DE29908205U1 - Device for converting solar energy into electrical energy and device on a building with such a device - Google Patents

Description

DE 7763 Patent Attorney

Graduate Physicist

Reinfried Frhr. v. Schorlemer

Karthäuserstr. 5A 34117 Kassel Allemagne

Telephone/Telephone (0561) 15335

(0561)780031

Fax/Telecopier (0561)780032

Autokühler GmbH & CoKG, 34369 Hofgeismar

Device for converting solar energy into electrical energy and installation on a building with such a device

The invention relates to a device of the type specified in the preamble of claim 1 and a device according to the preamble of claim 8.

Solar cell arrays are increasingly used to generate electrical energy using photovoltaics, with a large number of solar cells being combined to form what are known as solar cell modules. Depending on the efficiency of the solar cells used, however, such modules only convert a small part of the solar energy radiated into electrical energy, while the larger part is converted into heat. This means that the modules heat up considerably on hot days. Since the efficiency of a PV module decreases as the module temperature increases, it is common practice to assign cooling devices to solar cell arrays in order to keep them at a more favorable operating temperature.

In a known device of the type described above (DE 296 05 277 Ul), the solar cells are attached to a cooling body made of honeycomb aluminum. This cooling body is arranged in a cooling circuit and a liquid coolant, e.g. water, flows through it. A feed pump connected to the cooling circuit is usually used to circulate the coolant, although it has already been proposed (DE 29 50 274 Al) to change the flow of water by gravity by installing a special cooling water tank.

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However, no practical example of how this proposal can be implemented is given. Rather, it is considered advantageous to pump the water through the cooling device and to divert the energy required to operate the pump from the electrical energy generated by the solar cell arrangement. 5

A cooling circuit equipped with a feed pump has the disadvantage that the additional energy gained through cooling is at least partially used up again for the pump drive and the circuits required to control it. In addition, the cooling capacity of simply circulating the coolant is comparatively low. Cooling is therefore not very effective, particularly in small systems, and the additional energy gain does not usually justify the considerable additional costs required for installing the pump and the control system. In addition, a pump is a component that is subject to wear and tear. Pumps with a long service life can make the system considerably more expensive, while experience shows that low-priced pumps have a short service life. Finally, the repair and maintenance of the pump can be quite expensive and complicated due to the location of the installation. This is another reason why it is cheaper not to use such mechanically moving parts with electrical controls in the first place.

In contrast, the invention is based on the object of designing the device and the equipment of the types mentioned at the outset in such a way that no feed pump is required and yet a good cooling effect is achieved, an overall inexpensive construction is possible and a self-regulating adaptation to different outputs can be carried out with simple means.

The characterizing features of claims 1 and 8 serve to solve this problem.

The invention has the advantage that the cooling circuit contains an additional heat exchanger which, due to its arrangement above the cooling body, automatically starts and maintains the circulation of the coolant as soon as and as long as the temperature of the coolant at the outlet of the heat exchanger is sufficiently below

the temperature of the cooling body. Therefore, an additional feed pump is required; : :·· · Ii

An associated control system is also required, so that the overall system can be constructed simply. To adapt to different outputs of the solar cell arrangements, only the heat exchanger needs to be dimensioned accordingly.

Further advantageous features of the invention emerge from the subclaims.

The invention is explained in more detail below in conjunction with the accompanying drawings using exemplary embodiments. They show:

Fig. 1 shows a roughly schematic vertical section of a device according to the invention for converting solar energy into electrical energy by means of a solar cell arrangement;

Fig. 2 to 4 show, in roughly schematic vertical sections, a device according to the invention provided with a device according to Fig. 1;

Fig. 5 shows schematically the front view of a heat exchanger suitable for the device according to Fig. 1 to 4; and

Fig. 6 shows a particularly preferred embodiment of a solar cell arrangement in cross section.

According to Fig. 1, a device for converting solar energy into electrical energy contains a solar cell arrangement 1 which is exposed to solar radiation indicated by arrows. The solar cell arrangement 1 consists, for example, of an upper section 1a exposed to solar radiation with a large number of photovoltaic solar cells (not shown in detail) and a lower section 16 which is essentially designed as a cooling body and has an inlet 2 and an outlet 3 for a liquid coolant flowing through it, in particular a water-antifreeze mixture. The components required to produce an electrical photovoltaic circuit are generally known and are therefore not shown.

The preferably plate-shaped salad bowl arrangement J.jst z _v B..set up outdoors, in

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not shown, mounted on the ground, on house walls or on the roof and arranged so that it forms an angle with the horizontal level of the ground in Fig. 1 such that the outlet 3 is at the top or above the inlet 2. A schematically shown heat exchanger 4 is arranged slightly above the solar cell arrangement 1 or its outlet 3, which has an inlet connected to the upper outlet 3 by a line 5 and an outlet connected to the lower inlet 2 by a further line 6. The lines 5, 6 consisting of pipes, hoses or the like form a closed coolant circuit together with the cooling body of section Ib and the heat exchanger 4.

According to the invention, the heat exchanger 4 is arranged at least far enough above the solar cell arrangement that the coolant in the coolant circuit is automatically circulated in the direction of the arrows shown by gravity. In particular, the coolant heated in the cooling body and thus having a reduced density will rise in the direction of the heat exchanger 4 and flow through it, while the cooling medium cooled in the heat exchanger 4 will flow back to the cooling body via the line 6 due to its increased density. Due to this gravity effect, also known as the "thermosyphon effect", no feed pump or the like is required, and yet the additional heat exchanger 4 ensures good cooling of the coolant as soon as the circulation is automatically started when the sun shines.

The heat exchanger 4 can consist of a liquid/liquid heat exchanger. If the solar cell arrangement 1 is attached to a building or in the vicinity thereof, the liquid heated by the coolant in the heat exchanger 4 can be used, for example, for a heating system, domestic water preheating system or heat pump system, which serves to at least partially cover the energy requirements of the building. Alternatively, the heat exchanger 4 could also be used, for example, to preheat the water of a garden swimming pool or the like. Other applications are also possible.

In order to achieve a good heat exchange efficiency with the simplest constructional means, the heat exchanger 4 is preferably designed as a convector according to the invention. This consists of a constricted, stretched tube 7 (see Fig. 5) which is provided with • · · · ··· ··· .... . . . . i &igr;

a plurality of ribs or fins 8 extending perpendicular to the pipe axis, around which air flows and which create a large heat-exchanging surface on the air side. The pipe 7, one end of which is connected to the outlet 3 (Fig. 1) and the other end to the inlet 2, can be made of copper, aluminum or stainless steel, for example, and is preferably arranged horizontally or with a slight gradient in the direction of its outflow end. The air flowing in from below from the atmosphere is heated by the ribs 8 and flows out upwards, with the heat being released to the air practically solely by convection. To improve the heat exchange efficiency, the pipe 7 can have an oval or flat-oval cross-section. The ribs 8 can be pressed on, soldered on, welded on or clamped on by mechanically expanding the pipes.

To further improve the heat exchange performance, the invention proposes arranging the heat exchanger 4 according to Fig. 5 in the lower region of a preferably vertically arranged shaft 9 (Fig. 1) which is closed on all sides on the circumference but open at the top and bottom. The shaft 9 should have the effect of a chimney, discharging the air heated by the heat exchanger 4 upwards from the heat exchanger 4 as quickly as possible and thereby drawing in cold air. The kinetic energy for the cool air automatically generated in this way means that the heat exchanger 4 is always arranged in a cool air stream when exposed to sunlight and an intensive heat exchange with the coolant takes place in the coolant circuit. The internal cross section of the shaft is expediently large enough to accommodate the entire heat exchanger 4. So that the shaft 9 does not heat up too much when exposed to sunlight and the described effect is thereby impaired, the shaft is preferably provided on its outer circumference with a reflective, e.g. white, surface 10. Alternatively or additionally, a fan could also be assigned to the convector 7, 8. The electrical energy required for this could be diverted from the energy generated by solar radiation. The energy consumption for such a fan is far less than that which would be required for a feed pump for the coolant.

Fig. 2 to 4, in which the same parts are provided with the same reference numerals as in Fig. 1, show different, practical examples of application for the

Device according to Fig. 1 in connection with a building.

In the device according to Fig. 2, two solar cell arrangements 1 set up on the ground in a similar way to Fig. 1 are connected to the heat exchanger 4 designed according to Fig. 5 via the lines 5 and 6, which are designed here as collecting lines. The heat exchanger 4 is located in the lower, open end of a shaft 11, which is formed by a vertical wall 12 of the building and a shell 14 arranged in front of this wall 12, as is known, for example, from houses with additional thermal insulation. The solar cell arrangements 1 could also be integrated into the shell 14 or another facade of the building in accordance with Fig. 3. In this case, the solar cell arrangements 1 are arranged, for example, in the deepest area of the shell 14, while the heat exchanger 4 is mounted at a point above it and otherwise in the shaft 11, analogous to Figs. 1 and 2. The lines 5, 6 are expediently accommodated completely in the shaft 11.

In the device according to Fig. 4, the solar cell arrangement 1 is integrated into a roof structure 15 of a building, wherein a shaft 16 in the manner of a chimney can additionally be erected on the roof structure 15.

While the heat exchanger 4 in the device according to Fig. 1 is suitably set up in a shaded location to avoid excessive heating due to direct sunlight, in the devices according to Fig. 2 and 3 an additional radiation protection for the heat exchanger 4 can be provided on the building. This could, for example, consist of a gutter of the respective building, and a convector according to Fig. 5 could be mounted continuously below the gutter.

Analogous to the use of a liquid/liquid heat exchanger, it is also possible to use the thermal energy obtained by cooling the solar cell arrangement 1 when using a convector. For this purpose, it can be provided, for example, to use the shaft 11 as part of a ventilation or heating system for the building and the warm air generated to supply the building with warm air.

Fig. 6 shows a particularly preferred solar cell provided with a cooling device.

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arrangement 1, which contains at least one solar cell 24, which is manufactured, for example, using a technique that is common today and consists, for example, of an essentially plane-parallel plate with a size of approximately 120 mm x 120 mm in plan view and a thickness of a few millimeters. Any number of such solar cells 24 can be combined in electrical parallel and/or series connection to form a so-called module.

On their upper or front broad side, the solar cells 24 are covered with a transparent cover 25, which consists, for example, of a plane-parallel glass plate and covers all solar cells 24 that may be present. Each solar cell 24 is attached to the cover 25, for example, by means of a layer 26 consisting of an elastic adhesive that compensates for the different thermal expansions of the solar cells 24 and the cover 25.

A cooling body 27 according to the invention is attached to the lower or rear broad sides of the solar cells 24, through which the coolant can flow, for example in the direction of the arrows shown in Fig. 1. The cooling body 27 contains a large number of individual strips 28a, 28b, which are arranged one behind the other and parallel in the direction of flow and extend transversely to the direction of flow. The strips 28a, 28b are corrugated in a meandering manner transversely to the direction of flow, so that they have lower sections 29a and 29b, upper sections 30a and 30b and webs 31a and 31b lying between them. The rear sides of the sections 29a, 29b and the front sides of the sections 30a, 30b preferably lie essentially in planes that are arranged parallel to one another and at a distance from one another corresponding to the length of the webs 31a, 31b. The corrugations of successive strips 28a, 28b are also preferably offset from one another transversely to the flow direction.

The heat sink 27 is preferably manufactured in one piece, with the strips 28a, 28b being manufactured from a sheet by a rolling process using profile rollers or by a punching process. The sheet consists of a preferably thin, highly heat-conducting material, in particular metal sheets (e.g. copper, aluminum). The heat sink 27 expediently extends over all of the solar cells 24 present. However, several heat sinks 27 of the specified type arranged in parallel or in some other way can also be used. ....

The connection of the heat sink 27 to the solar cells 24 is expediently carried out in that the front sections 30a, 30b of the strips 28a, 28b are attached to the latter by means of a layer 32 made of a preferably elastic and highly heat-conductive adhesive which compensates for the different thermal expansions of the heat sink 27 and the solar cells 24.

Due to the described design of the heat sink 27, the sections 29a, 29b, 30a, 30b and the webs 31a, 31b form a plurality of passages or through-holes running in the direction of flow, which within the individual strips 28a, 28b alternately delimit open areas 33 and 34 to the front or top and to the back or bottom. The open areas 33 to the front are directly opposite the backs of the solar cells 24, so that a coolant flowing through these areas 33 comes into direct contact with the back walls of the solar cells 24 and causes intensive heat dissipation.

The areas 34 are open downwards or backwards, but their front sections 30a, 30b rest against the rear sides of the solar cells 24, so that a coolant flowing through them is involved in the removal of heat via these sections 30a, 30b. Overall, due to the corrugations, even with short webs 31a, 31b or flat heat sinks 27, a very large heat exchange surface is obtained and thus a good cooling effect, which is further increased by the offset of the strips 28a, 28b and the resulting intensive turbulence of the coolant flowing through the heat sink 27.

A rear wall 35 is attached to the rear of the heat sink 27 or to the sections 29a, 29b, which is connected to the cover 25, for example, by frame parts and seals, so that a housing is created which surrounds the heat sink 27 and is closed on all sides and is provided with the inlet 2 or the outlet 3 according to Fig. 1. In addition, in this case the housing could be provided with sections free of the heat sink 27 in the area of the inlet 2 or outlet 3, which form collection chambers for the coolant and improve its distribution across the width of the heat sink 27.

The invention is not limited to the described embodiments, which can be modified in many ways. In particular, the devices and equipment described are not limited to a specific number of solar cell arrangements 1. Adaptation to different outputs with a different number of solar cell arrangements 1 is easily possible with regard to the cooling capacity to be installed by dimensioning the heat exchanger 4 accordingly, which in the case of the convector 7, 8 according to Fig. 5 is possible simply by choosing its length. In addition, the devices and equipment shown in Fig. 2

to 4, which are only examples, can be modified in any way that is appropriate and/or adapted to the respective building. Finally, it is understood that the various features can also be used in combinations other than those shown and described.

Claims (15)

1. Device for converting solar energy into electrical energy with at least one solar cell arrangement ( 1 ), a cooling circuit ( 1b , 4 , 5 , 6 ) for a liquid coolant that can be circulated by gravity and a cooling body for the solar cell arrangement arranged in the cooling circuit ( 1b , 4 , 5 , 6 ), characterized in that the cooling circuit ( 1b , 4 , 5 , 6 ) has a heat exchanger ( 4 ) arranged above the cooling body through which the coolant flows and which starts and maintains its circulation. 2. Device according to claim 1, characterized in that the heat exchanger ( 4 ) is a liquid/air convector ( 7 , 8 ). 3. Device according to claim 2, characterized in that the convector ( 7 , 8 ) is arranged in the lower region of a preferably vertical shaft ( 9 , 11 , 16 ). 4. Device according to claim 3, characterized in that the shaft ( 9 , 11 , 16 ) is provided with a reflective surface ( 10 ) on its outer circumference. 5. Device according to one of claims 1 to 4, characterized in that the convector ( 7 , 8 ) is arranged free-standing. 6. Device according to one of claims 2 to 5, characterized in that a fan is associated with the convector ( 7 , 8 ). 7. Device according to claim 1, characterized in that the heat exchanger ( 4 ) is a liquid/liquid heat exchanger. 8. Device on a building for generating electrical energy from solar energy, characterized in that it contains a device according to one or more of claims 1 to 7. 9. Device according to claim 8, characterized in that the shaft ( 11 , 16 ) is formed by a wall ( 12 ) of the building and a shell ( 14 ) placed in front of this wall ( 12 ). 10. Device according to claim 8 or 9, characterized in that the solar cell arrangement ( 1 ) is integrated into a facade of the building. 11. Device according to one of claims 8 to 10, characterized in that the solar cell arrangement ( 1 ) is integrated into a roof construction ( 15 ) of the building and the shaft ( 16 ) is designed in the manner of a chimney. 12. Device according to claim 11, characterized in that it is provided with a radiation protection for the convector ( 7 , 8 ). 13. Device according to claim 12, characterized in that the convector ( 7 , 8 ) is arranged under a gutter. 14. Device according to one of claims 8 to 13, characterized in that the shaft ( 11 , 16 ) is designed as part of a building ventilation or heating system. 15. Device according to one of claims 11 to 13, characterized in that the liquid/liquid heat exchanger ( 4 ) is arranged as part of a heating, domestic water preheating and/or heat pump system.