WO2012063195A1

WO2012063195A1 - Improved photovoltaic collector

Info

Publication number: WO2012063195A1
Application number: PCT/IB2011/054971
Authority: WO
Inventors: Claudio Zenere; Michele Bidese
Original assignee: Koncentra Group S.R.L.
Priority date: 2010-11-09
Filing date: 2011-11-08
Publication date: 2012-05-18
Also published as: ITVI20110296A1; ITVI20100297A1

Abstract

An improved photovoltaic collector (1) comprising one or more photovoltaic cells (2) disposed within boxlike elements (3) provided with a first opening (4) to allow the passage of the light beams towards the photovoltaic cells (2). The collector (1) comprises passive heat sinks having closed chambers (12) containing fluids, embedded in the walls of the boxlike elements (3) and sticking out from said walls for a stretch (16). Said stretch (16) is in thermal contact with the photovoltaic cells (2) to facilitate the heat diffusion from the photovoltaic cells (2) to the whole body of the boxlike elements (3).

Description

IMPROVED PHOTOVOLTAIC COLLECTOR

D E S C R I P T I O N

Field of the invention

The present invention relates to the field of the solar panels for photovoltaic use and particularly concerns an improved photovoltaic collector.

More in detail, the present invention concerns the dissipation of the heat particularly developed on the photovoltaic cells belonging to a photovoltaic collector.

Background of the invention

It is known that one of the fields in which the research of new technologies is particularly pushed is the field of the new energetic sources with particular reference to the renewable energetic sources.

One of these last ones is the sun. Elements, called photovoltaic cells, are in fact known, which transform the light beams which come into collision with them into electric energy. On the base of these elements photovoltaic panels or collectors are particularly diffused which are typically movable follow the sun. They comprise an assembly of photovoltaic cells associated in a single collector, which sum up their work of traducing the light beams which collide with them into storable electric energy or into directly usable electric power.

However, a problem of the photovoltaic cells is their yield, that is their potential to efficiently transform the light beams into electric current. It is in any case evident how research pushes to find technologies and methods which allow to increase as far as possible the electric energy produced by a single collector trying, at the same time, to reduce its manufacturing and maintenance costs.

As consequence, a part of the research is engaged to increase the yield of the photovoltaic cells.

This last one is connected not only with the materials and the technologies employed in the manufacturing thereof, but also to the operating temperature. It is in fact known that with the increase of the operating temperature a photovoltaic cell loses efficiency in an even remarkable way.

It is however evident that on a photovoltaic cell high temperatures tend to develop because of the use. The photovoltaic cell has t be as much as possible subject to the radiations, reason why it absorbs heat. To increase the yield, fitting conveyers are often present, too, to convey on the cell as many radiations as possible.

Beside this, the generation and circulation of the current per se generate heat.

Not only to increase the yield of the cell, but also to avoid that an excessive heat may damage it, heat sinks also of big size are generally present. They typically consist of a big size metallic block, provided with a plurality of fins to increase the surface of thermal exchange with the environment. The metallic block is thermally connected to the photovoltaic cell.

The above thermal connection has to promote as far as possible the heat transfer between the cell and the sink, so that it generally concerns big size superficial areas of the cell as well as of the sink body. Obviously this implicates that this last one cannot be placed in front of the cell, because it would represent a shield against the arrival of the light beams on the cell.

For this reasons sinks are typically placed on the back of the photovoltaic cell. This solution, although obliged, is not optimal. It is in fact known that the above displacing is the least efficient for the dissipation of the heat almost totally generated in front of the photovoltaic cell.

Sinks are also known which have fans which increase the thermal Exchange between the sink and the environment However this leaves unchanged the problem pointed out above, that is the fact that the sink is placed on the less suitable side of the photovoltaic cell to perform the best possible heat dissipation.

One has further to keep into account that the photovoltaic cell is a complex element, generally placed on a support. Typically, therefore, the photovoltaic cells, which are assembled in a housing body, generally in aluminium because it is easier to work, are steadily associated by welding to the support which is made in a thrust resistant material. This material, therefore, has not only to ensure the thermal conductivity, but also to allow the welding, which is antithetical to conductivity. As a consequence, the manufacturing costs in terms of materials employed and welding methods are unacceptably high.

The support, moreover, even if manufactured in a thermally conducing material, however obstacles the transmission of the heat developed on the cell. Also the welding material may be an obstacle for the heat transmission, as well as possible inaccuracy in its manufacturing which leads to the generation of air or gas bearings inside the welding.

In the prior art, therefore, support materials and welding materials and techniques which allow to limit the above described drawbacks are used. However, this generally implicates high manufacturing costs of the photovoltaic collectors which lead to high costs per kilowatt of the so manufactured photovoltaic collector.

Dissipating elements are also known which consist of an hydraulic circuit inside which cooling fluids flow. Some examples are described in US 2007/089775 and in US 2009/308433. In them the hydraulic circuit is in thermal contact with the photovoltaic cell to dissipate the heat. The cooling fluid is moved by means of fitting pumps.

This solution, although it allows to properly control the temperatures of the photovoltaic cells, are expensive not only in economic terms because of the cost of the pumps which move the fluid, but also in energetic terms because of the electric energy necessary for the working of the pumps. The yield of the photovoltaic collector is therefore compromised.

Summary of the invention

The object of the present invention is to at least partly overcome the above drawbacks, by providing an improved photovoltaic collector which improves the dissipation of the heat which forms on the photovoltaic cells.

Within this general object, a particular object is to manufacture an improved photovoltaic collector wherein at least a part of the heat sink is thermally connected to the respective photovoltaic cell frontally or laterally.

In particular, an object at least part of the heat sink is placed in the direction of the highest propagation of the heat generated by the photovoltaic cell, that is in front of it. In other words, at least a part of the heat sink has to develop in the direction of maximum efficiency of dissipation of the heat generated by the photovoltaic cell.

Another object is that at least a part of the heat sink is thermally connected to the photovoltaic cell so as to minimize the use of special, and therefore expensive, materials to manufacture the support of the cell.

Another object of the present invention is that the classical heat sinks possibly used, that is those consisting of metal blocks having a plurality of fins, have smaller size and weight than those used in the prior art equivalent photovoltaic collectors. This would, in fact, allow to reduce the weight of the photovoltaic collector and, consequently, the cost of the moving means to move it. It is in fact known that the photovoltaic collectors are generally movable to facilitate the arrangement thereof in front of the sun throughout the day (hence the name of photovoltaic trackers). This allows to improve the yield of the collector.

Another object is that the heat sink is efficient and at the same time does not increase, but possibly reduces the manufacturing costs of the photovoltaic collector so that the yield, that is the cost per kilowatt, is better than the prior art equivalent collectors.

These objects, as well as others that will appear clearer hereinafter, are fulfilled by an improved photovoltaic collector according to one or more of the following claims which are integrant part of the present patent.

In particular, the improved photovoltaic collector may comprise one or more photovoltaic cells arranged singularly or in groups at least partially inside one or more boxlike elements provided with at least one first opening to allow the passage of the light beams towards the cells.

According to an aspect of the invention, the collector may comprise at least one passive heat sink having a closed chamber containing fluids and embedded in the walls of the boxlike elements. The passive dissipating element may also project from the walls so that a stretch of this projection may be placed into contact with the photovoltaic cells in order to promote the diffusion of the heat to the whole body of the boxlike elements.

In other words, the boxlike elements, which are a housing for at least one portion of one or more photovoltaic cells, would be at least partially arranged in front of the part of the cell which receives the sun beams. As the closed chambers for the passive heat dissipation are embedded in the walls thereof, heat would spread in the area in front of the cells allowing to dissipate more easily the developed heat. The effect of the interposition of barriers to the thermal propagation would result minimized.

Advantageously again, the boxlike bodies would also become passive heat sinks, so that the classical heat sinks which might be applied on the back of the cell would in any case have smaller size than those used in prior art equivalent collectors, with a consequent decrease of the manufacturing costs of the collector according to the invention. It has in fact lower components number and a lower total weight than the prior art equivalent collectors: this allows to use moving means for moving the collector having a lower power than those used in the prior art collectors of equivalent size.

The above passive heat sinks are extremely advantageous in the considered case.

As hereafter explained, they allow to dissipate the heat generated by the photovoltaic cells with great efficiency without need of pumps or the like to move the fluids contained in the closed chambers. The costs are therefore moderate and the yield definitely improved.

Brief description of the drawings

Further features and advantages of the invention will become more apparent from the detailed description of a preferred, non exclusive embodiment of an improved photovoltaic collector according to the invention presented by way of illustrating and non-limiting examples in connection with the accompanying drawings in which:

FIG. 1 represents a photovoltaic collector according to the invention partially in transparency;

FIG. 2 represents a detail of the photovoltaic collector of FIG. 1 in exploded section;

FIG. 3 represents another detail of the photovoltaic collector of FIG. 1 in section; FIG. 4 represents another detail of the photovoltaic collector of FIG. 1 in exploded section;

FIGS. 5 and 6 represent another detail of the photovoltaic collector of FIG. 1 in axonometric view.

Detailed description of some preferred embodiments of the invention

With reference to the above figures, and particularly to fig. 1, an improved photovoltaic collector 1 having a plurality of photovoltaic cells 2 is described.

Each photovoltaic cell is disposed partially inside a respective boxlike element 3 which, as observable in the detail of fig. 2, is provided with a first opening 4 to allow the passage of the light beams toward the cell 2.

In the described embodiment, to each boxlike element 3 corresponds a single photovoltaic cell 2. Obviously this has to be intended as non-limiting for different embodiments wherein more photovoltaic cells are associated to a boxlike element. Again, in the described embodiment of the photovoltaic collector 1, the photovoltaic cells 2 are only partially inserted in the boxlike element 3.

In particular, as said before, each photovoltaic cell 2 is assembled in a housing body 5 typically in aluminium, and joined in a single block 6 with the respective support 7. Typically, the junction between the photovoltaic cell 2 and the respective support 7 is made by welding.

In the case of the photovoltaic collector 1 according to the invention, each boxlike element 3 comprises a second opening 8 for each photovoltaic cell 2 associated thereto. The opening has such size and shape to allow the photovoltaic cell 2 to face completely the second opening 8 so that the beams coming from the first opening 4 may reach the whole photosensitive surface.

The association between the boxlike element 3 and the block 6 may take place for example by means of screw means which concern, in particular, the support 7.

Obviously this embodiment mustn't be considered as limiting for different embodiments according to which the second opening of the boxlike element does not exist and the photovoltaic cells are inserted therein through the first opening. Moreover, they may be directly associated to the inner surface of the boxlike element or to fitting supports projecting from said inner surface.

According to another aspect of the invention, each boxlike element 3 comprises a shaped body 10 the inner surface 11 of which reflects the electromagnetic radiations to facilitate the conveying of the light beams towards the photovoltaic cells 2. In other words, the boxlike element 3, which houses at least the photosensitive part of the photovoltaic cells 2, advantageously fulfils also the function of conveyer of the beams towards the cells 2 in order to increase the yield of the photovoltaic collector 1.

In this sense, the shaped body 10 has an appropriately, but not necessarily, substantially truncated cone shape open at the two ends, on one side to house a photovoltaic cell 2 and on the other side to allow the light beams to reach the cell 2.

According to a further aspect of the invention, the photovoltaic collector 1 comprises, as observable also in fig. 3, also a passive heat sink element which includes a pair of closed chambers 12 containing fluids.

These closed chambers 12 are embedded in the walls of the boxlike elements 3 and project from them for a stretch 16 which is placed into thermal contact with the photovoltaic cells 2 to facilitate the dissipation of the heat formed thereon.

In particular, one can observe that the closed chambers 12 consist of substantially tubular elements and have, in the stretch 16 projecting from the walls of the boxlike elements 3, an enlarged profile to increase the thermal exchange with the photovoltaic cells 2.

In other words, the closed chambers 12 spread the heat developed by the photovoltaic cells 2 on the boxlike elements 3 by means of which it is dissipated into the surrounding environment. The passive heat sink, therefore, comprises not only the closed chambers 12, but also the boxlike elements 3.

Advantageously, therefore, at least a part of the dissipation of the heat of the cells

2 takes place by means of a structural element of the collector 1 according t the invention allowing to spare in materials for the manufacturing of heat sinks.

As observable, in fact, a good part, if not the totality, of the dissipation of the heat generated by the cells 2, takes place by means of elements present in the photovoltaic collector 1 for other purposes. This allows to limit the use of fitting heat sinks which are not only associated to the cells 2 in the direction of a reduced dissipation efficiency, but also remarkably increase the weight of the collector 1 with a consequent increase of the structural costs of and of the moving means thereof where present.

Advantageously again, as the boxlike elements 3 substantially develop in front of the cells 2, the dissipation of the heat developed by them takes place in the direction of maximum efficiency.

On the whole, therefore, the heat dissipation is optimized, the weight of the collector 1 is reduced, the costs of the structural part are lower and lower are also the costs of the movement section of the collector 1. This leads to a consistent reduction of the cost per kilowatt of the collector 1 according to the invention with respect to the prior art equivalent collectors.

As said before, and as visible in particular in fig. 4 each of the closed chambers 12 consists of tubular elements embedded in the walls of the boxlike elements 3 or inserted inside fitting o cavities 14 present in the section of the walls of the boxlike elements 3. Obviously this is not limiting for different embodiments wherein each of the flowing pipelines comprises one or more stretches formed by the cavities. Also the number of closed chambers per boxlike element and of points of thermal contact with the photovoltaic cells may vary without departing from the scope of the invention.

In the described embodiment one can observe that there is a physical between the projecting stretch 16 and the housing body 5 of the photovoltaic cell 2. In this case, therefore, one can avoid to have to transmit the heat from the cell 2 to the heat sink exclusively through the support 7, which can be therefore manufactured also with materials with lower thermal conduction coefficients but lower prices, as well as through the welding between the support 7 and the photovoltaic cell 2, which can therefore be made with simpler methods and with more ordinary welding materials.

Possibly, to manufacture the housing body 5 of the photovoltaic cell 2 a material with a high thermal conduction coefficient may be chosen. Having to bear particularly limited mechanical thrusts and to have small size, it has in any case moderate costs. In any case, moreover, the distance heat has to cover on the housing body 5 between the projecting stretch 16 of the closed chambers 12 and the photovoltaic cell 2 is so reduced that it doesn't represent an important barrier for the heat diffusion.

Another advantageous aspect of the collector 1 according to the invention is that a real refrigeration cycle forms inside the closed chambers 12. In the closed chambers 12, in fact, there is a high thermal gradient between the stretch 16 in thermal contact with the photovoltaic cells 2 and the part embedded in the walls of the boxlike elements 3. This causes the diffusion of the heat from the projecting stretch 16 to the part of the closed chambers 12 embedded in the walls of the boxlike elements 3. This diffusion takes advantageously place without need of pumps or the like to move the fluid and therefore allows to use closed chambers 12 instead of open flowing channels for fluids connected to suitable pumps. In fact they move autonomously a san effect of the temperature gradient.

In case the fluids consist of water, for example, in the projecting stretch 16 water tends to evaporate and to lift towards the ends of the closed chambers 12 farther from the cell 2. The temperature decrease during the circuit allows the evaporated water to condensate and so to go back to its liquid state to flow back down towards the cell 2.

In this sense, therefore, the refrigeration cycle may be facilitated and optimized using cooling fluids or gases instead of water.

With this configuration, therefore, there is an optimized dissipation of the heat developed on the cells 2 with the advantage to keep the operating temperature thereof closet o the optimal values. All this happens without the employ of fans, pumps or the like which would mean not only an increase of the manufacturing costs, but also energetic waste in the operating step. All this stresses the reduction of the cost per kilowatt of the collector 1 according to the invention with respect to the prior art equivalent collectors.

As far as here we have seen how to dissipate efficiently the heat generated by the photovoltaic cells 2 employing the boxlike elements 3. However in doing so the heat, which is in any case an energetic source, is simply dissipated into the environment. According to another aspect of the invention, therefore, the photovoltaic collector 1 comprises, as observable in fig. 5, one or more pipelines 20 which go through respective passing through holes 21 made in the boxlike elements 3. These pipelines can be used, for example, for the flow of water to heat for sanitary uses or for the heating of rooms. Alternatively they can be used to heat any fluid which may be a valid transport vehicle of heat so to exploit it without dissipating it uselessly in the environment.

The above disclosure clearly shows that the improved photovoltaic collector according to the invention overcomes the drawbacks of the prior art improving the dissipation of the heat which forms on the photovoltaic cells.

In particular, in the improved photovoltaic collector according to the invention at least a part of the heat sink is thermally connected, frontally or laterally, to the respective photovoltaic cell and develops in the direction of maximum efficiency of dissipation of the heat generated by the photovoltaic cell.

Also the use of special, and therefore expensive materials for the manufacturing of the support of the photovoltaic cells is minimized. Moreover the use of classical heat sinks, which usually have remarkable size and weight and which do not allow to optimize the dissipation of the heat generated by the photovoltaic cells, is minimized, if not excluded.

The improved photovoltaic collector according to the invention is susceptible to many changes and variants, all falling within the inventive concept expressed in the annexed claims. All particulars may be replaced by other technically equivalent elements, and the materials may be different according to the needs, without departing from the field of the invention.

While the photovoltaic collector according to the invention has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Claims

C L A I M S

1 . An improved photovoltaic collector comprising one or more photovoltaic cells (2) at least partially placed, individually or in groups, inside one or more boxlike elements (3) having at least one first opening (4) to allow the passage of light beams to said photovoltaic cells (2), characterized in comprising at least one passive heat sink having a closed chamber (12) containing fluids, embedded in the walls of said boxlike elements (3) and sticking out from said walls for a stretch (16), said stretch (16) being in thermal contact with said photovoltaic cells (2) to allow the thermal dissipation from said photovoltaic cells (2) to the whole body of said boxlike elements (3).

2. Photovoltaic collector as claimed in claim 1, characterized in that said closed chamber (12) has a substantially tubular shape.

3. Photovoltaic collector as claimed in claim 1 or 2, characterized in that said stretch (16) of said closed chamber (12) has an enlarged profile to increase the thermal exchange with said photovoltaic cells (2).

4. Photovoltaic collector as claimed in any of the preceding claims, characterized in that said boxlike elements (3) comprise a shaped body (10) having an inner surface reflecting the electromagnetic radiation to facilitate the conveyance of said light beams towards said photovoltaic cells (2).

5. Photovoltaic collector as claimed in claim 5, characterized in that said shaped body (10) of said boxlike element (3) has a substantially truncated cone shape.

6. Photovoltaic collector as claimed in any of the preceding claims, characterized in that said boxlike elements (3) include at least one second opening (8) for the at least partial insertion therein of said photovoltaic cells (2).

7. Photovoltaic collector as claimed in any of the preceding claims, characterized in that said fluids include cooling gases.

8. Photovoltaic collector as claimed in any of the preceding claims, characterized in comprising one or more pipeline (20) passing through respective passing through holes made in said boxlike elements (3).