In response to your request on the web page, I am submitting this short
description of fuel cells.
Sincerely,
Marijan Papic, Ph.D., P.Eng.
A fuel cell is a device in which the chemical energy of reactants
(hydrogen and air) is converted directly into usable energy in the form
of electricity and heat without combustion as an intermediate step.
Fuel cell power plants are distinguished by high efficiency, low
emissions, fuel flexibility, quick installation and quiet operation.
A single fuel cell is composed of an anode (an electrode where oxidation
occurs) and a cathode (an electrode where reduction occurs) separated by
an electrolyte. The electrodes are porous plates sandwiched around
porous material holding the electrolyte.
The process concept is similar to that used in a common primary
electrochemical cell and is the reverse of the water electrolysis
process. Hydrogen rich gas is fed over the surface of anode where it is
oxidized into positive hydrogen ions by releasing electrons. Electrons
flow from the anode through an external circuit (wire) to the cathode
and hydrogen ions travel through an electrolyte to the cathode. Oxygen
rich gas (air) is fed over the surface of cathode where it is reduced to
negative oxygen ions by accepting electrons released by hydrogen.
Oxygen ions combine with hydrogen ions to form water. Electricity and
heat are generated in the process.
A single fuel cell generates direct current at low density and low
voltage (2 kA/m2, and 1V). Practical voltages are obtained by
connecting many individual cells in series, i.e. stacks or batteries.
Fuel cell stacks can further be configured in series, parallel, both
series and parallel or as single units, depending on particular
application.
There are different types of fuel cells identified by the kind of
electrolyte used: solid polymer electrolyte, phosphoric acid
electrolyte, molten carbonate electrolyte and solid oxide electrolyte
fuel cells. Different fuel cells are being developed for different
applications.
For a fuel cell power plant to be a practical energy generator it should
be able to use commonly available fuels and be able to produce
alternating current power, Thus a fuel cell power plant consists of
three major subsystems – a fuel processor (where hydrogen is produced),
a fuel cell power section (where dc power is produced) and a power
conditioner (where power is conditioned for practical use).
Fuel cells have been developed for a number of diverse applications
including space power, naval propulsion, electric vehicles, isolated
power sources and utility applications.
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