What are some renewable sources for electricity energy?

The main renewable sources of energy to generate electricity are:

1. hydropower (use of water from rivers, dams, tides and ocean waves)
2. wind energy (using wind turbines)
3. solar power (using the power of the sun to heat water or produce electricity)
4. geothermal (using the heat deep under the earth's crust)
5. ocean Thermal (using surface heat and deep cold water)
6. biofuel (producing ethanol from organic material like switch-grass, corn and sugar cane husks)

*Strictly speaking an energy source is not 'renewable' if you mean "can humanity restore it?", as it must with trees, for example.

Geothermal, for example, is self-renewing - the Earth is constantly giving off its heat to water which is close enough to the heat to be warmed by it. It is not diminished to any noticeable extent by our using it. It is possible to use a geothermal resource to capacity locally. One example is in the geothermal area of Rotorua, New Zealand, where too many thermal bores resulted in the decline of the geysers that were a tourist attraction. This has since been addressed by controls on the bores in the area, and the geysers are performing as before.

Heat or light from the sun, wind (turns turbines which produce electricity), and water (the power of the flow turns turbines which produce electricity).
wind, tidal, geothermal and hydroelectricity