Gas turbine

A gas turbine is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. (Gas turbine may also refer to just the turbine element.)

Micro turbines

Also known as:

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• Turbo alternators
• Gensets
• MicroTurbine® (registered trademark of Capstone Turbine Corporation)
• Turbogenerator® (registered tradename of Honeywell Power Systems, Inc.)

Micro turbines are becoming wide spread for distributed power and combined heat and power applications. They range from handheld units producing less than a kilowatt to commercial sized systems that produce tens or hundreds of kilowatts.

Related Topics:
Distributed power - Combined heat and power - Kilowatt

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Part of their success is due to advances in electronics, which allow unattended operation and interfacing with the commercial power grid. Electronic power switching technology eliminates the need for the generator to be synchronized with the power grid. This allows, for example, the generator to be integrated with the turbine shaft, and to double as the starter motor.

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Micro turbine systems have many advantages over piston engine generators, such as higher power density (with respect to footprint and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. However, piston engine generators are quicker to respond to changes in output power requirement.

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They accept most commercial fuels, such as natural gas, propane, diesel and kerosene. The are also able to produce renewable energy when fueled with biogas from landfills and sewage treatment plants.

Related Topics:
Natural gas - Propane - Diesel - Kerosene - Renewable energy - Biogas - Landfills - Sewage treatment

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Micro turbine designs usually consist of a single stage radial compressor, a single stage radial turbine and a recuperator. Recuperators are difficult to design and manufacture because they operate under high pressure and temperature differentials. Exhaust heat can be used for water heating, drying processes or absorption chillers, which create cold for air conditioning from heat energy instead of electric energy.

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Typical micro turbine efficiencies are 25 to 35 percent. When in a combined heat and power cogeneration system, efficiencies of greater than 80 percent are commonly achieved.

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Nye Thermodynamics Corporation http://www.nyethermodynamics.com is developing a wood fueled microturbine for cogeneration applications.

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