Co-generation is the concept of simultaneously producing two forms of energy. One of the forms of energy must always be heat and the other may be electricity or mechanical energy. In a conventional power plant, fuel is burnt in a boiler to generate steam. This steam is used to drive a turbine, which in turn drives an alternator through a high speed gear box to produce electric power. The exhaust steam is generally condensed to water which goes back to the boiler. However, in a co-generation plant, some amount of steam may be extracted from the turbine at the required pressure and temperature for use in the process.