W a n t e d : Some H a n d y Hydrogen National Carbon's new fuel cell works, an easy H2 source could m a k e it run almost anything J N o w T H A T T H E SEARCH for a w a y
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c o n v e r t chemical energy of g a s e s into electricity has p a i d off in N a t i o n a l Carbon's fuel cell, a n e w l u r e d a n g l e s b e fore researchers—a c h e a p source of hyd r o g e n . T o make t h e cell work, hydrogen a n d oxygen unite t o p r o d u c e electrical energy ( w a t e r electrolysis in rev e r s e ) . B u t before t h e cell c a n comp e t e with conventional p o w e r systems, b y d r o g e n has t o be easier a n d c h e a p e r to come b y . N a t i o n a l C a r b o n ( a division of U n i o n C a r b i d e ) itself suggests a few such hydrogen sources. These sources include: • Coal, which gives off h y d r o g e n w h e n treated w i t h steam. • Ammonia, plentiful right n o w , and should b e for several years to c o m e . • Petroleum. • Solar energy (C&EN, July 2 , 1956, p a g e 3 2 5 0 ) t o decompose water—this way, you get b o t h hydrogen a n d oxygen a t t h e same time. Hydrides might b e a possibility. A small amount of lithium h y d r i d e , for example, packs a lot of Hydrogen. A n d h y d r a z i n e , which can b e d e c o m p o s e d at room t e m p e r a t u r e , h a s some appeal for military uses of t h e cell. W h i c h one of t h e varied h y d r o g e n sources will make t h e g r a d e is anyone's guess. A s National Carbon's research vice president Clarence E . L a r s o n says, every c o m p o u n d t h a t c a n g i v e hydrogen b a s t o be thoroughly studied. Aiding t h e growing h u n t is t h e fact that the cell runs even w h e n h y d r o g e n has impurities in i t . ( O x y g e n p r e s e n t s no problem, since air can b e u s e d as a source). • How the Cell W o r k s - a r i d W h y . The fuel cell which National Carbon first showed off this w e e k is m a i n l y a jar into w h i c b hydrogen a n d oxygen are f e d t h r o u g h chemically t r e a t e d , hollow, porous carbon electrodes. The c o m p a n y isn't telling w h a t t e c h n i q u e s it's using to m a k e t h e electrodes since, as L a r s o n puts it, they a r e t h e secret of the cell's success. T h e electrodes are i m m e r s e d in potassium h y d r o x i d e solution. Concentration of t h e electrolyte isn't revealed either, b u t a h i n t m a y be
in the Bacon fuel cell. Cambridge's F . T. Bacon devised a fuel cell three years ago t h a t u s e d 2 7 % K O H and porous nickel electrodes. This ceil operated best at 2 4 0 ° C. and 8 0 0 p.s.i. National Carbon's works at room temperatures and atmospheric p r e s s u r e thanks to t h e carbon electrodes. W h e n t h e gases enter National Carbon's cell and diffuse through t h e electrodes into t h e K O H solution, water forms a n d an electron is freed electrochemically. This electron enters the electrical system t h r o u g h the external circuit. I t returns to t h e cell at the oxygen electrode where, during t h e reaction between oxygen and K O H , it's accepted. Another cell design is one with a concentric t u b e system. H e r e , one electrode nestles in t h e other, separated b y electrolyte. T u b e length is varied t o give t h e cell t h e volume n e e d e d for t h e current n e e d e d . > Cell's Future Bright. National C a r b o n feels t h a t t h e fuel cell h a s a terrific future. First application is to give silent electrical power for t h e army's "Silent Sentry"—the smallest radar set yet. A battery of cells is now working a t the U. S. Army Electronic Proving G r o u n d in Arizona, site of a three-day meeting b y the Association of the U . S.
IONIC CONDUCTIVITY
WATER I N HYDROGEN STREAM EXTERNAL CIRCUIT
Basically, here's h o w t h e fuel cell works
First use for fuel cell is t o power t h e Army's Silent Sentry, world's smallest radar set. Battery of the silent running cells give necessary 2 8 volts
Army's Communications a n d Electronics Symposium this week. During its operating life, says National Carbon's head fuel cell researcher Karl Kordesch, t h e cell doesn't change. Only one by-product, water, is made and this is removed by evaporation. So cell life is theoretically unlimited, Kordesch notes. Cells have been running 8 hours a day, 5 days a week for a year, h e claims, without signs of deteriorating; starts and stops are much tougher on the cell than continuous operation. Another reason for optimism is that voltage depends directly on t h e number of cells. E a c h cell yields about one volt. And the cell's efficiency, says Kordesch, ranges from 65 to 80%, depending on h o w it's used. By contrast, burning the two gases in a heat engine gives 25 to 3 0 % efficiency, according to an estimate Farrington Daniels made for C&EN last year. A few potential uses include military communications systems, mobile power units, a n d stand-by p o w e r plants. It could, says the company, b e an ideal source of power in remote locations where common fuels or water power are lacking. And as a portable power source, the fuel cell could someday run equipment such as lawnmowers, outboards, and even small cars, in Larson's opinion. SEPT.
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