[1]
The present invention relates to solar panels for obtaining energy from the sun by thermal means. More particularly, the present invention relates to the elements of the solar panels that form the heat transfer fluid circuit.
[2]
In conventional solar thermal systems for heating a fluid by forced convection, there is a primary circuit where a heat transfer fluid is heated by means of a solar panel, said fluid in turn circulating through an element which transfers the calorific energy, usually to an accumulator, where the fluid to be heated is disposed at a lower temperature.
[3]
The behaviour of a fluid when passing inside piping produces a loss of pressure. If the circuit is a set of pipes arranged with different lengths, as is the case for a conventional solar panel or array of solar panels in the prior art, there is an unequal distribution of the volume of water circulating in each of said pipes, and the shorter the travel and the fewer changes of direction (elbows, T couplings, radii, etc.), the greater the volume of water whereas the greater the travel and changes in direction in the path of the fluid between the fluid inlet and outlet, the smaller the volume of water. Therefore to cause the same volume of water to circulate through each of the different circuits, it is advisable to compensate for losses of load. This is achieved with balancing valves or by ensuring that the travel of the fluid with changes of direction (elbows, reducers, etc.) along all possible paths throughout the circuit of the system is exactly the same.
[4]
To achieve this object, it is known to send the heat transfer fluid through one end of the solar panel or array of solar panels and to cause it to return through the opposite end thereof, requiring a path to be produced outside the solar panel for sending or returning the heat transfer fluid to the heat exchanger.
[5]
Document US2010288264A US2010288264A discloses a fence or enclosure, which comprises solar panels and an auxiliary return line located inside the fence but outside the space for the solar panels. Said line is covered with insulating material. Said auxiliary line is equivalent to the return or auxiliary lines that run, having been insulated, outside the solar panels.
[6]
An object of the present invention is to provide a solution to said problems of the prior art. To achieve this, the invention relates to the sending or return of the heat transfer fluid without travelling outside the solar collector or with a smaller amount of travel outside the solar collector and is based on a solar panel inside which one or all of the elements of the circuit for recirculating the heat transfer fluid are arranged, so that the elements used to conduct the heat transfer fluid outside the solar collector are completely or partly eliminated. The effect thus produced not only reduces additional heating of the heat transfer fluid but also firstly eliminates a large number of components such as pipes, elbowed couplings, flanges, absorption, expansion and insulation elements, and the accessories thereof and secondly, and yet more importantly, it eliminates much of the work force involved in fitting the recirculation pipes to the connection and insulation elements thereof (the maximum reduction being achieved if said elements are welded together) as well as the insulation elements and the attachment thereof.
[7]
More particularly, the present invention comprises a solar panel of the type that has a main body consisting of a perimeter frame which defines an internal volume in which a collecting surface is situated adjacent to a heat transfer fluid circuit in an area exposed to sunlight, said circuit comprising at least one inlet and one outlet of the solar panel for the heat transfer fluid. In its inner casing, the solar panel comprises an inlet and an outlet for receiving a recirculation pipe for the heat transfer fluid. Preferably, said circuit further comprises a recirculation pipe that also has an inlet and an outlet for the heat transfer fluid from the outside.
[8]
The collecting surface and the circuit may be adjacent, in contact or interconnected totally or partly, without departing from the spirit of the invention.
[9]
Another factor to take into account is that the efficiency of the entire installation is increased, because the insulation inside the collecting surface (usually 40 to 60 mm) is normally much thicker than the pipe insulators (normally 20-25 mm). The only additional accessory compared with a conventional collector with no recirculation is one more connection element between the collectors, increasing the number of connection elements for each solar panel added to a group of solar panels from two to three.
[10]
Another factor to take into account is that all the elements inside the collector are protected from adverse atmospheric conditions, such as oxidation, galvanic corrosion, cracking, contact with acids, dirt, etc.
[11]
As mentioned above, partial incorporation is possible, by incorporating only the fluid recirculation pipe, which may be a sending (preferred) or return pipe and the supply or return pipe respectively plus the double connection elbow for recirculation outside the solar panel. In this case, the configuration of the solar panel is always the same and two external connection accessories are necessary.
[12]
However, total incorporation of the components inside the collector is also possible. In this case, the present invention provides for three possible preferred configurations:
a) If the array of solar panels has three or more solar panels, three solar panel configurations are necessary: the initial one (through which the heat transfer fluid enters and leaves), the intermediate one (for circulation between the initial and final solar panels) and the final solar panel of the installation (where the return of the fluid to the initial solar panel begins). b) If the solar panel array has two solar panels, the initial and final configuration will be sufficient, without the intermediate model. c) If the solar panel array has only one solar panel, it would not need a configuration that incorporates the initial and final solar panel.
[13]
Using the sending pipe for recirculation is considered preferable as the heat transfer fluid is colder than in the return pipe, and because the recirculation pipe has less contact with the collecting surface than in the rest of the heat absorber it has less effect on its efficiency. Furthermore, it enables better incorporation of other elements such as sensors or steam separators.
[14]
More particularly, the present invention consists of a solar panel, of the type that has a main body consisting of a perimeter frame which defines an internal volume in which a collecting surface is situated connected to a heat transfer fluid circuit in an area exposed to sunlight, said circuit comprising at least one solar panel inlet and one solar panel outlet for the heat transfer f…
