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A gas turbine is a heat engine that uses high-temperature, high-pressure gas as the working fluid. Part of the heat supplied by the gas is converted directly into mechanical work. High-temperature, high-pressure gas rushes out of the combustor and pushes against the turbine blades, causing them to rotate. In most cases, hot gas is produced by burning a fuel in air, which is why gas turbines are often referred to as "combustion" turbines. Because gas turbines are compact, lightweight, quick-starting, and simple to operate, they are used widely in industry, universities and colleges, hospitals, and commercial buildings to produce electricity, heat, and steam.
In such cases, "simple cycle" gas turbines convert a portion of input energy from the fuel to electricity and use the remaining energy, which is normally rejected to the atmosphere, to produce heat. This waste heat may be used to create steam to power a separate turbine. The attached steam turbine may generate electricity or power a mechanical load. This is referred to as a combined-cycle combustion turbine because two processes or cycles are derived from one fuel input to the primary turbine.
Simple-cycle (i.e., without external use of exhaust heat) efficiencies range from 21% to 40%. Turbines produce high-quality heat that can generate steam for combined-cycle or combined heat and power applications and significantly enhance efficiency. These systems capture and use the heat produced during the combustion process for steam, hot water, or thermally activated equipment such as absorption chillers. Taking advantage of the normally wasted heat means a tremendous gain in efficiency—nearly 90% in some cases.
Domestic and global potential markets for advanced turbines are large. At least half of all new power generating capacity added between now and 2010 is likely to use gas turbines. In addition, mid-sized turbines have tremendous potential for use as baseload, CHP, peaking, and standby/backup power in commercial and industrial settings.
For more information, visit the DOE Industrial Gas Turbines Web site.
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