Claims
The generator proposed by MTI will be attached to the heating system of a building. The furnace will use whatever fuel is normally available to supply high temperature heat to the FPSE. Between 15-25% of this heat energy will be converted to electricity by the engine, and the remainder will be passed
into cooling water, which becomes heated to suitable tem-
perature for space heating and domestic water heating,
(125-175°F). This heat can be used immediately or stored in
hot water tanks for a couple of days.
The FPSE is no louder than a domestic furnace and is suitable for operation in a living space. Since external com-
bustion is used, environmental degradation will be no greater
than with any furnace. Safety is better than a diesel genera- t6E<
The FPSE can be used as a stand alone system, or be con-
nected to other FPSE's, or the utility grid.
The power generated is 110v, 60 Hz and meets requirements
for normal household usage. Maximum output is 3kw; minimum
power is dependent on heat input.
MTI has developed estimates of unit costs for various
production volumes, as listed below.
Table 12 FPSE Costs
Production _..--.-Manufacturers Cost Retail cost Quantity FPSE Gas Combustor PSE + Combustor § FPSE_
3000 units/y $1145 $125 $1270 $1545
10,000 937 102 1039 1265
75,000 823 90 913 Aeleicl:
200,000 132 82 835 1015
The retail price is estimated by MTI to be approximately
130-135% of manufacturers cost (dependent of course on retail
location).
The installation cost is in turn dependent on how inter-
changeable the unit is with other standard home components.
The gas fired FPSE is a single skid mounted unit requiring
only standard gas and chimney connections, water connection
to the hydronic heating system, and electrical line to the
main breaker panel. Installation in new construction is
estimated to be about $200.
=24=
While the expected life of prototype units is estimated
at 10,000 hours, life span of production FPSE is estimated to
be 50,000 hours. Units destined for remote locations may be
designed for a life of 75,000 hours by simply lowering the
head temperature, with a slight decrease in performance. It
is expected that the technology will mature to yield even
longer life spans.
Maintenance of the engine is essentially zero, as the unit
is hermetically sealed. It may be possible to factory rebuild
a unit, since the head is the component most likely to wear
out.
The engine is easily started, after starting the combustor,
and is unaffected by temperatures. The cooling solution
would likely be a glycol-water mixture to prevent freezing.
These general characteristics will be used to develop
market estimates for Alaska. Sensitivity of the market areas
to changes in these characteristics will form the basis of the
design criteria.
B) Heating Systems
The TES concept implies that all the home heating needs
are met through use of the FPSE/TES machine, which logically
would supplant the normal home furnace and water heater. The
problem then is to describe a "normal" home furnace. Home
heating requirements, including hot water and often cooking,
are met by a potpouri of devices, systems, fuel types, and
attendent costs.
1. Present systems
Heating systems can be divided into central heating
systems and radiant heaters. Central heating systems,
generally called furnaces, are characterized by a heat
distribution system (forced air or hydronic), greater
controllability, larger size and cost, and are generally
located away from living space (basement or closet).
Their thermal efficiency is greater than space heaters.
The distribution system requires electric fans or pumps,
and is thermostatically controlled. Sometimes domestic
water is heated by the furnace, especially with hydronic
distribution.
There are production furnaces for all fuel types, but
only a few are interchangeable. Central heating systems
are installed in almost all new construction. Forced air
distribution is cheaper to install, and because it can't
freeze if the power fails, is predominate in very rural
locations. With forced air systems a separate water
heater is usually required.
-25-
Hydronic systems are generally preferred for large
homes.
Radiant heaters (space heaters) do not have a
distribution system but rely on direct radiation to heat
the surrounding space. Usually no electricity is required
for operation, thermal efficiency is generally lower than
for furnaces, and output is much less controllable.
Oil pot burners, wood stoves, propane and catalytic
kerosene heaters are examples of radiant heaters. They
are used as supplemental heaters in new construction and
as main heaters in remote homes without access to
electricity. Size, construction, and costs are consider-
ably varied. Some heaters are equipped with water heating
devices. The central position occupied by many heaters
allows for use in some food cooking tasks, although there
is usually a separate range or cook stove.
At one end of the cost/complexity scale would be a
remote trapper's cabin with barrel stove, Blazo can
chimney spacer, and single wall stovepipe. The stove also
functions as water heater and cookstove and represents a
cash investment of under $100 exclusive of labor. More
representative of modern construction is a home with an
oil fired boiler ($1200-2500), hydronic distribution
system ($600-4000), chimney ($500-1500), control system
$50-200), fuel storage ($300-1000), and water heater
($150-500). Thus the total installed cost might average
$2800-9700. A similar gas fired system would have a less
expensive boiler (save $300-400) and no oil tank (save
$300-1000) but would need a gas line installed. A wood
boiler is usually more expensive than oil ($100-300) but
uses a wood shed instead of an oil tank. Some high tech
gas furnaces require merely a vent instead of the chimney
system necessary with most solid fuel burners.
Forced air systems are normally less expensive than
hydronic, by about 25% in most mid-sized homes.
Distribution systems are also dependent on furnace
efficiency, since a high efficiency furnace will deliver
heat at lower temperature, requiring larger distribution
system.
Radiant heaters, by eliminating the distribution
system, are cheaper still. Wood stove costs range from
$400-1400, and after adding chimney and water heater the
installed cost is between $1000-3300, not including wood
shed.
Obviously, a "normal" heating system can't be easily
specified, and must take into account all accessories. A
TES entering the Alaskan market should have a wide range
=26—
of thermal outputs, flexibility in heat distribution systems, water heating capability, and range in size
and prices for each different fuel. Several different
models apparently are required.
2) FPSE/TES furnaces
The gas fired heater for driving the FPSE has an
estimated manufacturing cost of $82-125, depending on
production volumes, and might translate to a retail price
of $150-500 which would be comparable in function to a
gas boiler at less than half the cost. An accessory
burner would be included to increase thermal output to
meet the home's load. A similar oil burner for the FPSE
is expected to be $50 more expensive... A wood combustor
suitable for FPSE use will require temperatures and
controllability beyond the capabilities of radiant heaters
and consequently is expected to be comparable to a wood
fired furnace in size, cost, and heating function. A mid
range may be 1000.pounds and $2000.
Although this is well over the cost of a radiant
heater it also has increased functionality. Availability
of FPSE electricity enables use of distribution systems
in remote homes, as well as running water. Still, it
seems reasonable to expect that a wood combustor capable
of providing the high temperatures, controllability, and
efficiency to match the FPSE will cost more than a
standard furnace of similar output, at least in the
smaller sizes.
An additional feature that may be feasible with TES
use is heat storage. Heat rejected by the FPSE during
production of electricity may not be immediately needed,
and storing this energy as heated water may make economic
sense. Since the FPSE uses water (or glycol solution) for
cooling, it is relatively simple to reject heat into
insulated water tanks. Space heat and hot water are then
available on demand without increasing output of FPSE,
thereby increasing efficiency and heating capacity.
Determining amount of storage is a site specific engineer-
ing task.
This additional water storage might add $500 to the
combustor price. In the case of the gas boiler, this will
bring the price up to that of similar gas furnaces (about
$1000), and for the wood combustor, the price is increased
$500 more than equivalent furnaces, to total $2500.
==
B) Energy Balances
1) Single Structure
Energy flow is diagramed for a structure in Figure l. Simple First Law energy balance applies, with or without
use of FPSE. All energy is assumed to enter the structure either as furnace fuel or as utility electricity.
-28-
Figure 1 Energy Flow Diagram, FPSE/TES
Energy balances: DmOH U+F
U+F-S-W =
S+R+L
E+H+W
I-S-W
E+H+U+L
-29- many cq ws on i] Fuel supply
Stack loss
Heat supplied to building by FPSE ; Electricity generated by
FPSE
Electricity supplied by
utility (pos) or by
FPSE to utility (neg)
Heat normally lost
through building
envelope
Heat generated by FPSE
but not needed in
building
Total energy input
Heat output of furnace, input to FPSE
Building heat by-
Passing FPSE (stack
robber and stove
losses)
Although Figure 1 over simplifies energy flow, it does allow
easier understanding of the Total Energy System workings and relative
economics. Several selected installations of FPSE/TES can be easily
analyzed and energy flows identified:
Case l: Structure has no need of heat, is merely a generator shed.
FPSE is run full time, generating a maximum of 26,280 kwh (All values
in 106Btu/year)
Thus:
Case 2a)
2b)
E = 26,280 kwh = 90 Total electricity generated
U = -90 Electricity supplied to util.
H=Q=0 No heat used
E = .25 Efficiency = 25% for FPSE
R = 90/.25 = 360 Gross heat supplied to FPSE
R = E+H W = 90+0+W
W = 270 Heat wasted
F = R+S+L
S+L = .3F
R= .7F Furnace efficiency = 70%
F = 360/.7 = 514 Total fuel input
I = Ut+F = 424 Net energy input
Structure uses 1450 gallons of fuel, and 5000 kwh, supplied
by utility
F = (1450 gal) (138000 Btu/gal) = (200x106Btu) = 200 U = (5000 kwh) = (17x106Btu) = 17
I = U+F = 217
R=E=H=W=0 No use of FPSE
S = .3F, L = .7F 70% furnace efficiency
S = (.3)200 = 60
Q = U+F-S-W = 17+200-60-0 = 157
Same structure and use as a) but electricity is produced by
FPSE with no utility connection.
E = (5000 kwh) = 17
Qi.= 157
u=0
R = E/.25 = 68 = E+H+W e = .25 for FPSE
68 is less than Q; therefore there is no waste
from FPSE; W = 0.
H = R-E-W = 68-17-0 = 51
L = Q-E-H-U = 157-17-51 = 89 Heat bypassing head is
S = .3F increased to meet demand
F = .3F+R+L = 224
S = 67
I = FU = 224+0 = 224
Although the usuage of heat and electricity remain the same,
the total energy input increases by (U/.7-U), as that
energy is lost up the stack. This loss is less than that
from original generation and distribution of utility power.
-30-
Case 2c) FPSE is run full time, generating 26,280 kwh, and 270 x
106Btu of reject heat (Case 1). House requires 5000
kwh (17x106Btu) and normally uses 157xl06Btu of total
energy (Q=157).
E= 26280 kwh = 90 Electricity generated U = 17 - 90 = -73 Electricity to utility
Q = E+ H+ U Heating load
L=0O All bldg heat thru FPSE
H = Q-E-U = 157-90-(-73) = 140 Heat rejected for blg use
R = E/.25 = 360 FPSE 25% efficient
W = R-E-H = 360-90-140 = 130 Heat wasted
F = R/.7 = 514 Furnace 70% efficient
From Case 2a) F was 200, thus an additional 314 x 106Btu is
required to feed 21,280 kwh into the grid. This represents a
gross efficiency of 23%.
Case 3a) FPSE runs full time and structure has need of all heat
generated and 5000 kwh.
E = 90
U = 17 - 90 = -73
w= 0
H = 270
Q = E+ H+ U- = 90+ 270 -73 = 287
Q=U+tF-S-W S = .3F
-7F =Q-U+W
F = (287 - (-73) + 0) /.7 = 514
3b) Structure has heat load identified in 3a (Q = 287), and
uses 5000 kwh of utility power (U = 17) and does not use FPSE.
Q=U+F-S-wW : S =.3F, w= 0 F = (287-17) /.7 = 386
The difference in fuel consumption is 128 x 106Btu (928 gal)
which was used to produce 90 x 106Btu of electricity
(U, - U = 17 - (-73) = 90). The thermal efficiency of
geherattng 5000 kwh in Case 3a is 708%.
-31l-
Case 4a) Structure uses 26,280 kwh of utility electricity and
Case
Cas
2)
has a normal heat loss of 360x106Btu.
U = 90
Q= 360 = UtF-S-wW w= 0
F = (360-90) /.7 = 386
I = 476
4b) Same structure as 4a) but all power produced by FPSE with no utility tie.
U = 0, E = 90, Q = 360
E/Q = .25 This is not greater than efficiency of FPSE,
therefore W = 0 (theoretical)
Q=U+F-S-W
F = 360/.7 = 514
I = 514
The fuel input of b) is 128 x 106Btu greater than a), which
is used to generate 90 x 106Btu of electricity, for an effi-
ciency of 70%. The net generation efficiency is the same
whether power is used inside or out of the building, as long
as all heat is used. The 70% efficiency will increase in
direct porportion to any increase in furnace efficiency.
The total energy input, I, is only 38 x 106Btu greater, which
will later be compared with energy requirements of utility
generation.
e 4c) Assume 5% of electricity generated has no correspond-
ing heat demand, since E/Q is right at maximum efficiency.
That is, W = .05 (E+ H) = .05Q since U = 0
-7F = 1.059
F = (1.05) (360)/.7 = 550
Increase in fuel consumption is 35 x 106Btu over 4b). This
increase is about 7%, (5%/.7), and is valid only for maximum
use of FPSE. Proportionately less use of FPSE will see less
fuel increase for non-correspondence of loads.
Utility Energy Balance
To figure a meaningful comparable total energy balance, the
energy used to generate the utility power must be
considered. Different heat rates are found with different
prime movers:
1) Large diesel at good load factor 10,000 Btu/kwh (34%)
2) Medium diesel plant 11,000 Btu/kwh (31%)
3) Small diesel plant, .5 load factor 20,000 Btu/kwh (17%)
4) Large combined cycle turbine 8,000 Btu/kwh (43%)
-32-
In addition, utilities see from 6-10% line loss in the
distribution system. Consequently a typical village diesel
utility can have a net fuel to meter efficiency of 23%.
Thus in the previous example Case 2a), where 5000 kwh was
supplied by the utility, it required a total fuel input of:
T = 17/.23 = 74 (million Btu)
If this amount were added to the home's fuel input, the total
energy requirements of the home become:
I = 200 + 74 = 274 (million Btu)
This compares with the total energy input of 224 x 106Btu of
case 2b), using a FPSE/TES.
Similarly, in the full usage Case 4a) the energy input to
generate 26,280 kwh is 391 x 106Btu, and the building's total
energy use is increased to 777 million Btu. The same amount
of electricity and heat used by the building can be generated
by the FPSE/TES from only 514 million Btu as in Case 4b).
D) Homeowner Use of FPSE/TES
A homeowner with a FPSE/TES will have different use patterns
than he would using a diesel gen set. Power supply would be
continuous as long as the furnace is operating. The furnace
would be more controllable as to burn rate, and would be
responsive to both heat and electricity demand. In periods
of low heat and electric demand the furnace can be set at low
output or turned off, while at times of high electrical
demand the furnace is turned up to generate the required
power. Heat is rejected into cooling water, which can be
stored in large insulated drums if hot water or space heat are not immediately needed. If more heat is needed than is
being produced from the engine, heat is taken from storage.
If still more heat is needed, the furnace is turned higher,
until desired output is reached, with excess heat bypassing
the FPSE.
If more heat is produced than is needed or can be stored, it
is rejected outside. It is only in this case that reject
heat from the FPSE is wasted, and this case is likely to hap-
pen only on hot summer days when electricity usage is also
minimal.
As seen in Section Iv, the ratios of electricity to total
energy used remain relatively constant from month to month,
at least in Anchorage. Instantaneous ratios of course will
vary considerably, but utilizing storage for heat should make
the ratio fairly level. For analysis, it will be assumed
that only 5% of the electricity generated by a FPSE in a home
will not have a corresponding demand for the reject heat when
the TES is operated at close to peak efficiency.
=33=
E)
The fuel used for the generator is that normally used by the home. The FPSE unit may be the same in all applications, but
the combustor will be specifically designed for the fuel
used.
The 3 kw available power can be used with similar restraints
as if produced by a diesel gen set; some load management and
motor protectors are advisable to prevent simultaneous
starting of large motors.
A certain amount of electricity is available for consumption
whether it is used or not. This is a maximum of 25% of the
thermal requirements of the home (space and water heating),
and may vary from 3500 to 15,000 kwh per year for a normal
home. All of this is not prime power - i.e., available on
demand without regard for load control, and much of it will
either be unused or applied to resistive load dumps for
heating. Consequently, assessing a cost per kwh becomes dif-
ficult and cost per year becomes more meaningful.
The FPSE has an estimated life of 50,000 hours. If operated
continuously this would be 5.7 years, and if used 16 h/d,
life span would be 8.6 years. During this period, main-
tenance on the engine would be essentially zero, since the
engine is hermetically sealed. There is no lubricant to
change, filters to replace, or adjustments to make. The
heater head could be periodically checked for cleanliness or
damage, as can the cooling heat exchanger. Simple cleaning
is the only repair, and that should be no greater than would
normally be required by any furnace. Maintenance on the
additional hardware should be comparable to standard furnace
and electrical controls. If $500 additional hardware is
needed, $50/year maintenance will be charged.
Economics of FPSE/TES Use
Potential applications of FPSE/TES are extremely varied as
to displaced costs. The capital and operating costs of the
system are dependent on several very basis assumptions.
This section investigates a range of factors affecting
annual operating costs. Table 13 lists various factors and
their estimated costs, and relies on the following assump-
tions:
1) Costs and life spans, ("Interval"), assumed for FPSE
reflect longer life and reduced costs as production
matures. The capital cost here is derived from Table
12, with 3000, 10,000, and 200,000 units/y representing
limited, full, and advanced productions. The costs are
the retail estimates plus $200 installation charge, and
are listed under the heading Unit Cost. The limited
a=
2)
3)
4)
5)
6)
production run will probably not have reached the
design goal of 50,000 hour life, say only half that,
while advanced productions will have exceeded it. Level
annual capital costs are calculated at 11% discount
rate, and are listed under Annual Costs.
Only the cost of the combustor/heating system that
exceeds cost of conventional system is included. For
wood combustors, this premium is $500, but gas and oil
combustors will have no premium. A stand alone
generator, requiring no heat storage, will be charged
the actual combustor price; $2000 for wood, $500 for
gas, and $550 for oil. In stand alone systems, a
generator shed and fuel storage must also be included and
the $2000 capital cost at $330/year will be added for
oil. Wood and gas will be charged $1000 and $165/year.
Combustors will be capitalized at 11% annual discount
rate.
Energy production and consumption for degrees of FPSE
usage were examined in Section C, Energy Balances.
Cases 4a), b), and c) illustrate the Full Usage energy
requirements, and the difference between 4a) and c) is the extra fuel used; 550-386 = 164 x 106Btu.
Home usage, illustrated in Cases 2a) and b), reflects
heat and electricity usage for an "average" rural home.
Additional fuel requirements from using FPSE are 224-
200 = 24x106Btu. The additional fuel requirements are
not adjusted for fuel used by the utility.
Prices of this additional fuel consumption are
calculated from oil at $2/gallon, wood at $100/cord, and
gas at $2.2/mcf.
The two maintenance rates for the FPSE assume that
either:
a) some repairs can be made to system (which would
logically result in a longer lifespan), or;
b) nothing can be done to a hermetic unit, short of
sending it to the repair shop in exchange for a
rebuilt unit (reflected in cost and lifespan).
Annual maintenance on the heating system is 10% of the
additional cost attributed to the FPSE/TES for full use,
and 6.7% for home use.
Labor expenses for fueling TES are no greater than for
old stove, hence no additional labor is charged. For a
stand-alone generator, all fueling labor must be
charged. Oil will need pumping, changing filters, etc;
wood requires 1/2 hour/day for loading and cleaning
ashes; gas requires no Taber.
7) The annual cost is figured for different types of usage. Using
a FPSE as a generator, without any use as a heating system, implies
operation of 8760 hour/year producing a maximum of 26,280 kwh.
Large TES is used continuously producing the same amount of
electricity, but most heat generated is used by the building
(see 3 above). Home TES is used about 5840 hour/year, capable of
generating 17,520 kwh but only producing the home's needs of 5000 kwh (see 3). This methodology and cost assumes no connection to utility service.
Table 13 3 kw FPSE/TES Itemized Generation Costs
=-Annual Costs____ Unit Gener Large Home
Item Interval Cost ator TES TES
1) FPSE Cap Cost
a) limited prod. 25,000 hr. $ 1745 $ 744 $ 744 $ 537
b) full prod. 50,000 1465 361 361 273
c) advanced 75,000 1215 aet 227 181
2) Added cost of
furnace
a) oil
i) new home 130,000 500 70 61
ii) stand alone 130,000 2550 406
b) wood
i) new home 130,000 0 0 0
ii) stand alone 130,000 3000 443
c) gas
i) new home 130,000 0 0 0
ii) stand alone 130,000 1500 235
3) Additional fuel
used
a) oil $2/gal 7848 2377 348
b) wood 100/cd 2734 872 128
c) gas 2.2/mcf 1131 361 53.
4) Maintenance on
FPSE
a) some repairs 9,000 hr 300 300 300 200
b) no maintenance 0 0 0 0
needed
5) Maintenance on
heating system
a) generator and year see 2) 10% 10%
large TES
b) Home TES year see 2) 6.7%
6) Labor for fueling
a) oil 15/hr 300 0 0
b ood 5/hr 2750 0 0 8} gas }27pr 0 0 0 -36-
Using the itemized costs of Table 13, the total operating costs of a
building using a FPSE/TES can be compared to one without such a system. The methodology used in Table 14 is to choose a particular cost option from each of the components, add them together and arrive at a total annual cost for each type of FPSE usage. A corresponding annual
cost of existing alternatives is also estimated, and the cost per kwh
is calculated.
The payback period in years is the capital cost of the FPSE system minus the alternative, divided by the annual savings of the FPSE. If the FPSE is cheaper in both capital and operation, an instant payback
is noted.
Table 14 FPSE/TES Total Annual Costs
Stand Alter- Large Alter- Home Alter- Ex Components Alone native TES native TES native
1 la,2aii,3a, $/yr 9853 10,784
4a 5a,6a $/kwh .37 «55
Net capital cost: $ 4295 6,000
Payback: Instantaneous
In this example, an early model FPSE (la) is run on oil as
a stand alone generator in continuous duly (2aii, 3a,5a,6a).
Repairs to FPSE are budgeted (4a). The alternative is a 3kw
diesel examined in Table 11. This scenario is one of the most
disadvantageous for a FPSE; highest costs, most expensive fuel,
shortest life, and no heat utilization, yet is is still
cheaper in both capital and operating costs than the diesel
alternative, and payback is instantaneous.
2 la,2b,3b, $/yr 7271 10,784 2036 10,784 960 2519
4a,5a-b,6b $/kwh .28 <59 -08 55 -L3 1.26
Net capital cost $ 4745 6,000 2245 6,000 2245 6000
Payback: instantaneous
This example shows an early model FPSE fired by a wood
combustor. The reduction in capital cost is seen by substitu-
ing the combustor for the building's furnace. Credit for the
reject heat shows the value of the TES approach. Lower load
factor shows increase in rates between large and home TES.
In all cases, net capital cost and rates are consideraby lower
than the small diesel alternative.
—a7=
Table 14 (continued) Stand Alter Large Alter Home Alter Ex Components Alone native TES native TES native
3 la,2ci,3c $/yr 1105 1577 590 300
4b,5a-b,6c $/kwh 04 -06 12 -06
Net capital cost $ 1745 1745
payback: year 3.7 none
This example shows an early model sealed FPSE (no maintenance) running on natural gas. A large TES has a favorable payback
compared with urban utility rates, but the home use is more
expensive, assuming there is no initial utility hook up
charge, and flat rates are charged.
4 lb, 2ci,3c $/yr
4b,5a-b,6c $/kwh
Net capital cost $
Pay back year
722 1877 326 300
03 06 +07 -06
1465 1465
84 none
Full production FPSE has payoff under one year in full use,
but is not economical yet for small home use compared to urban
utilities.
5 lc, 2ci,3c S$/yr
4b,5a-b,6c $/kwh
Net capital cost $
Pay back year
The advanced model FPSE running on gas shows the lowest
capital and operating costs and even shows a good pay off
for small homes vs.
6 lc,2bi,3b $/yr
4b,5a-b,6b $/kwh
Net capital cost $
Payback year
urban utilities.
588 a 234 300
+02 -06 -05 -06
1215 1215
-6 335)
EZES 6570 403 1250
05 25 -08 225
EUES LIES
«23 -47
Advanced models of wood burning FPSE/TES show payoffs of only
a few months when compared to rural utilities, even if no
hookup fees are assessed.
-38-
In all exampies of Table 14, costs of FPSE/TES use are less than
for comparable alternatives. All cases are less than small
diesel generation, and wood fired TES is less than rural
utilities. The 2¢/kwh projected cost for advanced long life
gas fired FPSE/TES in steady state mode is less than any other
available electricity. Consequently, the use of FPSE/TES can
theoretically compete in any part of Alaska, if the given
assumptions are accurate.
F) Sensitivity Analysis
1) Fuel price
Operating costs are dependent on fuel type in two ways:
The combustor capital cost influences the annual cost; and
of course the actual fuel expense. Combustor costs were
examined in the Heating Systems section. Fuel price can
be expressed as a price per million Btu, rather than a cost
per gallon or cord. Since the use rates assumed additional fuel consumption of 164x106 and 24x106 Btu for Large and
Small TES, the effect of fuel price can be easily calculated,
and is shown in Table 15.
2) Furnace Efficiency
Consumption of fuel is less dependent on the efficiency of the
FPSE than on the efficiency of the furnace for all TES appli-
cations with use of reject heat. The maximum efficiency of
the FPSE in producing useful energy was limited to 70%
(Section C) by the furnace efficiency. Steady state modern
furnaces show higher efficiencies, up to 95% for gas, for
space heating applications, but would not be this efficient
for producing usable heat for the FPSE. Any decrease in
stack loss will lower the system's fuel costs, even if the
added heat only goes to space heating uses.
3) Power Used
Annual cost/kwh decreases with increasing load factor as seen
in Table 14 and has greater effect in the early systems
and for gas fuel, where the capital costs are the largest por-
tion of the total costs.
4) Cost of FPSE
The assumptions of engine cost/life are the most critical to
the total costs. The limited production scenario is half the
life of manufacturer's production system estimates. System
cost is more important in small usage.
-39-
5)
6)
7)
8)
FPSE Maintenance
Only one scenario required engine maintenance, and that was a
modest amount. With a sealed engine, this factor is included
under system life. The economics of rebuilding FPSE have
not been analyzed.
Heater Cost
The capital and maintenance costs of the heater are dependent
on what heating system is being displaced. Although a net
cost, less than the total, was assigned, there may also be net
savings if the new system is more efficient. This cost is
often a very significant portion of the total and will have to
be separately addressed for each installation.
The extra cost assumed for the wood furnace is the reason
wood FPSE generation costs are not much less than oil for
small outputs. The equivalency of function between oil/gas
TES and similar furnaces is a major factor in their economic
attractiveness.
Controls
An unknown factor in both the FPSE and heater cost is the spe-
cific controls required, which were assumed included in these
components. Since interface between TES/living space will
change with each installation, some adaptability of controls
may be required. Costs and maintenance are likely to be a
substantial portion of system cost. Specific controls will
be required for operation parallel to a utility grid.
Fueling Labor
Labor involved in keeping the fire going is essentially zero
for gas, will involve some cleaning and pumping for oil, and
will involve lots of attention with wood. No fuel labor costs
were addressed in the TES examples, which is probably valid
for oil and gas, but the extra wood consumed will require
extra labor. The type of wood delivered has large effect
on labor; split cordwood is certainly easier to use, and
more expensive. The value of this labor is usually not
considered for home heating systems, but would become a
large factor for full scale generation, especially if
constant stoking were required. Fueling labor would be
valued differently for a home TES compared to a stand alone
generator or commerical TES.
-40-
9)
G)
Other factors
If the FPSE is unsuitable for installation in a living space,
because of noise or safety, then additional capital expenses
will be entailed in constructing an external furnace room or
generator shed. Since the engine is water cooled, most of the
heat can still be captured, and operating costs will be
increased only the extra fixed and maintenance costs attribu-
table to additional construction. Additional inconvenience
in use may also be observed, resulting in lower consumer
acceptance.
Conversely, the FPSE may have greater value because of reduced
pollution. This is likely to happen, especially with wood and
other solid fuels.
If the FPSE does not meet minimum safety requirements, at
least comparable to a small diesel, it will not likely be
manufactured.
The previous analysis does not extend to cogeneration, which
is discussed later.
Comparison of FPSE/TES with Alternatives
Where the only comparison is a 3kw diesel gen set, almost any
set of circumstances shows the FPSE/TES to have considerable
advantage. Wood fired FPSE/TES are less expensive than rural
utilities, and gas fired units are cheaper than urban
utilities depending on load.
For capital cost, net fuel cost, and maintenance, the FPSE is
superior. Pollution and noise are possibly less in the FPSE.
Long term maintenance free service is possible with a FPSE
which is extremely difficult with small diesels.
The size of the FPSE will likely decrease with system
maturity, as will the TES. Projections for early FPSE
indicate a weight of about 350 lbs, which is comparable to a
diesel set of similar size but heavier than a gasoline set.
A large model wood combustor, exclusive of water storage,
might weigh 1000 lbs., comparable to equivalent wood fired
boilers but more than a radiant stove. Consequently, the
size and weight would eliminate the wood fired FPSE/TES
from competing in the lightweight portable generator class.
However, when total home facilities are compared, the FPSE/
TES will likely be much smaller than the combination of gen
set, generator shed, fuel tanks, furnace, and water heater.
The natural gas fired combustor is quite small and would
weigh under 100 lbs including accessories. The oil fired
version would be similar. These fuels can give a TES size no
larger than comparable oil or gas furnaces.
-41-
In comparison with a larger diesel or utility, quality of power must be considered besides price. Cost of power can be
significantly less with an independent FPSE, depending on assumptions and utility prices, but quality may be signifi-
cantly diminished. Demand is limited to 3kw, single phase, and higher voltages, while theoretically possible, will
entail greater capital cost. Conversely, a FPSE user with
cogeneration or several engines may have greater reliability
than the utility. These factors can not be assigned uniform
values.
The capital cost portion of a FPSE/TES system can be signifi-
cantly less than the new consumer hookup costs in a utility.
Each new consumer must be assigned a portion of generation and
trunk distribution facilities as well as any specific distri-
bution service. Matanuska Electric had a cost of over $6200
for new distribution plant per new consumer in 1982 , while
rural utilities often exceed $15,000 per new consumer.
Converting these costs to compatible numbers for comparison is
often difficult, as many utility systems are financed by
grants or subsidized loans and involve different amortization
terms. In rural utilities, the operation and maintenance
portion exclusive of capital payback usually exceeds total
annual costs of a FPSE/TES in same environment.
-42-
vI ALASKAN MARKET FOR RESIDENTIAL FPSE/TES
The extent of the market in Alaska for home FPSE is simply
defined as the number of residences where the installation of a
FPSE/TES will have a total annual cost less than any other alternative. This derivation depends on the chosen assumptions
(as in Table 14) and further assumes that all other factors are
equal.
Market penetration, defined as actual sales or installa-
tion is the important criteria to the manufacturer and is
considerably different from the definition of the extent of
market. Many factors other than potential savings must be
considered, such as available cash, marketing efforts, subsidies,
competition, consumer preferences, etc. Methods used for
analyzing market penetration are complex, usually requiring considerably more data than is now available. 19 Market penetra-
tion projections will be more meaningful if conducted following
actual demonstration in targeted applications.
The following market analysis determines the number of homes
for which use of FPSE/TES would be the least expensive means of
providing electricity, but does not investigate whether these
households have the means to afford it by themselves. This
criteria, however, is difficult to apply in light of historical
and projected rural electrification policies, since the State of
Alaska through various grants, subsidies, and consumption is the
major direct supporter of many rural electric utilities (see
Section VII D, Effect of Subsidies). This analysis assumes that
electricity will continue to be provided and examines the
economics of this service.
Defining the potential Alaskan market requires estimating
the number of homes with certain factors pertinent to operation
of FPSE/TES. The intrinsic variables such as engine life and
cost must rest on given estimates until demonstrated, but the
main external variables of fuel cost and utility rates can be
defined for all areas of the state, and will form the basis for
determining the extent of market for residential systems.
Table 15 includes estimates of numbers of residences that
would economically benfit from use of FPSE/TES of either early,
mature, Or advanced production.
Data from a wide variety of sources was used in compiling
this table, with conflicting estimates, definitions, methodologies,
dates, reliability, etc. When conflicts arose, the data from
actual field surveys was preferred if fairly recent. Estimates
are given for each census district and the state total.
-43-
Assumptions and specific methodologies included:
1) a) Number of housing units taken from 1980 census and 1981
state update, with 1981 the date chosen as being the
most recent for which reliable data is available.
b) The number of occupied housing units was also noted, from
same sources.
2) a) The number of residential utility consumers quite often
exceeded the census count of occupied housing units,
sometimes even more than the total housing units.
b) Households without utilities here is la-2a
c) Occupied homes without utilities is lb-2a
da) Actual homes without utilities is a judgmental choice
of b,c, or something more rational, realizing that there
are always some remote homes without utilities, but a
modern city will have very few such homes.
3) Number of households falling under each utilitiy tariff
(>26¢/kwh, 11-25¢,€10¢) is derived from the latest APUC
schedule and assumes the gross tariff, exclusive of
Power Cost Assistance, but including any unidentified
federal or state subsidies. All homes without utilities
are assigned cost > 25¢.
4) a) “Homes burning oil" is determined from census.
b) Range of retail price per million Btu is determined from
1983 Community Survey7?. Higher heating value of 138000
Btu/gallon is used.
c) The FPSE/TES cost in ¢/kwh is calculated using data of
Table 13 for a small system.
5,6) The same procedure is followed for wood and natural gas.
Wood is assigned a value even if the homeowner calls is
free. Wood is given a heating value of 18.8 x 106Btu/
cord. Gas is 1000 Btu/cubic foot. Bottled gas will
have costs closest to oil and is included there, while
coal is included with wood. Electric heated homes are
subtracted from estimate as FPSE can not compete.
in) The potential market at each assumption of engine
development is a function of the fuel cost and competing
cost of electricity. Judgment must be used for each case
as the highest fuel cost does not always correspond with
the highest or lowest electricity cost. In cases where
the FPSE rate is just higher than the utility rates, it
was assumed that a certain portion of the larger
residential consumers will find it cheaper to use an
advanced FPSE because of better economics of increased
use. -44-
Table 15
No. of residences
Occupied yr-round
Res Util Consumers
la) - 2a)
1lb)-2a)
Res w/o utility
Cost of Power>26¢/kwh
11-25¢/kwh
<10¢/Kwh
Homes with oil heat Oil Cost $/106Btu
i) FPSE ¢/kwh,early
ii) smMature
Lit) , advanced
Heat w Solid-fuel Fuel Cost $/106Btu
i) FPSE ¢/kwh,early
ii) »Mature
iii) , advanced
Homes with Gas Heat Gas cost $/106Btu
i) FPSE ¢/kwh, early
ii) , Mature
iii) , advanced
Early FPSE Market
Mature FPSE Market
Advanced FPSE Market
State Aleut. Anc
160,852
135,835
15,020
23,390
15,935
108,730
57,230
19,890
48,840
24,400
42,775
109,075
-45-
Alaskan FPSE/TES Residential Market Estimates
h- Bethel Bristol orage
1830 72423
1857 62657
1373 61822
457 10601
385 835 420 1500
1100 1500
700 1000
0 60000
1500 5000
9.7 8.6
20 19
10 10
8 8
200 1000
S25 6.4
19 20
10 10
8 9
60 44500
3 22
12 12
a a
5 5
1700 1500
1700 2500
1800 50000
3037
2651
2023
1014
628
900
1900
1000
0
2300
12.3
aL
Le
10
600
525
LS
10
2400
2900
2900
321
266
281
40
(-15) 80
300
0
0
300
10.5
20
10
300
300
300
Table 15 Alaskan FPSE/TES Residential Market Estimates
(continued)
Dilling Fair Haines Juneau Kenai Ketch- Kobuk
ham banks Penn ikan
a) a) 1391 23866 728 8132 10872 4296 1368
b) 1192 19682 583 7591 8965 4005 LEP
2) a) 767 18177 435 7901 10596 4561 966
b) 624 5689 293 #31 276 (-265) 402
c) 425 1505 148 (-310) (-1631) (-556) 205
d) 600 5000 240 150 300 100 350
3)
a) 800 5000 240 150 300 100 1300
b) 500 1000 435 100 100 100 0
@) 0 17000 0 7800 10400 4500 0
4) a) 1100 13500 430 6600 3300 3300 1000
b) 10.9 Be, 9.0 8.8 8.6 8.7 1257
iC) =i) 20 19 19 19 19 19 21
ii) 10 10 10 10 10 10 1l
iid) 9 8 8 8 8 8 10
5) a) 200 6500 240 600 1500 900 250
b) 4.5 6.0 4.3 6.6 5.0 4.2 5.3
G)—-1) 19 20 19 20 19 19 19
ii) 9 10 9 abt 10 9 10
iid) 7 9 7 9 8 7 8
6)
a) 0 0 0 0 3400 200 0
b) 2,3 6
c) i) 12 14
ii) 7 8
iii) 5 i
7) a) 800 5000 250 150 300 100 1300
b) 1300 6000 675 1500 2000 800 1300
c) 1300 10000 675 6000 7000 1200 1300
-46-
Table 15 Alaskan FPSE/TES Residential Market Estimates
(continued)
Kodiak Mat- Nome North Prince Sitka Skag-Yak
Island Su_ Slope of Wales Angoon
1)
a) 3389 7989 2383 1227 1368 2701 2277
b) 2963 6115 2014 1052 1E65 2479 41035
2)
a) 2977 8356 1473 933 897 2357 990
b) 412 (-367) 910 294 471 344 287
c) (-14) (-2241) 541 119 288 122 45
qa) 300 750 800 200 400 250 200
3)
a) 1200 750 2100 600 500 250 600
b) 1900 500 0 600 700 100 600
c) 0 6750 0 0 0 2200 0
4)
a) 2800 2800 1700 600 800 2100 1000
b) 9.8 8.6 14.5 15.6 8.8 8.3 9.4
ec) i) 20 19 22 Ze 19 19 20
ii) 10 10 LZ 13 10 10 10
i 1%) 8 8 3 B 11 8 8 9
5)
a) 300 2400 400 0 300 300 200
b) 5.3 4.5 533 4.2 455) 4.5
c) i) 19 19 19 19 19 19
id) 10 9 10 9 9 9
iii) 8 7 8 Ul iq a
6)
a) 0 0 0 600 0 0 0
b) 2 ofl: c) i) 12
a) 7
iii) 5
7) a) 1200 750 1800 600 500 250 600
b) 3000 1600 2100 1200 1200 700 1200
CG) 3100 5000 2100 1200 1200 1500 1200
—A=
Table 15 Alaskan FPSE/TES Residential Market Estimates (continued)
Valdez Wade Wrangell Yukon SE Fair Cordova Hampton Peterbg = Koyukuk banks
1) a) 3921 1154 2430 2698 2119
b) 2848 959 2196 2189 1699
2)
a) 2610 826 2067 1621 1826
b) 1311 328 363 1077 293
ce) 238 133 129 568 (-127)
d) 800 280 300 900 200
3)
a) 900 1100 500 2000 200
b) 2500 0 1800 500 1800
c) 80 0 0 0 0
4) a) 2500 700 1800 1100 1000
b) 8.6 15.6 8.3 13.0 10.7
c) i) 19 22 19 21 20
ii) 10 13 10 11 10
id) 8 1l 8 10 9
5) a) 900 400 500 1300 900
b) 4.5 5.3 4.5 5.3 4.5
CG). t) 19 19 19 19 19
ii) 9 10 9 10 3
bit) 7 8 7 8 7
6)
a) 0 0 0 0 80
b) 2.2
C)t) 12
ii) 7
iii) 5
7) a) 900 1100 600 2100 200
b) 3400 1100 2100 2400 1800
c) 3400 1100 2300 2500 2000
-48-
Discussion of Table 15
Utility rates in the State vary primarily by size of utility.
Small remote diesel utilities are usually well over 25¢/kwh, often
by a factor of 2. Larger utilities, fueled by cheap gas or hydro
are usually under 10¢. It is logical that the early FPSE/TES will
find its home in the remote areas.
The potential market for small FPSE/TES in its early development
stage is over 24,000 units in Alaska. This increases to over
100,000 units with advanced models.
The cost of FPSE generated electricity indicates a relative insen-
sitivity to fuel costs if only 5000 kwh is to be generated, but a
large sensitivity to capital costs as reflected in mature and
advanced system examples. This is certainly no different than
what large utilities experience through low load factors.
Conversely, if a FPSE generates less electricity the cost/kwh
increases. While many homes in rural areas get by on 2000 kwh or
less per year, it was assumed that if the cost of additional power
were minimal, as via a FPSE, home use would increase to approach
that of Anchorage homes (after subtracting all resistance heat-
ing), or about 5000 kwh/year. A large user of electricity and
heat will see his rate decrease to 33-70% of the small TES rate
depending on fuel cost and use (Table 14).
These derived costs assume that the FPSE operate as a true total
energy system, without connection to any utility. In areas with
existing utilities, cooperation of the utility and homeowner
through cogeneration will likely yield mutual benefits.
The accuracy of cost projections is not great at this time, owing
to obvious uncertainties in production volumes and costs, as well
as unproven estimates in engine life and performance. This
innaccuracy is especially critical for the advanced model predic-
tions, where small changes in performance or assumptions can make
vast changes in the market. The advantage of the FPSE/TES in the
rural and remote areas is much less sensitive to these uncertain-
ties.
-49-
VII
A)
MATURE SYSTEM CONSIDERATIONS
While the early FPSE/TES may have its greatest benefit in
comparison to small independent diesel gen sets, mature systems are likely to have widespread applications.
Cogeneration
Although cogeneration is sometimes referred to as simultaneous generation of power and heat for use on the premises, it will be
used here to mean generation of all heat needed on premises with
electricity sold to or purchased from the utility as needed.
This concept can have great benefits to both principals.
The owner can operate the FPSE continuously as long as heat is
needed, and sell excess power for less than the utility can
generate it themselves. Conversely, when heat is not needed, the
homeowner can probably purchase utility power for less than he can
generate it (depending on relative economics) .
The willingness of a utility to participate in cogeneration is
not universal, despite PURPA* regulations mandating consideration.
Determining economic criteria for participation in cogeneration is
difficult for most utilities. Revenue is generated by sales of
energy, at sometimes varying rates depending on type of service.
Utility expenses, and also those of a FPSE, are a combination of
fixed and usage costs, usually referred to as demand and energy
charges. These differ for each consumer, but the utility can't
afford to separate them except by gross areas. The current push
in tight times is to charge each consumer more proportionately to
the expense incurred in service.
This is seen in different rates for urban and rural users,
single and 3 phase, commercial, industrial, etc., as well as faci-
lities charges and graduated tariffs. Utilities themselves are
splitting into generation and distribution subutilities.
Several utilities have already established sell/buyback
contracts with cogenerators. However, the amount and reliability
of power is the major determinant in the rates. A single FPSE
generator will be at the bottom of both scales, but a village of
FPSE's will have a quantity and reliability of power possibly
greater than a primary utility generator, with an availability
curve matching that of the utility's normal load.
As an example, assume that the utility owns and operates
FPSE/TES in each large building and home in a village, in
addition to one modest diesel generator. Each FPSE is connected
to the grid and the building then either takes from or feeds power
to the grid, depending on specific need.
* Public Utilities Regulatory Policies Act
=50-
Since usually the required electricity is less than can be generated in the process of heating the buildings, there will be excess electricity to distribute to smaller homes and other users, like street lights.
The utility's small generator will be used primarily to generate the controlling frequency and provide for peaks that
might occur. Likely, a less expensive frequency control can be used if the peaks do not exceed the total capacity. The operation of systems in large buildings may be the responsibility of the utility, whereby they can control a certain amount of power for peak demand, even when heat is not needed. Individual homeowners will operate their systems to provide heat, with electricity a secondary product. Consequently, the FPSE/TES will be simpler,
needing no heat storage or on site frequency generator.
The function of the utility will then be one of service and modest load leveling. Generation will be done in the homes, eli-
minating the capital and fuel expense of large diesels. The
distribution system is very modest, requiring neither high
carrying capacity nor long distance. If a consumer is more than a
short distance away, he has a stand-alone system.
Economics of such a system are highly site specific, depending on costs of generation and distribution. The case cited would be applicable to a utility faced with high generation costs but
having a serviceable distribution system. Costs of electricity
would approach those in Table 13 for large TES.
Many variations of this example are possible. On the simpler
side of cogeneration, there is the commercial user with a base
consumption of power and heat. One or more FPSE generators,
separate or connected together, supply the heat load, and addi-
tional electricity is supplied by the grid. The FPSE loads are
not connected to the utility. The owner gets the benefit of
lowest possible power costs for the base load, and uses utility
power for the peaks, or times when heat is not needed. A higher
utility rate (demand charge) may apply, although likely not
during the utility's normal winter peak.
The underlying assumption for considering cogeneration is the
compatability of FPSE generation with utility power, primarily in
phase synchronization. Initial reports from MTI indicate that
this may be simply accomplished and that the FPSE operation bene-
fits from such connection.
Distribution safety with more than one generator requires that
all generators will be shut off a section of line if a break
occurs. Switching devices known as no break connections are used
on synchronous gen sets and may work for FPSE. In essence, they
sense the line frequency and match the gen set to it. If the line
frequency stops, the power is diverted from the line, but con-
tinues to supply domestic loads. When the line comes back on the
switch senses it, resynchronizes the gen set, and starts feeding
power back into the line.
-51-
B)
c)
Commercial and Other Markets
This project specifically focuses on solid fueled, residential
Alaskan markets, and these have been examined in depth. It
becomes obvious from the analysis that very favorable economics of
FPSE operation will be found in many commercial enterprises, espe-
cially if cogeneration or sales of excess electricity were con-
sidered.
Given the greater economics and possibly easier marketing,
FPSE/TES might first be found in larger buildings such as schools
and public buildings where a distributor (or utility) can operate
the units on a maintenance contract. Economics are dependent on
development of simple utility/FPSE interface.
There are many large public buildings such as hospitals,
hotels, etc., that own and maintain standby generation systems, at
least for lighting. The costs of this standby equipment would be
eliminated by use of FPSE, as the utility itself would be the
standby power.
Reliability of a FPSE is greater than a single small standby
set, but reliability of multiple interconnected FPSE sets becomes
much greater. This statistical elimination of the need for backup
becomes apparent with only a few units, in noted contrast with the
"all eggs in one basket" headache facing utilities with only one
or two prime-movers.
Development of Other Fuels
The cost of operation of mature full use FPSE becomes more
dependent on fuel price. Fortunately, any fuel, even solar, can
be used. The need for diesel fuel for generation promoted
development of large bulk storage and fuel distribution systems.
Without the specific need for diesel fuel, relative economics
may enhance development of cheaper local fuels, such as peat,
coal, or wood. This not only applies to extraction but also
silvaculture, distribution, agriculture, etc.
Instead of using only mature trees for cordwood, whole trees
can be chipped, resulting in more efficient use of resource.
Faster growing species, suitable for chipping, can be encouraged.
Wood chips and peat fuel pellets are more easily handled, are
cheaper than cordwood, and can be used with automatic burners.
FPSE generation will become cheaper and more convenient.
Successful deployment of FPSE/TES in Alaska is not dependent
on availability of solid fuels, but these systems will allow wider
use of local alternatives.
-52-
a .
D) Effect of Subsidies
E)
A subsidy is used here to mean any specific aid given by a government to a system or its components beyond normal economic supply and demand. Electric utility generation in Alaska is rife with subsidies at all governmental levels. Some of the more readily identifiable include:
1) State Power Cost Assistance where the state pays, by a sliding
formula, all (or most) consumer electric costs over a spe- cified rate;
2) Outright grants, state and federal, to build generation or
distribution facilities;
3) Below market rate loans for capital projects;
4) Bulk fuel loans for storage and fuel (also used for heating);
5) Housing programs that also pay utilities;
6) Village owned utilities with operating deficits;
7) Special tax breaks.
The only subsidy identifiable that would apply to a FPSE/TES
owner may be certain investment credits (tax breaks) and then
perhaps only if it were a commercial enterprise burning wood.
In the foregoing analysis, no special subsidies were assumed to
apply to FPSE systems. The utility rates, exclusive of Power Cost
Assistance, but including all other subsidies were used for
comparison in Table 16. The PCA subsidy has built-in sunset
clause, as the amount of subsidy decreases annually.
It is worthwhile to note that an unsubsidized FPSE/TES can
compete in almost all cases with a subsidized alternative,
allowing for removal of subsidies with no adverse effect on consumers.
In much of rural Alaska the State is also the major consumer of
electricity. Obviously, any market study must address the State's
needs in its various roles in rural electrification; builder,
operator, regulator and consumer. Through all these manifesta-
tions low consumer prices appears to be a primary goal, but
continued support on any level can not be assumed.
Uniqueness of Alaska
If the FPSE/TES concept is so great, why doesn't everybody have
one? Simply, the engine was only recently developed, and is not yet in production. Although, the FPSE may have major use in
Alaska, completely different economics limit its use in other
areas.
=59=
F)
Three major economic factors for FPSE/TES use include:
1) High cost of utility power
2) Concurrent demand for heat and electricity
3) Low cost of TES fuel
Clearly, remote locations in extreme climates are more likely to have combination of these criteria favoring Stirling engine use. These criteria seem to define the Arctic and sub- Arctic; Alaska, Canada, Russia, etc. Of all these Alaska as a state is most involved in electrification and is likely spending much more in alternative generation for each potential FPSE
installation.
Alaskans will not only have the most to gain for any invest- ment in individual systems, but are already making comparable
investments. in less desirable systems.
Future Use in Alaska
Two major external variables affecting economics of TES operation, fuel cost and utility rates, are subjects of many pre-
dictions, with some controversy as to their accuracy. There is more flexibility in home fuel than in fuel for generation of electricity, as the homeowner can change in a matter of days com- pared to several years for a utility. The homeowner can use the cheapest fuel, and avoid high costs caused by external fuel price
fluctuations, giving TES users greater security.
In all predictions, the cost of electricity will be substan-
tially more than fuel, whether gas, oil, or solid fuel. When a fuel used by both the homeowner and utility becomes more expen-
sive, relative economics favor the FPSE/TES because of its much
higher fuel efficiency.
Despite potential lowering of rates in some small diesel uti- lities through improved load and consumer density, the external
variables are likely to become more favorable to FPSE/TES.
As long as the conditions of inefficient fuel use and
distribution expenses significantly contribute to utility rates,
the Total Energy System concept is viable. Depending on
intrinsic characteristics, almost any prime mover can be used in
the TES. Another promising technology, modular fuel cells, may
be an ideal TES candidate for larger, 40kw and up, installa-
tions. In Europe today, TES using natural gas fired internal
combustion engines of 15kw and larger, are proving very
economical.17 System concept is identical, as these engines are
water cooled and soundproofed, but operating costs are greater
than with FPSE. The TES approach appears to be more receptive to further technological advances.
The method of analysis used in this investigation is
applicable to any candidate for use in Total Energy Systems.
-54-
The intrinsic variables, as expressed by the various assump-
tions on engine life and cost, will improve as the technology
matures. At very early development these engines will be extre-
mely competitive in remote areas, and competitive throughout the
state at mature and advanced technology levels.
The first targeted market for FPSE/TES will be remote homes
faced with onsite generation from small diesels, as well as small
settlements not yet served by utilities.
As the technology matures and becomes proven, utilities and
homeowners will begin to utilize it as an option to larger
central power plants. The process will be gradual, in contrast
to the major capital expenditures required for central stations.
The utility planning process becomes simple and safe, with no
expensive excess capacity or system wide shortages.
-55-
II
PART II
STIRLING ENGINE DEVELOPMENT PROJECT
SOLID FUEL STIRLING ENGINE CRITERIA DEVELOPMENT
INTRODUCTION
This project is specifically charged with development,
testing, and demonstration of a solid fueled Stirling engine for
use in a single family rural Alaskan residence.
As seen in Part I, this portion of the total Alaskan market
for FPSE/TES, although not the largest, will have the greatest
economic benefit per installation, especially in early systems.
While there is definite potential in rural homes for the cogenera-
tive system, in parallel with utility or other engines, demonstra-
tion of this aspect is not part of this project.
The method of economic evaluation in Part I assumed an equiva-
lency of function between the FPSE/TES and the systems being
compared. The stand-alone solid fueled system must be equivalent
or better in function than the combination of 3kw diesel gen set
and wood furnace in order for the economic analysis to be valid.
The design criteria development phase is the specification of
the desired technical characteristics required for the FPSE/TES
system to reach the potential market described in Part I.
Characteristics of the new system not as good as the old will logi-
cally cause a decrease in economic attractiveness, and this change
will be estimated.
METHODOLOGY
The system operation may be viewed as a combination of inter-
nal and external functions. The myriad internal workings of the
system; i.e., compression ratio, oil pressure, (diesel), flame tem-
perature, reaction rates (stove), or gas pressure, head temperature
(FPSE) are of no direct concern to the owner/operator. The exter-
nal workings of these systems are of real concern; economics;
quality and quantities of heat and power outputs; type and amount
of fuel input; pollution; safety; etc.
The design criteria will only specify these external func-
tions, and will use as a basis the 3kw diesel gen set/wood stove
combination earlier investigated. The internal design and system
workings required to effect this external function will be the
realm of the researchers and manufacturers.
-56-
Figure 1 is a simple schematic of a FPSE/TES. Although really two
systems, a furnace and generator, their combination as a total energy system requires joint analysis. A system envelope is defined where mass and energy balances apply. The flows across this envelope are the basis of the design criteria.
Figure 2 is a corresponding schematic for a system composed of a
diesel gen set/wood furnace, with the system envelope enclosing both of them, although very likely separated by some distance.
Figure l
FPSE/TES Schematic
Diesel Generator Set and
F Wood Furnace Schematic
F = fuel input
W = exhaust
E = electricity to building
T = thermal output
|
|
|
| Figure 2
l
'
|
|
(
I \ FURNACE
=—5 =
Each input or output is composed of many facets besides the quantity and costs described in Part I, and each is more or less important to the system owner.
III Criteria Specifications
A) Fuel Input
The quantities and costs of diesel and wood fuels were exa- mined in Part I, with the assumption that the diesel fuel required in Figure 2 will be replaced by wood. The wood utilized by the system of Figure 1 will be slightly greater quantities, but simi-
lar in other respects, to that used in the furnace of Figure 2.
Fuel input variables also include tree species, moisture content,
storage practices, stove design, and stove use.
All species are used, but birch and spruce are generally pre-
ferred. Wood is usually split to help drying and burning. The
smaller the pieces, the more work involved: wood for a cookstove
is usually about one foot long, split into two inch wide pieces
and well dried. By contrast, a barrel stove or space heater can
handle 16 to 24 inch logs, split two or more times (4-6 inches
thick) after the fire has been started, and sometimes small round
logs if fairly dry.
Dry wood has more useable heat per pound than wet wood, and is
somewhat dependent on species, as some trees are drier when
collected and some dry easier in storage. However, some stoves
are more easily controlled during long slow burns if green wood is
used.
Frequent additions of small amounts of dry wood will realize
more net heat output than fewer additions of large amounts, at
least on, gtoves where combustion occurs over the entire wood
charge. However, the extra firing requires attendance, which
some users find inconvenient. In cold months, the stove often is
kept going continuously.
The criteria for wood fuel are:
1) Species: Any species normally used in wood stove should be
useable in TES.
Unsuitability of any major species (birch, spruce) will
decrease market of system or increase price of fuel.
Suitability of use in TES of species less commonly used
(cottonwood, alder, willow) will add to system's potential
market or decrease the price of fuel.
-58-
2)
3)
4)
Size: Required fuelwood size should not be smaller (require more labor) nor be more restrictive in size or shape variation than normally used in wood stove. Logs 16-24 inches long, split to 4 inches thick or less, are normal. Special size restrictions on fuel will raise the price, directly affecting economics, or make the TES less convenient to use. Conversely, capability of using round logs may result in lower fuel prices, although drying would be hampered.
Moisture content: An average moisture content of 25% (wet basis) is considered normal. This includes some portions of greener wood used to prolong burn times.
Requiring drier wood may be inconvenient or raise prices if a storage shed or longer than normal drying times are
needed. Homes using wood fuel for cooking often have a
covered wood shed. Other homes may simply prefer not to
burn very dry wood. Many wood users prudently store a winter's wood supply, insuring an abundant, dry supply.
Moisture content is too high in cottonwood until after substantial air drying. In some areas, Such as old burns,
only very dry wood is available. If wood is too wet, bringing it inside may shortly result in acceptable moisture content.
Thus, there does not appear to be an easy means of spe-
cifying acceptable moisture content, except that below 20%
m.c. would likely entail more inconvenience through longer
storage in a covered shed.
Refueling frequency: FPSE/TES should be capable of 12 hours operation at full electrical output (3 kw), or 18
hours at low output.
This length of burn is much longer than for conventional
wood stoves, although smouldering burns can be maintained
this long if carefully banked.
The criteria for this fueling frequency is determined by
the equivalent fuel storage of a 3kw gen set.
Increasing the frequency of refueling to as low as 2 hours
at maximum output may not significantly decrease the value
of a system but would decrease is potential market.
The duration of burn at maximum output will likely be less
important to the homeowner than the low output (idle) burn
length. Assuming that the FPSE can increase output on
demand, then the mimimum length of low burn should be 18
hours.
-59-
5)
B)
1)
2)
3)
Other solid fuel types: Although peat fuel is not readily available, and coal is not a common fuel in remote homes, multi-fuel capability of the TES is moderately desirable. Much more desirable would be capability for supplemental oil firing, and this would likely be desirable in a market twice
as large as for wood alone.
Electrical Output -
Power shall be 3kw maximum and be suitable for all normal household appliances. Electrical qualities shall not cause
degradation of use more than would be experienced using 3kw
diesel gen set.
Voltage: 110 volts nominal + 7% . Greater voltage variation could be detrimental to some appliances. Less variation would
allow use of some additional special appliances but is not
expected to increase value or market of household systems.
Availability of 220 volts with neutral ground (i.e. + 110 v,-110v)) is likely to be useful primarily for some motors
(pumps etc.), as the resistance loads using 220 volts (water,
space heating) will mostly be eliminated. The FPSE can
produce 220v, but the mean voltage is at 110v rather than
zero as in utility systems. This may necessitate rewiring of
some appliances, or may otherwise present an intolerable
safety risk.
The increase in value to a FPSE from including 220 voltage is
hard to evaluatate, but present.
Voltage wave form: True sinusoidal is preferred. Deviations
from sine wave should not cause degradation of use in motors
or other appliances. '
Wild harmonics and non sinusoidal waveforms may cause motor
overheating or interference on electronic equipment, or feed-
back from these appliances may be felt in the rest of the
loads. In any case, if standard electronic filters can not
overcome any difficulties, then a severe reduction in the FPSE
usefulness may result, perhaps rendering the system unsuitable
for general household use.
Frequency control: Regulation of frequency shall be main-
tained within 1/2 % of 60 Hz. In step loads, variation
shall not be more than 3Hz and recovery shall be within 30
cycles.
Many appliances are insensitive to frequency variation, but
most motors will run properly only at rated frequency. Clocks
and synchronous motors are directly dependent on frequency.
-60-
c)
4)
5)
6)
It is unlikely that electric clocks would be a major con- Sideration so the major frequency criteria becomes operation of normal household induction motors.
Load Response: Voltage and frequency deviation in response to
a full power or partial step load shall not cause disruption
of operation of other appliances, and recovery shall be within
180 cycles.
Phase: Household units shall be single phase.
Few 3 phase appliances are designed for residences, but for
commercial applications, 3 phase is more common, although
power would be required greater than 3kw.
Electronic Interference: The telephone interference factor
and other electromagnetic interference, both radiated and con-
ducted, shall not interfere with standard operation of
electronic appliances.
Any interference occurring may be filtrable with standard
electronic filters, in which case only slight decrease in FPSE
usefulness would be experienced, no more than the cost of such
filters. If such interference restricts use of two-way
radios, telephones, or other common rural appliances, the
reduction in FPSE value becomes more severe. If interference
extends beyond the residence use of FPSE may be prohibited.
Thermal Output: Quantity, quality, and controlability of heat
output from TES shall be equal to or better than conventional
wood stove.
1)
2)
Power: The maximum thermal power output should be 70,000
Btu/hr continuous. This is large enough to handle most rural
homes. When incorporated with heat storage, instantaneous
heat output is increased, making the system more responsive
and convenient. Decreasing the maximum output may be possible
for most rural homes, depending on thermal storage included.
Temperature: Delivered heat temperature must be adequate for
the intended use. Space heat is required at about 80° F, but
temperature must be greater to effect heat transfer. Domestic
water temperature of 120°F is considered adequate. The TES
water loop temperature will de determined by engineering
tradeoffs of thermal efficiency and heat exchanger/storage
costs. No degradation of performance is expected if space and
water temperatures can be maintained through normal operating
conditions.
~-61-
D)
3) Controllability: Thermostatic control of room temperature and domestic hot water temperature is highly desirable.
Response to control signals should not be slower than in wood stove. Proportional response (low through high) rather
than on-off would be desirable.
Because of the existing wide variations in heating system
controls and use, coupled with house-thermal response, quan-
titative evaluation of the above characteristics is not
attempted. Personal preference will likely be a major design
option.
Exhaust
The total of all exhausts, including stack gases, particulates,
ash, odors, etc., shall not be a greater health risk or more
noxious than with the stove/diesel gen set.
1) Gaseous pollutants: Elimination of the odors and pollutants
from the diesel set will increase market and value of FPSE/TES
through personal preference. Oxides of sulphur and nitrogen
are more common in diesel exhaust than wood smoke, but a
smouldering wood fire often produces vast quantities of orga-
nic pollutants, some very noxious, which often makes the air
around wood buring settlements polluted in winter.
The nature of wood stove and gen set air pollutants is complex
with many different gaseous, liquid, and solid chemical
species. Wood stoves are notorious producers of airborne
particulates, a combination of soot, inorganic ash, and
condensed hydrocarbons.
An increase in pollutants is detrimental, although in only
rare locations is there any regulation on wood stove pollu-
tants. Reducing the quantity of airborne pollutants through
more efficient combustion is both likely and highly desirable.
Increased economic viability is expected, and greater consumer
and regulatory agency acceptance will result in increased
value of FPSE/TES plus wider markets.
Actual levels of pollutants and attendant values/costs of
improvements can not be estimated as they don't exist for
domestic stoves.
-62-
2)
3)
Ashes: Handling requirements should not be greater than for wood stove. Since the ash removed from a stove is in the order of 1-2% of the wood input, handling in a domestic system is relatively insignificant. Major factor is removing ash
from stove; if all ash falls to a removable bin, the process
is simple, and the TES should have this feature. Sweeping ash
out of inaccessible corners of a stove becomes tedious and
designs should avoid this.
Other dust and dirt from system use should not be greater than
with old stove/gen set. Considerable variation in cleanliness
exists, and eliminating the grease and grime of gen set
Operation will find increased consumer acceptance.
Odors: Smells from a furnace are usually emitted as gaseous
pollutants (see 1), but other smells and fugitive emissions
should be minimized. Eliminating the diesel fuel and hot
engine smells will result in some consumer approval. The
smell of wood in storage is relatively benign.
E) Other Factors:
1) Noise and vibration: FPSE/TES shall not be noiser nor cause
more vibration than a typical home furnace.
A reduction in noise/vibration levels from those found in a
gen set was assumed for the FPSE to enable installation in or
adjacent to a living space. While wood parlor stoves are
quiet, furnaces with their fans, pumps, blowers, etc. are
noisy and often installed in a basement or separate room.
Noise greater than this level would require additional cost in
soundproofing or a separate generator shed, with perhaps more
inconvenience in fueling.
Conversely, noise/vibration levels comparable to a refrigera-
tor will allow installation on a parlor stove in prime living
space, resulting in a wider market and greater value.
Actual noise/vibration technical specifications are rather
complex, including factors of generation, transmission, and
human response, with different specifications for various
activities and environments. Although less noisy systems are
generally to be preferred, any particularly obnoxious tone or
vibration should also be avoided.
A broad based bland background noise spectrum, such as RC (Room Criteria) 35 or less2l while often specified for pri-
vate offices, may not be realistic for homes.
-63-
2)
3)
4)
5)
Effect of Low Temperature: Freezing and extreme cold should not affect FPSE/TES operation nor damage the system.
Cold temperatures, to -60° F, can be experienced in the
Interior if if a system is left idle during winter. Startup
of at least the space heat portion of the TES should be
possible at any temperature with not more effort than on other
furnaces.
In the case of water heating systems, either antifreeze or
freeze protection (automatic drains) should be included.
While hydronic systems in more urban settings sometimes are
not protected, rural homes should be. The value of freeze
protection is proportional to the damage possible from
freezing and breakage of water lines, both in the TES and the
rest of the home.
Portability: FPSE/TES should not be more cumbersome than the
gen set and furnace it replaces.
The range of weights of the stove, gen set, and all
accessories varies from 700 lbs to a couple tons, and is very
rarely portable, consequently the FPSE/TES need not be por-
table to serve the defined market. Economics relative to
shipping weight were examined in Part I.
A wider market may arise if the FPSE coupled to a lightweight
stove were produced. This market is for lightweight, portable
gen sets, and has different use and economics than examined
for the home power case.
Labor Considerations: Installation of FPSE/TES should not be
more difficult than for a gen set and furnace, in either
trained personnel or special tools required. Increasing costs
of installation would be reflected in system economics, as
would savings from easier installation.
Total system maintenance as examined in Part I assumed a com-
bination of non-technical owner maintenance plus some spe-
cialized service. The cost of specialized service in the bush
is very high, even for furnace tune-ups. Consequently, to
avoid overruns of the allocated maintenance costs, components
requiring special service should be easily transportable to
shops.
Safety: The FPSE/TES should not create any greater danger to
health or property than the combination of wood stove and gen
set. Safety is a matter of degree rather than an absolute
value. Improperly operated stoves are the cause of house
fires, burns, and in some cases carbon monoxide poisoning,
each with attendant loss of life and property. Similarly,
improper use of gen sets can lead to fires, poisoning, and
electrocution. In all cases, the device may be functioning
properly, but installation or use is faulty. The FPSE/TES
should be designed so that hazards are minimized, despite
negligence in installation or operation.
-64-
F)
Applicable codes for both the combustor and FPSE construction as
well as chimney, electrical, and fuel storage installation will
have to be followed for each system. Much of Alaska has no resi-
dential construction codes, but this does not relieve system manu-
facturers from concern for safety. The FPSE should be UL listed,
at least for installation in public buildings. Concerns include
electrical safety, surface temperature, and pressure vessel
integrity. The safety concerns for the combustor will be no dif-
ferent than for other stoves and furnaces.
Use of the FPSE within the living space implies a greater risk to
health than if used outside. Consequently, demonstration of
safety, via UL listing and other code compliance, will certainly
enhance the marketability to residential users, especially those
in urban areas with building codes. Such proof of safety is a
prerequisite to installation in public buildings.
System Cost
To realize the economic predictions and market extent of Part l,
Section VI, the FPSE will have a full production retail cost of
$1,465.00 and the wood combustor/heating system will retail for
$2,500, or no more than $500 in excess of a conventional wood
furnace. The goal for total installed cost of a full size
combined system is then $4,000.00, exclusive of normal accessories
such as chimney, external heat distribution, breaker panels, etc.
No specifications on performance are ventured for smaller
combustors.
-65-
Iv Summary
The design criteria specified for the FPSE and the matching wood combustor are based on consumer preferences as deter- mined in the market analysis of Part I. External functions, such as tangible inputs and outputs, operation and safety
were investigatd to determine the effect on the value and
market of the FPSE/TES defined in Part I.
It is important to realize that there is a real market for
FPSE/TES at several times the projected system cost and with
diminished performance. Development considerations mandate
that a certain market volume be available to realize
favorable economics of production. This section on design
criteria gives a rough outline of the preferences of a
segment of the residential market, and these criteria will
serve as goals in the system design for this project. Their
purpose is to effect maximum utility to the widest market
segment defined in Part I.
-66-
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
73)
14)
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