Fuel Cell Systems-II - ACS Publications

29 Fuel Cells for Central Station Power N E A L P. C O C H R A N

Downloaded by UNIV OF LEEDS on June 18, 2016 | http://pubs.acs.org Publication Date: June 1, 1969 | doi: 10.1021/ba-1969-0090.ch029

U . S. Department of the Interior, Office of Coal Research, Washington, D . C. 20240

This paper describes a fuel cell system for producing electric power from coal or coal char. It outlines a solid electrolyte system with an ultimate projected efficiency of 70 to 80%. The cost of such a plant is included, along with a description of commercial-scale plants. How such plants might utilize national coal resources to produce power at low cost is shown. Additionally, how fuel cell plants might be used to create rural industrial complexes is shown. The plants projected require no cooling water and release no noxious compounds to the atmosphere. A total plant system for producing power at low cost with no air pollution is thus included.

' T ' h i s paper is not intended to be a learned discourse concerning details, experimental and otherwise, of a fuel cell energy conversion system. It is intended to describe what I believe to be a significant future for fuel cells i n the generation of commercial electric power. W e should all recognize that any attempt to peer into the future is similar to any field of projection, in that we can pretty well see what we wish to see and, even more important, we can, by our actions today, affect the reality of tomorrow. Advisory Committee Report No. 3, " N e w Methods of Power Generation," National Power Survey, Federal Power Commission, 1964, contains a prediction for new methods of power generation shown on Table I. This same report states: "It should be recognized that the forecasts indicated herein are based on research i n these areas continuing at its present, or even an increasing rate. They can be significantly accelerated by new develop ments or delayed b y handicaps. If research expenditures increase, as now seems quite possible, the commercial application of some of these new methods of power generation may materialize much sooner than is presently indicated. O n the other hand, difficulties now foreseen, but more difficult to solve than expected, or others not anticipated, may well A

383 Baker; Fuel Cell Systems-II Advances in Chemistry; American Chemical Society: Washington, DC, 1969.

384

FUEL

Table I.

CELL

II

Summary of Predictions for Thermo electric


SYSTEMS

Thermionic

Predicted generator size, kw. (year) : 1970 1975 1980

5 100 200

50-100 1,000 100,000

Segment of bulk power generation, percent (year) : 1970 1975 1980

None None Negligible

None Negligible Perceptible

Power generation efficiency, percent (year) : 1970 1975 1980

10 10 10

10 25 30-40

Capital costs, $/kw. net (year): 1970 1975 1980

1,000-2,000 500-1,000 200-500

— 1,000+ 200

This is based on information obtained by the committee of manufacturers and re search organizations knowledgable in these concepts. α

delay the commercial development of these new methods beyond the dates indicated." The fuel cell has, as we all know, been with us for over 100 years and has intrigued scientific men over that entire period. In the recent past, however, the need for high-efficiency systems for use in military and space applications has produced a renewed and reawakened interest. In considering fuel cells for commercial operations, the scientist and engi neer must drastically reornent his thinking with respect to the crucial overriding criteria of choice in any system. In space, weight is a primary consideration—indeed, possibly the only consideration. For military op erations, silence, compatibility with existing fuel systems, efficiency, weight, or some other criteria, may be all important. In commercial operations, we have the same yardstick that has existed since Phoenician times—money. For commercial fuel cells, we do not care about size or weight, but are concerned only with the cost of the end product—com mercial electric power. During the balance of my discussion, I propose to focus my attention on the potential of fuel cells as they may be applied

Baker; Fuel Cell Systems-II Advances in Chemistry; American Chemical Society: Washington, DC, 1969.

29.

C O C H R A N

Central Station Power

385

New Methods of Power Generation"


MHO

Fuel Cell

Nuclear Fusion

100,000 500,000 750,000

10 100 1,000

No prediction possible

Negligible Perceptible 2-5

None Negligible Approx. 1

None None None

— 50 55-60

50 60 60+

— 150-350 120-150

200-300 100-200 50-100

b

The capital costs do not include costs of converting d.c. to a.c.

to the generation of power from commercially available fuels and why such use can be a near term reality. Historically, capacity of the electric utility industry doubles about every ten years and this rate is expected to continue into the next century. During the past 12 to 15 years, large segments of the growth have been provided by the construction of large fossil-fuel fired central station plants. Even our regional hydro systems are finding it desirable to build large-scale thermal plants to firm up the hydro power from their systems. Utilities i n the Pacific Northwest, which are now over 90% hydro, are planning large coal-fired and nuclear steam plants. Today, the largest user of coal i n the United States is the T V A system, which began as a hydro system, and which consumed some 27 million tons of coal i n 1966. The creation of large central station systems was brought about by our old friend, the dollar, which I mentioned previously. To reduce costs, large utility systems construct very large mine-mouth plants at strategic points i n their system and link them together with high-voltage trans-



386

FUEL

Figure 1.

CELL

SYSTEMS

II

Conceptual coal-fuel cell power grid (1980-2000)

mission lines. Arrangements and agreements are reached that allow systems to intertie with one another so that we have, today, practically a nationwide grid system that has evolved in the days since W o r l d W a r II. If the fuel cell is to attain commercial use, I assume that it, too, w i l l produce an evolutionary change, requiring a number of years to mate it with the existing system of generation, transmission, and distribution. W e must recognize that the existing system of power generation and distribution d i d not spring into being full-blown overnight. It has, as a matter of fact, required over a half century to reach our current state of development. If we look into tomorrow, it seems to me we should visualize a national grid in which exceptionally large blocks of power (5,000 to 20,000 megawatts) are generated at the appropriate locations in the national grid systems. O n to this national grid, we could superimpose smaller sized plants (25 to 1000 megawatts) for reserve, emergency and local utilization. Careful review and consideration of such a system w i l l reveal the potential for wide-scale commercial use of fuel cells. A possible conceptual coal fuel cell power grid is shown on Figure 1. You w i l l note that this national grid shows how a small number of largescale plants, located in areas where large reserves of coal are available, could serve the entire Nation. In addition, we would expect both large



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387


and small-scale stations to be located on the grid to increase reliability. Coal energy is the lowest cost energy source at the point of origin and, with a fuel cell system and E H V transmission of direct current, large blocks of power can be distributed over these distances economically. Please remember that we are talking about a "potential" national grid system of the "future." What, then, is the current status? As a result of work currently going forward i n the private sector of the economy, i n government-sponsored contract research, and i n govern ment in-house research, sufficient information is in hand to design a largescale powerplant using one of the high-temperature cells. F o r such a powerplant, I would choose a solid electrolyte to be fired by coal i n a fashion substantially as shown on Figure 2 and as described by Archer (I). In this figure, you w i l l note that the coal is used indirectly by reaction with the oxides of carbon and hydrogen evolved i n a first bank of fuel cells. Some of the gas goes to a second or possibly a third bank for com plete utilization of the fuel value of the gas. Process costs w i l l determine the exact system to be employed. A t this time, it appears that two primary banks and one secondary bank ( a total of three banks i n all ) w i l l produce the most economical system. A unit of this sort can be expected to have an overall efficiency of about 70% today. F o r the fuel or utility man, this translates to a heat rate of about 4900 B.t.u.'s per kw. This is some-

JSPENT

Figure 2.

FUEL

Fuel cell power plant


G^S

388

FUEL

CELL

SYSTEMS

II

what higher than the figures presented to the Office of Coal Research by Jackson & Moreland ( 2 ) . The system of the future may include large plants something like the schematic shown on Figure 3. You w i l l note the convenient location of the plant with respect to the mine, as well as the satellite industries expected to grow i n the immediate area. As an aside, growth of these manufacturing centers located in coal areas w i l l make a substantial con tribution to the social well-being of these areas.


POWER TO T R A N S M I S S I O N

CHEMICALS

Figure 3.

Power center

The smaller sized plants to be superimposed on the grid, shown i n Figure 1, w i l l be arranged something like Figure 4. These plants could be fired by coal with some of them fired by gases that have been produced i n the coal plant complex shown on Figure 3. The benefit of this system to the ultimate consumer cannot be overstated. A n estimate for these conceptual fuel cell powerplants is shown on Table II. The estimate is taken from the Jackson & Moreland Report and shows a cost per kilowatt of about $95 to $110, an efficiency of 60%, and a net bus bar cost of 2.21 to 3.92 mills per kilowatt, depending on cost of coal, load factor, and other factors affecting the service. It is important to recognize that, in addition to lower electrical costs, the ultimate consumer of the future w i l l achieve many secondary benefits from our commercial fuel cell power system. There is no release of any sort of contamination at a l l into the atmosphere. The plant does not


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C O C H R A N

require cooling water. The lower cost of electricity w i l l make possible a complete comfort conditioned home with use of electricity for services not now deemed appropriate, such as melting snow, radiant heating of patios, mass transportation of people i n the highly urban centers of the Table II.

Fuel Cell Powerplant Summary of Annual Cost of Production $1,000 1,000-mw. Plant


60-mw. Plant Fixed Charges Operating Labor & Supe:rvision Maintenance—Fixed —Variable Supplies & Expense @ $0.02/10 B.t.u. Coal 6

Investor Owned

Public Owned

733 169 83 13

13,700 300 384 224

12,300 300 384 224

54 673

896 8,050

896 8,050

23,554

22,154

Total

Mills per kwh. Fixed Charges Operating Labor & Supervision Maintenance—Fixed —Variable Supplies & Expense Coal Total

1.549 .357 .175 .027 .114 1.422

1.740 .038 .049 .028 .114 1.022

1.562 .038 .049 .028 .114 1.022

3.644

2.991

2.813

1,000-mw.Fuel Cell Powerplant Effect of Varying Parameters on Production Costs Cost of ι Coal—$/10 B.t.u. Investor Owned Public Owned 6

Load Factor Energy, mills/kwh. Load Factor Energy, mills/kwh. Load Factor Energy, mills

0.18

0.20

0.25

0.18

0.20

0.25

0.9 2.99 0.8 3.22 0.7 3.51

0.9 3.10 0.8 3.30 0.7 3.62

0.9 3.39 0.8 3.47 0.7 3.92

0.9 2.81 0.8 3.02 0.7 3.28

0.9 2.93 0.8 3.10 0.7 3.41

0.9 3.21 0.8 3.29 0.7 3.70

a

Energy, mills /kwh. a

13.7 2.99

% Fixed Charges—Investor or Public Owned 7.0 8.5 10.0 12.3 11.6 2.81 2.73 2.62 2.40 2.21

@ $.18/106 b.tu.-—0.9 load factor.



390

FUEL

CELL

SYSTEMS

II

country, and, i n certain cases, the completely enclosed comfort condi tioned shopping center. By what process of evolution do we arrive at this "tomorrow" I have projected here? During the next ten years, it w i l l certainly be demonstrated that direct current can be produced electrically from fossil fuels via systems using magnetohydrodynamics, thermionic devices, ther mal-electric generators, and fuel cells. As I have stated previously, we could today design a fuel cell system capable of using fossil fuels, notably coal, to produce energy at an overall efficiency of about 6 0 % . F o r trans portation purposes, such as rail locomotives, I would estimate that we could produce a system with an overall efficiency of greater than 5 0 % . In each case, of course, the end result would be direct current. F o r the locomotives, the direct current could be used immediately and the first fuel cell powerplants w i l l probably utilize direct current i n the same manner, that is, for production of aluminum, i n the electrolytic industry, or perhaps i n specialized electric furnace applications. The economics of direct energy conversion are such that systems of this sort w i l l be developed. Construction of first generation plants, therefore, w i l l be i n those areas where we already have a built-in market for direct current. Total use of direct current i n various industries i n 1966 was about 70 X 10 kwh. 9

d^c POWER

RECYCLE GAS

Figure 4.

Fuel cell power plant



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391

If we compare a plant of today, located i n a coal area adjacent with a large-scale powerplant, we would find that the aluminum producer would pay about 5 to 7 mills for his power. This includes an estimated cost of about $90 per kilowatt for the generating plant, and $25 per kilo watt for the rectifier. The overall efficiency might be as much as 42%, with possible air and water pollution problems. Given the same circum stances, a fuel cell powerplant would produce this direct current at an overall efficiency of 60% from an installed generating capacity of less than $110 per kilowatt. (Note: N o air or water pollution would occur from the fuel cell plant. A l l noxious products would be treated for release to the streams or injected into deep disposal wells. ) The cost of power under these cirmustances would be about 3 to 4 mills. The ultimate user would have another advantage. The fuel cell plants I am discussing could be built for the estimated price I have shown in any size from about 20 megawatts up. This is not true of the large central station steam plant of today. After a number of these plants have been designed, constructed, placed into operation, and subsequently modified as dictated by circum stances, we can only expect the costs to be still further reduced. If we look at existing power costs vs. power costs fifty years ago, we find they have decreased in terms of constant dollars. There is certainly every reason to believe that we could achieve improvements in the fuel cell system and we may confidently then look forward to a period, 1975-1985, when our central station plant can be expected to have an overall efficiency of not less than 70%. This is an extremely significant difference from what we have today. W e should also remember that it has taken the utility industry fifty years to increase its efficiency from the average 20% of 1910 to the best plant efficiency of about 40% in 1960. I firmly believe that, during the next twenty years, we w i l l more than double the efficiency of our commercial powerplants with use of the fuel cell. During this same period, the capital costs for fuel cell plants w i l l be reduced, transmission and use of direct current w i l l increase and new uses for electric power w i l l become commonplace. This w i l l insure rapid development and commercial adoption of fuel cells. Literature

Cited

(1) Archer, D . H., Elikan, L., and Zahradnik, R . H., ADVAN. CHEM. SER. 47, 343 (1965). (2) Jackson and Moreland Div., United Engineers & Constructors, Inc., OCR Rept. No. 17 (Dec. 1966). RECEIVED

November 20,

1967.


Fuel Cell Systems-II - ACS Publications

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