Renewable energy is that energy that comes from practically inexhaustible natural sources. They are considered inexhaustible either because of the large amount of energy they contain or because they can be regenerated naturally.
Examples of renewable energy
Renewable energy can be used to generate electricity but it can also be used in other applications. Here are some examples of renewable energy:
- Solar photovoltaic panels.
- Solar thermal energy for heating.
- Pool heating by solar energy.
- Thermal centers by geothermal energy.
- Heating systems using geothermal wells.
- Wind farms.
- Hydropower in swamps.
- Sailing boats.
- The flight of gliders and paragliders without motor, which take advantage of the updrafts of air.
In a more generic way, renewable energies can be classified depending on the natural resources that are used.
Solar energy is the energy that takes direct advantage of solar radiation. Although the Sun does not have an inexhaustible life, it is estimated that the Sun's life is millions of years old. So, on a human scale, solar energy is considered an inexhaustible source and solar energy a renewable energy.
We distinguish two ways of harnessing solar energy: solar thermal energy and photovoltaic solar energy.
- Thermal solar energy. The use of thermal solar energy consists of using the heat energy obtained through the Sun's radiation to heat a fluid that, depending on its temperature, is used to produce hot water and even steam.
- Photovoltaic Solar Energy. The use of photovoltaic solar energy is carried out through the direct transformation of solar energy into electrical energy through the so-called photovoltaic effect. This transformation is carried out by means of photovoltaic cells that are manufactured with semiconductor materials (for example, silicon) that generate electricity when the solar radiation hits them.
Wind energy is a renewable energy because the wind is an inexhaustible source. To a certain extent, the wind is a consequence of solar energy due to the fact that the wind moves due to pressure and temperature differences caused directly or indirectly by the Sun.
There are two types of wind installations:
- Isolated wind energy installations, to generate electricity in remote places for self-consumption. It is very common for these installations to be combined with photovoltaic panels.
- Wind farms, formed by a set of wind turbines, to sell the electric power generated to the network.
The current technological development, as well as a greater knowledge of the wind conditions in the different zones, is allowing the implementation of wind farms connected to the electricity grid in numerous regions around the world.
Hydraulic energy takes advantage of the potential energy of water to obtain mechanical work. If we use this mechanical work that we have in kinetic energy form to drive a generator we obtain electrical energy. In this case, we will be talking about hydroelectric power.
Hydraulic energy is considered a renewable energy because the water cycle remains invariable and is inexhaustible. As in wind energy, the water cycle (and therefore hydraulic energy) has a strong dependence on solar energy.
Hydraulic energy takes advantage of the potential energy of the water coming from a jump to produce electrical energy. The water moves a turbine whose rotational movement is transferred by an axis to an electricity generator.
When the power of these generators is less than 10 MW it is called mini-hydraulic energy.
There are basically two types of hydroelectric power plants:
- Hydroelectric power stations of flowing water: Those hydroelectric plants that capture a part of the circulating flow through a river and take it to the plant to be turbinated and generate electric power. Afterwards, this flow is returned to the river bed.
- Hydroelectric power plants at the foot of the dam: This is hydroelectric power plants located downstream of reservoirs destined for hydroelectric uses or for other purposes such as supplying water to populations or irrigation. They have the advantage of storing energy (water) and being able to use it at times when it is most needed.
Biomass is a source of renewable energy based on the use of organic matter of vegetable or animal origin, including the products and by-products resulting from its transformation. Under the name of biomass, energy materials of very different kinds are collected: forest residues, woody and herbaceous agricultural waste, waste from various industrial processes, energy crops, organic materials contained in urban solid waste, biogas from livestock waste or biodegradable waste of industrial facilities, urban wastewater treatment or landfill, etc.
Biofuels, which have their main application in transportation, can also be included under the name of biomass.
Applications of biomass can be included in two groups:
- Domestic and industrial applications that work by direct combustion of biomass.
- Applications linked to the appearance of new resources and new transformation techniques, such as gasification and pyrolysis of biomass.
Wave and tidal energy
The energy released by the sea water in its movements of rising and falling tides (ebb and flow) is used in the tidal power plants, passing water through hydraulic turbines.
Obviously these maritime movements are inexhaustible, so we can consider tidal energy a renewable energy.
The energy of the waves is produced by the winds and it is very irregular. This has led to a multitude of types of machines for its use.
Finally, the conversion of oceanic thermal energy is a method of converting into useful energy the difference in temperature between surface water and water that is 100 m deep. A difference of 20 ° C is sufficient for the use. The advantages of this energy source are associated with the fact that it is a permanent and benign thermal jump from the environmental point of view.
Tidal energy would be a variant of hydraulic energy since it uses water to take advantage of its kinetic energy or potential energy.
Geothermal energy is the manifestation of thermal energy accumulated in rocks or waters that are at high temperatures inside the earth. Geothermal energy is the branch of science that explains this phenomenon.
The large amount of heat and thermal energy stored inside the Earth is so great that the exploitation of this energy resource has practically no effect on the internal energy of the Earth. For this reason it is considered a renewable energy source.
For use in areas with special thermal conditions, for example volcanic zones, a fluid is circulated in them that transports the heat energy to the surface in the form of heat accumulated in the hot zones.
Geothermal energy has the main advantage that its environmental impact is minimal, and has yields that allow it to compete with fossil fuels such as oil, coal or natural gas. But its main disadvantages are that they require large investments and that geothermal fields are relatively scarce and often are located in unfavorable areas.
- Renewables 2007 Global Status Report (PDF)
Last review: January 3, 2018