&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research EPA-600/7-79-1Q5a
Laboratory April 1979
Research Triangle Park NC 27711
Comparative Assessment
of Residential Energy
Supply Systems That
Use Fuel Cells
(Executive Summary)
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
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tems. The goal of the Program is to assure the rapid development of domestic
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EPA-600/7-79-105a
April 1979
Comparative Assessment of Residential
Energy Supply Systems That Use Fuel Cells
(Executive Summary)
by
R.V. Steele, D.C. Bomberger, K.M. Clark, R.F. Goldstein, R.L Hays, M.E. Gray
and
G. Ciprios, R.J. Bellows, H.H. Horowitz, C.W. Snyder (Exxon)
SRI International
333 Ravenswood Avenue
Menlo Park, California 94025
Contract No. 68-02-2180
Program Element No. EHB534
EPA Project Officer: Gary L Johnson
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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SRI INTERNATIONAL
COMPARATIVE ASSESSMENT OF RESIDENTIAL
ENERGY SUPPLY SYSTEMS THAT USE FUEL CELLS
EXECUTIVE SUMMARY
What Are Fuel Cells?
Are Fuel Cells Commercially
Available Today?
Fuel cells are devices capable of converting the
chemical energy stored in a fuel directly into
electrical energy without a step involving combustion.
Hydrogen contained in the fuel is chemically combined
with oxygen from the air to produce water and an
electric current that can be regulated and used.
Fundamentally, the process is just the inverse of the
electrolysis of water into its component parts, a
process often demonstrated in high school chemistry
classes. Practically, a fuel cell consists of two
electrodes, a catalyst used to promote the chemical
reaction, and an electrolyte (a chemical substance that
conducts electricity) separating the electrodes. As
might be suspected, a device of such fundamental
simplicity was first conceived long ago—in 1839 by Sir
William Grove, a British jurist.
Although old in concept, as practical devices for
producing electricity in significant amounts, fuel cells
are in their infancy. For space missions, fuel cells
have been shown to be ideal power sources, partly
because they convert on-board stores of hydrogen and
oxygen to electrical power without producing
excessive heat or vibration-producing mechanical
motion. In fact, they provided electrical power in
Gemini and Apollo spacecraft, but were still
considered novel and exotic devices.
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Made in limited quantities, and to extreme reliability
standards, fuel cells for space craft are understandably
expensive. Nevertheless, much has been learned from
the space program about fuel cells and that knowledge
is beginning to find earthbound applications in
much-improved and less costly devices.
More than 60 small (12.5 kW) fuel-cell power plants
were field tested in 1972 and 1973. A 40-kW device
was demonstrated in 1975, and now work is underway
to demonstrate a 4.5-MW fuel cell in the Consolidated
Edison (New York) utility system by 1980. Fuel-cell
technology has come a long way and is nearing
commercial readiness.
Do Fuel Cells Possess Much of the present interest in fuel cells derives from
Attractive Attributes? their unusually low environmental impact and their
high efficiency. Because no combustion is involved,
even fuel cells that use common fuels produce very
low emissions of nitrogen or sulfur oxides; the
emissions are many times below federal standards.
Moreover, fuel cells generally consume no water and
operate very quietly.
As a result of its environmental good- neighborliness, a
fuel-cell power plant can easily be located very near
the power demands it serves, thereby lessening the
need for high voltage electric transmission lines.
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The ability to site fuel-cell power plants locally is
much enhanced by their modular design (which allows
off-site manufacturing) and their rapid installation.
Accordingly, electric power utilities may soon have
commercially available a device that enables system
expansion in small increments.
How Might Fuel Cells Fit
into Electric Power Systems?
Besides being suitable for small, dispersed, locally
sited power stations, fuel cells can easily operate in
applications that require output to follow demand
closely. In fact, electric utility interest in fuel cells
often centers on mid-1980s deployment for
load-following. Again, because of their cleanliness,
fuel cells may be installed in buildings or residential
complexes where the combined production of electric
power and heat could be used to satisfy heating and
cooling demands in an integrated (or "cogeneration")
fashion. The fuel-cell-derived electricity would be
used to operate heat pumps to provide cooling and
supplemental heating.
Can Fuel Cells Use Coal
or Coal-Derived Fuels?
Fuel cells, like most fuel-consuming devices are
indifferent to the origin of the fuel—as long as in final
form it conforms to the chemical requirements of the
device. Accordingly, natural gas, petroleum products,
or similar fuels are perfectly acceptable in fuel cells
provided that the fuels are first reformed to hydrogen
and carbon dioxide and that harmful sulfur
contamination is removed before the fuels enter the
fuel cell proper.
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Fuel cells, therefore, can have a place in a largely
coal-based U.S. energy future.
What Are Leading Coal-Based Already, U.S. electrical power is largely generated in
Alternatives to Fuel Cells? coal-fired plants and the federal government is pushing
for even more in an effort to save relatively scarce
and expensive oil and natural gas for other uses.
Larger, conventional coal-fired power plants, often
located in remote areas and connected to urban load
centers by high voltage transmission lines, certainly
provide a well-proven alternative to electric power
generated from fuel cells.
So-called "combined-cycle" electrical power
generation—a conventional boiler and steam turbine
generator supplemented by a high-temperature gas
turbine—is an improving technology gaining
considerable attention among utilities. Certainly, by
the time fuel-cell systems are perfected sufficiently
to allow commercial deployment, combined-cycle
systems will already be in use and fuel-cell systems
will have to compete with them.
Much of the U.S. space heating demand is met by the
combustion of natural gas. Because so many
consumer-owned heaters are already in place, gas
utilities have strong incentive to supplement natural
gas supplies with coal-derived substitutes that would
not require alteration of either consumer appliances or
habits.
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Synthetic natural gas, (SNG) derived from coal, then,
offers strong competition for the electric heating role
a fuel-cell/heat pump combination could play in the
market place.
Can Fuel Cells be Compared
with the Alternative
Technologies?
Because fuel cells must compete with so many electric
power and heat-producing fuel and technology
combinations, the relative advantages and
disadvantages of fuel cells have proven difficult to
discern clearly. Consequently, as a part of its mission
to preserve and enchance environmental quality, the
U.S. Environmental Protection Agency commissioned
this study precisely to learn more about what might be
expected from fuel cells when actually deployed in
utility systems.
To address this question, SRI International
conceptually designed twelve energy systems able to
provide residential heating and cooling using
technologies projected to be available toward the end
of this century. Only a few systems used fuel cells.
As in most comparisons, some constraints were
imposed to eliminate unnecessarily confusing
complexities while providing a uniform framework for
comparison. Accordingly, all systems use western coal
as the primary energy resource, and all residences are
assumed to have identical heating and cooling demands
typical of the mid-continent United States. After
winnowing out the clearly least attractive
combinations, we selected five systems and compared
them in great detail.
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For all the comparisons, we examined the entire chain
of the system, starting with the coal mine and ending
with the heating and cooling of residences, to be sure
that the claimed environmental advantages of the fuel
cells at the point of electric power generation did not
distract us from some important environmental
impacts elsewhere in the system. Our five surviving
systems, four of which use heat pumps for heating and
cooling are:
o System 1—A coal-fired power plant supplies
electricity and a coal gasification plant supplies
SNG to residences; electricity powers air
conditioners and SNG is burned in gas furnaces.
o System 2—A 26-MW fuel-cell power plant fueled
by coal-derived SNG supplies electricity to
residences with heat pumps.
o System 3—A 26-MW fuel-cell power plant fueled
by coal-derived naphtha supplies electricity to
residences with heat pumps.
o System 4—A combined-cycle power plant fueled
by coal-derived fuel oil supplies electricity to
residences with heat pumps.
o System 5—A 100-kW fuel-cell power plant fueled
by coal-derived SNG, sited in a housing complex,
supplies electricity to townhouses with heat
pumps; heat recovered from the fuel cell supplies
supplemental space heating and hot water.
Of these five, the first one most resembles the
existing order in the utility industry, and the fourth
constitutes an already evident evolutionary change of
the industry.
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What do the Comparisons
Show?
The scorecard for the various systems is mixed—no
single system stands out as superior in all the
attributes that will ultimately decide which systems
will be deployed. Nevertheless, some very interesting
facts emerge about energy systems that use fuel cells.
Which System Costs the
Consumer More?
Are There Differences in the
Capital Investment Required?
Which Has the Best System
Performance?
The three fuel-cell systems provide heating and
cooling to our standard residences at considerably
higher cost that the two more conventional systems.
In fact, the annual energy bill to a consumer using
System 5 is over 63% higher than for one using System
1, the most conventional and lowest cost option. The
order of cost, from the least expensive system to the
most expensive, is 1,4,2,3,5.
The scorecard for the capital intensiveness of the five
systems largely follows the pattern of the annual cost
to consumers. In order, from least to most capital
intensive, are Systems 1, 4, 3, 2, 5. Because capital is
itself a scarce resource, utilities most likely will show
most interest in Systems 1 and 4.
Because all five systems contain at least one element
not yet proven in commercial service, such things as
reliability, the degree of redundancy needed in a
system, and the ability to integrate smoothly the new
devices into a system are difficult to assess, more so
than for most other comparison attributes. We judge,
however that, overall, the most conventional system is
most likely to give the best performance. System
performance, from best to worst comes in this order:
Systems 1, 2, 4, 3, 5.
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Which System is Most
Efficient?
What About Air Quality?
Are There Differences in
Water Quality?
When making a comparison of system efficiency, we
were careful to account for energy losses at every step
in proceeding from the coal mine to the heated and
cooled residence. All fuel-cell systems are
considerably more efficient than the most
conventional system, System 1. Indeed, System 5 is
75% efficient, while System 1 is only 41% efficient.
Systems 2, 3, and 4 possess nearly equal efficiencies in
the 64% to 67% range. This attribute is particularly
important because it shows that the systems using fuel
cells required less coal to accomplish the same end—a
virtue that, besides conserving resources, carries over
into lessened environmental impact.
Because maintenance of air quality around electric
power generation plants is a vexing and costly
problem, the relative scores for this indicator could
prove especially important to utilities in the years
ahead. We weighted equally pollutants emitted at the
fuel production site and the fuel consumption site
(both overwhelm the emissions from fuel
transportation). Again, all three systems using fuel
cells are superior to the two more conventional
systems, with System 5 being the cleanest and System
1 emitting the most pollutants. In order, from least to
most polluting are Systems 5, 2, 3, 4,1.
For this indicator we weighted equally effluents and
water consumption at the fuel production and the fuel
consumption locations.
vlii
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All three fuel-cell systems are cleaner than the two
more conventional systems. Again, System 5 is the
cleanest, but this time System 4 degrades water
quality the most. In order of cleanliness are Systems
U} Zy «5j ly 4*
How Do They Compare on
Solid Waste?
Most solid waste for this set of five systems is
produced as ash in converting the coal to a more useful
energy form. Consequently, scores in this category
essentially mirror the overall system energy efficiency
ratings—the most efficient System 5 also produces the
least solid waste and the least efficient System 1
produces the most solid waste. Systems 2, 3, 4 are
nearly tied, and produce about the same intermediate
quantities.
What About Land Use, Noise
and Aesthetics?
Is There a Pattern in the
Comparison?
The three parameters are closely linked because
aesthetics and human exposure to noise produced are
greatly affected by location and the amount of land
occupied or disturbed. Overall, least obtrusive is
System 5 and the most obtrusive is System 1.
A striking pattern emerges when we assemble the
scores for all categories of comparison. The fuel-cell
systems are the most costly—to build and install as
well as in end-use cost to consumers—but are the most
environmentally benign and consume the least coal to
get the heating and cooling job done.
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We expected from the outset of this study that the
fuel cells themselves would be clean compared to
alternatives, but our finding that entire fuel-cell
systems from resource extraction to final demand
offer overall environmental benefits is new.
Will Fuel Cell Systems
Actually Be Used?
How the trade-off between environmental cleanliness
and economic cost will be valued in the next several
decades will prove crucial to the question of whether
fuel-cell systems resembling those we have examined
will actually be deployed in meaningful numbers. One
thing is certain: Fuel-cell systems possess a mixture
of attributes much different from the more
conventional electric power systems. As a result, U.S.
utilities will have available an important new electric
power option in the years ahead.
Full analysis is available in the 500-page report:
"Comparative Assessment of Residential Energy
Supply Systems That use Fuel Cells," Environmental
Protection Agency, Report No. 600/7-79-105b, 1979.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/7-79-105a
2.
3. RECIPIENT'S ACCESSION NO.
J. TITLE ANDSUBTITLE
Comparative Assessment of Residential Energy
Supply Systems That Use Fuel Cells (Executive
Summary)
6. REPORT DATE
April 1979
6. PERFORMING ORGANIZATION CODE
R v. Steele,D. C. Bomberger ,K. M. Clark,
R. F. Goldstein, R. L. Hays, M. E. Gray, G. Ciprios*,
R.J.Bellows*.H.H.Horowitz, and C.W.Snyder*
8. PERFORMING ORGANIZATION REPORT NO.
I. PERFORMING ORGANIZATION NAME AND ADDRESS
SRI International
333 Ravens wood Avenue
Menlo Park, California 94025
10. PROGRAM ELEMENT NO.
EHB534
11. CONTRACT/GRANT NO.
68-02-2180
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 9/76 - 1/79
14. SPONSORING AGENCY CODE
EPA/600/13
^.SUPPLEMENTARY NOTES JERL-RTP project officer is Gary L. Johnson, MD-63, 919/541-
2745. (*) Coauthors are Exxon personnel.
16. ABSTRACT The rep0rt gives results of a comparison of residential energy supply sys-
tems using fuel cells. Twelve energy systems, able to provide residential heating
and cooling using technologies projected to be available toward the end of this cen-
tury, were designed conceptually. Only a few systems used fuel cells. All systems
used Western coal as the primary energy source, and all residences were assumed
to have identical heating and cooling demands typical of the mid-continent U.S.
After screening, five systems were analyzed in detail. The entire energy cycle,
from coal mine to end use, was examined for costs, efficiency, environmental im-
pact, and applicability. The five energy systems are: (1) a coal-fired power plant
supplying electricity and a coal gasification plant supplying SNG; (2) a 26-MW fuel-
cell power plant fueled by coal-derived SNG supplying electricity; (3) a 26-MW fuel-
cell power plant fueled by coal-derived naphtha supplying electricity; (4) a combined
cycle power plant fueled by coal-derived fuel oil supplying electricity; and (5) a
100-kW fuel-cell power plant fueled by coal-derived SNG, sited in a housing com-
plex, supplying electricity to heat pumps, with heat recovered from the fuel cell
supplying supplemental space heating and hot water. Results indicate that the fuel
cell systems are most costly, most efficient, and have least environmental impact.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
>.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
pollution
Assessments
Fuel Cells Coal Gasification
Energy Conversion Coal
Techniques Naphthas
Residential Buildings Fuel Oil
Heating
Cooling Systems
Pollution Control
Stationary Sources
Substitute Natural Gas
Natural Gas
Heat Pumos
13B
10B
10A
13M
13A
14B
13H
21D
07C
DISTRIBUTION STATEMEN1
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
12
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EpA Form 2220-1 (9-73)
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