KR20010079615A - Photovoltaic device - Google Patents

Abstract

The present invention relates to a photovoltaic device which includes a rear face for converting radiant energy into electrical energy while lying opposite the front face exposed to radiation. And a cooling device disposed between the front of the photovoltaic module and the radiation source is used for the conversion. The chiller has one liquid medium, preferably water is used as the liquid medium. The water conducting layer and the water allow for the passage of the radiation fraction used for the photovoltaic effect, while allowing longer wavelengths of radiation, and broadly the heating of the photovoltaic module. To prevent this, it acts as an optional filter that converts the heat to an instantaneous dissipation.

Description

Optoelectronic device {PHOTOVOLTAIC DEVICE}

Photoelectric generators are usually fixed towards the main insolation direction. Each of these systems is equipped with a uniaxial or biaxial solar follow-up device, or solar concentrators are inserted.

However, in the case of using the light collecting devices, there is a problem in that the obtainable efficiency is lowered when the temperature of the photoelectric device is increased. This is due to the partial thermal recombination of the electrons emitted through incident light photons, thereby reducing the available external current flow in the photovoltaic module.

This problem is solved in the prior art by providing a heat conducting plate on the back of the photovoltaic module, similar to an electrical component, to improve heat loss.

If a higher temperature is obtained, the coolant is led through the back of the module, while the photovoltaic modules are actively cooled.

However, methods for actively and passively transferring heat are very rarely used because they are structurally expensive.

The present invention relates to a photovoltaic device comprising a front surface exposed to radiation and a back surface for converting radiant energy into electrical energy using a cooling device opposite thereto.

1 is a plot of the relative intensity of the solar spectrum by wavelength, and the permeability of a 10 cm thick fluorescent polymer thin film and a 5 cm thick water strata by wavelength.

2 is a view of a single-layer photovoltaic device.

3 is a cross section of a photovoltaic module;

4 is a table relating to the temperature distribution on the layer thickness of the photoelectric module shown in FIG.

5 is a view of a photovoltaic device consisting of two layers.

FIG. 6 is a view of a two layer photovoltaic device comprising a light collecting device and a precooler. FIG.

Therefore, it is an object of the present invention to continuously develop photovoltaic devices according to types so as to obtain higher efficiency.

This object is solved by the cooling device comprising one liquid medium disposed between the front face and the radiation source.

In order to ensure that the radiation impinging on the optoelectronic device is not reduced, so far coolers have been proposed which are always arranged on the rear of the optoelectronic device. The invention is based on the idea that a cooling device realized using a liquid medium can also be arranged on the front side of the optoelectronic device. The selection of the liquid medium in which the region of the solar spectrum effective for the photovoltaic effect is not absorbed by the liquid medium or only slightly absorbed, while the radiant energy in the region having a secondary meaning to the photovoltaic effect is In the manner absorbed by the medium.

Therefore, the medium absorbs other radiation energy while passing effective radiation energy for the photovoltaic effect.

This proves to be particularly suitable as a liquid medium a liquid which preferably consists substantially of water. However, depending on the photovoltaic module used, oils, alcohols or the like may be used. The medium is preferably added with a substance which optimizes the filter characteristic curve in solution or suspension.

Simple photovoltaic devices are achieved by the flow of a liquid medium between the front side and the radiation source based on the gravity between the warm and cold medium. Known under the name thermosiphon, the arrangement consists of a service water storage tank, in which one cooling water outlet is located. Cooling water flows from the outlet into the lower region of the photovoltaic device and rises from within the photovoltaic device to the upper end of the device, from which the water again flows into the storage tank. Since hot water enters the storage tank at a higher position, a temperature gradient is formed in the water storage tank with coolant at the bottom and hot water at the top. The heated water can be discharged directly from the storage tank. However, preferably, while the water heat exchanger is arranged in the storage tank, it is possible to heat the cold water to the desired water temperature.

In a preferred embodiment, it is proposed that the chiller comprises one pump for the liquid medium. This allows the liquid medium to pass through the chiller, thereby allowing it to continuously dissipate heat.

Preferably the chiller comprises a temperature controller capable of regulating the pump. This makes it possible to combine sufficient cooling with effective hot water securing. The temperature and pumping level adjusted by the thermostat are determined by the required hot water temperature and the required refrigerating capacity.

Particularly preferred refrigeration capacity is achieved by the liquid medium flowing directly over the photovoltaic element. The increase in efficiency is achieved by the liquid medium first flowing over the back side and then over the front side of the optoelectronic device. The still cold medium is then heated at the rear of the device and receives another thermal energy at the front of the device. Thereby, effective cooling of the optoelectronic device is achieved on the one hand, and on the other hand a liquid medium having a relatively high temperature is provided for another application.

Another increase in efficiency is achieved by a plurality of chillers that are switched in parallel or in series. In a preferred embodiment, it is proposed that another cooler is spaced apart from the front. The spaced apart chillers are mainly used as selective filters, while the chillers placed directly on the photovoltaic modules enable simultaneous filter effects and cooling of the modules.

Special filter characteristics are achievable with the choice of coolant. It has been found to be particularly preferred when a layer which selectively transmits radiation is arranged between the liquid medium and the radiation source. The selective radiolucent layer serves to conduct fluid on the one hand, and on the other hand, the combination of the radiolucent layer and the liquid medium produces a filter characteristic that is adapted to the solar spectrum to be used for the photovoltaic effect. .

It has been found to be preferred when the radioactive layer is coated on the side facing in the direction of the radiation source, preferably selectively transmitting radiation. Different coating materials and methods are also influenced by the filter properties, thereby achieving an optimum filter characteristic curve in the desired type and manner.

In an extensive series of experiments, it has been found that one plate or foil of fluorescence polymer results in particularly desirable results as a radiation transmissive layer. In particular fluorescent polymer thin films are advantageous to produce, and not only suitable for conducting liquid coolant, but also as radiation filters. Good results have also been achieved with acrylics, polycarbonates, glass, etc., because the materials provide high transmission in the incident spectrum, are also mechanically stable, stable and weather resistant to weathering. This is achieved inexpensively using, for example, acrylic (PMMA)-and polycarbonate double-webbed plates.

Preferably the radiation transmitting layer forms one cover surrounding the liquid medium. The cover is therefore a single sealed component that can be used as a filter but interchangeable in a simple type and manner.

Embodiment variants described above are available for condensed radiation as well as uncondensed radiation.

The description and embodiments of the invention described are illustrated in the drawings and are described in detail below.

In Fig. 1, the left longitudinal coordinate 1 is the relative intensity, and the right longitudinal coordinate 2 has the radioactivity γ in percentage and the abscissa 3 in wavelength in nanometers. In the coordinate system, the region 5 of the spectrum 4 effective for the solar spectrum 4 and the photovoltaic effect is sketched. Transmission of the 5 cm thick hydrous layer is shown by line 6, and line 7 is the transmission of a 100 μm thick fluorescent polymer thin film.

The figure shows that the 5 cm thick functional layer passes almost all radiation in the spectral region effective for the photovoltaic effect and only absorbs longer wavelength radiation. In contrast, the thin film absorbs a portion of the radiation in only a short wavelength region, passing the radiation over the entire spectral region with little change. Therefore, almost all radiation effective for the photovoltaic effect is emitted to the photovoltaic module disposed under the water-containing layer, while longer long-wave radiation is absorbed by the water-containing layer, thereby heating water.

This effect is used in the optoelectronic device shown in FIG. In this case, the functional layer 11 flows over the photovoltaic module 10, whereby the module is cooled. The water-containing layer 11 is surrounded by the transparent thin film 12, whereby water is induced in the thin film 12. The pump 13 pumps from the reservoir (not shown) through the photovoltaic device 14 to the storage tank 15, from which water can be discharged while being metered at the outlet 17 via the valve 16. have. If the heat of the water produced by the photovoltaic device is not sufficient, the heating coil 18 will allow the reheating of the water.

The photovoltaic device 14 is arranged with a temperature sensor 19 so that if the temperature sensor 19 achieves a defined and adjustable threshold temperature, always heated fluid is pumped into the storage tank 15. The temperature sensor controls the pump 13 in such a way that fresh, cold fluid flows into the structure.

The filters 11 and 12 described are selective because the filter only passes radiation with a constant wavelength. However, the filter is also recuperative, because the filter actually regains the heat flow occurring on the surface of the photovoltaic module 10 by two mechanisms. One mechanism is heat exchange, which is achieved by direct fluid contact with the hot module top surface. Another mechanism is for the module surface to emit radiation that is displaced in long waves with temperature according to the Wien's displacement law. The radiation is absorbed by water 11, the filter fluid according to the invention, and converted into heat.

In the case of cooling according to the invention, long-wave photons, which cannot cause any photoelectric effect, are converted to heat before they reach the module, while the photons must be absorbed in the module in the case of known photovoltaic devices. And, the generated heat flow must be removed continuously as it passes through the module. The advantage of the photovoltaic device according to the invention is therefore that the uppermost layer, ie the side facing in the radiation direction, is particularly exposed to intensive cooling. This is of particular importance, for the photovoltaic module, as shown in FIG. 3, the light quantum of the radiation 21 in the top layer 22 of the photovoltaic module 23 having the layer thickness d. 20 is absorbed, thereby resulting in a temperature gradient such as that shown by line 24 in FIG. The line 24 shows a linear temperature progression between the lower side 25 of the photovoltaic module 23 having the temperature Tu and the upper side 26 of the photovoltaic module 23 having the temperature To. . The figure once again clearly shows that the front cooling of the module according to the invention is particularly preferred. This is because the cooling takes place directly on the surface of the module 23 at the highest temperature.

FIG. 5 is another improvement of the photovoltaic device shown in FIG. 2. In the case of the photovoltaic device 30, the first fluid layer 32 is on the side facing in the direction opposite to the radiation and the second fluid layer 33 is on the side facing in the direction of the radiation. Is flowing. The pump 34 promotes the water flow 35 along the rear face 36 of the photovoltaic module 31 in the first layer 32, wherein the water cools the rear face of the photovoltaic module 31. The deflecting device 37 conducts the flow of water 35 at the lower end of the photovoltaic module 31 to the upper side 38 about the module, and the upper side 38 at the second layer 33. ) Will flow upwards. Then the water, which is continuously heated at the front, flows into the storage tank 39 and is discharged from the tank to the outlet 41 via the valve 40.

The water conductive layer 32 on the backside may be a spiral tube in good thermal contact with the backing, or may consist of a single planar plate heat exchanger. In order to minimize heat loss to the outside, the milky heat insulation 42 and the second transparent cover 43 are additionally supplemented to the entire arrangement. The second transparent cover 43 is spaced apart from the transparent fluorescent polymer thin film 44 at regular intervals. Thermostatic control 45 makes it possible to intentionally adjust the temperature rise of the cooling fluid. The temperature obtained at the outlet 41 may be set at 30 ° C., for example for swimming pool heating, depending on the application. On the other hand, in the case of shower water requires 40 ℃. These two typical applications of solar heated hot water apply for a half year period including summer in temperate latitudes. Since the average temperature of the photovoltaic module is more than 50 ° C. during this period, the system according to the present invention not only supplies current and hot water, but also increases current efficiency.

According to the present invention, it is possible to create a module that generates current and hot water with a total efficiency of 60% with a plane element that has generated current from a radiation source with efficiency of about 10%.

6 shows that the system according to the invention is in principle also applicable to photovoltaic arrangements using solar condensation. As soon as the energy density of the module surface is raised, the described and preferred selective and electrothermal heat extraction mechanisms become even more powerful.

In the case of focused radiation, the energy content of the portion of the long wave that is effective as non-photovoltaic power of the solar spectrum when using the photovoltaic device shown in FIG. 5 is used to heat water to a relatively low temperature. If the coolant flow is heated to a higher temperature, the efficiency of the photovoltaic module will be reduced.

Therefore, in the case of focused radiation, the photoelectric device shown in FIG. 6 is proposed. The optoelectronic device 50 is substantially composed of a concentrator lens 51, a precooler 52, a cooled photovoltaic module element 53, and the like. Instead of the condenser lens 51, other concentration optic systems may also be used, such as for example a reflector system. The photovoltaic module 53 corresponds to the photovoltaic device 30 shown in FIG. 5 in structure. The precooler 52 serves as a preliminary filter composed of a transparent ashlar having a dimension of focal line at the position in the case of the linear condenser. In the case of a point collector, a flat hollow hollow cylinder with dimensions of focal spot at this position is used.

Hollow ashlar or hollow cylinder 54 will flow through the fluid, and the fluid has a boiling point as high as possible with the selectivity shown in FIG. Therefore, the system pressure can be kept low. In the above case water is used with the corresponding additives. The water is heated to a temperature in the range of about 100 ° C. by radiation 54 condensed using lens 51 in hollow rhombus or hollow cylinder 54. When the preset temperature is achieved, the temperature sensor 56 acts on the pump 57, whereby a new fluid flow is pumped in the hollow space 54. The heated water leaves the hollow 54 through line 58. This produces a very high temperature at the focal point of the lens 51, which temperature is used to heat the selective radioactive fluid.

Therefore, current 60, water heat 61, high-temperature process heat 62, and the like can be generated from the energy 59 irradiated primarily with the device 50. . At this time, the effective energy of the high temperature heat may be converted into mechanical work or additional current through, for example, a thermodynamic machine.

Nevertheless, with one connection formed between the line termination 61 and the pump 57, the amount of hot water generated in the photovoltaic module device 53 can also be continuously heated in the preliminary filter 52.

The optoelectronic devices described are based on the correct choice of fluids and transparent cover materials and the like. Many types can be used in the area of liquids, from water to oils, alcohols and the like. Since photovoltaic modules of different structures (silic acid, GaAs, ZnS, etc.) can be used, the selective filter must always be adjusted to the spectral region which is activated with the required photovoltaic power. This adjustment is realized relatively accurately by the filter characteristic curve of the transparent cover material and / or the liquid, if necessary. The cover material itself may be selectively coated to modify the filter properties, and additives may be added to the liquid.

In the described applications, a 100 μm thick fluorescent polymer thin film was used as the cover. The thin film can be processed chemically inert, harmless to the environment and flexible. Care should be taken in the application of the thin film, buckling in the form of cushions, such that mechanically suitably supporting the moisture transport layer or dividing it into channels to form a relatively uniform thickness of the water-containing layer over the entire surface. Is avoided.

Optoelectronic elements are usually covered with a glass or plastic surface on their top side to protect the active photoelectric surface before being subjected to mechanical influences. When using a cover for the conduction of a liquid overlying an active photoelectric surface, covering the photoelectric element once again can be avoided, since the water conducting element is responsible for protecting the surface. For example, a so-called box-shaped plate can be used to guide the liquid onto the photoelectric element while at the same time protecting the photoelectric element. Of course, conventionally used panes may also be equipped with a liquid permeable channel extending into the plate plane, or the pane may enable a liquid conducting layer as a double plate.

As the selective fluid water was used in the described embodiments. Water is cheap and harmless to the environment. When adding additives to water, a heat exchanger is needed to generate water. However, the temperature of the amount of hot water produced can be adjusted so that water can be used without additives. If so, the use of heat exchangers can be avoided.

Claims (11)

A photovoltaic device (14) comprising a front face exposed to radiation and a back face placed against the front face to convert radiation energy into voltage using a cooling device, The cooling device is characterized in that it comprises a liquid medium (11) disposed between the front face and the radiation source. The photovoltaic device according to claim 1, wherein the liquid medium (11) is substantially water. 3. Optoelectronic device according to claim 1 or 2, characterized in that the liquid medium (11) flows between the front face and the radiation source based on the difference in gravity between the warm and cold medium. The photovoltaic device according to claim 1, wherein the cooling device comprises a pump (13) for a liquid medium (11). 5. Optoelectronic device according to claim 4, characterized in that the cooling device comprises a temperature controller (19) which makes it possible to adjust the pump. 6. Optoelectronic device according to any of the preceding claims, characterized in that the liquid medium (11) first flows over the rear face (36) and then over the front face (38). 7. Optoelectronic device according to any one of the preceding claims, characterized in that the cooling device or further cooling device (52) is arranged spaced apart on the front surface. 8. Optoelectronic device according to any of the preceding claims, characterized in that an optional radiation transmissive layer (12) is preferably arranged between the liquid medium (11) and the radiation source. 10. The photovoltaic device according to claim 8, wherein the radiation transmitting layer (12) on the side facing in the direction of the radiation source is preferably coated to selectively transmit radiation. 10. Optoelectronic device according to any one of claims 8 to 9, characterized in that the radioactive transmitting layer (12) comprises a fluorescent polymer thin film or fluorescent polymer plate. The photovoltaic device according to claim 8, wherein the radiation transmitting layer (12) forms a cover surrounding the liquid medium (11).