Renewable energies: characteristics and types

The so-called renewable energy sources (sun, wind and water) are those that can be used on a permanent basis because they are inexhaustible, unlike non-renewable sources (oil or coal).

From an environmental point of view, there are two types of energy sources: renewable and non-renewable.

Characteristics of non-renewable energy sources and their types.

Non-renewable energy sources are characterized by the following:

• Their exploitation and use causes pollution, since they generate emissions and waste.

• They are limited energy sources, which is why they are also known as exhaustible energy sources. Their reserves are limited and, therefore, they are exhausted with their consumption.

• These are sources that cause dependence on foreign sources, since they are not indigenous sources.

Non-renewable or exhaustible energy sources include fossil fuels (coal, oil, natural gas) and nuclear energy.

Renewable energy sources are characterized by the following:

• Its use has a very low impact on the environment. No waste is generated.

• They are unlimited energy sources, which is why they are also known as inexhaustible energy sources, since they do not run out when consumed.

• These are indigenous energy sources.

Among the types of renewable or non-depletable energy sources are: solar energy, wind energy, hydroelectric energy, biomass and biofuels, geothermal energy, and energy generated by waves, tides and ocean currents.

Solar energy.

It is the energy obtained directly from the sun (which is, at the same time, the source of all renewable energies). Depending on the mechanism used, heat or electricity can be obtained.

• Photovoltaic solar energy: it is the use of the energy coming from the sun and its transformation into electrical energy. The electrical current produced can be directly consumed, stored in batteries or accumulators or adapted for incorporation into the electrical grid.

• Solar thermal energy: consists of taking advantage of the energy received from the sun to obtain heat, which can be used to air-condition buildings, produce hot water or for industrial applications.

• Solar thermal power: In solar thermal power plants, a fluid is heated to generate pressurized steam, which produces electricity that can be fed into the power grid.

One of the options that photovoltaic solar energy and small wind power allows is to generate its own electricity, known as self-consumption. Through this self-consumption:

• The consumption of the energy produced by the installation of renewable energy is made possible at the times when its use is required in buildings and dwellings.

• When the energy is not needed, as there is no electricity consumption, it can be discharged to the power grid.

Wind energy.

It consists of harnessing the energy of the wind, by means of wind turbines or windmills. The wind turbine is the main element of this renewable energy system, the most common being the one that converts the energy of air movement into electrical energy that is finally transmitted to the electrical grid. Typical wind installations are off-grid mini wind farms and grid-connected wind plants or wind farms.

Small off-grid mini-wind installations use batteries to accumulate the electricity produced for later consumption, for example, in homes. These small installations are of small power and can be complemented with other renewable systems such as solar photovoltaic.

Low-power wind power installations (as well as photovoltaic solar energy installations) make it possible for any consumer to self-consume electricity, i.e. to generate his or her own electricity.

Other types of renewable energy sources.

1) Biomass.

These are the biodegradable fractions of products or waste of biological origin from agricultural and fishing activities, forestry, and the organic fraction of industrial and municipal waste. When biomass is processed for energy use, it is converted into biofuels (solid: wood chips, shredded and pressed wood, etc.; liquid: biodiesel, bioethanol; or gaseous: biogas).

The energy content of biomass can be used in different transformation processes to obtain thermal energy or heat, or electricity or mechanical energy (biofuels).

2) Biofuels.

These are fuels of renewable origin that can be used as substitutes or additives to traditional fuels such as gasoline and diesel. Two types of biofuels are highlighted:

• Biodiesel: produced from vegetable and animal oils and fats that are transformed into fuel similar to diesel.

• Bioethanol: alcohol of vegetable origin obtained from the fermentation of sugar substances.

3) Geothermal energy.

It is a type of renewable energy that stores the earth's interior in the form of heat (inexhaustible and non-polluting energy source).

4) Hydroelectric or hydraulic energy.

It consists of harnessing the potential energy of water to produce electricity.

5) Marine energy.

The force of the sea (waves, tides, ocean currents, thermal gradients) is used to generate energy.