How does a solar panel work? Let’s be clear. The solar heat collector (or solar thermal panel) consists of a radiator/absorber , usually made of a metal such as copper, with good conduction capacity. Is able to absorb the heat of the sun’s rays and transfer it to the water tank. The function of a solar thermal panel can be compared with a greenhouse. Of the sun’s rays that reach the glazed surface only a small part is reflected, the rest passes through the glass and is absorbed by a black capture plate. So how does a solar panel work? This capture plate, it warms up, and restores energy in the form of infrared radiation.
The glass behaves as if it were opaque, thus holding the ENERGY inside (greenhouse effect). So the temperature of the primary vector fluid tends to warm up. Then the liquid moves in the coil towards the tank with three different types of circulation: natural, forced or emptying. The insolation depends on the orientation of the panel regard to the sun. A panel receives more solar energy when it is oriented directly towards the sun. The fixed panel provides the best yield when facing south and is inclined 10 degrees less than the latitude of the place (to produce hot water). 10 degrees more if it is used for heating.
Glass solar heat collector
How does a solar panel work, let’s talk about the most used solar panel. The glazed one, which is composed as follows:
* A sheet of transparent glass, placed above the absorber, which allows the passage of sunlight. The glass can withstand hail (tested with hail of 25mm in diameter).
* Inside there is a sunlight absorber, consisting of a sheet similar to a radiator ,which may be made of steel or copper. Inside there is a bundle of tubes in which flows the liquid of the primary circuit intended to be heated. This fluid is water with antifreeze so as to withstand the winter cold without freezing. The absorber, by heating up, emits energy in the form of infrared radiation. But the glass, against these radiations, attenuates the dispersion outside because it is opaque.
* Underneath the panel there is a thermal insulator (in glass fibre) that reduces heat dispersion. The panel is closed at the back by a shell, often made of sheet metal.
* Thermally insulated frame. Glass, absorber and tube bundle, thermal insulation and rear body, is held together by a chassis that assembles the parts and gives the panel strength and stability.
Glass solar heat collector Non-selective
Unlike the selective ones, the absorber is simply painted black. How does a solar panel work .First generation collectors, consisting of an insulated chamber between a tempered glass directly exposed to the sun and an insulated rear body. A blackened metal absorber is inside the solar panel, in order to increase its efficiency. This type of solar panel is the cheapest and most widespread solution for summer homes or areas that enjoy abundant sunshine.
Glass solar heat collector Selective
The absorber undergoes electro-chemical treatment under vacuum to obtain a surface with a high absorption coefficient and a low reflection coefficient up to a temperature of 140° C. Electrochemical treatment consists of a deposit of black chrome on nickel, vacuum treatment with titanium oxide vapours and pigmentation with metallic paints. The reduction of the reflection allows low of heat losses. These panels have a higher performance than traditional panels, and cost of 10% more compared to other panels. Able to work better in colder and less sunny periods. For this reason they can also be used with the heating system.
Uncovered panels (not glazed)
They don’t have the cover, the insulation and the containment box. Are made of black plastic material (polypropylen, neoprene, PVC). This facilitate the absorption of heat and consist of a bundle of pipes. Inside passes the water where it is heated directly by sunlight before being used.
How does a solar panel work. They work with an ambient temperature of at least 20°C . Below the balance between stored and dispersed energy is unfavourable. The maximum temperature of the water does not exceed 40°C. The simple structure of this panel boasts a lower. Consequently the performance is lower. Is recommended use on summer for swimming pools, hotels, bathing establishments.
Solar Vacuum tube
Are made up of a group of glass vacuum tubes, each containing an absorber (usually a copper plate) that absorbs the solar energy and transfers it to a fluid that carries the heat. Thanks to the insulating properties of the empty space, the heat losses are very low and temperatures of about 100°C above the ambient temperature can be reached. Solar vacuum tube is more complex and expensive to manufacture than flat panels.
Are less resistant, but at the same time have a high yield thanks to lower energy losses obtained through the use of vacuum tube. This technology is suitable for use in places with low insolation or for applications where high temperatures are required. Excellent performance in all months of the year and is suitable for installation even in harsh climatic conditions (low ambient temperatures, frost).
Concentrating solar collectors
These are concave collectors designed to optimize the concentration of solar energy at a specific point. They are only effective with direct sunlight because they must follow the movement of the sun. This type of collector, being able to reach high temperatures (400-600 °), are used for solar generators or solar power plants. Systems with concentrating solar collectors, called “thermodynamic solar”. are not pure solar thermal systems and are feasible in large installations and not suitable for civil and industrial contexts of medium to small size.
Solar Hot Air Collectors
Hot Air Collectors is glazed solar thermal panels that circulate air instead of water inside them. Here, instead of tubes that allow the circulation of the vector fluid, there is air circulating between the glass and the absorber and between the absorber and the bottom of the panel. The hot air, then transfers its heat to the domestic water, producing hot water proportional to the surface of the panel. These panels are designed in a way that the air remains as long as possible in the solar panel why it exchangeswater better than heat.
There may be an integrated storage tank, suitable for locations with a very harsh climate. A particular type of Solar Hot Air Collectors are the cladding panels. Used for the external curtain walls civil and industrial buildings. These are not glazed but consist of an external metal box surface that acts as an exchange and heats the air inside the panel. Can be introduced into the rooms with a special suction system.
Panels with integrated tank
In the panels with integrated tank, the heat absorber and the storage tank are contained in a single block and the solar energy heat the water. The tank, therefore, is covered by the absorber and, inside it there is a resistance that can heat the water in case of prolonged absence of the Sun. Convective motion is created inside the tank that distributes the heat captured to the entire mass of water.
The panels with integrated tank are recommended for those areas that are not cold. In fact, due to their structure, as temperatures drop, the water inside the panel risks freezing and damages the system. Easy to transport and install, these solar panels have a low cost and are perfect for uses in a summer holiday home. However, compact systems suitable for all weather conditions are also available on the market.