DE29913202U1 - Solar cell arrangement - Google Patents

Description

Solar cell arrangement

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The invention relates to a solar cell arrangement, wherein the solar cells are connected to a fluid for dissipating heat.

Such solar cell arrangements are well known. The background to such technology is the most effective use possible of both the electrical energy that the solar cells generate and the thermal energy that is released by the solar cells when solar radiation is converted into electricity, and this is the case for up to 90° of the incident energy. The thermal energy released on the surfaces of the solar cells during the conversion of electrical energy is reduced or used more effectively in favor of the electrical energy yield. Such solar cell arrangements can be used in single-family and multi-family homes, mobile objects such as boats and trains, in municipal, agricultural and industrial objects and the like. In any case, wherever both electrical energy and heat, e.g. for hot water preparation, are required or can be used.

It is known, not least from the patent application mentioned at the beginning, to apply solar cells to a heat exchanger-like element through which liquid or gas flows and to dissipate the heat released during the generation of electrical energy through the wall of this element and to use it. The heat emission increases the efficiency of the conversion of solar energy into electrical energy and thus the overall efficiency when using the heated heat transfer medium.

of solar energy conversion. The composite solutions proposed so far are very advantageous for certain applications, but it should be noted that the production of such a composite is technologically and economically complex, and a large number of individual problems must be taken into account, particularly with regard to different expansion quotients, different short- and long-term load capacities of the solar cells or the coating materials and element materials. In addition, complex encapsulation of the solar cells is required in order to enable reliable protection of the sensitive solar cells from external influences such as corrosion, dust, hail, etc.

Based on the above-described prior art, one aim of the present invention is to provide a solar cell arrangement with which both thermal and electrical energy from solar radiation can be utilized as advantageously as possible.

This object is first and foremost achieved by the subject matter of claim 1, whereby the fluid can flow around the solar cells directly at the front and back. According to the invention, it has been recognized that a radiation-transparent fluid, which can be a gas, but also, as explained in more detail below, preferably a liquid, can also be guided past the front of solar cells due to the significantly better heat transfer conditions, whereby the advantages achieved by dissipating the resulting radiation heat of the solar cells more than compensate for the slightly, but not significantly impaired, radiation still impinging on the front of the solar cells after passing through the fluid.

However, with this arrangement, the solar cells can be made significantly "weaker" because they are not directly exposed to external influences, i.e. not much effort is required to protect them mechanically. In one embodiment, the solar cells themselves are not encapsulated. According to the invention, the complete, contacted solar cells are therefore used directly in the form in which they are manufactured. It is also provided that the solar cells are surrounded by fluid due to natural convection. The flow paths in front of and behind the solar cells are designed in such a way that a clear natural convection is created and maintained. This is preferably achieved, for example, by the depth of the flow paths, i.e. the thickness of a fluid layer, being different on the front and back of a solar cell. It is recommended that the fluid thickness on the front of the solar cell be relatively small, but on the back of the solar cell relatively large. For example, the depth of the flow path on the front side can be 2 to 5 mm, while on the back side it can be several times as deep, e.g. two to four times as deep. It is also preferred that the fluid is not electrically conductive. This makes it possible to leave the solar cells in their raw state, so to speak, with regard to the electrical connections. Extensive insulation of the connections or other parts of the solar cells is not necessary. It is also preferred that the fluid is a transparent liquid, with an oil, e.g. silicone oil, being recommended in this context. Silicone oil is toxicologically harmless, chemically inactive with regard to solar cells and also recyclable. A paraffin-based fluid, such as is used for latent heat storage systems, is also particularly preferred.

is known (see below). In order to adapt to the function to be performed by the fluid in the present context, it is desired that the fluid is liquid over a wide temperature spectrum, for which purpose a C14 paraffin is preferably used. In a further embodiment, it is provided that the fluid which flows directly around the solar cells flows in a closed system. Preferably, the system essentially consists of only one flow path on the front and one flow path on the back of the solar cells. In addition, short-circuit-like flow paths, distributed over the height, can also be provided between the solar cells. This makes sense, for example, if the solar cell arrangement is partially shaded. A certain circulating flow can then also form in only one (lower) part of the solar cell arrangement. The fluid is heated on the front, while the rear flow path of the fluid is in turn led to a second fluid in the heat exchange. A flow path for the second fluid is accordingly formed in the form of a further layer below or level adjacent to the flow path of the fluid on the rear side of the solar cells. The flow path for the second fluid is preferably over the entire length (and correspondingly also width) of the flow path of the first fluid on the rear side of the solar cells. In this context, it is particularly preferred if the second fluid is a latent storage medium of a latent heat storage device or is in heat exchange with such a latent heat storage device. With regard to the latent heat storage device, reference is made to an extensive prior art, for which, for the sake of simplicity, reference is made here to patent application 42 43.202.2 and the further literature cited there. The aforementioned patent application _# is hereby incorporated by reference with regard to its disclosure.

The invention is fully included in the present application. Further advantageous measures relate to the mounting of the solar cells with respect to the front and rear flow paths of the first fluid. In this context, it is preferred that the solar cells are mounted by means of spacer studs on the front and rear. For example, the structure can be designed in detail such that studs are arranged in a grid-like manner on a housing wall (transparent front wall), onto which the solar cells can be placed. Studs are arranged in the same way on another housing wall (rear wall). By putting the studded sides of these two housing walls together, an overall housing is produced which consists of a first housing wall, studs, the solar cells placed between them, further studs on the second housing wall and the second housing wall. The first housing wall is accordingly designed to be radiation-transparent in order to allow the solar radiation to pass through to the solar cells. The stud lengths are provided differently in accordance with the above statements, so that on the front of the solar cells, which faces the solar radiation, a flow path is smaller in depth (thickness) than on the back of the solar cells. In this context, it may also be advisable to design a wall, e.g. the front wall, to be flexible. This can be particularly important if it is desired to change the distribution of the exploitation between electrical and thermal energy. By changing the depth of the flow path on the front of the solar cells, the relative yield of electrical energy also changes. Increasing the thickness of this flow path leads to a reduction in the yield of electrical energy, conversely reducing the thickness leads to an increase in the yield of electrical energy.

Energy. If one or both housing walls are flexible, the system pressure of the fluid can be increased or reduced by means of a pump or the like. Although, as described in detail above, natural circulation of the first fluid is preferred, forced circulation by means of a pump or the like can also be recommended, not least with regard to the control of the distribution of the energy yield mentioned above.

The invention also relates to an arrangement for thermal insulation, with a front and a rear housing wall, the housing walls being transparent and the distance between the housing walls perpendicular to a plane of the housing walls being small, for example 5 to 10 mm. For such an arrangement, which basically corresponds to a normal double-pane window, there is a need to achieve effective thermal insulation. For this purpose, it is provided that the space between them is filled with a latent heat storage material, in particular based on paraffin. The above statements on the paraffin material also apply fully here. Preferably, it is also provided that in this arrangement a latent heat storage device, which can be described as quasi-static, is formed between the housing panes. For this term, reference should first be made to DE-Al 27 41 829. From this it is known, for example, to use amounts of paraffin enclosed in a plastic sleeve as a heat storage medium in a latent heat storage device. The plastic sleeves are in turn located in a storage vessel filled with water. In such latent heat storage systems, the heat is transported only by heat conduction through the plastic casing to the paraffin. Such storage systems are referred to as static storage systems. Furthermore, so-called

Dynamic latent heat storage is known, for which reference is made to DD 23 68 62 and DD 28 01 13. Regarding the state of the art, reference is also made to DE-Al 41 22 859.

In this arrangement, the gap is filled to a very large extent, e.g. 95% or more, with latent heat storage material, preferably paraffin-based. The remaining volume can be filled with water, for example, or possibly oil, the latter acting as a heat transfer medium. The heat transfer medium has a certain dynamic behavior - to a very small extent - which is why we spoke above of a quasi-static latent heat storage device, which is formed by the arrangement described here. The - albeit slight - dynamic character of the latent heat storage device is of particular importance in that it significantly promotes the desired foam formation. Foamed paraffin (in the solidified state) or paraffinic hydrocarbon is even more advantageous in terms of the achievable thermal insulation values than homogeneously solidified paraffinic hydrocarbon. The ratio of heat transport medium, e.g. oil, to paraffinic hydrocarbon can be in the order of 1:100, for example. A residual volume in the gap remains free. In addition, there can be either overpressure or underpressure in this intermediate pressure. Realistically, the overpressure will be in the range of up to about 1 A, the underpressure in the range of 0.1 to 0.5 A up to almost complete vacuum.

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Accordingly, the latent heat storage material can contain a foaming state, for example in the form of a known surface-relaxing agent. The tendency of the latent heat storage to foam is, as already mentioned, deliberately supported. Overall, the arrangement is preferably designed like a window, or is intended to be used as a window. In practice, a conventional insulating glass window can be further developed according to the above idea in accordance with the invention by filling the evacuated gap in the manner described with latent heat storage material, preferably paraffin-based. In a further embodiment, it is also provided that the arrangement has three housing walls, each with a small vertical distance from one another, and that both gaps are filled with latent heat storage material. In this context, it is particularly recommended to fill the two gaps thus formed with latent heat storage material with different melting points. While the latent heat storage material in one gap has a melting point of 5° C, for example, the latent heat storage material in the other gap can have a melting point of 10° C.

When used as a normal window, for example in industrial buildings, the effect is that the filling is completely transparent at temperatures above the melting point, i.e. especially in summer. Heat storage only occurs via sensible heat. Nevertheless, heat transport is comparatively poor, i.e. the thermal conductivity is (as desired) very low. The effect is that solar radiation is buffered in summer (reduction in overheating of rooms without complex ventilation systems; delayed release to the outside at night).

the rooms or the environment). The heat transfer coefficient (reduced) improves to at least half the values of known designs (thermoglass has a value of around 2.4 W/m²/degree, while an arrangement described here can achieve a value of 0.8 W/m²/degree, for example). And this even with small vertical distances between the housing walls, i.e. between 5 and 10 mm. If the temperature falls below a certain level, the nature of the latent heat storage material causes a phase change; the low-melting material solidifies at a constant temperature within a certain time. However, as it solidifies, the heat transfer value also changes and small heat losses occur constantly. This is particularly the case when, as is preferred, the latent heat storage material foams up to a certain extent. During this time and afterwards, the foaming results in an increased insulating effect. On sunny winter days, the material may even melt, allowing solar energy to be used (passively), which is then passed on - with a time delay - to rooms on one side of the window. A certain degree of control can even be achieved. The heating requirement is reduced. If the solar radiation falls below the limit, the material will solidify again, preventing a sudden cold snap in the rooms through the windows. The amount of control required for the heating system is reduced. The inventive idea is not limited to one gap, but can also extend to several gaps, continuing the system described. It can also be advantageous to provide latent heat storage material with different melting points in the individual gaps.

The invention is further explained below with reference to the accompanying drawing, which, however, represents only one embodiment. Here:

Fig. 1 is a plan view of a rear housing wall with a studded grid, partially covered with solar cells;

Fig. 2 is a sectional view of a solar cell arrangement;

Fig. 3 is an enlarged sectional view of a detail from the illustration according to Fig. 2;

-Fig. 4 .a cross section through an arrangement for

Thermal insulation with two housing walls;

Fig. 5 is a perspective, partially sectioned view of the article according to Fig. 4;

Fig. 6 is a cross-section through an arrangement according to Fig. 4, with three housing walls;

Fig. 7 is a perspective view, partially sectioned, of the article according to Fig. 6.

Referring first to Fig. 2, a solar cell arrangement is shown which consists of solar cells 1 which are arranged between a front, transparent housing wall 2 and a rear housing wall 3. On the top and bottom of the arrangement shown, flow connections 4 and 5 are created, which allow the paraffin-based fluid in the housing to flow around the solar cells 1 from a front flow path 6 to a rear flow path 7.

gen flow path 7. Overall, the system of flow paths 6, 7 including the diversions 4, 5 is a closed flow system.

The solar cells 1 are unclad solar cells in the usual design for manufactured solar cells. Since the fluid is also electrically insulating, no further insulation measures are required on the electrical connections of the solar cells. The use of a paraffin-based fluid also has another significant advantage. If the temperature of the system drops so low that the fluid solidifies, the circulation is interrupted. In this case, the fluid also acts as a cold-insulating agent, so that the discharge of the thermal storage system connected downstream is hindered or significantly delayed.

In the embodiment shown, a heat exchanger housing 8 is provided further to the rear or underside of the rear flow path 7, in which a second fluid flows as a heat transfer medium, preferably in countercurrent to the first fluid. The fluid flowing in the second housing is guided via a line 9, for example to a consumer or a heat accumulator, in particular a latent heat accumulator. The return is provided via the lower line 10. The heat transfer medium in the housing 8 can be, for example, ordinary water. Further below the housing 8 or, as shown in Fig. 2, in a further layer, thermal insulation 13' is provided.

The front housing wall is transparent, i.e. it is made of glass or clear plastic, for example.

A depth (thickness) ti of the front flow path 6 is significantly smaller than a depth (thickness) t2 of the rear flow path 7. This allows an effective natural circulation of the first fluid to be achieved. When flowing through the first flow path 6, the fluid is exposed to solar radiation and also absorbs heat from the solar cells 1 in the heat exchange, so that overall the fluid flowing in the flow path 6 heats up considerably. This is associated with expansion, whereas on the back, in the flow path 7, heat is dissipated and the fluid contracts accordingly. Overall, this achieves an effective natural circulation.

It can also be seen that the solar cells__l _ are held by studs 11, 12 which extend from the rear housing wall 3 or the front housing wall 1. In addition, the studs can be connected to one another by locking means.

This is explained in more detail with reference to Fig. 1. Here, the rear housing wall 3 can be seen, on which studs 12 are arranged in a grid. In the upper area of the housing wall 3, in the illustration according to Fig. 1, a row of solar cells 1 is already placed on the studs 12.

It is also preferably provided that a mask-like plastic part 13 is placed on the knobs 12, which has a plurality of generally square openings 14.

As can be seen in particular from the cross-sectional view according to Fig. 3, a step 15 is also formed in the plastic part 13, in

which the solar cells 1 can be inserted. You can also be arrested there. On the other hand, it is

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To hold the solar cells 1 in the installed state, it is also possible to widen the base of an upper stud 11.

In Fig. 1 it is also indicated that in a, preferably lower, area of the solar cell arrangement in the plastic part 13 through openings 16 are formed between two inserted solar cells 1. This makes it possible that in the short circuit or bypass, as indicated by the arrows in Fig. 2, only a circulating flow limited over a certain section can form or additionally form.

The plastic part 13 can also - although not shown in detail - have openings at the intersection points of the webs forming the openings 14, i.e. in the assembled state in the area of the studs 11 and 12, through which a connecting rod can be inserted between individual studs 11 and 12, which can be firmly connected to one of the studs 11 or 12, for example, and for which a receiving hole can also be formed in the other stud. On the other hand, the plastic part 13 can also have such extensions which are received in corresponding receiving holes in the studs 11 and 12 after assembly.

Fig. 4 shows an arrangement for thermal insulation with a front housing wall 2 and another housing wall 3, the vertical distance t2 between which is comparatively small, ranging from about 5 to 10 mm. The housing walls 2, 3 can be made of window glass, for example. The space between the two housing walls 2, 3 is filled with a heat storage material on

Paraffin base. There is a certain overpressure or underpressure in the space 17, such as

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This is explained in more detail above.

In Fig. 5, the object of Fig. 4 is shown in perspective, partially sectioned form. It is clear that this can be a conventional window construction, with the exception of the filling of the gap 17.

Fig. 6 shows a cross-section of a comparable arrangement with three housing walls 2, 3, 18. Correspondingly, this creates gaps 19 and 20 which are filled with a latent heat storage material in the same way as described above. The latent heat storage material in the gap 20 has a different melting point than the latent heat storage material in the gap 19. For example, the melting point in the gap 20 can be 10° C and in the gap 19 5° C. It can also be advisable to design the gaps with different vertical distances to the housing walls. For example, the gap facing the interior of the room when installed has a larger vertical distance. The amount of latent heat storage material therein is then correspondingly larger. If the lower melting point is set here at the same time, the outer gap will first reach the melting temperature (solidification temperature) when the temperature on the outside drops. When the larger space facing the interior reaches the melting temperature (solidification temperature), the relatively large amount of heat released will benefit the space to a very large extent, since the outer intermediate layer with

15

the already solidified latent heat storage material now has a significant insulating effect.

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In Fig. 7, the object according to Fig. 6 is shown in perspective, partially sectioned form.

Claims (24)

1. Solar cell arrangement, wherein the solar cells ( 1 ) are connected to a fluid for dissipating heat, characterized in that the fluid, which is transparent, can flow around the solar cells ( 1 ) immediately at the front and back. 2. Solar cell arrangement according to claim 1 or in particular according thereto, characterized in that the solar cells ( 1 ) are unencapsulated. 3. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid flows around the solar cells ( 1 ) due to natural convection. 4. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid is electrically non-conductive. 5. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid is a liquid. 6. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid consists of paraffin. 7. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid is an oil, for example silicone oil. 8. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that a layer thickness of the fluid on a front side of the solar cells exposed to solar radiation is thin, for example 2 to 5 mm. 9. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid circulates in a closed system which essentially only consists of the flow paths in front of and behind the solar cells ( 1 ). 10. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the fluid flowing around the solar cells ( 1 ) is guided in heat exchange to a second fluid. 11. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that a flow path of the second fluid is formed corresponding to a further layer below a flow path ( 7 ) of the first fluid on the rear side with respect to the solar cells ( 1 ). 12. Solar cell arrangement according to one or more of the preceding claims or as a whole according thereto, characterized in that the second fluid is a latent storage medium of a latent heat storage device or is in heat exchange with such a device. 13. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the solar cells ( 1 ) are held by means of front and rear spacer studs ( 11 , 12 ). 14. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the spacer studs ( 11 , 12 ) hold the solar cells ( 1 ) between a front, transparent wall ( 2 ) and a rear wall ( 3 ), which walls ( 2 , 3 ) simultaneously delimit the front and rear flow paths ( 6 , 7 ) of the fluid. 15. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that one wall ( 2 , 3 ), for example the front wall, is flexible. 16. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the flow of the first fluid, for example achieved by an intermediate pump, is a forced flow. 17. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that a fluid pressure of the first fluid is adjustable. 18. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the solar cells ( 1 ) are accommodated in a plastic part ( 13 ) having openings ( 14 ). 19. Solar cell arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that the plastic part ( 13 ) with the inserted solar cells ( 1 ) is held between the knobs ( 11 , 12 ). 20. Arrangement for thermal insulation with a front and rear housing wall ( 2 , 3 ), wherein the housing walls ( 2 , 3 ) are transparent and a distance (t2) perpendicular to a plane of the housing walls ( 2 , 3 ) between the housing walls ( 2 , 3 ) is small, for example 5 to 10 mm, characterized in that the intermediate space ( 17 ) is filled with a latent heat storage material, in particular based on paraffin. 21. Arrangement according to claim 20 or in particular according thereto, characterized by a window-like design. 22. Arrangement according to one of claims 20 or 21 or in particular according thereto, characterized in that three housing walls ( 2 , 3 , 18 ) are provided, each with a small vertical distance from one another, and that both intermediate spaces ( 19 , 20 ) are filled with latent heat storage material. 23. Arrangement according to one of claims 20 to 22 or in particular according thereto, characterized in that the intermediate spaces ( 19 , 20 ) are filled with latent heat storage material of different melting points. 24. Arrangement according to one or more of the preceding claims or in particular according thereto, characterized in that a melting point of the latent heat storage material is comparatively low, for example at 10°C.