Renewable energy it is energy that comes from natural resources, such as light sun, wind, rain, tides and geothermal heat, which are renewable (completed naturally).

Solar energy. The sun - the nearest star The sun is the closest star to us and the largest source of energy in the system solar. The sun, with a radius of 696,000 km, a mass of 1.99 x 1030 kg, an average temperature of 57000 K, the age of 5.5 x 109 years and the average distance of 1,496,108 km from Earth is the center of our planetary system. The sun is therefore a huge source of energy, either directly or indirectly (energy water, fossil fuels). We can imagine the Sun as a giant reactor nuclear, in which thermonuclear reactions take place, based on the conversion of hydrogen into helium.

Wind power. The capacity of global wind power plants increased by a quarter in 2010 compared to the previous year and reached the level of 197 GW. According to the information provided by the Global Wind Energy Council (CGEE), China was the largest in 2010 market, adding impressive capacity of 18.9 GW, surpassing the United States and becoming the country with the largest capacity on the wind energy market. Globally, the leaders are: China (44.7 GW), the United States (40.2 GW), Germany (27.2 GW) and Spain (20.7 GW).

Hydraulic energy is the ability of a physical system (water) to perform a mechanical thing when moving from one position to another (flow). Due to the natural water circuit, automatically maintained by the Sun's energy, hydraulic energy is a form of renewable energy. Hydraulic energy is a mechanical energy formed by the potential energy of the water given by the level difference between the accumulation lake and the power plant, exactly by the kinetic energy of the moving water.

Tidal energy is the energy that can be captured by exploiting the potential energy resulting from the vertical movement of water masses at different levels or kinetic energy due to tidal currents. Tidal energy results from the gravitational forces of the Sun and Moon, as well as from the Earth's rotation.

The potential osmotic energy or salinity gradient energy is the energy available from the difference in salt concentration between seawater and riverwater. It is a renewable energy. Two practical methods for this are reverse electrodialysis (EDI) and delayed pressure osmosis (POP). Both processes are based on osmosis with ion-specific membranes. The key waste product is brackish water. This by-product is the result of the natural forces that are exploited: the flow of fresh water into the sea water, salty.

Geothermal energy is a form of renewable energy obtained from the heat inside the Earth. Hot water and steam, captured in areas with volcanic and tectonic activity, are used to heat homes and to produce electricity. 

The energy incorporated in biomass (biodiesel, bioethanol, biogas) is released by various methods, which, however, ultimately represent the chemical process of combustion (chemical transformation in the presence of molecular oxygen, process by exergonic excellence). Biomass is the biodegradable part of agricultural products, waste and residues, including plant and animal substances, forestry and related industries, as well as the biodegradable part of industrial and urban waste. Biomass is the most abundant renewable resource on the planet. It includes absolutely all the organic matter produced by the metabolic processes of living organisms. Biomass is the first form of energy used by man, with the discovery of fire. Forms of energy recovery of biomass (biofuels): Direct combustion with thermal energy generation; Combustion by pyrolysis, with generation of singaz; Fermentation, with generation of biogas or bioethanol; Chemical transformation of vegetable oil biomass by treatment with an alcohol and generation of esters; Enzymatic degradation of biomass with ethanol or biodiesel; Cellulose can be enzymatically degraded to its monomers, carbohydrate derivatives.