LETTERS
DESIGN OF ELECTROCHEMICAL SYSTEMS Sir : Professor John Newman’s “Engineering Design of Electrochemical Systems” in the April issue of I&EC seemed of particular interest to me in connection with electrochemical energy converters-those heavy and bulky galvanic cells we call batteries, and those clumsy and fearfully expensive gas batteries with the fancy name, fuel cell. Unfortunately, despite 85 numbered equations and as many literature references, I found no hints for engineering designs except that “considerable work remains in systematizing this knowledge in a form suitable for engineering design.” Professor Newman concludes that “electrochemical systems provide a convenient experimental means of studying mass transfer problems. . . ” Quite true, and from a pedagogical point of view, highly desirable. The mere fact that this article could be written on such a broad basis would indicate that the time may finally have arrived, after well over 150 years of empirical (electro-) chemical engineering, when electrochemical reactors might be designed by other than purely empirical means. I don’t know why this empiricism has persisted in the field of electrochemical power sources. Perhaps the conventional galvanic cell is small enough so that applied electrochemists could, and did, develop it without the help of chemical engineers. Engineering of fuel cells is still in its infancy, of course, so that the pioneers who wanted to build useful systems had to take the only possible course: They simply scaled u p laboratory cells, connected them in series and parallel (both chemically and electrically), and superimposed external controls on these “systems.” We are beginning to see signs of
the application of basic science and basic engineering to electrochemical energy conversion. Dr. C. Bocciarelli has developed a theory of (e1ectro)catalysis that, for the first time in catalytic history, predicted an optimum catalyst instead of being an ex post facto explanation. Professor W. Vielstich converted kinetic data into a recipe for a mixture of anodic reactants to run a fuel cell for one year. Dr. T. Lindholm is using both theory and experiment to determine the optimum structure of a fuel-cell electrode, choice of catalyst, and concentration of electrolyte. Still, we are a long way from having applied even a major fraction of the available basic knowledge in electrochemical and chemical reactor engineering to upgrading practical systems. Chemical and electrochemical engineers, particularly those steeped in the body of basic lore of this field, could make a tremendously important contribution by doing nothing more than “systematizing this knowledge in a form suitable for engineering design.” For example, a lightweight, reliable, relatively cheap battery could have quite an impact on the market for electric trucks. I n the case of fuel cells, application of such knowledge could make the difference between their commercial life or death. A “rational route to commercial reactor design” (ibid., p. 6) is yet to be found. Dr. Newman’s paper is a welcome and valuable signpost. As a followon, will you please print a similar paper on the application of engineering design to electrochemical systems? We are in dire need of some plain, simple recipes.
Ernst M . Cohn Head, Electrochemical Systems, NASA, Washington, D.c.
about your requirements. If you’re interested i n exploring improved yields and reaction efficiencies through photochemistry, Hanovia can supply Mercury Vapor lamps, immersion wells and accessories made to your specific requirements. We can supply the following from stock: Radiation Lamp
Arc
Model _ _length _ -in.- - Watts 608A 654A 679A 673A
2.9 4.5 4.5 4.5
100 200 450 550
output, Watts 11.5 25.2 175.8 207.7
Hanovia lamps are scaled to fit readily into conventional apparatus, and are also available as lowpressure custom made arcs that provide sources of radiation of short wave uv without the heat of the medium and high pressure arcs. For more information on Hanovia laboratory, pilot plant and industrial photochemical systems, contact:
I VOL. 6 0
Circle No. 8 on Readers’ Service Card NO, 8 A U G U S T 1 9 6 8
11
