Microturbines

The Capstone microturbine is an American development that has been commercially available since 2000. The original idea for the development of this product was to develop a light and powerful power generator for the American military. Today, the microturbine is mainly used in decentralized energy supply for the generation of electricity and heat.

Thanks to the innovative and environmentally friendly technology of air storage and the integrated recuperator (heat exchanger), electrical efficiencies of up to 33% are achieved, making the microturbine suitable for an increasing number of applications and uses.

The basis for microturbines is turbocharger technology and developments in the aviation industry. Electricity is generated by a high-speed generator directly coupled to the turbine.

Microturbines are typically single-shaft machines in which the generator, compressor, and turbine are mounted on a single shaft. These single-shaft machines use a high-speed permanent magnet generator and an electronic gearbox for grid coupling.

Functional diagram of a turbine

The functional diagram below also shows the main assemblies and interfaces of microturbines. They are divided into fuel supply, turbine generator unit and the power controller, which is responsible for the grid coupling (electronic gearbox).

Thermodynamic details

Combustion air enters the microturbine via the generator, cooling it in the process. Then the air is compressed to about 4 bar in the centrifugal compressor and guided through the internal recuperator where it is preheated by the hot exhaust gases.  Afterwards the hot air enters the combustion chamber where fuel is added and ignited. The hot combustion gases expand in the chamber, driving the turbine shaft with compressor and generator. After the exhaust gases are once more guided through the recuperator, they leave the MicroTurbine through the exhaust path, ready for beeing used directly or in an aditional heat exchanger.