Solar collector it is all that 'collects' light and heat and makes them become other forms of energy. Plants, for example, are all excellent biological-solar collectors capable of transforming the light and heat of the sun accumulated with chlorophyll photosynthesis into woody biomass.
Glass can also be considered a solar collector because it allows heat and light to penetrate inside the rooms, leaving the cold and wind outside. Speaking of glass, it can be said that its discovery was certainly a huge step forward on the path of technologies that exploit the contribution of the sun.
THE solar collectors they fall into the family of active solar technologies, together with photovoltaic systems, because they operate an energy transformation. Conversely, passive solar technologies are those that make a direct exploitation of solar radiation without intermediate transformations, for example windows and greenhouses.
The above is to clarify that i solar collectors they are not just ugly objects to be seen on the roofs of houses, although this is the fame they have seen that i solar collectors they are more commonly known by the name of solar panels, and actually indicate systems capable of capturing thermal energy from the energy of the sun for heating water and also for cooling the air.
THE solar collectors making up a solar thermal system can be of three types depending on the technology used. A first type are i solar collectors discovered, consisting of plastic tubes exposed directly to sunlight which heats the liquid circulating inside them.
A second type are i solar collectors glazed floors, in which the solar radiation is absorbed by a flat metal collector and transferred to the liquid flowing in conduits positioned in the lower part of the panel. The function of the glass is to prevent the dispersion of reflected radiation. Of the third type are i vacuum solar collectors, consisting of pipes covered by an absorber material and enclosed in vacuum glass ducts.
In addition to the technology of solar collector, a solar thermal system can be classified on the basis of the connection methods with the hydraulic systems: natural circulation systems, in which the liquid circulates according to the convective-gravitational process, and forced circulation systems where it is necessary a pump system.
Currently in Italy about 90% of the solar thermal systems installed are forced circulation. A third classification of solar thermal systems is possible based on the use of the heat generated by the system: production of domestic hot water and simultaneous production of domestic hot water and heating.