Micro gas turbine

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A micro gas turbine - also briefly microturbine called - is a particularly small gas turbine , developed especially for use in decentralized power supply in the power range up to 200 kW electric. Micro gas turbines are characterized by their compact design, high speed, low combustion chamber pressures and temperatures. They can be operated with a wide range of fuels such as natural and biogas, as well as liquid fuels.

construction

Section through a micro gas turbine

Micro gas turbines are usually single-shaft machines in which the generator, radial compressor and turbine are mounted on one shaft. The shaft rotates at up to 96,000 rpm. It should be emphasized that this shaft is air-bearing , thus works without lubricants and thus significantly reduces maintenance intervals and costs. In addition, the micro gas turbine does not need any cooling water , which together with the lack of lubricants enables a compact design.

An important difference to the gas turbines used in large power plants is the recuperator , a heat exchanger in which the compressed combustion air is preheated by the hot exhaust gases from the turbine. This increases the electrical efficiency of the micro gas turbine.

The combustion air enters the micro gas turbine via the generator and cools it in the process. The air is then compressed in the radial compressor to around 4 bar (g). In the recuperator, it is preheated by the hot exhaust gases. The fuel is added to the combustion chamber and ignited. The hot combustion gases are expanded by the power turbine and thus drive the compressor and generator. After the exhaust gases have given up part of their thermal energy in the recuperator, they leave the micro gas turbine in the direction of the exhaust gas heat exchanger or chimney.

Thanks to the recuperator technology, electrical efficiencies of 29% to 33% (based on Hi ) can be achieved. A recuperator uses the thermal energy from the turbine exhaust gases and uses it to heat the compressor outlet air before it reaches the combustion chamber. This reduces the fuel consumption required and higher electrical efficiencies can be achieved.

Function description

The basis for the development of micro gas turbines was the turbocharger technology and the development from the aviation industry. Thus, similar to the auxiliary engines of the aircraft in current over a permanent magnet - generator generates coupled without interposition of a mechanical transmission.

The permanent magnet of the generator is arranged directly on the drive shaft of the turbine, so that the generator is operated at the same speed as the turbine (e.g. 96,000 rpm). The high-frequency alternating current generated in this way with a frequency of 1,600 Hz is first rectified in the power electronics of the turbine and then converted into alternating current with a frequency of 50 Hz and a voltage of 400 V.

Areas of application

Areas of application of the micro gas turbine due to its technical characteristics are the supply of objects with electricity , heat, cold and steam. This opens up a wide range of options for both private and industrial areas of application. The energy demand structures of larger residential complexes, old people's homes and hospitals, office and administration buildings as well as swimming and fun pools offer possible uses for micro gas turbines.

The micro gas turbines are suitable for the regulated, decentralized energy supply due to the small power units and the good operating properties (almost constant efficiency over a wide load spectrum). By using the microturbine in the power heat coupling, overall efficiencies of up to 85% (based on Hi ) can be achieved in standard heating systems with temperatures of 60/80 ° C. Higher efficiencies are possible by optimizing the heat exchanger for the application.

Micro gas turbines in combined heat and power

Combined heat and power , which represents the combined generation and use of electricity and heat, makes optimal use of energy .

Advantages:

  • Thermal use of the exhaust gas heat with low pressure loss on the exhaust gas side
  • Integration into modern heating systems
  • Optimization of the annual degree of utilization
  • Adaptation to the electricity tariff structure (reduction of peak power, avoidance of operation in off-peak times)
  • Turbine for renewable energies

Due to its simple structure, the turbine is particularly suitable for use with regenerative gases such as sewage gas, landfill gas or biogas.

Micro gas turbines in combined heat, power and cooling

By simply coupling an absorption chiller, the micro gas turbine offers the possibility of guaranteeing the entire energy supply for a building. That includes electricity, heating and cooling. Such an installation achieves efficiencies of up to 90% and is particularly suitable in:

  • commercially used high-rise buildings
  • larger supermarkets
  • Hospitals
  • Banks
  • Commercial units
  • Apartment buildings
  • large hotels

particularities

  • Electronic gear
  • No synchronization equipment required
  • Island operability
  • Low exhaust emissions (NOx <30 mg / m³)
  • Low maintenance costs
  • Low noise emissions (approx. 65 dB (A))
  • Light weight
  • Compact design
  • Exhaust gas temperatures of around 280 ° C
  • Can be used for combined heat and power (cold)
  • Different fuels possible: natural gas , liquid gas , flare gas, biogas, kerosene and heating oil

literature

Web links

Commons : Microturbines  - Collection of images, videos and audio files