Resources

1. Renewable energy comes from resources that are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves and geothermal heat
2. Non-renewable energy comes from resources that are not renewed at a sufficient rate for sustainable economic extraction in meaningful human time-frames, such as fossil fuels
3. Ultimately, all energy on Earth originates from nuclear fusion in the Sun

Extraction of useful energy

1. Chemical energy stored in guel can be released, generally through combustion, as heat energy and often harnessed into mechanical energy via an engine

2. Water

   1. The up-down motion of wave power is harnessed by devices, which typically use the water to drive generators, turbines or pumps, on the surface of the ocean, generally around the coast
   2. The tides contain kinetic and gravitational potential energy that can be harnessed, using tidal stream generators, which are similar to wind turbines, and tidal barrages, which store an incoming tide in an estuary before letting it back out again, respectively
   3. Hydroelectric dams are large-scale turbines that harness the energy from falling or flowing water
3. Geothermal resources are hot rocks deep within the Earth from which thermal energy can be harnessed using heat pumps, where cold water is pumped down and is heated, driving a turbine that converted the thermal energy into electrical energy
4. Nuclear fusion of uranium in a nuclear reactor releases huge amounts of energy
5. Heat & light from the Sun can be captured using solar cells & panels and converted into electrical energy

Advantages and disadvantages

Efficiency

1. Efficiency is useful outputtotal input⋅100%