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Pratt and Whitney-batteries based on the distinguished work begun over thirty years ago by Mr. F. T. Bacon.

Portable (carriable by one or two men).-Successful application within three years seems certain with power sources for military communication equipment in a preferred position.

Transportable (carriable by vehicle with batteries for propulsion excluded).— Already installed by Brown Boveri (Figure 4). Successful military applications of other types at higher ratings seem likely.

Propulsion.-Successful applications will come first on military vehicles. Golf carts with hydrazine batteries have been demonstrated by Allis-Chalmers. Military fork-lift trucks should operate on fuel batteries within 10 years. The Swedish submarine effort was mentioned above.

The passenger automobile seemingly affords the fuel battery a great opportunity, but unit capital cost is such a formidable hurdle now that other problems are scarcely worth discussing. For the present, effort should be concentrated on automobiles that use storage batteries (8) perhaps new types not yet in use, which might be replaced or augmented by satisfactory fuel batteries. English opinion holds that the locomotive or the fuel-battery-powered railroad car is a more promising application than the passenger automobile. Hydrogen/ oxygen batteries to operate all three could be built at a high price today; it will be remembered that Allis-Chalmers used such a battery to power a tractor in 1959.

The Home.-Steady progress (Broers, TNO, Holland; Institute for Gas Technology, Chicago) being made on methane/air batteries with molten-carbonate electrolytes leads one to expect experimental home installations exceeding 20% in comparative thermal efficiency within 5 years; such fuel batteries would be connected to banks of storage batteries as energy reserve for peak loads.

Central Stations.-The earlier prediction (6) stands with a few added remarks. The central station ranks with the passenger automobile in difficulty as an application for the fuel battery. It differs from the automobile in that unit capital cost is a less serious hurdle here than overall energy cost. The future of the fuel battery in the large-scale generation of electricity seems linked to the future of natural gas. The growth of atomic energy installations, and the effect this will have on the coal industry, both enter the picture because one must look perhaps a decade ahead for the earliest time that a centralstation fuel-battery might begin to be used. But there is hope for the fuel battery in smaller central stations that serve a single community-stations in which the use of heat and of electrical energy will be efficiently combined, and distribution costs will be reduced.

The reader wishing to reconcile our prediction with that of Reference 7 will note that we have stressed fuel batteries of low ratings, and included space and military applications.

A logical position at present seems to be that fuel-cell research should continue so long as significant progress is made, and that the engineering development of H2/O2 and of H2/air batteries for favorable applications should be 'emphasized. Fuel batteries will prove themselves indispensable in some applications and useful in many others.

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I gladly thank Dr. E. J. Cairns for his help on this paper.

REFERENCES

1. Standards Publication No. CV 1-1964, "Fuel Cell Definitions", National Electrical Manufacturers Association, New York, is much less restrictive. By their definitions, an electrochemical cell in which cesium and fluorine combine continuously would have to be called a fuel cell.

2. Private communication, H. G. Plust, Brown, Boveri and Company, March 22, 1966.

3. H. A. Liebhafsky and E. J. Cairns, General Electric Report No. 60-RL2382C, "The Fuel Cell and The Power Industry", March 1960.

4. G. D. Friedlander, IEFE Spectrum, 1, No. 10, 58. October 1964.

5. Abrams v. U.S., 250 U.S. 616, 624 (1919), Holmes. J., dissenting.

6. H. A. Liebhafsky and D. L. Douglas. Ind. Eng. Chem., 52, 293 (1960).

7. Lord Rothschild, Science Journal, 1, 82 (1965).

8. See for example Maxwell Boyd, "Electric 60 mph 'mini' out soon", London Sunday Times, Feb. 27, 1966.

Figure 1. By their chemical natures, fuels tend to give up electrons and oxygen tends to capture them. This tendency leads to a transfer of electrons from fuel to oxygen during combustion. In the fuel cell, the same process is made to proceed at two electrodes in more orderly fashion.

Electrons are given up by the fuel at the anode, flow through the external circuit where they can do work, and are captured by oxygen at the cathode. The circuit is completed by the flow of ions through the electrolyte, which is virtually impervious to electrons. Note that the electrical transport resulting in work is a directed process throughout. This explains why the fuel cell escapes the Carnot-cycle limitation, which applies when heat energy (random) is converted into work (directed).

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Figure 2. The First Fuel-Battery System (1842). Grove several years before had the dream of "effecting the decomopsition of water by means of its composition"-in our language, of using a hydrogen-oxygen fuel battery (four cells of which are shown connected in series above) as the power source for an electrolysis cell in which hydrogen and oxygen are produced. Twenty-six cells in series were required to decompose water in the upper cell. Sulfuric acid was the electrolyte, and the electrodes were platinum.

The combination of fuel battery and electrolyzer is the basis of regenerative electrochemical systems for energy storage.

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Figure 3. Another dream: "Electricity direct from coal" (Jacques, 1896). This carbon-air battery delivered 16 amperes at 90 volts and was said to have been in operation for 6 months when the picture was taken. The electrolyte was molten potassium hydroxide (costly) which was changed to potassium carbonate (cheap) as the battery operated. This alone makes the battery uneconomic. In addition, its efficiency-erroneously placed at "82 per cent of the theoretical"was grossly overestimated, and the inventor did not come to grips with the difficulties that would have arisen from impurities (ash, sulfur) had he used coal.

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Figure 4. The fuel-battery system for Project Gemini. (Courtesy Direct Energy Conversion Operation, General Electric Co., Lynn, Mass.) Water transport to the accumulator is accomplished without moving parts by means of wicks and a pressure differential across a porous member,

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