What Are Different Types of Green Energy Sources?

Green versus Non-Green "Alternative-Renewables"

• Although today's green energies are considered "alternatives" (alternative energies) to fossil or nuclear fuels and are renewable, not all alternative and renewable energies are "green." Such is the case with biofuels and geothermal energy.

  Biofuels are created from living material. Currently, some of the most widely used biofuels derive from corn (ethanol), soy (diesel) and sugarcane (ethanol). Studies have shown that they have a much greater than anticipated negative impact on the environment through excessive greenhouse emissions and natural resource depletion.

  Geothermal energy is power derived from the heat contained in Earth's crust, generated from core radioactivity and tectonic plate movement. Although geothermal energy can be extracted with little to no environmental damage, methods used to obtain power from indirect sources (deep within the planet) can be comparatively detrimental.

  So, as some experts have pointed out, even though biofuels and geothermal power are alternative and renewable energies, they are not actually "green" in the true sense of the word.

Water Power

• Water power is energy generated from using the movement or temperature of bodies of water. Also called hydropower, water power has been used by humans for centuries to meet various household, commercial and industrial needs. Even though the use of water energy diminished with the utilization of fossil fuels to create electricity, current global energy concerns have made water power a modern alternative, renewable and green energy option. Forms of hydropower include wave, tidal and ocean thermal energy. Wave and tidal power capitalize on the weight and force of water movement to produce electricity while ocean thermal energy utilizes the temperature of warm water in tropical regions to generate electricity.

Solar Energy

• Solar energy is produced by converting the sun's radiation (sunlight) into electricity. Solar cells (photovoltaics) and concentrated solar energy systems transform sunlight into concentrated beams. The heat from these beams can be used to operate pumps and other apparatus for generators that produce electricity.

Wind Power

• Wind power is generated by harnessing the energy from the air's motion and using it to operate various systems that produce electricity. Wind power is captured through the use of horizontal-axis or vertical-axis turbines.