WO2012016678A1 - Thermoelement, photovoltaic module and photovoltaic installation - Google Patents

Abstract

The present invention relates to a thermoelement for a photovoltaic module comprising a media channel for a heat exchanger medium, a first surface section, which is suitable and intended for coming into direct thermal contact with the photovoltaic module, and a second surface section. According to the invention, the thermoelement, photovoltaic module and the photovoltaic installation are distinguished by the fact that the second surface section is in direct thermal contact with the ambient air.

Description

 Thermocouple, photovoltaic module and photovoltaic system

The invention relates to a thermocouple for photovoltaic modules, a photovoltaic module with at least one thermocouple and a photovoltaic system with at least one photovoltaic module.

Basically, solar energy can be used to generate heat energy by means of a collector or to generate electricity through photovoltaic (PV) modules. Hybrid collectors which combine the function of heat generation and the function of power generation in one module are known, for example, from EP 1 873 843 A2 and DE 20 2007 010 901 U1. Such hybrid collectors are sandwiched and have a cover layer, a photovoltaic module (usually consisting essentially of a plurality of solar cells and a heat-conducting rear surface), a heat exchanger for simultaneously cooling the solar cell and heating water, and a heat-insulating layer.

However, an extension of existing photovoltaic modules to hybrid collectors is often difficult, since many suitable heat exchangers (thermocouples) are not available. The replacement of existing photovoltaic modules by hybrid collectors, however, is uneconomical. Therefore, to expand a existing PV system by a solar thermal collector, for example, on a house roof, usually omitted on hybrid collectors and it will be added to separate solar panels. This leads to a poor utilization of space, whereby among other things, the energy gain that can be achieved for a given useful area is reduced.

Furthermore, the current and hot water yield is not optimally matched in known hybrid collectors. In order to increase the warm water yield, an insulating layer is attached to known hybrid collectors. However, the efficiency of power generation of PV elements decreases at a higher temperature and with the same floor space, the hot water yield is often much better than the current yield anyway. But excess electricity can be used more meaningful than surplus hot water in particular by the good price situation for fed into the grid solar power.

It is now an object of the invention to provide thermocouples for easy retrofitting for existing photovoltaic modules and a photovoltaic module expandable by a thermocouple. Another goal is to optimize the coordination between electricity and hot water yield in hybrid collectors.

According to the invention a thermocouple for photovoltaic modules according to claim 1 and a photovoltaic module according to claim 6 is provided. Advantageous embodiments emerge from the subclaims.

Accordingly, the invention comprises a thermocouple for photovoltaic modules with at least one media channel for a heat exchange medium, a first surface portion and a second surface portion. The first surface portion is formed so that a direct heat exchange between the PV cells and the thermocouple is effected by heat conduction. The second surface portion is inventively designed so that a direct heat exchange takes place by heat conduction between the thermocouple and the ambient air. The first surface portion is suitable and determined to face the PV element during assembly. The second surface portion is suitable and determined to be facing away from the PV element during assembly and to be in contact with the ambient air at the back of the PV element.

The media channel has at least one flow connection and at least one return connection for the heat exchange medium and can be designed, for example, in the form of a pipe coil. The thermocouple can also be designed as a hollow chamber plate. The heat exchange medium is preferably a fluid having a high heat capacity, for example, water-based.

Heat can thus be delivered from the PV cells to the thermocouple, from where it is dissipated by the heat exchange medium in the media channel on the one hand and by heat exchange with the ambient air on the other hand. The second surface portion is in thermally conductive connection with the first surface portion and thus at least indirectly with the photovoltaic cells. Due to the direct thermal contact of the second surface portion with the ambient air, no waste heat is accumulated in the region of the thermocouple.

By avoiding heat build-up in the thermocouple and the additional removal of heat by the ambient air better cooling of the PV element is achieved at the expense of heat recovery of the heat exchanger medium compared to prior art hybrid collectors. The ratio of current efficiency to warm water yield is thus shifted in favor of the current efficiency, which is desirable as explained at the beginning.

Due to the simple design, the thermocouples according to the invention are also suitable as retrofit elements. Preferably, the thermocouple of the invention has a plate-like shape with two substantially parallel surfaces corresponding to the first and second surface portions.

In one embodiment, the first and / or the second surface portion has a smooth surface, in another embodiment, the first and / or the second surface portion has a rough and / or structured surface.

In a further embodiment, the heat exchanger is made of materials that conduct good heat at least in the area of the first and / or second surface section and / or media channel. This can be achieved for example by a thin-walled design with a good heat-conducting material, such as sheet metal or aluminum. Optionally, there is also an intermediate layer which improves the heat conduction. Suitable materials and / or intermediate layers preferably have a thermal conductivity of more than 1 W / (m K), preferably more than 5 W / (m K), and more preferably more than 10 W / (m K).

In one embodiment it is provided that the second surface portion has no means for reducing the heat conduction between the thermocouple and the ambient air, in particular no insulating means such as an insulating layer of insulating material or a vacuum layer.

In one embodiment, the second surface portion includes means for enhancing heat exchange between the thermocouple and the ambient air. Suitable means for enhancing the heat exchange include, for example, passive heat sinks, such as cooling fins, cooling fins or even a simple corrugated metal sheet. Optionally, the passive heatsinks are made of aluminum.

In one embodiment, the thermocouple has means for fixing to the sun-remote surface of the photovoltaic module, which are formed are that the thermocouple can be attached to the first surface portion adjacent to the photovoltaic module. The means for fixing are preferably designed so that a reversible fixation is made possible. Suitable means include screws, clamps, connectors, snap-in connections and the like. The means for fixing the thermocouple may be suitable and / or intended for attachment to the frame of existing PV modules or directly on the back surface of the PV module itself. Furthermore, a non-reversible fixation such as sticking or welding is conceivable.

In one embodiment, the thermocouple has no means for fixing to the sun-facing surface of the photovoltaic module, and is suitable and intended to be clamped in the frame at the back of the PV module or held by secondary components anchored to the frame or frame members become.

For existing photovoltaic modules without thermal heat collectors, the thermocouple is formed in a further embodiment as a retrofit. So existing PV modules can be retrofitted to hybrid modules.

The invention further relates to a photovoltaic module with a thermocouple, which has at least one media channel for a heat exchange medium. The photovoltaic module may also have a plurality of thermocouples. A first surface portion of the thermocouple is in direct thermal contact with the PV module and preferably abuts directly on its side facing away from the sun (back).

According to the invention, a second surface section on the side of the thermocouple facing away from the PV module is in direct thermal contact with the ambient air. This promotes heat exchange between the PV cells of the module and the ambient air. Waste heat generated in the PV cells is on the one hand through the heat exchanger medium in the media channel and on the other hand additionally dissipated at the second surface portion by heat exchange with the ambient air.

In such a hybrid collector according to the invention, a better cooling of the PV element is achieved at the expense of the heat yield of the heat exchanger medium in comparison to the previously known hybrid collectors. The ratio of current efficiency to warm water yield is thus shifted in favor of the current efficiency, which is desirable as stated in the introduction.

Preferably, the thermocouple and / or the PV module have a flat, in-plane shape, such as a plate, with two substantially parallel surfaces. Particularly preferred is the use of a thermocouple according to the invention according to one of the embodiments described above.

Due to the lack of an insulating layer on the second surface portion of the thermocouple created by the heat generated at the PV cells heat accumulation. The cooling is optionally enhanced by passive heat sinks. By this additional heat dissipation to the ambient air, the efficiency of the PV cells can be increased.

The thermocouple is attached to the solar back side of the PV module. The first surface portion of the thermocouple thus adjoins the solar side facing away from the PV module. The second surface portion of the thermocouple faces away from the PV module.

The PV modules with thermocouple according to the invention are in one embodiment substantially plate-shaped and have a multilayer sandwich construction. The corresponding stratification includes a transparent and weather-resistant front layer on the sun-facing side, underlying solar cells and a back lining of resistant and highly thermally conductive material. The individual layers are optionally held together by a frame. The back lamination borders directly or over a good heat-conducting intermediate layer of the first surface portion of the thermocouple. This may, for example, be jammed in the frame at the back of the PV module, or held by secondary components anchored to the frame or frame members.

In one embodiment, the thermocouple is a modular part of the photovoltaic module and is reversibly removable. This accomplishes favorable maintenance properties by an interchangeability of the thermocouples. Furthermore, a photovoltaic module which has no thermocouple can be retrofitted.

The invention further relates to a photovoltaic system with at least one or more PV modules according to the invention.

Further advantageous embodiments of the invention will become apparent from the following figures and embodiments.

In the figures show:

1 shows a perspective view, a side view and a front view of a photovoltaic system with a photovoltaic module according to the invention,

FIG. 2 shows a cross section through a photovoltaic module without a thermocouple,

FIG. 3 shows cross sections through various embodiments of a PV module according to the invention,

Figure 4: a cross section of an embodiment of a PV module according to the invention, and FIG. 5 shows a rear view of an embodiment of a PV module according to the invention.

Figures 1a, 1b and 1c show a photovoltaic (PV) system 1 with a plurality of plate-shaped photovoltaic (PV) modules 10. The system comprises a frame 5, which fixes the individual modules, spaced from each other, and the individual plates the sandwich constructed modules holds together.

In Figure 1a, this Appendix 1 is shown in a perspective view, in Figure 1 b in a side view and in Figure 1c in a front view. The sun-facing side or front side of the PV system 1 or of the PV modules 10 is marked with the letter A, the side facing away from the sun with the letter B.

FIG. 2 shows a cross section through a PV module 10 without a thermocouple. The module consists essentially of a multilayer plate which is pressed between two frame members 5 below a nose 6. The nose 6 and one or more projections 9 on the underside of the frame members 5 form recess 8, which receives the PV module. The projection 9 may extend horizontally over the entire frame, or it may be present only at selected locations individual projections 9. These serve optionally as an attack surface for fasteners 9a (shown here as screws) for connecting the system 1 with a frame.

FIG. 2 also shows an optionally present putty 7 between the PV module and the frame elements, which seals the joints occurring between the PV module 10 and the frame elements 5 on the front side A and / or the back side B against water entry and during pressing can seal similar.

The PV module typically does not completely fill the recess 8 of the frame 5, and at the rear B remains between the PV module and the or the projections 9, a gap 8a with the height hi. This gap 8a may for example represent a reserve of space, or possibly also allows easier access to the fasteners 9a by a fitter. Typical values for height h1 include, for example, the range of between about 30 mm and about 50 mm, preferably between about 35 mm and about 45 mm.

The module 10 has on the sun-facing front side A a weather-resistant, transparent layer 11 such as a glass plate. Typical layer thicknesses are for example between about 3 mm and about 7 mm. The solar cells, for example, made of polycrystalline silicon form the underlying layer 12. On the back side facing away from the sun B is the back side lamination 13, for example one or more weather-resistant and / or good heat-conducting films, e.g. Plastic films.

FIGS. 3a, 3b and 3c show various embodiments of a PV module 10 according to the invention with a thermocouple 20. The structure of the PV module 10 has already been described in connection with FIG. The thermocouple 20 adjoins the rear side B facing away from the sun and / or the sun-remote surface of the back side covering 13 of the PV module.

The thermocouple 20 has a calender-shaped media channel 21 for a heat exchange medium, preferably water.

In the embodiment shown in Figure 3a, the thermocouple 20 as well as the PV module 10 is pressed between the frame members 5 so that it is in direct thermal contact with the back of the PV module 10. A putty 7 may also seal at the back B of the thermocouple 20 any resulting during pressing joints. The thermocouple 20 takes a part of the gap 8a between the PV element 10 and projection 9 a. It may already be incorporated during the production of the PV module, in particular be pressed into the recess 8 miteebesst. Further, it is possible for the thermocouple 20 Add later or stick to the back cover 13. The thermocouple can be optionally retrofitted or replaced.

The hybrid module is thus constructed modularly from PV module 10 and thermocouple 20.

By heat conduction through the Rückseitenkaschierung 13 and the thin wall of the heat exchanger channel or the thermocouple, for example, an aluminum sheet, a good heat exchange between the solar cell and the heat exchanger medium is made possible. On the side facing away from the PV module, or in other words on the side facing away from the sun B of the module rear side of the thermocouple 20 no insulation is provided. Rather, by heat conduction through the thin rear wall of the heat exchanger duct or the thermocouple, for example, an aluminum sheet, a good heat exchange with the ambient air is made possible.

The embodiment illustrated in FIG. 3b substantially corresponds to the embodiment shown in FIG. 3a. On the back of the thermocouple

However, 20 here is also a passive heat sink 22a (here: cooling fins) to enhance the heat exchange with the ambient air.

In the embodiment shown in FIG. 3c, a passive heat sink 22b (here in the form of an aluminum corrugated sheet) simultaneously represents the structure of the thermocouple 20. The corrugated sheet is, like the thermocouple in the embodiments described in connection with FIGS. 3a and 3b, in the gap 8a the back B of the PV module 10 between the frame elements 5 is pressed.

Due to the compression caused by the corrugated sheet structure of the passive heat sink 20, which essentially determines the channel course, even media webs

21 for the cooling medium. The density of such a thermocouple on the side panels can be improved by a putty 7 yet. By the heat sink favored in a PV module according to the invention cooling of the solar cells by the additional heat exchange with the ambient air can be further enhanced.

FIG. 4 shows a cross-section through a further embodiment of a PV module 10 according to the invention with a thermocouple 20 arranged on the rear side. This embodiment is structurally similar to the embodiment shown in FIG. 3a, but two further fastening mechanisms of the thermocouple 20 on the rear side of the PV Module 10 is shown.

On the left side, a spring 27 is shown, which is inserted between the thermocouple 20 and a projection 9 at the rear end of the frame 5 in the gap 8a and presses the thermocouple 20 to the back of the PV module. On the right side, a frame 25 is shown, which is fastened by means of the screw 26 on the frame 5 and acts as a fixation for the thermocouple 20. Of course, each of the illustrated fastening mechanisms can also be used on both sides, in addition to or instead of a compression between the frame members. 5

The plate-shaped thermocouple is flush mounted by the fastening means and flat on the back side lamination 13 of the PV module 10 adjacent. Alternatively, the thermocouple 20 can also be glued to the back. It is advantageous if the thermocouple 20 covers the back of the PV module substantially completely. Alternatively, only a part of the back can be covered.

FIG. 5 shows a PV module according to the invention from FIG. 3b from the sun-facing side B. FIG. The thermocouple 20 completely covers the back surface of the photovoltaic module 10 and the back cover, respectively. The calender-shaped media channel 21 with flow connection 23 and return connection 24 is shown as a dotted line. A heat exchange medium is with low temperature via feed line 23 into the media channel, while the flow through the media channel 21 is heated by waste heat from the PV module and leaves the thermocouple through the return line 24th

Due to the constant heat dissipation through both the heat exchange medium and the ambient air, the PV module is cooled particularly effectively, resulting in a better current efficiency.

Claims

claims 1. thermocouple for a photovoltaic module with a media channel for a heat exchange medium,  a first surface portion suitable and destined to come in direct thermal contact with the photovoltaic module, and  a second surface portion, characterized in that the second surface portion is in direct thermal contact with the ambient air. 2. A thermocouple according to claim 1, wherein the second surface portion has no means for reducing the heat conduction between the thermocouple and the ambient air. 3. A thermocouple according to claim 1 or 2, wherein the second surface portion comprises means for enhancing the heat exchange between the thermocouple and the ambient air. 4. Thermocouple according to one of the preceding claims, wherein the thermocouple comprises means for preferably reversible fixation on the sunab- turned surface of the photovoltaic module. 5. Thermocouple according to one of the preceding claims, wherein the thermocouple is a retrofit part for photovoltaic modules. 6. photovoltaic module with a thermocouple, which has at least one media channel for a heat exchange medium,  wherein a first surface portion of the thermocouple is in direct thermal contact with the photovoltaic module, characterized in that a second surface portion of the thermocouple is in direct thermal contact with the ambient air. 7. A photovoltaic module according to claim 6, wherein the second surface portion has no means for reducing the heat conduction between the thermocouple and the ambient air. 8. A photovoltaic module according to claim 6 or 7, wherein the second surface portion comprises means for enhancing the heat exchange between the thermocouple and the ambient air. 9. Photovoltaic module according to one of claims 6 to 8, wherein the thermocouple is a modular part of the photovoltaic module and is preferably reversibly removable and / or exchangeable and / or retrofittable. Photovoltaic system with at least one photovoltaic module according to one of claims 6 to 9.