There are different types of solar collectors: flat collectors, vacuum tubes and some plastic collectors (unglazed polyethylene) specific for swimming pool climate control.
For hot water, the type of thermal collector will be defined by the final water temperature. For most cases (60 ° C), the flat solar collector is usually sufficient.
TYPES OF SOLAR THERMAL COLLECTORS
If you need water at a higher temperature (to heat with radiators, for example), the vacuum tube collectors are more suitable.
If you only need to heat the pool, polyethylene collectors can be a good solution. The water in the pool can go directly through the collector, the low temperature needs are suitable for this technology.
Flat solar collector
It is the simplest solar collector. The sun shines on the top plate of the solar collector, this is called the cover plate. The plate is transparent and guarantees that the heat is retained in the collector. Then the sun’s rays fall on a black plate. This is heated by absorbing the rays and, therefore, is called absorbent.
Under the absorbent there are tubes that contain a liquid. The liquid is heated in the absorbent and then drains the heated liquid. This heat can be used or stored. The solar collector is surrounded by an insulating cover.
This allows the temperature in the collector to be as high as possible. The temperature in a flat plate solar collector can rise to 200 degrees Celsius. This collector can be used for several purposes.
Vacuum tube solar collector
These vacuum tubes are placed next to each other and are made of double glazing. The vacuum is inside these tubes, which means that the heat can be retained well. A special coating was also applied inside the tubes. This ensures that the heat stays even better. Each tube contains a copper absorber.
The heat accumulates in the upper part of the tubes and is placed in the copper solar collector. This ensures that the heat is transferred to the circulating water. The vacuum tube solar collector is common in warm countries such as Portugal, Turkey and Greece.
Parabolic solar collector
The parabolic solar collector is the most powerful collector. This uses a plate-shaped mirror to concentrate all the solar energy at a focal point.
At this point the air is heated to 1,000 degrees centigrade. The air immediately becomes movement in an engine. The movement can be used to produce electricity.
By concentrating the solar rays at a point, you can increase the intensity of solar energy. The parabolic collector uses this method. Parabolic mirrors reflect sunlight towards a focal point through which a tube passes.
The tube contains a means of transport that, thanks to concentrated solar energy, reaches temperatures of 400 degrees Celsius. The collector’s mirrors rotate with the sun, so the sun always falls perpendicular to the parabolic profile. The high temperature of the medium is used to generate electricity. The heat is first converted into steam and then converted into electricity in a steam turbine.
The parabolic solar collector only works when the sun shines directly on it. Sunlight that is scattered by clouds and particles in the atmosphere can not be used. Therefore, the collector is not applicable in the Netherlands, since 50% to 60% of the annual radiation is scattered here.
This solar collector heats a large surface under a transparent glass roof. The air below is heated and rises through the center of the tower. The air you want to ascend has a large volume, while the chimney is relatively thin. This causes the air to move at high speed. By using wind turbines, the energy of moving air can be converted into electricity.
A solar tower is in the middle of a field with mirrors. This field is generally a few square kilometers in size. It contains large mirrors that reflect the sun’s rays to a specific point of the tower.
Therefore, the means of transport in this tower can be heated to 1,000 degrees centigrade. This is then converted into steam and the steam turbine drives a generator that produces electricity. The mirrors in the field rotate with the sun.