What is solar power?
Solar power can be used to generate two types of energy:
- Electric (photovoltaic system)
- Thermal (photothermal system)
In the photovoltaic system, sunlight is captured by solar panels and transformed into electrical energy for use. In the photothermal system, on the other hand, sunlight is captured by solar thermal collectors and used to generate heat.
The possibilities of harnessing solar power also include passive techniques implemented by bioclimatic architecture for the construction of sustainable structures. These consist of designing structures for greater use of climate resources; for example, solar power as a source of natural lighting or temperature control for spaces.
When did solar power start to be used?
Solar power has been used since antiquity as a heat source and for heating and drying food. However, technology for using solar power dates back to 1839, when the French physicist Alexandre Edmond Becquerel discovered the photovoltaic effect.
The first photovoltaic cell was created in the United States by Charles Fritts in 1883. It consisted of a layer of selenium on a thin layer of gold, and the goal was to measure the amount of light plants received. This primitive cell had an efficiency of just 1%.
It was not until 1954 that the first photovoltaic device composed of solar cells with silicon in a solid state was developed. It was created by American scientists Daryl Chapin, Calvin Fuller, and Gerald Pearson. It was just 4 cm2 and produced an electric current of about 0.1 amperes at a voltage of 0.5 volts. The efficiency of these cells was only 6%, while today’s solar panels reach an efficiency of around 25% – and even 47% in laboratory conditions.
What is a solar panel, and how does it work?
A solar panel is a plate composed of a set of semiconductor devices mainly made of silicon that are called solar cells.
A panel’s solar cells are interconnected, and they convert solar power into electricity through the photovoltaic effect; this means that photons of sunlight excite the electrons in the semiconductor material of the solar cells, creating an electric current.
The current generated by the solar panels is a direct current. This current must pass through an inverter to be transformed into alternating current and go into the power grid.
What is a solar thermal collector, and how does it work?
A solar collector is a device designed to capture and use solar power to raise the temperature of a fluid. This fluid can have different applications such as domestic heating, food preparation, swimming pool climate control, and even less obvious applications like refrigeration (heat exchanger) and fossil fuel substitution within conventional electrical installations.
Depending on the application, different types of collectors can be used:
- Low temperature: for domestic applications. These may be flat (also known as solar panels) or have tubes.
- High temperature: known as a solar concentrator, it works with a mirror system.
- Very high temperature: known as a solar oven, can reach very high temperatures and also works with mirrors.
What are the advantages and limitations of solar power?
The main advantages of solar power are related to sustainability. Since sunlight is a virtually infinite resource, it is considered the largest source of renewable energy.
Thanks to its popularization, the technology to take advantage of solar power has also become more affordable, thus creating a virtuous circle of sustainability in both environmental and economic terms.
The main disadvantages have to do with the nature of this energy, which varies throughout the day and the year, as well as with specific climatic conditions, so there is no exact prediction for production.
Solar power is often more abundant at times of lower demand, like in winter: when there are fewer hours of daylight, more energy is used to produce electric light and heat spaces. Also, less artificial lighting is needed during daylight hours. This is why the biggest challenges in solar power have nothing to do with production but with its storage and distribution.
Finally, another difficulty is the need for large areas for the installation of solar panels. This problem is mitigated by using dead surfaces, such as roofs, which are constantly exposed to sunlight; without panels, they are just idle surfaces.
What are the world powers in solar power?
According to a 2021 ranking, the world’s leading installed photovoltaic power is China (54.9 GW), followed by the United States (26.9 GW), which exceeds the entire European Union by 0.1 points.