The solar thermal collectors that allow the energy coming from the sun to be taken advantage of for the purpose of saving energy are widely known. However, these conventional solar collectors reach high stagnation temperatures, around 200° C. in flat plate collectors and 300° C. in evacuated tubes. These temperatures generate overheating in the solar energy installation, bringing about a series of unwanted consequences such as corrosion, scaling, electrical pump cavitations, loss of anti-freeze, degrading of the heat carrying liquid, degrading of the selective surfaces of the collectors and material stress. The end result is that the solar energy installation stops working due to said overheating.
In order to prevent this problem it is a common practice to install manual or automatic heat dissipating systems. However, these systems are not reliable because they depend on human action (covering the collectors with canopies, blankets, plates, etc.) and electrical mechanisms (servo-motors, electro-valves, electro motor pumps and fans, etc.), hence being sufficient a momentary stop of the electrical supply and/or a failure of one of these mechanisms, to provoke the overheating and the resulting harm to the solar power installation. As can be supposed, there is the subsequent need to replace all those damaged parts, with the financial costs that this brings about.
Another disadvantage of these dissipating systems lies in the fact that the thermostatic valves that regulate the inlet of heat carrying fluid into the dissipating system are outside of the solar thermal collector and therefore cannot take into account the temperature that the fluid on the inside of the solar thermal collector reaches; consequently the sensing element in the valve is not activated until the solar thermal collector has reached a temperature that is too high.
In general these systems return the heat carrying fluid coming from the dissipating system to a lower part of the hot water installation by means of gravity. This requires the use of more piping that increases the complexity and consequently the cost of the assembly.
In addition, to provide the solar energy installation of solar thermal collectors with dissipating systems, it requires qualified people to take part so as to study the arrangement of the differing components of the solar energy installation in order to obtain optimum results. This means additional costs in labour, materials and transport, with the additional risk that the assembly is not carried out correctly. The final result increases the visual impact by adding more piping and dissipaters to the original installation.
Document U.S. Pat. No. 4,473,063 describes a solar thermal collector provided with a dissipating system to prevent overheating that has an effect on the above mentioned disadvantages. The dissipating system is not integral to the solar thermal collectors, but is separate, therefore its installation is more complex and costly, the visual impact is more negative and its dissipating system is exposed making it vulnerable to the elements and providing no protection against burns and injuries for installers and users. In addition, the thermostatic valve is away from the area of the solar thermal collector where the excessively high temperatures are reached, and said thermostatic valve is not activated either at the right moment or reliably with the needs of a true temperature safety limitation.