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Microturbine
A microturbine (MT) is a small gas turbine with similar cycles and components to a heavy gas turbine. The MT power-to-weight ratio is better than a heavy gas turbine because the reduction of turbine diameters causes an increase in shaft rotational speed. Heavy gas turbine generators are too large and too expensive for distributed power applications, so MTs are developed for small-scale power like electrical power generation alone or as combined cooling, heating, and power (CCHP) systems. The MT are 25 to 250 kW (34 to 335 hp) gas turbines evolved from piston engine turbochargers, aircraft auxiliary power units (APU) or small jet engines, the size of a refrigerator. Early turbines of 30–70 kW (40–94 hp) grew to 200–250 kW (270–340 hp).
They comprise a compressor, combustor, impeller/turbine and electric generator on a single shaft or two. They can have a recuperator capturing waste heat to improve the compressor efficiency, an intercooler and reheat. They rotate at over 40,000 RPM and a common single shaft microturbine usually rotates at 90,000 to 120,000 RPM. They often have a single stage radial compressor and a single stage radial turbine. Recuperators are difficult to design and manufacture because they operate under high pressure and temperature differentials.
Advances in electronics allows unattended operation and electronic power switching technology eliminates the need for the generator to be synchronised with the power grid, allowing it to be integrated with the turbine shaft and to double as the starter motor. Gas turbines accept most commercial fuels, such as petrol, natural gas, propane, diesel fuel, and kerosene as well as renewable fuels such as E85, biodiesel and biogas. Starting on kerosene or diesel can require a more volatile product such as propane gas. Microturbines can use micro-combustion.
Full-size gas turbines often use ball bearings. The 1,000 °C (1,270 K; 1,830 °F) temperatures and high speeds of microturbines make oil lubrication and ball bearings impractical; they require air bearings or possibly magnetic bearings. They may be designed with foil bearings and air-cooling operating without lubricating oil, coolants or other hazardous materials.
To maximize part-load efficiency, multiple turbines can be started or stopped as needed in an integrated system. Reciprocating engines can react quickly to power requirement changes while microturbines lose more efficiency at low power levels. They can have a higher power-to-weight ratio than piston engines, low emissions and few, or just one, moving part. Reciprocating engines can be more efficient, be cheaper overall and typically use simple journal bearings lubricated by motor oil.
Microturbines can be used for cogeneration and distributed generation as turbo alternators or turbogenerators, or to power hybrid electric vehicles. The majority of the waste heat is contained in the relatively high temperature exhaust making it simpler to capture, while reciprocating engines waste heat is split between its exhaust and cooling system. Exhaust heat can be used for water heating, space heating, drying processes or absorption chillers, which create cold for air conditioning from heat energy instead of electric energy.
Microturbines have around 15% efficiencies without a recuperator, 20 to 30% with one and they can reach 85% combined thermal-electrical efficiency in cogeneration. The recuperated Niigata Power Systems 300 kW (400 hp) RGT3R thermal efficiency reaches 32.5% while the 360 kW (480 hp) non recuperated RGT3C is at 16.3%. Capstone Turbine claims a 33% LHV Electrical Efficiency for its 200 kW (270 hp) C200S.
In 1988, the NEDO started the Ceramic Gas Turbine project within the Japanese New Sunshine Project: in 1999 the recuperated twin-shaft 311.6 kW (417.9 hp) Kawasaki Heavy Industries CGT302 achieved a 42.1% efficiency and a 1,350 °C (1,620 K; 2,460 °F) turbine inlet temperature. In October 2010, Capstone was awarded by the US Department of Energy the design of a two-stage intercooled microturbine derived from its current 200 kW (270 hp) and 65 kW (87 hp) engines for a 370 kW (500 hp) turbine targeting a 42% electrical efficiency. Researchers from the Lappeenranta University of Technology designed a 400 kW (540 hp) intercooled and recuperated two-shaft microturbine with an efficiency of 40.2%, resulting in the formation of Aurelia Technologies LLC and the ultimate commercialization of the A400 small gas turbine.
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Microturbine
A microturbine (MT) is a small gas turbine with similar cycles and components to a heavy gas turbine. The MT power-to-weight ratio is better than a heavy gas turbine because the reduction of turbine diameters causes an increase in shaft rotational speed. Heavy gas turbine generators are too large and too expensive for distributed power applications, so MTs are developed for small-scale power like electrical power generation alone or as combined cooling, heating, and power (CCHP) systems. The MT are 25 to 250 kW (34 to 335 hp) gas turbines evolved from piston engine turbochargers, aircraft auxiliary power units (APU) or small jet engines, the size of a refrigerator. Early turbines of 30–70 kW (40–94 hp) grew to 200–250 kW (270–340 hp).
They comprise a compressor, combustor, impeller/turbine and electric generator on a single shaft or two. They can have a recuperator capturing waste heat to improve the compressor efficiency, an intercooler and reheat. They rotate at over 40,000 RPM and a common single shaft microturbine usually rotates at 90,000 to 120,000 RPM. They often have a single stage radial compressor and a single stage radial turbine. Recuperators are difficult to design and manufacture because they operate under high pressure and temperature differentials.
Advances in electronics allows unattended operation and electronic power switching technology eliminates the need for the generator to be synchronised with the power grid, allowing it to be integrated with the turbine shaft and to double as the starter motor. Gas turbines accept most commercial fuels, such as petrol, natural gas, propane, diesel fuel, and kerosene as well as renewable fuels such as E85, biodiesel and biogas. Starting on kerosene or diesel can require a more volatile product such as propane gas. Microturbines can use micro-combustion.
Full-size gas turbines often use ball bearings. The 1,000 °C (1,270 K; 1,830 °F) temperatures and high speeds of microturbines make oil lubrication and ball bearings impractical; they require air bearings or possibly magnetic bearings. They may be designed with foil bearings and air-cooling operating without lubricating oil, coolants or other hazardous materials.
To maximize part-load efficiency, multiple turbines can be started or stopped as needed in an integrated system. Reciprocating engines can react quickly to power requirement changes while microturbines lose more efficiency at low power levels. They can have a higher power-to-weight ratio than piston engines, low emissions and few, or just one, moving part. Reciprocating engines can be more efficient, be cheaper overall and typically use simple journal bearings lubricated by motor oil.
Microturbines can be used for cogeneration and distributed generation as turbo alternators or turbogenerators, or to power hybrid electric vehicles. The majority of the waste heat is contained in the relatively high temperature exhaust making it simpler to capture, while reciprocating engines waste heat is split between its exhaust and cooling system. Exhaust heat can be used for water heating, space heating, drying processes or absorption chillers, which create cold for air conditioning from heat energy instead of electric energy.
Microturbines have around 15% efficiencies without a recuperator, 20 to 30% with one and they can reach 85% combined thermal-electrical efficiency in cogeneration. The recuperated Niigata Power Systems 300 kW (400 hp) RGT3R thermal efficiency reaches 32.5% while the 360 kW (480 hp) non recuperated RGT3C is at 16.3%. Capstone Turbine claims a 33% LHV Electrical Efficiency for its 200 kW (270 hp) C200S.
In 1988, the NEDO started the Ceramic Gas Turbine project within the Japanese New Sunshine Project: in 1999 the recuperated twin-shaft 311.6 kW (417.9 hp) Kawasaki Heavy Industries CGT302 achieved a 42.1% efficiency and a 1,350 °C (1,620 K; 2,460 °F) turbine inlet temperature. In October 2010, Capstone was awarded by the US Department of Energy the design of a two-stage intercooled microturbine derived from its current 200 kW (270 hp) and 65 kW (87 hp) engines for a 370 kW (500 hp) turbine targeting a 42% electrical efficiency. Researchers from the Lappeenranta University of Technology designed a 400 kW (540 hp) intercooled and recuperated two-shaft microturbine with an efficiency of 40.2%, resulting in the formation of Aurelia Technologies LLC and the ultimate commercialization of the A400 small gas turbine.