132 Electrical Power Systems Technology
reactants from an external source. Ordinarily, hydrogen gas is delivered to
the anode of the cell and oxygen gas or air is delivered to the cathode. The
reaction of these gases is similar to the reverse of electrolysis. (During the
electrolysis process, an electric current decomposes water into hydrogen
and oxygen.)
Fuel cells were developed long ago. It was known early that elec-
trochemical reactions could be used to convert chemical energy directly
to electrical energy. The first commercial fuel cells were used as auxilia-
ry power sources for United States space vehicles. These were hydrogen-
oxygen fuel cells. The development of fuel cells has brought about some
cells with a power capacity of up to 500 watts. Some cells that are in the re-
search stages have a power output of up to 100 kilowatts. These fuel cells
produce low-voltage direct current. Several cells may be connected in se-
ries-parallel configurations to produce greater voltage and current levels.
Several large companies are performing experiments with the design of
fuel cells. Many new technological approaches to fuel cells are being devel-
oped. Large-scale systems are planned that may use phosphoric acid as an
electrolyte. This system will operate with a variety of hydrocarbon fuels.
Cells presently being developed use high-temperature carbon or alkaline
electrolytes. Cells in the developmental stages might use synthetic fuels
derived from coal.
Some problems have been encountered in the development of fuel
cells. The chemical reaction brought about by the fuels requires a cata-
lyst. The importance of the catalyst is greater at lower operating tempera-
tures. At higher temperatures, cheaper and more abundant catalysts may
be used. However, some designers speculate that the catalysts required for
lower temperature operation may become unavailable or, if not, at least
very expensive in the future. At present, the initial cost of a fuel-cell sys-
tem is very great. A system, at this time, would not be competitive with
other power systems in operation. Another developmental problem is that
of water disposal. A vast amount of water is produced by the chemical re-
actions of the fuels.
In addition to space applications, other applications could potentially
include mobile electrical power sources. It has been suggested that fuel
cells could be used as power sources to drive electric cars. Also, fuel cells
are being considered as power sources for trains, submarines, and mili-
tary vehicles. However, the use of fuel cells for large-scale power systems
would not be feasible.