Describe the process of electricity generation and the efficiency and economics of it

The process of producing electric energy or the amount of electric energy produced by transforming other forms of energy into electrical energy; commonly expressed in kilowatt-hours (kWh) or megawatt-hours (MWh). Electric power plant efficiency η is defined as the ratio between the useful electricity output from the generating unit, in a specific time, and the energy value of the energy source supplied to the unit in the same time period. For electricity generation based on steam turbines 65% of all prime energy is wasted as heat. The maximum theoretical energy efficiency is defined in more detail by the Rankine cycle. For modern practical systems this is about 40% but less for older generating plant. The efficiency falls still further if fuels with lower energy content such as biomass are used to supply the plant. The economics of power generation based on reciprocating engines depends to a large extent on the use to which the engine is to be put. The cheapest engines available are small petrol-driven engines based on car engines, which are manufactured in large numbers each year.