Environmental Engineering Reference
In-Depth Information
13.2 Fuel Cells: Bearers of Hope
Fuel cells are considered the key to the future energy use of hydrogen, because they
can convert hydrogen directly into electric energy. Theoretically at least, this results
in higher effi ciency levels than with combustion in conventional thermal power
plants.
The principle of fuel cells has been known for a very long time. There is some
controversy about who actually invented the fuel cell. The German-Swiss chemist
Christian Friedrich Schönbein conducted the fi rst tests in fuel cell technology in
1838. The English physicist Sir William Robert Grove built the fi rst fuel cell in
1839. Well-known scientists like Henri Becquerel and Thomas Edison were subse-
quently involved in its further development. A suffi ciently advanced stage of devel-
opment was fi nally reached in the mid-twentieth century, enabling NASA to make
major use of fuel cells by 1963.
Since the 1990s fuel cell development has been moving ahead at full speed. Car
manufacturers and heating companies have adopted the technology and are looking
to profi t from a positive image as a result.
Fuel cells basically involve a reversal of electrolysis. A fuel cell always contains
two electrodes. Depending on the type of fuel cell, pure hydrogen (H
2
) or a fuel
containing hydrocarbons is fed through the anode and pure oxygen (O
2
) or air as an
oxidation material is fed through the cathode. An electrolyte separates the anode
and cathode (Figure 13.5). As a result of this, the chemical reaction is controlled.
Electrons fl ow over a large circuit and emit electric energy. The remaining positively
charged ions diffuse through the electrolyte. The waste product is water.
Figure 13.5
Working principle of fuel cells.
There are different types of fuel cells that essentially differ from each other based
on electrolytes, the permissible fuel gases and operating temperatures. In practice,
the following abbreviations are used to identify the fuel cell types:
