Definition:
This type of energy is mainly used to produce electricity on a large scale through distribution networks, but it also allows to power numerous autonomous applications and devices, as well as to provide mountain shelters or houses isolated from the electricity network. Due to the increasing demand for renewable energy, the manufacture of solar cells and photovoltaic installations has advanced considerably in recent years.
The economic incentive programs, first and then, the self-consumption photovoltaic systems and the net balance without subsidies, have supported the installation of photovoltaic energy in a large number of countries. As a result, photovoltaic solar energy has become the third most important renewable energy source in terms of installed capacity globally, after hydroelectric and wind energy. As of early 2017, an estimated 300 GW of photovoltaic power has been installed worldwide.
Operating principle
When a doped semiconductor is exposed to electromagnetic radiation, it emits a photon, which hits an electron and removes it, creating a hole in the atom. Normally, the electron quickly finds another hole to replace it, and the energy supplied by the photon is dissipated as heat. The principle of a photovoltaic cell is to force electrons and holes to move to the opposite side of the material, instead of simply recombining in it: thus, there will be a difference in potential and therefore voltage between the two sides of the material. , as it happens in a cell.
To do this, a permanent electric field is created by means of a pn junction between two doped layers respectively, p and n. Therefore, in silicon cells, which are the most used, are created:
The top layer of the cell, which is made up of the silicon-doped type. In this shell, there are more free electrons than in a pure silicon shell, hence the name n, negative doping. The material remains electrically neutral, since both the silicon atoms and those of the contaminating material are neutral: but the crystal lattice has a greater global presence of electrons than in a pure silicon lattice.
The bottom layer of the cell, which is made up of a type doped with silicon. This layer therefore has a lower average number of free electrons than a layer of pure silicon. The electrons connect to the crystal lattice, which is therefore electrically neutral, but has positive holes (p). Electrical conduction is ensured by these load carriers, which move through the entire material.
What are the benefits of photovoltaic energy?
The electrical energy generated by photovoltaic solar panels is inexhaustible and does not pollute, which contributes to sustainable development, in addition to promoting the development of local employment. In the same way, it can be used in two different ways: it can be sold to the electricity grid or it can be consumed in isolated places where there is no conventional electricity grid.
For this reason, it is a system especially suitable for rural or isolated areas where the power line does not reach or is difficult or expensive to install or for geographical areas whose climate allows many hours of sunshine per year.
The cost of installing and maintaining solar panels, which have an average life of more than 30 years, has decreased significantly in recent years, as photovoltaic technology has developed. It requires an initial investment and small running costs, but once the PV system is installed, fuel is free and for life. Therefore these benefits can be summarized as:
- Renewable
- Endless
- Non-polluting
- Scalable from large plants to residential systems
- Suitable for rural or isolated areas
- Contribute to sustainable development
- Promotion of local employment
Photovoltaic energy efficiency
Depending on the construction, photovoltaic modules can produce electricity from a frequency range of light, but generally cannot cover the entire range of solar energy (specifically, low or diffuse, infrared, and ultraviolet light). Therefore, much of the energy from incident sunlight is not used by solar panels, which could provide much higher efficiencies if illuminated with monochromatic light.
Therefore, another design concept is to divide the light into different wavelengths and direct the beams into different cells tuned for these ranges. This is designed to increase efficiency by 50%. Scientists reported the development of multi-junction solar cells with an efficiency greater than 40%, a new world record for photovoltaic solar cells, they also predict that the concentration of solar cells can achieve efficiencies of more than 45% or even 50% in the future, with theoretical efficiencies of around 58% in cells with more than three junctions.
Currently, the best conversion rate of sunlight to photovoltaic energy in new commercial products achieves an efficiency of solar modules of around 21.5%.
Applications of photovoltaic solar energy
- Use of photovoltaic solar energy for public lighting.
- The main application of a photovoltaic solar energy installation is the production of electrical energy from solar radiation.
- Energy production can be on a large scale for general consumption or on a small scale for consumption in small houses, mountain huts or isolated locations.
Types of photovoltaic installations
Photovoltaic installations for grid connection:
When the energy produced is used entirely for sale to the distribution network.
Isolated photovoltaic installations:
They are used for self-consumption, be it a single-family home, a telecommunications relay station, pumping water for irrigation, etc.
Among the applications of photovoltaic energy not connected to the network, we find it in many areas of daily life. Photovoltaic energy is used in small devices such as calculators, such as public lighting in certain areas, to eliminate electric motors, and even cars and airplanes have been developed that work exclusively using solar radiation as an energy source.
Within the photovoltaic facilities connected to the grid there are photovoltaic solar power plants. A photovoltaic plant, also a solar park, is a large power plant designed to sell its production to the electricity grid. It is also known as a solar park, especially if it is located in agricultural areas.
History of photovoltaic energy
The photovoltaic energy generated with the photovoltaic effect was recognized for the first time in 1839 by the French physicist Becquerel. However, it was not until 1883 that Charles Fritts built the first solar cell with an efficiency of 1%. During the first half of the 20th century, there were several improvements to increase its efficiency.
In 1946, Russell Ohl patented the modern bonding of semiconductor materials used today. But the most important technological advance came in 1954, when Bell Laboratories, experimenting with semiconductors, developed the first silicon photovoltaic cell, with a yield of 4.5%.
Photovoltaic Solar Energy
Only available when the sun shines (in terms of generation), photovoltaic solar energy is what allows to capture sunlight to convert it into electricity that meets the needs of any home or commercial space.
If all this is possible, it is thanks to what is known as the photovoltaic effect, which is crucial for the production of electricity from the sun. Several components come into play here. The first, the particles that make up sunlight (photons) and their impact on solar panels, with which electrons are released.
This is where the most important components of photovoltaic plates come into play, specifically the conductors that incorporate, in most cases, silicon. Generally composed of a positive and a negative, these create an electric field through which the electrons circulate once activated, so that the current is produced.
Photovoltaic solar installation
Panels are obviously essential within that mechanism. The process described above is produced, in particular, the small portions of the panel, which is divided into a multitude of solar cells made of silicon, in general, or other materials that also allow the use of energy, and promote a reduction in costs. .
Thus, the panels in which the impacts of light are formed by a multiplicity of small cells that give rise to modules and, these, to a panel itself. Although this is a fact, it is worth noting: more panels, more electricity generation. Now, calculating the number of panels well is one of the keys to any installation, because erring in excess will increase their costs without the need to exist. If, on the other hand, it is defective by default, the captured energy will not be enough to satisfy the needs.
