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Photovoltaic Solar Energy

Photovoltaic Solar Energy

Photovoltaic solar energy consists of the direct transformation of solar radiation into electrical energy. This type of energy is often directly called photovoltaic energy.

This transformation into electrical energy is achieved by taking advantage of the properties of semiconductor materials using photovoltaic cells. The most common material used for photovoltaic systems is amorphous, polycrystalline or monocrystalline silicon, cadmium telluride, and indium copper selenide / sulfide.

Photovoltaic solar energy has specific advantages as an energy source:

Energy production can be large-scale for general consumption or small-scale for consumption in small houses, mountain huts or isolated sites.

What is the current situation of photoelectric energy?

Photovoltaic energy is the third largest source of renewable energy in terms of global capacity. The renewable sources that occupy the first position are after hydro and wind energy.

The International Energy Agency expects growth from 700 to 880 GW from 2019 to 2024. According to the forecast, photovoltaic energy could become the technology with the highest installed capacity in the mid-2020s.

In 2018, installed PV capacity worldwide increased to more than 515 gigawatts (GW) covering approximately two percent of global electricity demand.

How is solar radiation transformed into electricity?

Photovoltaic panels are used to transform solar radiation into electricity. These panels are made up of photovoltaic cells. These cells have the particularity that when they receive radiation from the Sun, they generate an electric current.

Photovoltaic installations can be mounted on the ground, on the roof, on the wall or floating. The mount can be fixed or use a solar tracker to follow the sun across the sky.

Silicon

The manufacture of photovoltaic cells is an expensive process, both economically and in time. The silicon with which most of the photovoltaic cells are made is a very abundant material on Earth. However, silicon processing is laborious and complicated. Silicon ingots are made through very complicated processes. Subsequently, the wafers ( photovoltaic cells) will be cut from these silicon ingots.

Another source for obtaining silicon is recycling from the electronics industry.

Other higher performance materials are currently being prepared.

How efficient is photovoltaic energy?

Photovoltaic Solar Energy

Depending on the construction, photovoltaic modules can produce electricity from a specific range of light frequencies. In general, however, it cannot cover the entire solar range (specifically, ultraviolet, infrared, and low or diffuse light).

Much of the energy from incident sunlight is not harnessed by solar panels. If the panels were illuminated with monochromatic light, much higher efficiencies could be obtained.

Therefore, another design concept is to divide the light into different wavelengths and direct the beams into different tuned cells in these ranges. This has been designed to be able to increase efficiency by 50%.

Scientists at Spectrolab, a Boeing subsidiary, reported the development of multi-junction solar cells with an efficiency of more than 40%. This improvement was a new world record for photovoltaic solar cells. Spectrolab scientists also predict that concentrating solar cells could reach 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 rate of conversion of sunlight to photovoltaic energy in new commercial products achieves a solar module efficiency of around 21.5%.

What are the uses and applications of photovoltaic solar energy?

Photovoltaic Solar Energy

The main application of a photovoltaic solar energy installation is the production of electrical energy from solar radiation.

Photovoltaic systems range from small, roof-mounted or building-integrated systems with capacities ranging from a few to several tens of kilowatts, to large utility-scale power plants of hundreds of megawatts.

The main applications are as follows:

  • Integrated systems in roofs and buildings. Rooftop photovoltaic systems are often adapted to existing buildings, generally mounted on the existing roof structure or on existing walls.
  • Hybrid thermal photovoltaic solar collector These systems are systems that convert solar radiation into thermal and electrical energy.
  • Photovoltaic concentrator. Hubs use curved lenses and mirrors to focus sunlight on small solar cells. In this way a much higher photovoltaic power is achieved.
  • Rural electrification. This type of solar application is used in rural villages where the electric lines are very far from the population.
  • Power plants. These plants are solar farms to obtain a high production of electrical power.
  • Floating solar. Floating solar energy systems are installed where there is little available land surface. Solar panels, in this case, are floating on an aquatic surface such as in a swamp, lake, etc.
  • Independent systems. The clearest example of these systems are solar calculators.
  • In transport. Used to obtain motive power.
  • Telecommunications and signaling.
  • Spacecraft applications.

Isolated facilities and connected to the network

Mainly two types of photovoltaic installations are differentiated:

  • Grid-connected photovoltaic installations, where the energy produced is used entirely for sale to the electricity distribution network.
  • Grid-insulated photovoltaic installations, which are used for self-consumption, whether it be an isolated house, a telecommunications repeater station, or other remote places. It allows obtaining electricity, pumping water for irrigation, etc.

Among the applications of photovoltaic energy not connected to the grid we find in many areas of daily life. Photovoltaic energy is used in small devices such as calculators, such as for public lighting in certain areas, to eliminate electric motors, and even automobiles and airplanes have been developed that operate exclusively taking advantage of solar radiation as an energy source.

Within the photovoltaic installations connected to the network there are photovoltaic solar energy plants. A photovoltaic power plant, also a solar park, is a large power generation plant, designed for the sale of its production to the electricity grid. It is also known as a solar farm, especially if it is located in agricultural areas.

History of photovoltaic energy

Photovoltaic energy generated with the photovoltaic effect was first recognized in 1839 by the French physicist Becquerel. However, it was not until 1883 that the first solar cell was built by Charles Fritts with an efficiency of 1%. During the first half of the 20th century, there were several improvements to increase its efficiency.

In 1946, Russel Ohl patented the modern bond between semiconductor materials that is currently used. But the most important technological advance came in 1954 when Bell Laboratories, Experimenting with semiconductors, developed the first siliconphotovoltaic cell, with a yield of 4.5%.

 

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    References

    1. Roper, L. David. World Photovoltaic Energy
    2. Swanson, R. M. (2009). Photovoltaics Power Up
    3. «Photovoltaic Effect»  Mrsolar.com
    4. «The photovoltaic effect»  Encyclobeamia.solarbotics.net.
    5. "Photovoltaic is already rubbing shoulders with nuclear . " The energy newspaper.
    6. "Renewables 2019". IEA. Retrieved 26 January 2020.
    7. "PV report 2019" (PDF). Fraunhofer ISE.

    Last review: March 25, 2020