At the origin of all the renewable energies that humanity exploits today, there are only two great sources: the Sun and the Earth. However, specialists like to classify these energies into five main types, each of which presents its specificities.
The term renewable energy is used to refer to energies that, on the human scale at least, are inexhaustible and available in large quantities. Thus there are five main types of renewable energy: solar energy, wind energy , the hydraulic energy , the biomass and geothermal . Their common feature is that they do not produce polluting emissions (or little) during the exploitation phase , and thus help to fight against the greenhouse effect and global warming .
Photovoltaic or thermal solar energy
Solar energy is called the energy that can be drawn from the radiation Sun.
Photovoltaic solar energy must be distinguished from solar thermal energy . The photovoltaic solar energy is the electricity produced by the so-called photovoltaic cells. These cells receive the light of the Sun. and are able to transform part of it into electricity. Modularity counts for one of their benefits. In fact, photovoltaic panels can be used for domestic purposes as well as for large scale energy production.
In a solar thermal or thermodynamic system , solar radiation is used to heat a fluid. Water, for example, as in some domestic water heaters. When a concentration system – a set of mirrors – is added to it, the Sun can heat the fluid up to some 1,000 ° C and the technology becomes exploitable, for example, for the generation of electricity.
The disadvantage of solar energy is that it is an intermittent energy. It can – today in any case – be exploited only when the sun shines.
The air that causes wind energy
The ancestors of the wind mills are the wind. The wind turbines produce energy – electricity for example, when coupled to a generator – from the displacement of air masses. They exploit the kinetic energy of the wind.
Wind turbines can be installed on land . We are talking about onshore wind turbines. These are technically the easiest to imagine. Even if spaces that can be reserved for them could quickly run out. And the most effective could be wind turbines installed offshore that are called offshore wind turbines.
Like solar energy, wind energy is intermittent energy. Wind turbines only produce when the wind is blowing. On the other hand, unlike solar panels, it can be difficult to install a wind turbine in your garden. Technology is rather reserved for large installations.
Hydraulic energy thanks to the sea currents
The term hydraulic energy refers to the energy that can be obtained by exploiting water. A category of energy less subject to weather conditions, but which remains reserved for a major production. In the hydraulic energies, we find:
- Dams that release large amounts of water on turbines to produce electricity.
- The tidal energy that plays on the potential energy of the tides , an energy related to the differences of water levels and the currents that these induce.
- The tidal energy that exploits the marine currents.
- Wave energy that relies on the kinetic energy of waves and waves.
- The thermal energy that can be extracted – in a careful way to avoid any disturbance of the natural flows of the seas – from the difference in temperature between the deep and the surface waters.
- The osmotic energy that produces electricity thanks to the difference of pressure that generates the difference of salinity between the sea water and the fresh water.
Biomass energy from organic matter
The biomass can become a source of heat , electricity or fuel. Several techniques can be used to derive energy from it: combustion, gasification, pyrolysis or methanation, for example.
Biomass energy can be produced locally. But care must be taken in some cases that it does not compete with the food chain.
Biomass energy includes:
- The ancestral source that is wood . It can produce heat, electricity or bio-fuels ( hydrolysis of cellulose into glucose and fermentation into ethanol).
- Bio-fuels, liquid or gas, from the processing plant such as rape or beet (1 st generation), from materials cellulose (2 e generation) or from microorganisms such as micro-algae (3 e generation).
It should be noted that biomass can only be considered as a renewable energy source if its regeneration is greater than its consumption.
Tapping the energy of the soil, geothermal energy
The geothermal energy is renewable energy from the extraction of the energy contained in the soil. This heat results essentially from the radioactive decay of the fissile atoms contained in the rocks. It can be used for heating, but also for the production of electricity. It is one of the only energies that do not depend on atmospheric conditions.
On the other hand, it depends on the depth from which it is drawn. The geothermal deep – some 2,500 meters to 150 to 250 ° C – to generate electricity. The average geothermal energy – in the water deposits especially from 30 to 150 ° C – feeds the urban heat networks. Geothermal energy at very low energy – between 10 and 100 meters deep and below 30 ° C – is the one exploited by heat pumps.
Note however that for geothermal energy remains sustainable, the pace at which this heat is drawn must not exceed the speed at which it travels inside the Earth.
To learn more about renewable energy topics, visit these websites: Clean Energy Ideas and Wikipedia.