How do photovoltaic solar panels work?

Photovoltaic solar panels: what they are, types of panels and how they work

Photovoltaic energy Photovoltaic self-consumption Energy transition

The term photovoltaic - from the Greek phos, meaning light, and voltaic, referring to the field of electricity - dates back to the mid-19th century, before the first solar cell was even manufactured. That first device had an efficiency of just 1 %, and it took decades before photovoltaic panels, devices that are capable of capturing the energy of solar radiation and transforming it into electricity for use, began to find their first applications. 

Interestingly, these came hand in hand with the space race when they were used in the first artificial satellites. Vanguard 1, launched in 1958 by the United States, was the fourth satellite ever put into orbit and the first to use solar panels. As a result, it was able to continue transmitting for seven years even though its chemical batteries were depleted in just 20 days. Today, Vanguard 1 is the oldest satellite still in orbit. 

Today, the growth of solar photovoltaics as a renewable energy is on an exponential curve, making it a regular, clean and cheap source of electricity. According to the International Energy Agency, electricity generation capacity from renewable energy will grow by 50 % in five years. And 60 % of that increase is attributed to an increase in the installation of solar photovoltaic panels. 

What are solar panels? 

Solar panels are devices that capture the energy that comes from solar radiation and transform it into electricity that can be used. It should be noted that this term is sometimes also used to refer to solar collectors, i.e., those that use solar energy thermally to produce domestic hot water. Photovoltaic panels, on the other hand, are those that generate electricity using photovoltaic solar energy. 

How do solar panels work?  

The photovoltaic cells in solar panels are those that have the capacity to generate electricity from the impact of solar radiation. These cells, which are usually made of crystalline silicon or gallium arsenide, are mixed with other components such as phosphorus or boron which 'dopes' and modifies the conductive properties. This creates two parts, one negatively charged, the other positively charged. When exposed to the sun, photons (light energy) move electrons (electrical energy) and a direct current is produced. 

By means of an inverter, direct current is transformed into alternating current, i.e., the current that is commonly used in households. 

What are the plans of a solar panel?

A solar panel is made up of several parts, the most important of which is undoubtedly the solar panel - where the photovoltaic cells are located - itself. The rest of the elements aim to protect and guarantee the functionality and durability of the solar panels. Thus, the different components would be: 

Solar panels: 
They are formed by the union, by means of metallic conductors, of photovoltaic cells or cells, i.e., devices capable of generating electricity when the impact of solar radiation hits them.

Encapsulated layers: 
They protect the solar cells and are composed of a type of polyethylene made of various compounds (ethylene and vinyl acetate) called EVA plastic. This material is a great thermal insulator while allowing the sun's rays to pass through to the photovoltaic cells. 

Structure and support frame:

These are usually made of aluminium to ensure both lightness and durability. The frame is attached to the structure which determines variables such as the tilt and orientation of the panel to ensure that the panel is in optimum condition. In addition, the structures on which the photovoltaic panels are mounted can be fixed, mobile, ballasted or floating. 

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Types of photovoltaic solar panels and their characteristics

There are three main types of solar panels: 

Monocrystalline: 
As the name suggests, these are composed of single-crystal cells. They are characterised by the fact that the silicon in the solar cells is cut into sheets, thus offering greater purity and efficiency. They are considered to be 15 to 25 % more efficient than other models. They are best recognised by their deep black colour.

 Polycrystalline: 
Easily identifiable by their dark bluish colour, polycrystalline panels are obtained by melting silicon and pouring it into moulds. Their price is lower, but so is their efficiency, although good progress has now been made in reducing their reflective losses and improving their light harvesting. 

Thin film: 
This is the most commonly used type of panel in housing due to its price, its homogeneous appearance and its flexibility, which allows it to adapt to all types of surfaces. They are also the least efficient, although their performance is not usually affected as much by high temperatures or shading.  

Photovoltaic self-consumption, how photovoltaic solar panels work on a house

Photovoltaic self-consumption is the name given to installations whereby individuals or companies produce the energy they consume, thus helping to curb climate change. These installations can be of two types; those that produce surplus that users sell and inject into the grid and those that do not 'return' this surplus. Both can be connected to batteries to store surplus production. 

Solar panels for self-consumption must be accompanied by some fundamental elements to complete the installation. These would be: 

Inverters:
These are responsible for converting the energy generated by the solar panels from direct current to alternating current, which will be used by all the equipment and electrical appliances in the house.

Meter or regulator:
A bi-directional device that sends power to the grid when the panels generate more energy than demanded and receives power when more energy is demanded than the panels generate (e.g., at night). 

 Batteries (optional):
They are particularly useful for use at night, for example, but it is also true that they are one of the most expensive elements of the photovoltaic installation.