Speaking of solar energy is commonly understood as the electric or thermal energy obtained by exploiting the rays of the sun that, every day, affect
Every moment the Sun transmits on Earth’s orbit 1367 Watts per m². Taking into account the fact that the earth is a sphere and that,
Speaking of solar energy is commonly understood as the electric or thermal energy obtained by exploiting the rays of the sun that, every day, affect the Earth. The energy with which the sun radiates our planet is enormous , even if it is partly absorbed by the atmosphere and partly reflected by clouds. In addition to absorbing a certain percentage of radiation, the atmosphere modifies and alters its spectrum, but the solar radiations that reach the Earth determine the process of chlorophyll photosynthesis , and make the life of animals and plants possible.
Considering the energy potential that is poured on the earth’s surface every day, some methods have been studied to take advantage of it. Obviously, precisely because of the dispersion and the vastness of the earth’s surface, it is impossible to convert all the energy received from the sun in a useful way. However, the various technologies allow excellent results, both in terms of efficiency and in terms of the environment.
A system to exploit the energy of the sun is the installation of solar collectors (or panels) : these are devices that convert solar radiation into thermal energy, useful for heating or for the production of hot water. This type of system can be natural circulation (without electric pumps), taking advantage of the heat characteristic to rise upwards to favor the flow of the heat-carrying liquid in the exchanger, or forced circulation, with the presence of electric pumps speed up the process. Forced circulation, of course, increases the efficiency of the panel, and is necessary in the case of rigid external temperatures, or to produce hot water in the absence of sun and during the night.
The solar panels at a concentration acting through a series of reflecting mirrors, which concentrate the sun’s rays directing toward the heat transfer fluid, generating the steam used to produce electricity. Compared to solar collectors, concentration systems offer higher yields at reduced costs. This is a system that has recently been used for the operation of solar power plants: thanks to the presence of hundreds of mirrors, the heat generated moves the turbines and produces huge quantities of electricity .
The photovoltaic panels represent the solution for the production of electricity in residential and business environments, with the advantage of a strong reduction in costs with a minimum investment. The plant is made up of panels made of silicon cells which, if hit by the sun’s rays, are able to produce electricity. Placed so as to be constantly reached by sunlight, the photovoltaic panels provide the supply of electricity, varying according to position, irradiance, temperature and other parameters.
Solar energy is in any case a valid alternative way to provide the hot water and electricity needs and to heat the environment with excellent results and considerable savings. The photovoltaic system can be autonomous, allowing the storage of the energy produced and then deliver it at a later time, or connected to the electricity grid: in this case, the energy produced by the plant is “sold” to the grid operator , which in some cases proceeds to count it on credit.
Every moment the Sun transmits on Earth’s orbit 1367 Watts per m². Taking into account the fact that the earth is a sphere and that, moreover, rotates, the average solar irradiation is, at the European latitudes, of about 1000 watt / m2.
Multiplying this average power per square meter by the surface of the earth’s hemisphere moment by moment exposed to the sun gives a power greater than 50 million GW.
A GW is the energy produced at full capacity by a large diesel or nuclear power plant.
The amount of solar energy that arrives on the earth’s soil is therefore enormous, about ten thousand times higher than all the energy used by humanity as a whole.
The plant: How it works Photovoltaic system
The panels, or rather the modules, photovoltaics are used to directly convert light into electrical energy and are made up of cells of different materials. The conversion of the energy takes place by means of a photoelectric effect inside the cell and does not include any moving mechanical parts, this gives the plants great reliability. To date, most of the photovoltaic cells produced are silicon (one of the most common materials on earth).
In addition to silicon, which is found in three different layers: monocrystalline, polycrystalline and amorphous, other materials are used such as: indium and copper diselenium (cells called CIS), indium copper and gallium diselenium (cells called CIGS), cadmium teloride (cells called CdTe).
The differences between the various types are identifiable in different efficiencies in photovoltaic conversion, production cost and pay back time. In one system, the modules are placed side by side and connected in series to one another to form groups called strings, which are then placed in parallel to form the photovoltaic field.
The systems can be isolated from the electricity grid, such as some mountain huts, water pumping systems, road signaling systems, etc. Or they can be connected to the network.
To connect them, it is necessary to transform the direct current produced by the modules into alternating current very similar to that used in our homes, this transformation takes place by means of the inverter.
In the plant there is also a device (usually inside the inverter) that serves to check that there are no malfunctions and that allows the connection of the system to the local power grid.