On Earth, solar energy is at the origin of the cycle of water, wind and photosynthesis carried out by the plant kingdom, on which the animal kingdom depends via the food chains. Solar energy is therefore at the origin of all energies on Earth except nuclear, geothermal and tidal energy.
There are several ways to capture solar energy:
- Photovoltaic solar energy is the electricity produced by transforming part of the solar radiation into a photovoltaic cell. Several cells are connected to each other in a photovoltaic solar module. Several modules are grouped together to form a solar installation at a private home or in a photovoltaic solar power plant. The solar installation can supply a requirement on site (in combination with a storage medium) or be injected, after transformation into alternating current, into an electrical distribution network (storage is not necessary);
- Solar thermal energy is to use the heat from the sun's rays. This radiation can be used in different ways, either directly (water heaters, solar heating including solar cookers and dryers for example) or indirectly, with heat used for another purpose: solar cooling, thermodynamic solar power plants;
- Thermodynamic solar energy concentrates the sun's rays using mirrors to heat a heat transfer fluid that generally produces electricity.
Wind energy is wind energy and more specifically, energy directly derived from the wind by means of a wind generator device such as a wind turbine or windmill. The technology currently most commonly used to capture wind energy uses a propeller on a horizontal axis.
There are mainly 4 types of wind power plants :
- Onshore wind energy which consists of the installation of wind power plants on land is the most common use of this energy;
- Offshore wind energy which consists in the installation of offshore wind farms is one of the ways in which wind energy can be developed, as it largely avoids the problem of aesthetic and neighbourhood nuisances. On the other hand, the wind is much stronger and more constant than on land ;
- Urban wind energy is a concept consisting in installing and operating wind turbines in urban areas. Urban wind energy is looking for compact wind turbines capable of offering decentralized electricity production, which would free itself from transmission and losses generated. ;
- Wind power in isolated areas can be a solution for power generation in isolated areas not connected to the grid.
In the field of energy, and more particularly bioenergy, the term biomass refers to all organic matter of plant origin (including algae), animal or fungal matter that can become a source of energy by combustion (e.g. wood energy), after methanisation (biogas) or after new chemical transformations (agrofuel).
We thus distinguish the 3 different uses of biomass:
- Combustion consists essentially of the use of wood (or green waste) as a fuel;
- Methanization is the natural biological process of degrading organic matter in the absence of oxygen. The controlled methanisation produces biogas which can then be used to produce electricity and/or heat;
- Biofuel production is made from non-fossil organic materials, derived from biomass.
Hydroelectric energy, or hydroelectricity, is a renewable electrical energy obtained by converting hydraulic energy, from the various natural water flows, into electricity. The kinetic energy of the water flow is transformed into mechanical energy by a turbine, then into electrical energy by an alternator.
There are mainly 2 types of hydroelectric power plants:
- Run-of-river power plants, mainly located in lowland areas have low-level reservoirs. They use the flow of the river as it is, without significant modulation capacity per storage. They provide a very low-cost base energy and generally have a low impact on the environment;
- Locked power plants have larger lakes, allowing them to be modulated during the day or even the week. Their management makes it possible to monitor the variation in consumption over these time horizons (morning and evening consumption peaks, difference between working days and weekends, etc.). They are typical of developments in the mid-mountain region.
- Lake power plants correspond to the structures with the most important reservoirs. These allow seasonal storage of water, and modulation of production to pass peak electricity consumption loads: summer for countries where peak consumption is determined by air conditioning, winter for those where it is determined by heating. These power plants are typical of medium and high mountain developments.
Biogas is defined as gaseous effluents, mainly methane, resulting from the fermentation of organic matter contained in landfills, sewage treatment plants, etc. Methane is a powerful greenhouse gas and its capture is highly desirable. It can be considered as an energy resource, often via its combustion to produce steam and/or electricity; its direct use in poor gas engines can also be considered. Biogas is a combustible gas, composed on average of 65% methane (CH4) and 35% CO2.