Renewable energies are those energies that use an energy or fuel source that is considered inexhaustible or that can be regenerated at the same rate at which it is consumed.
The classification of renewable energies depends on the natural resources that are used. Among them we highlight:
- Solar photovoltaic and thermal energy.
- Wind power.
- Hydraulic energy.
- Seawater energy.
- Biomass energy
- Geothermal energy.
The use of photovoltaic solar energy is done through the direct transformation of solar energy into electrical energy through the so-called photovoltaic effect. This transformation is carried out by “solar cells” that are made of semiconductor materials (eg silicon) that generate electricity when solar radiation strikes them.
- Isolated wind power installations, to generate electricity in remote places for self-consumption. It is very common that these facilities are combined with photovoltaic panels.
- Wind farms, formed by a set of wind turbines, to sell the electricity generated to the grid.
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 many regions around the world.
Mini hydraulic power
The use of the potential energy of water from a jump to produce electrical energy is what is known as Hydraulic Energy. The water moves a turbine whose rotation movement is transferred by means of an axis to an electricity generator. This type of energy is considered renewable when the power is less than 10 MW (Mini Hydraulic Energy).
There are basically two types of hydroelectric plants:
- Flowing water stations: Those that capture a part of the flow through a river and take it to the plant to be turbinated and generate electricity. Afterwards, this flow is returned to the riverbed.
- Centrals at the foot of the dam: Those located downstream of reservoirs destined for hydroelectric uses or other purposes such as water supply 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 an energy source based on the use of organic materials of vegetable or animal origin, including the products and by-products resulting from their transformation. Under the name of biomass, energy materials of very different kinds are collected: forest residues, woody and herbaceous agricultural residues, waste from various industrial processes, energy crops, organic materials contained in urban solid waste, biogas from livestock waste or biodegradable waste industrial facilities, urban wastewater treatment or landfill, etc. They can also be included under the name of biomass, biofuels, which have their main application in transport.
Biomass applications can be included in two groups:
- Domestic and industrial applications that work by direct combustion of biomass.
- Applications linked to the emergence of new resources and new transformation techniques, such as gasification and pyrolysis of biomass.
Tidal and wave energy
The seas and oceans are huge solar collectors from which energy can be extracted from diverse sources (waves, tides and thermal gradients).
The energy released by seawater in its movements of rise and fall of the tides (flow and reflux) is used in tidal power plants, passing the water through hydraulic turbines.
The energy of the waves is produced by the winds and is very irregular. This has led to many types of machines for use.
Finally, the conversion of oceanic thermal energy is a method of converting the temperature difference between surface water and water 100 meters deep into useful energy. A difference of 20 ° C is sufficient for use. The advantages of this energy source are associated with the fact that it is a permanent and benign thermal jump from an environmental point of view.
Geothermal energy is the manifestation of thermal energy accumulated in rocks or waters that are at high temperature inside the earth.
For the use in areas with special thermal conditions, for example, volcanic areas, a fluid is circulated in them that transports heat energy to the surface in the form of heat accumulated in hot areas.
The energy generated according to its temperature (high, medium or low) is used, either to produce electricity, or for water heating and heating.
Geothermal energy has the main advantage that its environmental impact is minimal, and has yields that allow it to compete with oil. But its main disadvantages are that they require large investments and that geothermal fields are relatively scarce and are often located in unfavorable areas.