Direct Energy, 2018a

232 9.6 Fuel Cells
9.6.3 Practical Considerations of Fuel Cells
The history of fuel cells goes back almost as long as the history of batteries.
The concept of the fuel cell dates to around 1802 [3, p. 2,222] [60, p. v].
Working fuel cells were demonstrated in the 1830s [3, p. 222] [60, p. v],
and the rst practical device was built in 1959 as pure materials became
commercially available [5, p. 46] [60, p. v, 26]. While both batteries and
fuel cells are commercially available, batteries have found a home inside
almost every every car, computer, and electronic devices while fuel cells
are more specialized products. There are a number of limitations of fuel
cell technology that have prevented more widespread use. One limitation
is their cost. Some fuel cells use platinum as the catalyst, and platinum is
not cheap. Some cells that do not use platinum catalysts have the problem
that their eciency is reduced in the presence of carbon monoxide or carbon
dioxide, which are commonly found in air. Hydrogen gas or methane are
used as the fuel in some cells, and the delivery and storage of these fuels
pose challenges. Additionally, some of the more ecient systems are large
and require xed space, air or water cooling, and additional infrastructure,
so these devices do not lend themselves to portable applications.
Fuel cells have advantages which lead to useful applications. Many fuel
cells produce no harmful outputs. If hydrogen gas is used as the fuel and
oxygen from the air is used as the oxidizer, the only byproduct is pure water.
It is hard to nd an energy conversion device which generates electricity
and is easier on the environment than this type of fuel cell. The left part
of Fig. 9.10 shows a photograph of a proton exchange membrane fuel cell.
The right part of Fig.9.10 shows an image of the water formed during its operation.
The image was obtained by the neutron radiography method, and
it was taken at the National Institute of Standards and Technology Center
for Neutron Research in Gaithersburg, Maryland. These gures are used
with permission from [150]. In some applications, the water production is a
main advantage. NASA space vehicles have used fuel cells to produce both
electricity and pure water since the Gemini and Apollo projects dating to
the 1960s [3, p. 250]. They have been used to produce both electricity
and water on military submarines since the 1960s too [3, p. 250]. Another
advantage of fuel cells is that they can be more ecient than other devices
which generate electricity. High temperature and higher power units can
have eciencies up to 65% [128]. Since some of the highest eciencies are
achieved in higher temperature and higher power devices, fuel cells have
found a niche in large and stationary applications generating kilowatts or
megawatts of electricity.