Renewable energy is energy that comes from virtually inexhaustible natural sources. They are considered inexhaustible either because of the large amount of energy they contain or because they can be regenerated naturally.
Among the main advantages of renewable energies we highlight the following:
Renewable energies are respectful with the environment and do not pollute. In this sense, they are safer and pose fewer health risks than other sources of non-renewable energy. The more energy generated by clean energies will need to generate fossil energy mes and decrease, thus, the generation of greenhouse gases.
In most cases they are simple to dismantle and it is not necessary to guard their waste, as it happens in the case of nuclear energy, for example.
Renewable energies, by definition, come from sources that are inexhaustible and that allow to obtain an energy benefit without exhausting resources, as happens with energies related to fossil fuels.
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:
- Panels of photovoltaic solar energy.
- The installations of solar thermal energy for heating.
- The air conditioning of pools by solar energy.
- The thermal centers through geothermal energy.
- Heating systems using geothermal wells.
- The wind farms.
- The use of hydraulic energy through swamps.
- Sailing boats.
- The flight of gliders and paragliders without motor, that take advantage of the ascending currents 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 uses solar radiation directly. Although the Sun does not have an inexhaustible life, it is estimated that the life of the Sun is millions of years old. So, on a human scale, solar energy is considered an inexhaustible source and solar energy a renewable energy.
- The 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 made 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 solar radiation falls on them.
Wind energy is a source of renewable energy because wind is an inexhaustible source. To some extent the wind is a consequence of solar energy because the wind is displaced by differences in pressures and temperatures 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 that these facilities are combined with photovoltaic panels.
- Wind farms, formed by a set of wind turbines, to sell the electric power generated to the grid.
The current technological development, as well as a greater knowledge of wind conditions in different areas, is allowing the implementation of wind farms connected to the electricity grid in many regions around the world.
The hydraulic energy takes advantage of the potential energy of the water to obtain a mechanical work. If we use this mechanical work in the form of kinetic energy to operate a generator, we obtain electrical energy. In this case, we will be talking about hydroelectric power.
Hydropower is considered a renewable energy because the water cycle remains unchanged and is inexhaustible. As in wind energy, the water cycle (and therefore hydraulic energy) has a strong dependence on solar energy.
The 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 rotation movement is transferred by an axis to an electricity generator. The main advantage of hydraulic energy is that energy can be stored in the form of potential energy and generate electricity at times of demand.
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 plants of flowing water: Those hydroelectric plants that capture a part of the circulating flow through a river and take it to the power plant to be turbinated and generate electric power. Then, this flow is returned to the river bed.
- Hydroelectric power stations at the foot of the dam: Those hydroelectric 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 materials 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 waste, 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 transport, can also be included under the name of biomass.
Applications of biomass can be grouped into 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.
Tidal and wave energy
The seas and oceans are huge solar collectors from which energy can be extracted from various sources (waves, tides and thermal gradients).
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 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 temperature difference between surface water and water that is 100 m deep. For the use, a difference of 20 ° C is sufficient. 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.
Geothermal energy is the manifestation of thermal energy accumulated in rocks or waters that are at high temperature 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 virtually 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, the 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.
The main advantage of geothermal energy is that its environmental impact is minimal, and it has energy yields that allow it to compete with fossil fuels such as oil, coal or natural gas. On the other hand, the main disadvantages of geothermal energy are that they require large investments and that geothermal fields are relatively scarce and are often located in unfavorable areas.
- Renewables 2007 Global Status Report (PDF)
Last review: July 16, 2019