DE202007000300U1 - Solar energy collector has Fresnel lens concentrators and photovoltaic cells combined with thermal heating of a fluid - Google Patents

Abstract

The solar energy collector system has a housing [16] with glass Fresnel lenses [22] that concentrate the energy onto photo voltaic cells [20] that are mounted on a thermally conductive plate, eg copper [32]. The heat energy in the plate is used to warm fluid, eg water, in piping [50] connected to a user unit [14].

Description

The The invention relates to a photovoltaic device according to the preamble of the attached Claim 1. as described in the article A.W. Bed et. Al: FLATCON AND FLASHCON CONCEPTS FOR HIGH CONCENTRATION PV. Proc. 19th European Photovoltaic Solar Energy Conference and Exhibition, Paris, France, 2004, page 2488 is known. In particular, the invention relates to a photovoltaic module (PV module) for direct conversion of light into electrical energy, where the incident light is before hitting a majority much smaller solar cells is concentrated (PV concentrator module). The invention also relates to a plant for the use of solar energy, which at least one, preferably several such photovoltaic devices (PV concentrator) having.

A possibility The use of solar energy is the conversion of sunlight in heat, like she is known as solar thermal. A typical application is the Solar collector. Solar thermal applications are all the more efficient the more absorbed by the sunlight and the less the resulting heat by heat radiation, heat conduction or heat transfer get lost. To one as possible To achieve high efficiency, have so-called absorbers of Solar panels over a selective coating. This has a particularly high absorption capacity (Absorptance) for the spectral range of sunlight in which most of the energy is irradiated while the radiation of infrared heat radiation through a low emissivity is minimized. Simple black color On the other hand, radiation absorbs radiation as well as it gives off heat radiation.

The direct use of solar energy usually takes place via solar panels in thermal solar systems. Commercially available collectors achieve efficiencies between 60% and over 70%. That is, they convert 60% to 70% of the solar energy incident on the collector surface into usable heat. In Europe, depending on the season and the sun, between 200 and 1000 W / m ^{2 can} occur in sunshine.

Further there are solar thermal power plants where the solar energy is bundled with mirrors, causing the focal point Temperatures up to 1300 ° achieved be used industrially well. The high energy concentrations become mechanical with a steam power plant or a Stirling engine Energy and then converted into electrical energy with a power generator.

at a flat collector meet through a glass plate (if possible made of solar glass) incident sunbeams on an absorber. At the Impact of the sun's rays becomes short-wave, high-energy radiation in long-wave radiation (heat radiation) transformed. The released heat must not be lost, why the collector is thermally insulated on all sides. Heat that is not directly from the absorber recorded or emitted by this as an emission, gets back through the glass reflected. She is thus trapped in the collector. The heated absorber transfers the heat the copper or aluminum tubes permanently connected to the absorber flowing Heat transfer fluid. This transports the collected heat energy to a consumer or a heat storage.

Of the Absorber should catch direct and diffuse radiation as well as possible and in Convert heat (Absorption). At the same time he should as possible little heat again in the form of radiation release (emission). He should be selective behavior.

Around minimizing energy losses will occur in a few sun-drenched countries high-selective coatings set, the absorption values over 90% and emissions below 10%. One of the possible Coatings is the black chrome coating. She gets in one galvanic process on the existing copper or aluminum Absorber sheet applied.

At the The most widespread today is a sputtered layer based on titanium with blue color on the market, which is slightly worse compared to black chrome Absorption values, but significantly lower emissions and thus achieved a better overall efficiency.

Currently Particularly good absorber layer systems are under the trade name "sunselect" and "mirothermic" from the company ALANOD SUNSELECT GmbH & Co. KG, Sohnreystraße 21, 37697th Lauenförde available. These absorber layer systems can be used in solar thermal systems according to form an absorber body.

at all usual Absorber layer systems, the light entry layer is an anti-reflection layer.

In addition to the coating absorbers of different manufacturers differ in their basic structure. Frequently absorbers, which consist of individual fins in the form of about 10-15 cm narrow strips on the back of each a thin tube is welded, which are then soldered at both ends in a manifold, so that a kind of "harp" is formed. In addition, there are surface absorbers, which consist of a single absorber sheet, the piping is soldered at this usually serpentine-like on the back or ge welded. A third design is the cushion absorber. Like surface absorbers they consist of a single continuous absorber sheet, but on the back instead of a pipe a press-formed second sheet is applied; the heat transfer fluid flows between these two sheets.

Though Solarthermische plants find in recent times, always broader Use, in particular in the heating of buildings and the hot water supply. The generation of electrical energy generated by such systems thermal heat However, it is associated with high costs and high losses, so that These systems are hardly used for the production of electrical energy.

in the However, the area of solar energy use has been around for 50 years known that solar energy through silicon also directly into electrical Electricity can be converted. In today's standard solar cells is usually mono- or multicrystalline Silicon used. The performance of these solar cells is, however relatively small, since they only hit a limited spectrum of the Convert radiation into electricity. Great successes towards one significantly higher Efficiency with over 39% conversion of solar radiation have been in recent years with High-performance PV cells from higher-value semiconductor compounds (III-IV semiconductor material) such as. Gallium arsenide (GaAs) has been achieved.

Such semiconductor-based cells can be constructed in steps as tandem, triple or quadruple-stack cells and thereby use a wider light-frequency spectrum. However, the large-scale production of such cells is very expensive. It has therefore been known in the art - see the article by Bett et al. Mentioned in the opening paragraph. - the approach chosen to focus the incident sunlight on a very small area of, for example less than 1 mm ^2. Only for this small area then a solar cell is necessary. The material usage can then be less than 1% compared to the areal use of such cells. Due to the concentration, the high light output of high-performance PV cells of z.Zt. use over 39%. Since only the connection of several solar units allows economical use of such a PV system, these are preferably combined to form a PV Konzentnatonmodul.

These High-performance PV cells are very sensitive to environmental influences, already dust grains and small particles of dirt or moisture can impair their function. Therefore, the solar cells of individual modules in a closed casing accommodated. A Fresnel lens - more precisely a plate with a Variety of Fresnel lens fields - serves as a light entrance plate and optical unit for concentrating through this light entry plate incident sunlight on the much smaller solar cells. simultaneously This Fresnel lens forms the upper side of the module housing, which laterally completed by side plates and bottom by a base plate is, on which the individual solar cells are arranged like a grid.

Problematic However, in such PV concentrator modules, that is the high concentration the sunlight on the small solar cells to an extreme warming of the Lead solar cells can. This problem is reinforced by the closed housing. It Therefore, it is important to find an effective design for dissipating the heat. These problems persist even in recent years Concentrator systems with small area Optics, which also z.T. a more than 500-fold concentration of sunlight, continued. The articles A.W. Bett et al. FLATCON AND FLASHCON CONCEPTS FOR HIGH CONCENTRATION PV, Proc. 19th European Photovoltaic Solar Energy Conference, and Exhibition, Paris, France, 2004, page 2488 and the article G. Siefer et al. ONE YEAR OUTDOOR EVALUATION OF A FLATCON CON-CENTRATOR MODULE, Proc. 19th European Photovitaic Solar Energy Conference and Exhibition, Paris, France, 2004, page 2078 describe the current state of the art for such PV concentrator modules, which is the preamble of the attached Claim 1 forms.

Especially is the exhaustion high heat concentrations from the closer Environment of the solar cells not optimally solved. This dissipation of heat concentration from the closer Surrounding the solar cell but plays a special role, as the Efficiency of a solar cell rapidly with the increase in temperature decreases. In the above mentioned known PV concentrator systems become the high heat concentrations from the closer Surrounding the solar cells of a PV concentrator module by means of passive air cooling dissipated (See the article Gerhard P. Willeke HIGH CONCENTRATIVE PHOTOVOLTAIC LARGE FACILITIES, Status and Perspectives, page 61 at www.fv.sunenergie.de/fileadmin/fvsonne/publikationen/Hochkon_01.pdf). A merely passive air cooling is not very effective, so the solar cells are overheated and their efficiency drops. An active cooling would be part of the consume energy.

task The invention is a photovoltaic device having the features of the preamble of claim 1 in such a way that the solar energy better exploited.

These The object is achieved by a photovoltaic device according to claim 1 solved.

advantageous Embodiments of the invention are the subject of the dependent claims.

Thus, according to the invention a photovoltaic device created with the solar energy directly is convertible into electrical energy. The device according to the invention has a light entry plate made of translucent material, through which the sunbeams enter. Next there are a variety of solar cells, each spaced from the light entry plate are arranged on the sun-facing sides and in total a smaller area as the light entry surface have the light entry plate. An optical unit concentrates the through the light entry surface incoming solar radiation on the smaller surface of the solar cells. The solar cells can so also from expensive material and especially as high-performance photovoltaic cells be educated. Due to the small area, the costs are still manageable. The incoming light is transmitted through the optical unit on these smaller surfaces projected. Next, a heat dissipation device is now provided according to the invention, the the heat energy, which by the sun thus taking place in the photovoltaic device occurs and thus to heat the solar cells and thus to a leads to poorer efficiency of solar cells, by means of a heat transfer medium receives and actively dissipates. The heat dissipation device is further formed such that they then the heat transfer medium one thermal utilization supplies.

On This way, not only the solar cells by means of the heat transfer medium cooled, the to be discharged Thermal energy will be added still used in other ways.

The Thermal use may be for heating or heating purposes, such as for warming of buildings, for heating or heating of industrial water, etc. are used. It is also possible with the heat energy thus obtained coolers to operate.

Appropriate Coolers, which by means of heat energy while releasing the heat produce a cooling effect at a different temperature level are as Absorption chillers known and used for example by Japanese manufacturers Nishiyodo and Mayekawa offered. Accordingly, with such Devices through the heat transfer medium supplied heat energy too for one cooling effect be exploited. After the photovoltaic device in question here their best efficiency in countries with a high level of sunlight, it is particularly interesting the dissipated from the photovoltaic devices heat energy for the operation of Air conditioners to use.

The Inventive photovoltaic device can also for any other thermal use, for which today also known solar thermal Installations can be used, exploited. So could with the heat energy also mechanical work can be done and also about this Detour electricity will be generated.

The Light entry plate and the optical unit are preferably, like this in principle is already known, as a unit executed by namely the Light entry plate is designed as a Fresnel lens or more precisely a variety such Fresnellinsen (fields) has. Preferably, the light entry plate is in divided several fields, each associated with a solar cell is, wherein in each field a lens structure, the light radiation entering there concentrated on the respective solar cell.

The Solar cells are more preferably on one of the light entry plate spaced base plate arranged in particular grid-shaped. The light entry plate and the base plate can the top and bottom of a hermetically sealed housing form, with the solar cells are arranged inside. Thereby the solar cells are good against external influences, in particular Protected from dirt, moisture or the like. The hermetic in one closed housing, radiating into the light, resulting heat can be through the heat dissipation device according to the invention easy to handle and dissipate.

The heat sink can then be inside the case be arranged and, for example, by a multiple within of the housing guided Pipe may be formed with ribs or fins.

In preferred embodiment, however, the base plate is formed of a thermally conductive material, so the heat from the housing.

If the base plate made of a very good heat conducting material is, you can then by contacting the base plate with the heat transfer medium a cooling the base plate and a transmission the heat reach the heat transfer medium.

For this the base plate is preferably part of a heat exchange unit for discharging the Heat from the base plate to the heat transfer medium.

The Base plate can be formed in particular to the various types be as absorbers in the introductory mentioned prior art for Solar thermal is known.

Prefers are piping for the heat transfer medium formed, which are in contact with the base plate or else lead through the base plate or at least partially formed by the base plate.

In Preferred embodiment, the base plate with absorber material be equipped as they are known from solar thermal and in the description introduction closer explained are.

Therefore the heat sink can a have selective absorber, which short-wave solar radiation, For example, scattered light within the housing, receives, longer-wave radiation but absorbed. In this way, the absorber radiates in particular in the case no or only little heat radiation off, so the available standing heat, in particular the heat introduced into the solar cells via contact heat conduction, be completely discharged into the heat transfer medium can and the thermal use can be supplied, in addition also still scattered light for heat generation is exploitable.

The Base plate can be one piece be constructed, or is (preferably) divided into several fields, with expansion joints in between. A good distribution of the cooling effect the heat transfer medium let yourself reach through the well conductive base plate, so that the heat from each of the grid-shaped arranged solar cells dissipated is. Alternatively or in addition This can also be a piping system of the heat dissipation device provide such that the heat transfer medium to each of the solar cells for the purpose of cooling the same and dissipating the heat to thermal usage becomes.

The Pipelines can be formed serpentine-like and / or there may be several Pipelines be provided, which at their two ends in headers for the Flow and return of the thermal utilization system open.

In especially cheaper Execution becomes a corresponding line system simply facing away from the light entry surface Side of the absorber or the base plate attached, in particular welded or soldered. The conduit system is preferably made of metal, in particular of copper, trained, as is also known in solar thermal systems.

The Heat transfer medium is preferably depending on the desired thermal use and desired cooling effect the solar cells selected. As heat transfer media can liquid and / or gaseous Substances are used. Especially easy are liquids to handle that over remain liquid throughout the expected temperature range; for example can here water, oils or emulsions are used, as in heating systems or cooling systems use Find. But it is also possible Heat transfer media used in the heat dissipation device be evaporated, so the evaporation energy for cooling the To use solar cells. The heat transfer medium is then in gaseous Condition of thermal utilization fed where it is under liquefaction his heat energy gives up again.

A corresponding system consisting of a photovoltaic device according to the invention and the corresponding device for the use of thermal energy composed is the subject of the secondary claim.

One embodiment The invention will be explained in more detail with reference to the accompanying drawings. In this shows:

1 a schematic partial sectional view through a plant for the use of solar energy with a photovoltaic device in the form of a concentrator photovoltaic module and a device for the use of thermal energy; and

2 a perspective view of a in the photovoltaic device of 1 used heat dissipation device which dissipates heat energy from solar cells of the photovoltaic device and supplies a thermal utilization.

In 1 is a plant 10 for the use of solar energy, comprising a plurality of photovoltaic devices in the form of concentrator photovoltaic modules 12 (Only one such module is shown) and at least one device 14 for thermal utilization of the concentrator photovoltaic modules 12 having supplied heat energy.

Every module 12 has a housing 16 on, in which a variety of each with a solar cell 20 provided photovoltaic facilities 18 is housed. Every photovoltaic device 18 has an optical unit in the form of a Fresnellinsenfeldes 22 and the associated, from the Fresnel lens field 22 spaced solar cell 20 on. The Fresnel lens field 22 is each formed so that it by their respective light entry surface 24 incoming light - graphically represented by the sun's rays 26 - on the opposite to the light entry surface 24 much smaller solar cell concentrated. For example, the area of the solar cell 20 only one percent of the associated light entry surface 24 and the respective Fresnel lens structure concentrates this through the light entry surface 24 incoming light 100 times on the solar cell 20 , The individual photovoltaic Einrich obligations 18 are arranged in a grid next to each other. For this purpose, the individual Fresnel lens structures as fields 22 a light entry plate 28 made of glass or the like translucent material. The light entry plate 28 forms the upper end of the case 16 ,

The housing 16 is sideways by side walls 30 and below by a single or multi-part base plate 32 completed. On the base plate 32 are the individual solar cells 20 according to the grid of Fresnel lens fields 22 each arranged in their concentration areas.

The base plate 32 consists mainly of a good heat conductive material, such as copper or aluminum. On the base plate 32 Additionally, individual insulated against the base plate interconnects for contacting the solar cells 20 applied by known techniques. These tracks 34 (please refer 2 ) are connected to one pole of the solar cells, while the other pole of the solar cells with the base plate 32 is contacted.

In addition to these electrical properties for connecting the solar cells 20 serves the base plate 32 due to their thermally conductive material to heat from the solar cells 20 derive. The base plate 32 is thus part of a heat dissipation device 40 in total 2 is shown. On the light entry surface 28 opposite side of the base plate 32 has the heat sink 40 a piping system with copper piping 44 through which a heat transfer medium such as in particular water or oil can flow. The pipe system 42 is total in 1 indicated.

How out 2 It can be seen in close proximity to each row of solar cells 20 one each of the copper pipes 44 guided. The one mouth of each copper pipe 44 flows into a supply manifold 46 and the other end respectively ends in a return manifold 48 , From the supply manifold 46 leads a supply line 50 the heat transfer medium 52 to the device 14 for thermal use, where the thermal energy is thermally exploited. As a device 14 for thermal use is a heating of a building, a water heating system for service water or the like, a device for generating mechanical energy, an air conditioner or absorption refrigeration system, which is operable by means of heat, or a similar device. The list of examples of such devices 14 for thermal use is not exhaustive. In 1 is this device 14 therefore only shown as a block.

From this device 14 for thermal use is a return line 54 to the return manifold 48 led, where the heat transfer medium 52 turn on the multitude of copper pipelines 44 is distributed.

As in 1 is indicated in the pipe system 42 at least one suitable pump device 56 to obtain a cycle of the heat transfer medium 52 through the pipe system 42 intended. The extra energy for the pump device 56 can through the module 12 or through the device 14 be supplied for thermal use.

As in 1 shown, the base plate 32 be provided with a selective coating, although the light rays for absorption by the base plate 32 lets through, it's the base plate 32 however not permitted, longer-wave heat radiation back into the housing 16 irradiate.

In an alternative embodiment of the invention, not shown, instead of on the back of the base plate 32 arranged copper pipes 44 also a middle of the base plate 32 guided pipe system and / or through the housing 16 be provided guided pipe system (both not shown). Especially in the latter case, the Lichteinnittsfläche 24 the Lichteinsnittsplatte 28 with the selective coating 60 be provided. The whole in the case 16 radiated energy is then only through the heat dissipation device 40 discharged and the thermal use in the device 14 fed.

Other embodiments not shown here result from the fact that the Konzentnator photovoltaic module 12 with one or more of the non-prepublished German patent applications 10 2005 033 272.2-33 and 10 2005 047 132.3-33 disclosed features and equipment are provided. It will give more details about the concentrator photovoltaic module 12 expressly referred to these two earlier, unpublished patent applications.

10

investment for the use of solar energy

12

Concentrator photovoltaic module (Photovoltaic device)

14

contraption for thermal use

16

casing

18

Photovoltaic facility

20

solar cell

22

Fresnellinsenfeld (optical unit)

24

Light entry surface

26

Sunbeams

28

Light entry plate

30

side walls

32

baseplate

34

electrical pathways

40

Heat dissipating device

42

line system

44

Copper pipe

46

Flow manifold

48

Return manifold

50

Flow line

52

Heat transfer medium

54

Return conduit

56

pump means

60

selective coating

Claims (11)

Photovoltaic device ( 12 ) for the direct conversion of solar energy into electrical energy, comprising: a light entry plate formed from a light-transmissive material ( 28 ), a plurality of solar cells ( 20 ), each at a distance from the light entry plate ( 28 ) are arranged on the side facing away from the sun and a smaller area than a light entry surface ( 24 ) of the light entry plate ( 28 ), a Fresnel lens structure ( 22 ) for concentrating or bundling the light through the surface ( 24 ) incoming solar radiation to the smaller areas of the solar cells ( 20 ), a heat dissipation device ( 40 ) used for deriving in the photovoltaic device ( 12 ) heat energy generated by solar radiation by means of a heat transfer medium ( 52 ) and for supplying the thus heated heat transfer medium ( 52 ) to a thermal use ( 14 ), characterized in that the solar cells ( 20 ) on one of the light entry plate ( 28 ) spaced arranged one or more parts thermally conductive base plate ( 32 ) are arranged, wherein on the side facing the sun of the base plate ( 32 ) a highly selective absorber ( 60 ) is designed for solar thermal purposes, which has absorption values over 90% and emission values below 10%. Photovoltaic device according to claim 1, characterized in that the base plate ( 32 ) as part of a heat exchanger ( 32 . 44 ) for removing heat from the base plate ( 32 ) to the heat transfer medium ( 52 ) is trained. Photovoltaic device according to one of claims 1 or 2, characterized in that the heat dissipation device ( 40 ) Pipelines ( 44 ) for the heat transfer medium, the base plate ( 32 ) or at least partially formed by the base plate or formed in the base plate. Photovoltaic device according to one of the preceding claims, characterized in that the light entry plate ( 24 ) a closed housing ( 16 ) within which the solar cells ( 20 ) are housed, wherein in the housing ( 16 ) heat generated by solar radiation through the heat dissipation device by means of the heat transfer medium ( 52 ) dischargeable from the housing and a thermal utilization ( 14 ) can be fed. Photovoltaic device according to one of the preceding claims, characterized in that the heat dissipation device ( 40 ) a pipe system ( 42 . 44 ) for the distribution of the heat transfer medium such that each solar cell ( 20 ) through the heat transfer medium ( 52 ) is coolable. Photovoltaic device according to one of the preceding claims, characterized in that lines ( 44 ) of the pipe system ( 42 ) on the side of the base plate facing away from the sun ( 32 ) are mounted. Photovoltaic device according to one of claims 5 or 6, characterized in that lines ( 44 ) of the conduit system made of metal, in particular copper, are formed. Photovoltaic device according to one of claims 5 to 7, characterized in that the line system ( 42 ) has at least one serpentine conduit. Photovoltaic device according to one of Claims 5 to 8, characterized in that the line system ( 42 ) several thin pipes ( 44 ), which at both ends in a respective collection tube ( 46 . 48 ), has. Photovoltaic device according to one of the preceding claims, characterized in that the heat transfer medium ( 52 ) Is water or oil. Investment ( 10 ) for using the solar energy with at least one photovoltaic device ( 12 ) according to one of the preceding claims for generating electrical energy and for supplying thermal energy, further comprising: a heating device for heating by means of the thermal energy supplied by the photovoltaic device, a cooling device for cooling buildings, devices, equipment, vehicles or the like wherein the cooling device is operable or driven by means of the thermal energy supplied by the photovoltaic device, and / or • a device for generating mechanical and / or electrical energy from the thermal Energy supplied by the photovoltaic device.