Things that produce heat are known as sources of heat.
The Sun is the Earth's main source of heat.
Heat can also be obtained from burning fuels such as:
petroleum
Petrol,diesel,kerosene and liquefied petroleum gas (LPG) are refined from petroleum.
Nuclear power stations generate intense heat through nuclear fission and this heat changes water into steam. The steam drives turbines, which are linked to generators to produce electricity.
Many electrical appliances give off heat.
Most light sources are also sources of heat, such as candles and light bulbs.
Friction also produces heat.