Boiler – burns fuel (coal, oil, natural gas, wood, garbage – just about anything that burns) heating water into steam, which (using a steam turbine) turns a generator

Photovoltaic Device - A solid-state electrical device that converts light directly into direct current.

Turbines – converts the flow of a fluid (air, steam, water, or hot gases) into mechanical motion, which turns a generator

Fuel Cells – An electrochemical device that converts chemical energy directly into electricity.

Engine – converts the expansion of a burning fluid (gasoline, natural gas, alcohol) into mechanical motion, which turns a generator

Hydro-electric - the force of water falling through a water turbine spins a generator

Nuclear – converts the heat produced by decaying radioactive material into steam, which (using a steam turbine) turns a generator

Solar – converts the heat of the sun into steam, which (using a steam turbine) turns a generator

Wind – spins a propeller attached to a generator

Geothermal – uses the heat below the earth’s surface to heat water into steam, which (using a steam turbine) turns a generator