Cogeneration
There are many types of power stations: electricity can be generated from sunlight or from below the surface of the Earth's crust (photovoltaic or geothermal power stations), from the mechanical energy produced by water or wind (hydroelectric and wind power stations) or from the nuclear fission of uranium atoms (atomic power stations). The most common type are the thermo-electric power stations where gases obtained from the burning of combustible fossil fuels (like carbon, gas or petroleum) turn a turbine connected to a generator which then produces electricity.
Combined cycle cogeneration power stations are an evolution of such power stations.
They produce electricity and heat from a single primary source and allow for the recovery of a part of the heat which would normally be dispersed in traditional thermoelectric power stations: also the exhaust gases, which are extremely hot, are in turn used to heat water, to feed a turbine and to produce electricity.
Cogeneration is obtained by using residual heat for district heating.
A further evolution of cogeneration is trigeneration which, not only simultaneously produces electricity and heat, but also makes use of the thermal energy to obtain cooled water which can then be used for district air-conditioning.
