The cogeneration plants work according to the principle of Combined heat and power (CHP). Using this principle the gasous primary energy carrier (natural gas, liquid gas, biogas, sewage gas, or special gas) is converted into mechnical energy in a specially designed gas engine.
A highly efficient synchronous generator converts the mechanical energy into electrical energy. The electrical power can be consumed inside the own grid, or it can be exported into the public electrical grid.
The produced thermal heat energy from the engine and the thermal energy from the exhaust gas is used for heating up the living space and for heating up service water. Furthermore the excess heat from the exhaust gas can be offered as process heat or production of steam.
Because of the combined generation of heat and power the cogeneration plants of IET show a total efficiency of around 90% which is considerably higher than with the conventional processes with separated generation of heat and power. Not using the excess heat a nuclear power plant or a coal power plant only achieves an efficiency of 33-38%; 50% of the primary energy is lost.