Thursday, January 24, 2008

Reversible Fuel Cell

Reversible Fuel Cell
A fuel cell is an electrochemical energy conversion device. It is two to three times more efficient at converting fuel to power than conventional combustion technologies (e.g., internal combustion engine) of the same size.
A fuel cell produces electricity, water, and heat using fuel and oxygen in the air through a single electrochemical process.
Water is the only emission when hydrogen is the fuel.
As hydrogen flows into the fuel cell on the anode side (see figure Fuel Cell Mode), a platinum catalyst facilitates the separation of the hydrogen gas into electrons and protons (hydrogen ions). The hydrogen ions pass through the membrane (the center part of a fuel cell) and, again with the help of a platinum catalyst, combine with oxygen and electrons on the cathode side producing water. The electrons, which cannot pass through the membrane, flow from the anode to the cathode through an external circuit containing an electric load which consumes the power generated by the cell. The overall electrochemical process of a fuel cell is called "reverse hydrolysis," or the opposite of hydrolyzing water to form hydrogen and oxygen.
A reversible fuel cell can accomplish "hydrolysis" through the supply of electricity to the cell and supply of water to the cathode (see figure Electrolyzer Cell Mode).
Only certain fuel cell types are reversible, that is, can also accomplish the electrochemistry associated with both the production of electricity from fuel and oxidant and the production of fuel and oxidant from water when supplied with electricity. The Reversible fuel cell concept is one that incorporates a reversible fuel cell that can accomplish both hydrolysis and reverse hydrolysis in the same cell. This allows one to consider the completely renewable production of electricity by using a renewable energy supply (e.g., solar, wind) to produce hydrogen and oxygen from water which can subsequently be used to produce electricity through the same fuel cell from the fuel and oxidant produced previously.

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