The sun can provide enough energy to power the entire planet. But you can’t do it directly. Solar panels are the intermediary that makes sunlight serve us as energy. Its design is simple, very efficient and allows self-consumption, which promotes sustainability . In the near future, the panels will generate electricity even at night.
A single hour of sun would be enough to supply the energy demands of humanity for a whole year. The statement is not exaggerated and explains better than any graph would, the importance of the human being being able, through different processes, to convert into electrical energy what the sun gives away. Solar energy as an alternative for the future of humanity.
But how is this almost miraculous process carried out? Through two simple installations: solar photovoltaic panel installations (better known as plates or solar panels) and thermal installations. Both are different and are made up of also different teams.
To fully understand what these photovoltaic panels are, it is best to go back a few years (even a century). “We are talking about a 21st century energy, although in reality it was discovered at the end of the 19th century. And it was during the 20th century when it began to develop”, explains Carlos Montoya, head of the Solar Department of the Institute for Energy Diversification and Saving (IDAE) , attached to the Ministry for Ecological Transformation and the Demographic Challenge, to BBVA. “In 1920, Albert Einstein already discovered the photovoltaic effect and for this he took the Nobel a year later.”
How does this effect work? It is a physical phenomenon that consists of the emission of photoelectrons by a material when it receives light energy. “This phenomenon makes it possible for us to exploit solar energy to produce electricity,” says Íñigo Ramírez González, a photovoltaic solar energy researcher at the Polytechnic University of Madrid.
Knowing this concept, now it is important to explain what a photovoltaic solar installation is . It is a rectangular structure with a basic unit of transformation that is the solar cell and that measures approximately 10 square centimeters. A panel joins several of these cells on a plate, which are covered with a plastic called EVA. It is a type of polyethylene made up of various compounds (ethylene and vinyl acetate) that is one of the great allies of the photovoltaic industry. Because? Because this polymer can withstand extreme conditions and temperatures and also allows light to pass through, but not ultraviolet rays, which are more damaging to the skin.
A solar panel is made up of about 60 cells , although this size varies depending on the manufacturer, and its thickness is around four centimeters. Íñigo Ramírez points out: “The energy they produce is direct current and we use alternating current in our homes, so the panels also have an essential element that is the inverter, capable of transforming the current so that we can use that energy.”
Silicon since 1954
The first photovoltaic cells were developed in 1954. Daryl Chapin, electronic engineer; Gerald Pearson, a physicist, and Calvin Fuller, a chemist, the three researchers from the American Bell Laboratories, presented their great discovery to the world: it was the first cell that captured energy from the sun and with it a transistor could be made to work. That cell had a particularity: it was made of silicon. “This is precisely the fundamental material that absorbs sunlight and through which that light is transformed into electricity. It is a semiconductor with very good characteristics for manufacturing solar cells and it is very abundant on earth, as well as being cheap”, explains Ramírez.
Photovoltaics is a source of energy that has become more and more important over the years. Before the 1970s, its use was merely aerospace , but from then on, it came down to Earth. It is modular, that is, its efficiency does not depend on its size, so it is scalable and can be located in the home.
However, in countries like Spain its use is still eminently industrial. “The more than 10,000 megawatts (MW) of photovoltaic power installed in the country mainly supply companies and industrial buildings ”, explains the head of the IDAE Solar Department. We still have a long way to go to reach China, the world’s largest power in photovoltaic energy.
Solar panels: make the most of the sun and save energy
Returning to these panels, another of the most frequently asked questions is whether the farms (as these facilities are known) of solar panels move with the sun. There are two answers, some panels are installed on fixed inclined structures and others are installations with a tracker, that is, they have an intelligent motor that moves them so that they are at their most efficient point every day of the year.
Regarding the power that standard size panels can generate, it is calculated that a 2 x 1 meter module – between 60 and 72 cells – provides approximately between 300 and 445 Wp (peak watts) for each hour of sunshine.
Photovoltaic future
The future of the panels passes through the present of scientific research. At Stanford University (USA) they have just developed a facility capable of generating electricity when the sun has gone down. Solar panels ‘in reverse’ take advantage of the energy that the panels radiate after many hours of sun. This phenomenon is known as ‘radiative cooling’ and occurs when a body loses heat after high temperatures. Recovering that heat that is given off, even at night, could be a solution for the panels to perform better.
Solar farms in elevated installations on agricultural fields or greenhouses to optimize space and, at the same time, keep the panels cooled by the humidity released by the plantations; solar trackers to track the sun more economically and efficiently, or solar cells made with organic components that transform the windows of industrial or residential buildings into semi-transparent solar panels are some of the solutions underway.
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