Renewable Resources

A natural resource qualifies as a renewable resource if it is replenished by natural processes at a rate comparable or faster than its rate of consumption by humans or other users. Resources such as solar radiation, tides, and winds are perpetual resources that are in no danger of being used in excess of their long-term availability. Natural resources such as fresh water, timber, and biomass might be considered as renewable, depending on usage and location. They can become non-renewable resources if used at a rate greater than the environment's capacity to replenish them. For example, groundwater may be removed from an aquifer at a rate greater than the sustainable recharge.
Hydropower
Mechanical energy is derived by directing, harnessing, or channeling moving water. The amount of available energy in moving water is determined by its flow or fall. Water flows through a pipe, or penstock, then pushes against and turns blades in a turbine to spin a generator to produce electricity. In a run-of-the-river system, the force of the current applies the needed pressure, while in a storage system, water is accumulated in reservoirs created by dams, then released when the demand for electricity is high. The reservoirs or lakes are used for boating and fishing, and often the rivers beyond the dams provide opportunities for people to raft or kayak.

Solar Power
Solar energy is energy from the Sun in the form of heat and light. Solar energy technologies harness the Sun's heat and light for practical ends such as heating, lighting and electricity. Solar energy technologies utilize heat and light from the Sun for practical ends. Technologies date from the time of the early Greeks, Native Americans and Chinese, who warmed their buildings by orienting them toward the Sun. Heat and light from the Sun, along with secondary solar resources such as wind and wave power, hydroelectricity and biomass, account for most of the available flow of renewable energy on Earth. The power we obtain from solar engery may only be able to be used during day light hours if it is not conserved into batteries of some sorts.

Tidal Power
Tidal power, sometimes called tidal energy. It is a form of hydropower that exploits the movement of water caused by tidal currents or the rise and fall in sea levels due to the tides. Although not yet widely used, tidal power has potential for future electricity generation and is more predictable than wind energy and solar power. In Europe, tide mills have been used for over a thousand years, mainly for grinding grains. This is the only form of energy which comes from the tidal forces by the Moon and the rotation of the Earth in the Earth-Moon system. Tidal energy is generated by the relative motion of the Earth, Sun and the Moon, which interact via gravitational forces. The stronger the tide, either in water level height or tidal current velocities, the greater the potential for tidal energy generation.

Geothermal
Energy generated by heat stored beneath the Earth's surface or the collection of absorbed heat in the atmosphere and oceans. The largest group of geothermal power plants in the world is located in The Geysers, a geothermal field in California. Geothermal power supplies less than 1% of the world's energy. From an environmental standpoint, the energy harnessed is clean and safe for the surrounding environment. The hot water used in the geothermal process can be re-injected into the ground to produce more steam. Although geothermal sites are capable of providing heat for many decades, eventually specific locations may cool down. In these locations, the system was designed too large for the site, since there is only so much energy that can be stored and replenished in a given volume of earth.