How do photovoltaic plants work?

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Photovoltaic solar energy is obtained by converting sunlight into electricity using a technology based on the photoelectric effect. It is a type of renewable, inexhaustible and non-polluting energy that can be produced in installations ranging from small generators for self-consumption to large photovoltaic plants. Discover how these huge solar fields work.


Photovoltaic solar energy is a clean, renewable source of energy that uses solar radiation to produce electricity. It is based on the so-called photoelectric effect, by which certain materials are able to absorb photons (light particles) and release electrons, generating an electric current.

A semiconductor device called photovoltaic cell is used for this purpose, which can be made of monocrystalline, polycrystalline or amorphous silicon, or other thin-film semiconductor materials. The cells made from monocrystalline silicon are obtained from a single crystal of pure silicon and achieve maximum efficiency, between 18% and 20% on average. Those made from polycrystalline silicon are made in blocks from several crystals, so they are cheaper and have an average efficiency of between 16% and 17.5%. Finally, those made from amorphous silicon have a disordered crystalline network, which leads to a lower performance (average efficiency between 8% and 9%) but also a lower price.


There are two types of photovoltaic plants: those that are connected to the grid and those that are not. Within the former there are two sub-classes:

  • Photovoltaic power plants: all the energy produced by the panels is fed into the electricity grid.
  • Generator with self-consumption: part of the electricity generated is consumed by the producer (in a dwelling, for example) and the rest is discharged onto the grid. In addition, the producer takes from the grid the energy needed to meet their demands when the unit does not supply enough.

These grid-connected installations have three basic elements:

  • Photovoltaic panels: these are groups of photovoltaic cells mounted between layers of silicon that capture solar radiation and transform the light (photons) into electrical energy (electrons).
  • Inverters: they convert the direct electrical current produced by the panels into alternating current, suitable for consumption.
  • Transformers: the alternating current generated by the inverters is low voltage (380-800 V), so a transformer is used to raise it to medium voltage (up to 36 kV).

Off-grid facilities operate in isolation and are often located in remote locations and on farms to meet lighting demands, support telecommunications and run pumps in irrigation systems. These isolated plants require two additional elements to function:

  • Batteries: to store the energy produced by the panels that is not used when it is generated, the stored energy can then be used when needed.
  • Controllers: to protect the battery from overcharging and prevent inefficient use of the battery.


How do photovoltaic power plants work?#RRSSHow do photovoltaic power plants work?

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Find out about the process in detail

  • Thanks to the photoelectric effect, the electromagnetic radiation emitted by the sun is converted directly into electrical energy.
  • Photovoltaic panels are formed from cells that absorb light particles (photons) and release electrons or direct electric current. To obtain the desired power, the panels are connected in series forming chains.
  • The continuous electrical energy produced by the panels is converted into alternating current by the inverters. These elements also control the quality of power sent to the grid.
  • Transformers raise the electricity to a medium voltage (up to 36 kV).
  • The alternating electric energy, now suitable for consumption, is distributed along transmission lines, capable of transporting the current over long distances. Bare metal conductors are used in their construction, they are made by placing metal wires around a central wire.

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  • It is a renewable, inexhaustible and non-polluting type of energy that contributes to sustainable development.
  • It is a system particularly suitable for rural or isolated areas where power lines are not available or are difficult or expensive to install, or for geographical areas that receive many hours of sunshine per year.
  • It is modular, so it can be used in installations ranging from huge photovoltaic plants on the ground to small roof panels.


In keeping with the our pledge to combat climate change, Iberdrola group is wagering on renewables to drive the energy transition and the much-needed decarbonisation and electrification of the economy. To get there, photovoltaic solar generation is a core focus for the company, which boasts the greatest photovoltaic power plant in operation in EuropeNúñez de Balboa, in the Spanish province of Badajoz, producing 500 MWp— and plans to build an even larger plant: Francisco Pizarro, in the province of Cáceres, which is set to produce 590 MWp.

But the group's work to boost solar power has only just begun. Iberdrola plans to invest €4.2 billion between 2020 and 2022 and €5.5 billion between 2023 and 2025, which will mean a growth of 6 GW and 8 GW respectively, adding up to an overall installed capacity of 15 GW in 2025. By year end 2019, the group had 1 GW in operation, 2,700 MW under construction and 6,000 MW secured.