Commercial and utility plants currently use nuclear fission reactions to heat water to produce steam, which is then used to generate electricity.

Nuclear power provided about 15% of the world's electricity.

Nuclear power reduce greenhouse gas emissions as no coal or fossil fuels are burnt, no carbon dioxide is released into the air.

Fossil fuelled power plants may also use a steam turbine generator or in the case of natural gas fired plants may use a combustion turbine.

A coal-fired power station produces electricity by burning coal to generate steam, and has the side-effect of producing a large amount of carbon dioxide, which is released from burning coal and contributes to global warming.

A bulk of the world's electric energy is produced by fossil fuel in particular coal fired power plants

Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels.

Alternative energy is that which is produced without the undesirable consequences of the burning of fossil fuels, such as high carbon dioxide emissions, which is considered to be the major contributing factor of global warming.

The nature of what is regarded alternative energy sources changes considerably over time, because of the variety of energy choices and differing goals of their advocates.