What are Renewable Energies ?

Renewable energies are energies from sources that are naturally inexhaustible (water, sun, wind) or sources that are inexhaustible provided they are well managed (geothermal energy, biomass). At the origin of all renewable energies sources is the solar energy; it is not an alternative energy, it is the original and continuing primary energy source: the solar energy that is absorbed by the earth and atmosphere drives the great cycles of weather and ocean currents, distributing the energy over the face of the earth.

Renewable energies composed by:

Ø      Wind energy: it is seen as one of the most promising technologies for electricity generation with costs, in good wind regimes, comparable to fossil alternatives.

Ø      Photovoltaic: the use of semiconductor materials to convert sunlight directly into electricity. It is now widely viewed as cost competitive for many grid-connected, building-integrated uses, and for off-grid applications ranging from telecommunications to village power.

Ø      Solar thermal technologies provide heat and hot water for residential, commercial and industrial end uses, and have a long history of commercial use. For many of the applications, the technologies are now reasonably mature and competitive.

Ø      Solar thermal electric technologies, also known as concentrating solar power, create heat to produce steam and/or electricity. Commercial applications, from a few kilowatts to hundreds of megawatts, are now technically feasible though not yet economically competitive.

Ø      Biomass resources are coming in a variety of forms: wood, grasses, crops and crop residues. These can be converted to energy through thermal or biological conversion or as feedstock to produce different kinds of liquid or gaseous bio-fuels.

Ø      Geothermal technology is mostly used for power generation, though its use for space heating is becoming increasingly important. Geothermal electricity generation can be a low-cost option if the hot water or steam resource is at a high temperature and near the earth’s surface.

Ø      Hydropower is the most mature form of renewable energy and has a significant share of electricity generation worldwide. While expansion of large-scale hydro has been hampered due to environmental constraints, there is considerable interest and potential in small hydro applications.

Ø      Oceans energy: tidal forces, ocean currents, wave power and thermal gradients can all be captured to produce electricity, using technology similar to underwater windmills, and these are starting to be deployed. Ocean energy systems need a relatively extended R&D effort, but full-scale prototypes have already been constructed.

Ø      Hydrogen from renewable sources has long been pinpointed as a major potential contributor to the sustainability of the energy sector.

In France, around 6% of the energy produced is from renewable sources (essentially wood energy) and 11% of the electricity consumed is from renewable sources (Source-DRIRE).