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Radio Applications of Fuel Cells
Your choices for powering a transmitter or studio site now include the use of a technology invented in 1839: The fuel cell. Until recently, the costs to purchase and install fuel cells have been prohibitive; but, lower costs, more choices of fuel and federal tax incentives might make them a viable alternative for your facility.
In simple terms the fuel cell is a device that combines hydrogen and oxygen creating an electrochemical reaction that produces heat, water and electricity. The hydrogen is produced from common hydrocarbon-based fuels such as natural gas, gasoline, diesel or methanol. Oxygen is pulled from the air around it. The combination produces a chemical reaction, not completely unlike a standard battery. The fuel cell is essentially a battery with a system that constantly feeds the proper fuel into the cell. The process does not use combustion and as such produces no emission products.
There are several types of fuel cells, particularly for higher-power applications, but they are expensive and tend to operate at very high temperatures (up to 1,000 C). However, the Polymer Exchange Membrane Fuel Cell (PEMFC) is the technology currently used for the small-scale power generation used for transportation and other power applications. PEMFC systems operate at a lower temperature (less than 180 F) and have a higher efficiency. The most common fuels are LP or natural gas.
The system components
A fuel cell is created with six basic process components.
Fuel Processor/Reformer — This system extracts the hydrogen from the hydrocarbon fuel. The generic term reforming is generally applied to the process of converting liquid or gaseous light hydrocarbon fuels to hydrogen and carbon monoxide. This process separates the fuel into hydrogen, water, carbon monoxide and heat.
Electrodes — As in any battery, there is an anode (negative) and a cathode (positive). The anode has channels that disperse the hydrogen gas equally over the surface of the catalyst. The hydrogen molecules are split into positively charged ions, giving up one electron each. The positively charged ions then migrate through the electrolyte to the positive post (cathode). The negatively charged electrons travel through the external circuit to produce electric energy.
Electrolyte — The electrolyte transports the positively charged hydrogen ions to the cathode in order to complete the electric circuit. In addition, it provides a physical barrier to prevent the fuel and oxidant gas streams from directly mixing.
Oxidant — Typically oxygen that is pulled from the air surrounding the fuel cell. The oxidant is channeled through the cathode.
Fuel Cell Stack — Each fuel cell produces 0.7V. Several fuel cells are connected together to produce the desired output, 12V or 24V are most common.
Power conditioning — converts and/or conditions the dc power to ac (if desired). Fuel cells typically need some time to start producing power; many systems utilize capacitor banks to store power to ensure a constant power source in the event of transfer from grid power to fuel cell, this gives the fuel enough time to start while providing uninterrupted power.
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