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Photovoltaic module

Photovoltaic modules are made up of a mosaic of solar cells. Here is a description of their main features and of Enel Green Power’s innovative solution.

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Photovoltaic modules, commonly known as solar panels, are a web that captures solar power to transform it into sustainable energy. A semiconductor material, usually silicon, is the basis of each individual solar cell. It is light sensitive and generates electricity when struck by the rays of the sun thanks to a physical phenomenon called the photovoltaic effect.

Composition, efficiency and duration

Photovoltaic modules are made up of many individual, interconnected photovoltaic cells. To ensure the modules are tilted correctly and facing the sun, they are housed in support structures. Every module has two output terminals that collect the generated current and transfer it to the management systems at a solar power station.

A photovoltaic module’s efficiency is quantified as the ratio between the electrical power going out of the terminals and the power of the sun’s rays striking the module’s surface. The standard value used to indicate solar radiation is 1,000 watt/sqm. If every square meter is struck by 1,000 watts of sunlight, the percentage of energy actually converted into usable electricity is what constitutes the efficiency. The average life of a photovoltaic module is around 25 years.

Monocrystalline and polycrystalline

The most common types of photovoltaic module are monocrystalline silicon, polycrystalline silicon and thin film.

  • Monocrystalline silicon: These dark blue almost black modules have cells with blunted edges and are made of silicon crystals all facing the same direction. In the presence of perpendicular light, they generate electricity with 18-21% efficiency. 
  • Polycrystalline silicon: These almost iridescent blue modules are made of silicon crystals facing different directions. They are less efficient (15-17%) when struck by sunlight perpendicularly, but they take better advantage of sunlight throughout the entire day.
  • Thin film: These modules are the least efficient, but they work well with diffused light and at high temperatures. 


Bifacial solar panels

While additional technologies are being added to the main three, they are currently in the testing or development phases and are not yet mature enough to be implemented on a large scale. Enel Green Power has made an important innovative advancement at its Italian 3SUN factory, the world’s only producer of a new bifacial photovoltaic panel with cutting-edge heterojunction technology (HJT) that uses amorphous crystalline silicon.

The heterojunction solar cells produced by Enel Green Power are already in use at various solar parks, and in February 2020, they set the world efficiency record for this type of technology by achieving a certified performance of 24.63%. HJT technology guarantees high performance and low deterioration, so this type of solar panel is more efficient and competitive.

The back of the double-faced panel also captures sunlight, so it produces 10-15% more electricity than traditional single-faced panels. Consequently, less panels need to be installed to achieve the same output, thereby reducing the space taken up by solar parks. Compared to other photovoltaic modules, the HJT panels produced by 3SUN are robust enough to last over 30 years.

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