Photovoltaic solar energy is obtained by converting sunlight into electricity using 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. Find out how these huge solar fields work.
WHAT IS PHOTOVOLTAIC ENERGY?
Photovoltaic solar energy is a clean and renewable energy source 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.
To do this, a semiconductor device called a photovoltaic cell is used, which can be made of monocrystalline, polycrystalline or amorphous silicon, or other thin-film semiconductor materials. Monocrystalline silicon cells are made from a single crystal of pure silicon and achieve the highest efficiency, between 18% and 20% on average. Polycrystalline silicon is made from several crystals in a block and is therefore cheaper and has an average efficiency of 16% to 17.5%. Finally, amorphous silicon has a messy crystalline network, which leads to poorer performance (average efficiency between 8% and 9%) but also a lower price.
TYPES OF PHOTOVOLTAIC PLANTS
There are two types of photovoltaic plants: those that are connected to the grid and those that are not. Within the former there are, in turn, two other types:
- Photovoltaic plants: all the energy produced by the panels is fed into the grid.
- Self-consumption generator: part of the electricity generated is consumed by the producer himself (in a house, for example) and the rest is fed into the grid. At the same time, the producer takes from the network the necessary energy to cover its demand when the unit does not supply enough.
These installations with a connection to the grid have three basic elements:
- Photovoltaic panels: these are groups of photovoltaic cells mounted between layers of silicon that capture solar radiation and transform light (photons) into electrical energy (electrons).
- Inverters: these 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 installations operate on islands and are often located in remote locations and on farms to meet demands for lighting, support telecommunications and pump irrigation systems. These off-grid plants require two additional elements to operate:
- Batteries: in charge of storing the energy produced by the panels and not demanded at that moment for when it is necessary.
- Regulators: protect the battery against overloads and prevent inefficient use of the battery.