In this article we will talk about Solar energy definition. The Sun is one of a billion stars, but it is of special importance to us because it is closer to Earth. The electromagnetic radiation they emit makes life possible for all organisms and is the engine of their evolution. Almost all the energy generated in the Sun’s core as a result of thermonuclear reactions is emitted as radiation that travels through space. The power of this energy is estimated at 1023 kW.
Solar energy definition
Solar energy definition : it is the electromagnetic radiation of the sun . It is the result of the vibrations of the magnetic and electromagnetic fields. Solar energy obtained from the Sun is very energetic and is available all over the Earth. It can successfully replace conventional energy sources such as natural gas , crude oil , uranium, or coal . It is very important from the point of view of protecting the environment and obtaining clean energy.
Why solar energy?
Today, the demand for energy is satisfied mainly from fossil fuels such as coal, oil and natural gas. However, these are non-renewable resources and someday their resources will be depleted. To be ready for this moment, we are already looking for alternative energy sources that will meet the demand in the future. The ideal solution seems to be energy from the sun. The use of this energy does not produce negative effects on the environment , such as burning coal or biomass . According to estimates, the sun will shine 4,500 million years, much longer than the life human .
The sun generates energy through the fusion processes of the conversion of hydrogen into helium. These processes take place at a very high temperature , which is produced by the solar core. Energy in the form of solar radiation reaches Earth, where:
- 20% is reflected
- 40% dispersed in the atmosphere – due to gases and dust suspended in the atmosphere,
- 40% reaches the earth’s surface and is used to produce electricity and heat .
Solar radiation does not reach all parts of the earth with the same intensity and intensity, and this is due, among other things, to the elliptical shape of the planet, which makes the illumination of the surface uneven. The lighting also changes according to latitude, season and day. Some of the rays fall directly to the ground and some are reflected off various obstacles.
The use of solar energy
Many technical solutions allow you to get solar energy. Systems that allow this can be divided into liabilities (liabilities) and assets (assets).
Passive systems use the phenomena of radiation , conduction and convection to convert solar radiation into heat . They are very simple and do not require a lot of money. An example of a simple passive system is a winter garden, where the sun simply heats the glass room. Currently, passive buildings are constructed that are shaped in that they are able to use the sun’s energy to heat the building as much as possible. The elements that receive energy from the sun can be large windows that face the right side of the world, large glazed surfaces, such as glass or concrete ceilings or brick walls . Active systems convert solar energy into usable energy with the help of specially prepared devices. They are solar collectors and photovoltaic cells . Photothermic conversion takes place in solar collectors, that is, the conversion of solar radiation into thermal energy. On the other hand, photovoltaic cells work on a different principle and solar radiation is converted into electricity. This process is called photoelectric conversion.
Photons are quanta of radiation that are the energy of solar radiation. The frequency of the radiation determines the energy carried by the photon. The conversion of solar radiation into electricity in photovoltaic cells does not require the use of additional mechanical devices, since there is no indirect energy conversion, as is the case with collectors, where heat is converted into mechanical work to generate electricity.
Photovoltaic power plants use devices to control the cells and the voltage-current converters necessary to transmit the generated energy to the electrical grid. Photovoltaic cells produce current continuous low voltage. The voltage is also highly dependent on the amount of radiation reaching the cell. The generated current is sent to the electrical network after passing through inverters that convert direct current into alternating current .
The cells are made of silicon wafers. Silicon is a material that is widely used in electronics and is common on earth. Creates monocrystalline, polycrystalline and amorphous structures. Monocrystalline silicon cells are better than polycrystalline silicon, but the production price tends in favor of polycrystalline silicon, which is much cheaper.
To make cell production less expensive and to save valuable material, thin film technology is used. It consists of placing a thin layer of a semiconductor on a base of other much cheaper materials. The advantage of this technology is that the cell can be given any shape that allows the cells to be integrated into the building’s façade or to create a cell on a base of flexible materials. Thin film technology also made the creation of multiple junction cells possible. This cell is composed of several layers of materials, each of which has different properties to absorb the spectrum of solar radiation. Since each layer of such a cell is capable of absorbing a different wavelength , in the end the entire cell performs better than one made of one type of material. Photovoltaic systems, compared to other renewable energy sources, such as wind farms, do not produce the annoying noise . The construction of photovoltaic systems does not require transformation of the natural environment
and changes in land use, since no harmful substances are produced during the production of thermal energy. Then there is no environmental pollution and production of gases of greenhouse .
Solar collectors are used to obtain heat from solar energy. They work on a slightly different principle than photovoltaic cells. An important element of the collectors is the absorber , which absorbs the solar energy and transfers it in the form of heat to the mechanical element. Solar collectors are divided into different mechanical elements, that is:
- liquid collectors,
- air collectors.
Liquid collectors are classified into the following types:
- flat collectors,
- vacuum manifolds,
- storage manifolds,
- flexible manifolds.
The most used to heat water are flat collectors, which consist of a system of flow channels, a heat carrier, which in this case is a liquid , a solar radiation absorber, an outer casing and a thermal insulation layer. The task of thermal insulation is to separate the lower surface of the collector from the housing. From the top, the collector is covered with a transparent glass that allows it to capture sunlight.
Air collectors are divided into the following types:
- with a flat absorbent,
- with an absorbent with a developed surface,
- with a porous absorbent.
The heat is absorbed by the air flowing above or below the absorber. To increase the amount of heat that can be absorbed, the surface of the absorber is corrugated. Air collectors have some advantages over liquid collectors, namely, the heat carrier does not change its state of aggregation (it does not boil or freeze) and it has a simple channel structure. The disadvantage is that, compared to liquid collectors, there is a resistance to the transfer of energy from the absorber to the air , which ultimately increases the temperature of the absorber and leads to heat losses to the environment.