WO2012136850A1

WO2012136850A1 - Solar collector having a transparent cover

Info

Publication number: WO2012136850A1
Application number: PCT/EP2012/056464
Authority: WO
Inventors: Helmut Jäger; Kai Wendker
Original assignee: Solvis Gmbh & Co. Kg
Priority date: 2011-04-08
Filing date: 2012-04-10
Publication date: 2012-10-11
Also published as: DE102011107393A1; EP2694886A1

Abstract

The invention relates to a solar collector has a transparent cover having an outside facing the solar radiation. An element that absorbs the solar radiation and converts the solar radiation into a different form of energy is located inside the solar collector. An intermediate space is arranged between the outside of the cover facing the solar radiation and the element that coverts the solar radiation into a different form of energy. Said intermediate space has a controllable value for the heat flow.

Description

Solar collector with transparent cover

The invention relates to a solar collector with a transparent cover with one of the solar radiation facing outside, with a solar radiation receiving and converting into another form of energy element inside the solar collector.

Solar collectors, also referred to as solar panels, there are essentially in two different forms, namely on the one hand as a thermal solar collectors u nd the other hand, al photovoltaic Solarkol lektoren. In both cases, the solar collectors are exposed to solar radiation by arranging the solar collectors, in particular, on roofs or the like. The solar radiation falls through a cover in the form of a transparent glass pane on the elements inside the solar collector.

Thermal solar collectors are used in building services to provide energy for heating and hot water. Inside the solar collector are highly selectively coated absorber sheets, which absorb the solar radiation and convert it into heat. This heat is transferred into fluids that contain mostly water. These fluids flow through tubes that run along the side of the absorber facing away from the sun. The cover of the thermal solar collectors consists of a transparent glass pane as standard. Between the glass sheet and the absorber are usually given about 20 mm air gap.

The back of the absorber with the pipes running along there is usually equipped with a rock wool insulation with an insulation thickness of for example 50 mm to 60 mm thickness. These thermal solar collectors reach operating temperatures of about 50 ° C to 90 ° C. If no heat is removed, the thermal solar collectors can also reach so-called standstill temperatures of up to 230 ° C. The efficiency of the thermal solar collectors decreases with increasing operating temperature.

An example of a solar thermal collector with a wave-shaped or roof-shaped absorber in the interior of the collector is described in EP 2 058 604 B1.

Currently, developments are moving towards high temperature applications with higher operating temperatures and process heat. This requires double glazing or a frontal reduction of heat losses. This additionally increases the standstill temperatures and the requirements placed on the materials used.

Photovoltaic solar collectors, which are in the form of solar modules or photovoltaic systems, are used to generate electricity. Inside these solar collectors are sensitive, power-generating wafers. These silicon wafers are often embedded in a film of ethylene vinyl acetate (EVA).

The cover for protecting the silicon wafers usually consists of a thin transparent glass pane on or under which the photovoltaic wafers are laminated. The efficiency of the power generation of photovoltaic solar collectors increases with decreasing operating temperature. For this reason, the back of the solar panels is not thermally insulated. The operating temperatures, even at idle, when no electrical power is removed, do not exceed 80 ° C.

Also in recent publications, such as in DE 10 2009 035 869 A1 and DE 10 2010 004 874 A1, so-called PV-T solar collectors have been described, which are currently being developed. This PV-T Solar collectors combine the heat generation of the solar thermal collectors and the power generation of the photovoltaic solar collectors. The PV-T solar collectors consist of photovoltaic modules, which are fastened to the discharge of the heat generated in the wafers differently formed by flowing through fluids channels. In this way, by cooling the wafer in the photovoltaic modules, an increase in efficiency of the power generation of the photovoltaic region is achieved. These PV-T solar collectors will be more interesting in view of the limited available roof areas in the future.

Both in the solar thermal collectors as well as in the PV-T solar collectors there is the interest not to increase the temperature in the solar collector too far, since in both cases with increasing temperature, the efficiency decreases and due to the rising temperatures, a special attention to the used materials must be addressed. Thus, there is great interest in limiting the temperatures both during operation and at standstill.

In the past, attempts have already been made by various constructive measures to develop appropriate shutdown safeguards for solar collectors by, for example, spanned films are provided with mechanical drive rollers for additional coverage of the solar panels against further sunlight. Mechanically changeable air gaps between the cover and the absorber elements or a switchable ventilation have also been proposed.

All of these attempts have not yet led to solutions that are both functional and economical and stable over time. The interest is, however, unchanged, just because cheaper plastics and other cheaper components in the production of solar collectors would be a significant economic advantage. An object of the invention is therefore to propose a possibility for a better limitation of the temperatures in the interior of solar collectors, in particular of solar thermal collectors or PV-T solar collectors, which also leads to an economical and durable solution.

This object is achieved in generic solar collectors with the invention in that between the solar radiation facing the outside of the cover and the solar radiation into another form of energy converting element, a gap is arranged, which has a controllable value for the heat flux.

With such a concept, the problem can be solved surprisingly. Namely, it becomes possible to fully automatically consider in which state and in what mode the solar collector is straight, and depending on this, the heat transmission value can be changed.

With such a scheme can be taken to ensure that either a good insulation, which is important for thermal solar collectors during operation, to use as much of the recovered heat and remove it via a fluid and to use in a heating or hot water.

However, if no hot water or warm water is needed at all, ie there is a standstill phase with an impending overheating of the solar collector, the heat flow can be regulated and increased in or through the gap, so that the heat is then released to the exterior space accelerated. In this way, the overheating of the solar collector is avoided. The heat can then be released into the exterior.

Similar advantages also arise in photovoltaic solar collectors, the optimal by an appropriate control on the temperature can be maintained, which allow for the photovoltaic elements, so the PV wafers, the highest efficiency.

Such a controllable possibility for the forward current can be obtained by applying a controllable vacuum in the intermediate space. If the vacuum is "perfect", you also get a "perfect" insulation. If you let the vacuum after, so let small amounts of gas flow into the gap, the heat transfer coefficient increases accordingly and allows a higher value for the heat transfer Ström.

Similarly, it is in a noble gas filling, in which the height of the heat transfer coefficient depends on the pressure of the noble gas. Here can be taken by a corresponding valve control and / or by means of pumps in very fine and metered control influence on the heat transfer coefficient and thus the heat flow.

It has proven itself in tests if the heat transfer coefficient or heat transfer coefficient of the solar collector can be regulated at least by a factor of five. Depending on the choice of gas, noble gas or vacuum, a control of about 0, 8 W / m ² K to 4 W / m ² K on the one hand and from about 10 W / m ² K to 20 W / m ² K on the other hand preferred. Of great advantage is that a so-called intrinsically safe operation is possible. It can be ensured that when the system is currently not in operation, also a corresponding high heat flow current flows, so that so no heat build-up inside the solar collector can build.

For this purpose, for example, a normally open valve can be used. This valve allows gas to enter the collector in the event of a malfunction inflow so that the maximum collector temperature is even limited to less than 100 ° C.

It is thereby possible to achieve collector standstill temperatures of less than 80 ° C. In this way, cheaper materials for different elements of the collector are possible, which can not be used at higher collector standstill temperatures. This concerns in particular a number of technically interesting plastics with advantageous properties that are not sufficiently resistant to high temperatures.

Due to the fact that usually several solar collectors of the same or similar type together form a solar system, a common vacuum network of these various solar collectors can also be constructed.

An additional possibility arises from the fact that in the region between the solar radiation receiving and converting into another form of energy element and a rear wall of the solar collector, a further region is arranged with a controllable value for the heat flow.

In this way, the possibility for an improved or deteriorated heat transfer is created to the other side of the solar collector, which can be controlled in a similar manner.

When used in combined PV-T solar collectors, the solar collector could be run at low energy and low thermal transmittance coefficients when heat is not needed. This is the case, for example, in summer when the storage tank is already at the desired relatively high temperature. In another situation, a PV-T solar collector with moderate power generation and high heat output can be run if the heat transfer coefficient is set low. There are two preferred ranges for the space arrangement. On the one hand, a double-glazed pane or laminated glass pane can be used as the cover. Here, it makes sense to arrange the gap between the two panes of the cover, especially as a result of a relatively easy to be performed Rundumabdichtung and sealing against the other interior of the solar collector is possible. The gap is thus within the cover, but in any case between the outside of the cover and the solar absorber or more generally expressed the solar radiation in another form of energy converting element. The other alternative for the arrangement of the intermediate space is to arrange it below the cover or in the area between the cover and the element which converts the solar radiation into another energy form. This is just as possible with single-pane glass as a cover, as with the use of double-glazed panes. The advantage of this embodiment is that the heat present in the absorber can be controlled more directly by changing the pressure in the intermediate space. However, this advantage can be achieved even with double glass panes, if they rest directly on the absorber.

Further preferred embodiments are characterized in that on the underside of the cover and / or on the upper side of the lower pane of a double glass pane and / or on the upper side of the solar radiation receiving and converting into another form of energy element and / or on the underside of the Solar radiation receiving and converting to another form of energy element a low-e-layer is arranged. By low-e-layer is meant a layer that reflects infrared radiation. The common abbreviation in the professional world refers to coatings that are often used to act as a kind of mirror for thermal radiation and thus to avoid excessive heat input. Depending on the application of this layer, it avoids that certain areas are too warm, so provides heat protection, or retains the heat.

This is quite useful in the context of the present invention to enhance the effect and can be used selectively.

The insulation of the rear side of the absorber can optionally be designed as a 3 cm to 10 cm thick, fibreglass-supported structure with a so-called vacuum insulation panel (vip). The structure may be interrupted several times, for example, two to five times by films that reflect infrared radiation. Thereby, a further improvement can be achieved. The vacuum is realized via a diffusion-tight film. Such a system can be clocked in time with a very small vacuum pump to a pressure in the range between 0, 1 hPa and 1 hPa be evacuated. This is sufficient for vacuum insulation panels to suppress the thermal conductivity.

The control and the realization of this vacuum can be provided together with the vacuum provided according to the invention in the intermediate space. With various embodiments of the invention, it is also possible to build a defrosting function for snow. Snow is a considerable problem for solar collectors of all shapes and sizes. If snow falls on a solar collector and remains there, it prevents the use of the solar collector over days and weeks as it prevents any solar radiation. Snow will remain even when climatic conditions already prevail, which would in itself make an effective use of the solar collector easily possible. So far, it is necessary to mechanically remove the snow from the solar collector in order to use it again. However, this is always omitted in practice, as this would have to be found a way to enter the roof after a snowfall in winter or at least to gain access to the roof and there mechanically remove the snow from the solar collector, without the solar collector or to damage its transparent cover. This effort is only very rarely operated. However, if the possibility is provided according to the invention to make the heat flow through a gap in the solar collector below the transparent cover adjustable, so this can find a way. Since at this time favorable thermal energy is available in the memory of the solar system, according to warm fluid is pumped in the morning, for example, at sunrise in and through the absorber with the involvement of the solar pump. At the same time, the vacuum in the space is reduced, so that the insulation decreases and again a heat flow can flow through the gap easily.

In this way, unlike the other approach in solar collectors intended heat in the absorber is now intended to flow out through the transparent cover and thaw the snow there and possibly lying there ice and move it to drain.

Once the snow and ice have thawed and run off, the solar collector is ready for use again, the vacuum can be rebuilt and the solar collector can be fed to its usual purpose.

These various measures can be automatically provided or driven accordingly by the user of the system or the day before be selected. It makes sense to carry out the thawing early in the morning, as this will allow the daylight to be used for the solar collector and at the same time avoid further defrosting at night, as in the case of late-night use.

It is of particular advantage if the absorber is decoupled from the edge assembly of the solar collector, that is, for example, a surrounding tub. Without lateral storage, it is possible to thermally and mechanically relieve the edge bond.

Particularly preferably, occurring forces in the solar collector can be transferred directly via the absorber and pipes to the rear wall of the solar collector. The intermediate space according to the invention with the controllable value for the heat flow is preferably provided with a circumferential vacuum seal. As a result, the property of the controllable value for the heat transmission current can be defined in a particularly defined manner, that is to say the intensity of the vacuum or the pressure of the gas present in this intermediate space. Particularly preferred is a circumferential vacuum seal made of Viton used.

In order to achieve a particularly low heat transfer and thermal decoupling of the absorber from the cover, ie preferably the glass pane, spacers are used which are in particular punctiform and preferably have a contact surface of at most one hundredth of the surface of the cover.

According to the invention, it is preferred to provide a solar collector with a particularly flat design, that is, for example, only 20 mm to 40 mm height or distance between the rear wall and the cover. Further features and advantages of the invention will become dependent claims or the following description of the figures.

In the following, a number of embodiments of the invention will be explained in more detail with reference to the drawing. Show it:

Figure 1a is a schematic section through a first embodiment of a solar collector according to the invention;

Figure 1b shows a schematic section through a second embodiment of a solar collector according to the invention;

Figure 2a shows a schematic section through a third embodiment of a solar collector according to the invention;

Figure 2b shows a schematic section through a fourth embodiment of a solar collector according to the invention;

3a shows a schematic section through a fifth embodiment of a solar collector according to the invention;

FIG. 3 b shows a schematic section through a sixth

Embodiment of a solar collector according to the invention;

Figure 4a shows a schematic section through a seventh embodiment of a solar collector according to the invention;

FIG. 4b shows a schematic section through an eighth embodiment of a solar collector according to the invention;

Figure 5a shows a schematic section through a ninth embodiment of a solar collector according to the invention;

FIG. 5b shows a schematic section through a tenth embodiment of a solar collector according to the invention; a schematic section through an eleventh embodiment of a solar collector according to the invention; a schematic section through a twelfth embodiment of a solar collector according to the invention; a schematic section through a thirteenth embodiment of a solar collector according to the invention; a schematic section through a 14th embodiment of a solar collector according to the invention; a schematic section through a 15th embodiment of a solar collector according to the invention, similar to the embodiment in Figure 8a; a schematic section through a 16th embodiment of a solar collector according to the invention, similar to the embodiment in Figures 8a and 8b; a schematic section through a 17th embodiment of a solar collector according to the invention, according to the embodiments in Figures 8a and 8b; a schematic section through an 18th embodiment of a solar collector according to the invention; a schematic section through a 19th embodiment of a solar collector according to the invention; a schematic section through the edge region of a solar collector according to the invention; a schematic section through an edge region of another embodiment; a schematic section through an edge region in a further modified embodiment; a schematic section through an edge region of another conception; a schematic section through an edge region in still further modified embodiment; a schematic section through an edge region by a renewed embodiment; a section through another detail; a schematic section through a detail similar to Figure 13a; a schematic section through a detail similar to Figures 13a and 13b; a schematic section through a detail similar to Figures 13a to 13c; a schematic section through a further embodiment of a solar collector according to the invention; a schematic section through a detail of the figure 14; a schematic section through a detail similar to Figure 14a; a section through a detail similar to Figures 14a and 14b; FIG. 15 a section through a further embodiment of a solar collector according to the invention; FIG. 16 shows schematic collector characteristics of various solar collector types; and

FIG. 17 shows a depiction of the dependence of the heat transfer coefficient on the pressure in various embodiments of the invention.

The sectional views in the figures each show a vertically taken section through a solar collector. The exposure to sunlight takes place in the representations from above, so that in the mounted state, the underside of the illustrated solar panels is mounted approximately on a roof.

The corresponding solar collectors each have a frame 1. From the frame you can see corresponding sections on the left and right of the solar collector.

Upwards, each solar collector is covered by a solar glass pane as cover 2. This cover 2 consists of a transparent material, in particular a glass. This transparent material allows sunlight to fall from above through the cover 2 into the solar collector.

Viewed from above, the cover is rectangular and largely dictates the areal extent of the solar collector. The frame 1 runs around the outside of the cover 2 and thus encloses the solar collector from four sides.

Common to the embodiments of all figures 1a to 7, an absorber 6, the surface and approximately parallel to the cover 2 and is arranged to the solar glass in I nneren of the solar collector. The absorber 6 is in most embodiments a sheet metal plate which may be selectively and optionally low-e coated. As sheet material are primarily aluminum and steel into consideration.

On the underside of the absorber 6 each heat transfer tubes 1 1 can be seen in section. This heat transfer tubes 1 1 are in contact with the underside of the absorber 6. You can see the heat transfer tubes 1 1 in section, which therefore protrude perpendicularly through the plane and parallel to the side walls of the frame 1 to be recognized. The heat transfer tubes 1 1 may be connected to the plate of the absorber 6 via welding points or welds, not shown.

Down the solar collector is completed by a rear wall 10. This rear wall can be made of aluminum or of a plastic.

The heat transfer tubes 1 1 can be supported on the rear wall 10 of the solar collector d by springs 1 9. In particular, they can be long-feathers.

In the region of the absorber 6 on the side facing away from the sun, and thus between the absorber 6 and the rear wall 10, there is in most cases an insulation 9 of different types. The insulation 9 is usually made of rockwool, foam, Hard foam, plastic hollow chamber profiles and / or porous, non-conductive bulk materials such as perlite.

Between the frame 1 and the cover 2, a side insulation 17 is additionally provided circumferentially, which also extends between the frame 1 and the outer edge of the absorber 6 and the frame 1 and the outer edge of the rear wall 10 and with the frame 1 to the Solar collector runs around. Between the cover 2, through which the sunlight falls into the solar collector, and the absorber 6, there is a gap 15, to which the invention pays special attention, unlike conventional solar collectors. This gap extends over the entire surface of the solar collector within the frame 1 or almost over this entire area, limited for example by the side insulation 17 and a circumferential, this gap bounding seal third

The aforementioned gap 15 is thus formed in the majority of embodiments, gap-like with a substantially constant thickness.

The majority of the embodiments illustrated in FIGS. 1 a to 7 have the above-described features and elements. In the details, however, differ the individual embodiments.

The embodiment shown in Figure 1 a has as cover 2 a transparent glass pane. The gap 15 is here in the form of an air gap with a thickness between about 1 mm and 10 mm, so that the underside of the cover 2 and the top of the absorber 6 have a distance of 1 mm to 10 mm from each other.

The gap 15 may be filled with air or with inert gas or another gas. The selection of the gas can take into account that particularly desirable insulating values are achieved and / or that at the same time corrosion protection in the intermediate space 15 between the cover 2 and the absorber 6 is achieved and condensation formation is prevented.

One sees a valve 13 indicated schematically. By means of this valve 13, the pressure of the gas in the intermediate space 15 can be regulated.

By means of the valve 13 so the adjustment and regulation of a pressure in the interior of the inner space 15 can be made or even a be introduced into the intermediate space 15 for the first time or during maintenance.

FIG. 1 a shows a so-called PV-T solar collector. He therefore has so-called PV wafer 5, which are applied to the top of the absorber 6. These wafers 5 can be embedded directly on the sheet of the absorber 6 in an EVA (ethylene-vinyl acetate) layer. These may be, for example, PV silicon wafers. Alternatively, a PV thin film foil can also be laminated onto the absorber 6 or applied by coating. At least currently, a much better efficiency in the use of a variant with crystalline silicon can be achieved, but the invention is not limited thereto and can be designed differently depending on future developments. On the EVA (ethylene-vinyl acetate) layer, the PV thin-film or the PV coating, a so-called low-e coating for reducing the long-wave thermal radiation to the outside is optionally applied. Such a low-e coating can also be optionally mounted on the underside of the upper glass pane.

The heat transfer tubes 1 1 can be laser-welded to the sheet of the absorber 6. Alternatively, it is also possible to press them over a to be recognized in the figure 1 a spring 19 to the absorber plate 6 from below. In this case, a positive recess in the insulation 9 prevent slippage of the heat transfer tubes 1 1 and the spring 19 in the horizontal plane.

In this illustration in Figure 1 a, a conventional insulation 9 can be used approximately from rock wool, foam or Rockwool. The cover 2 itself may be tightly sealed with an edge seal against the frame 1, but this is not required with a hundred percent tightness. A small leak rate is tolerable in this embodiment of the invention, which brings a great advantage in terms of manufacturing technology. The Small leak rate is acceptable in that anyway a pump and a valve is provided, with which the pressure in the gap 15 or the quality of the vacuum can be readjusted. Due to the leak rate in the interspace 15 penetrating particles or molecules thus represent only a temporary and due to the other regulation easily eliminable or be considered disturbance.

The gap 15 is filled as mentioned by the valve 13 with a pressure-controllable gas. The valve 13 is purely schematic; One can also imagine a vacuum pump connected to the intermediate space 15, with which a controllable vacuum of different intensity can be drawn.

Alternatively, the valve 13 may be thought to controllably relax the mentioned vacuum when certain constraints exist. As a measuring sensor, for example, serve a pressure sensor.

This regulation can now be automatic. Is festgestel by suitable measuring devices (not shown), that in Fal-egg nes thermal operation of the PV-T solar collector heat dissipation does not occur, so the heat in the heat transfer tubes 1 1 is not sufficiently dissipated, so wi rd the vacuum decreased, so that the heat conduction from the top of the absorber plate 6 to the cover 2 and thus to the outside space is greater and thus overheating of the solar collector is avoided.

In the case of a controllable inert gas filling of the intermediate space 15, the filling level of the solar collector could be regulated via the valve 13, which in this case is connected to a noble gas container. In an application can then be reduced by a nighttime lowering of the temperatures in the solar collector connected to the collector at high, for example, atmospheric pressure in the space by increased heat transfer through the solar panels to the environment, the collector downtime or avoided and thus in a special PV-T application, the PV yields are increased.

Thus, depending on the optimum operating point of the solar collector can be operated as needed between the various characteristics, which are shown in Figure 8 for a simple covered collector with, for example, 20 mm air gap at atmospheric pressure.

FIG. 1b shows an alternative embodiment. This shows that as well as the transparent cover 2 facing the front of the absorber 6 and the rear of the absorber 6 m with the heat transfer tubes 1 1 adjustable with air, inert gas or vacuum or other gases are applied and so the heat loss and thus the characteristics of the solar collector can be further influenced.

Structurally, in this case, in addition to the elements of FIG. 1 a, a further seal is provided circumferentially around the solar collector within the frame 1 and the side insulation 17 between the absorber 6 and the rear wall 10. Alternatively, the use of a deep-drawn, in this area sealless housing material is considered, which is shown in an embodiment in Figure 7.

In the figure 7, a housing 26 made of plastic, steel or aluminum is provided in trough shape, in which the frame 1 and the rear wall 10 are integrally formed and merge into one another. Nevertheless, a side insulation 17 can be seen.

An additional sealing surface is avoided, however. If an evacuation is to be carried out in the region between the absorber 6 and the rear wall 10 or the tub housing 26 in the embodiments of FIGS. 1 b or 7, then the rear wall 10 or the tub housing 26 must face the absorber 6 be supported. The insulation 9 should further preferably have no thermal bridges.

The insulation 9 can assume a dual function for insulation and support, in particular when a hard foam, in particular rigid polyurethane foam, a hollow plastic chamber profile or a porous, non-heat-conducting bulk material such as perlite is used as materials.

If, however, the functions of the insulation and the support are separated from each other, it is also possible to use supports and webs or a trough with webs or supports, the spaces between the webs and supports remaining empty in this case.

As tests have shown, the heat transfer coefficients of a solar collector of about 0.8 to 4 W / m ² K and of 10 W / m ² K to 20 W / m ² K can be controlled by such measures.

In the embodiments of FIGS. 1 a, 1 b and 7 it is also already apparent that the absorber 6 can also be supported relative to the cover 2, for example with spacers 20, which can have the form of rods or balls, for example, and can be directly on the Support absorber 6. The spacers 20 should preferably be transparent and constructed in the form of a grid with a column spacing of approximately 50 mm. FIG. 2 a shows an alternative embodiment in which the cover 2 is designed as a laminated glass pane. It should be noted that the sectional view in FIG. 2a is not to scale. The laminated glass of the cover plate 2 has upper and lower glass sheets, and the lower glass sheet is laminated directly onto the absorber 6.

In the illustrated PV-T solar collector variant, the wafers 5 are applied to the upper side of the lower pane, they are thus within the Cover 2 or within the laminated glass pane. Here too, the PV wafers 5 can be accommodated in an EVA layer, a PV thin-film foil laminated or a PV coating applied. On the EVA layer, the PV thin film or the PV coating is optimally applied a low-e-layer.

A low-e layer can also be applied optically on the underside of the upper glass pane. In the figure 2b, a further modification is now made, and indeed the structure of Figure 2a is shown, in which case additionally the rear K value between the absorber 6 and the rear wall 10 is regulated.

For this purpose, a valve 14 is indicated, with which the pressure in this area can be regulated similarly as in FIG. 1 b.

The embodiments in FIGS. 3a and 3b show a construction which follows that in FIGS. 2a and 2b to a large extent. There is a difference in that the PV wafers 5 are laminated directly on the absorber 6 embedded in an EVA sheet 12, a laminated PV thin film or a PV coating. The laminated glass of the cover 2 is then laminated on the EVA film 12 in this case. The lower pane of the cover 2 is here optionally low-e coated on the top, as well as the underside of the upper glass pane.

Again, the heat transfer via the adjustable vacuum or a noble gas filling with adjustable pressure on both sides of the absorber 6 in the embodiment of Figure 3b can be adjusted. Figures 4a and 4b show two further embodiments of the invention. You start from an absorber 6 in sandwich construction. The or the heat transfer tubes 1 1 are preferably welded to the sheet of the absorber 6. In the embodiment in FIG. 4 a, a hollow-chamber profile 22 of, for example, plastic, steel or aluminum is inserted under an upper optionally selectively coated absorber sheet, preferably of aluminum. Below is another sheet, preferably made of aluminum.

On the other hand, the embodiment in FIG. 4 b has a sandwich construction with a corrugated profile 21. In this embodiment, the heat carrier tube 1 1 can be welded onto the absorber sheet 6 or the sheet metal of the corrugated profile 21 or with a longitudinal spring 19 against the absorber 6 pressed, which is supported on the lower plate, similar to that described in connection with Figure 1.

The embodiment in FIGS. 5a and 5b are equipped with an optionally selectively coated, full-surface-flow plastic absorber. Again, there is a controllable heat loss coefficient of the cover 2 and optionally in the figure 5b and for the insulation 9 to the rear wall 10th

In the embodiments in FIGS. 6 a and 6 b, a selectively coated honeycomb absorber 23 is supported directly on the cover 2. Optionally, a PV thin film may also be laminated. Alternatively, a PV coating may also be applied.

The PV thin film or PV coating may optionally be low-e coated. This in turn results in a controllable heat loss coefficient of the cover 2 and optionally in the figure 6b and the insulation 9 of the rear wall 10. The honeycomb profile 23 roughly corresponds to what is known from the washing drums washing machines such as the provider Miele. A profile with a honeycomb key width of about 33 mm is preferred. This honeycomb profile is slightly modified by forming so-called pins with contact to the cover 2 of the solar collector. Again, there is a controllable heat transfer coefficient of the cover and optionally the insulation 9 of the rear wall 10th As has emerged in experiments, a low-e coating is particularly useful and advantageous on the surface that limit the gap 15 on the bottom. Likewise, optionally may be applied to the underside of the upper glass pane, a low-e-layer.

In addition, an anti-reflection coating (AR coating) can optionally be applied to all the glass panes of the cover 2 used on the upper side and / or the lower side.

A variety of other combinations and permutations of the embodiments of Figures 1 to 7 is conceivable.

In order to determine the degree or the height of the vacuum in the intermediate space 15, depending on the intended use of the solar collector, a different handling may be expedient. As mentioned above, solar collectors are used inter alia for hot water or for process heat. There is a trade-off between the desired intensity of vacuum for the required operating temperatures and economic considerations. It should be noted that constructive measures to support the cover 2 and to build the edge seal in the area of the seals 3 and 4 with respect to the frame and the frame 1, the cover 2 and the rear wall 10 are to meet. A pressure of 5 times 10 ^"2 hPa to 10 ^{" 3} hPa (corresponding to the same values in mbar) for the space 15 between, for example, the two panes of a laminated pane for the cover 2 is generally sufficient for the intended applications in solar collectors To achieve a sufficiently good heat transfer coefficient and thus a sufficiently good collector characteristic and at the same time to consider a still tolerable design effort for the support of the glass of the cover 2 due to the forces occurring in the vacuum. The mentioned pressures of 5 times 10 ^"2 hPa to 10 ^{" 3} hPa can with relatively favorable Vacuum pumps can be achieved, for example with rotary vane vacuum pumps. In this way, the overall price of the system remains economical.

A jerk of 1 0 ^"4 hPa allows a further increase in the thermal collector performance for applications with high operating temperatures, ie considerable process heat.

FIG. 8 a describes a further embodiment of a PV-T collector in a well housing with a shaped support for a vacuum-tight laminated glass pane 24. Alternatively, the laminated glass pane consists of a glass-applied PV module and a solargium solar cell. The glass panes are connected to one another via spacers. At the glass edges of the formed glass interior is sealed with a seal 3 vacuum-tight with respect to the environment. Through a passage through the pan and seal the laminated glass pane can be controlled by an external vacuum pump, the pressure in the glass space. Between the edge of the bath and the double glazing silicone adhesive ALS silicone sealing 28 is used for sealing to the outside. The contacted PV wafers are laminated with ethylene vinyl acetate (EVA film) directly on the absorber plate of the absorber 6 of the thermal collector for the best possible heat transfer, alternatively, the PV module (thin film or wafer) is directly applied to the absorber , The absorber plate preferably has no lateral contact with the edge seal on the tub housing, so that, firstly, no thermal bridge is created and, secondly, the seal 3 of the vacuum is not unnecessarily thermally stressed.

Absorber plate and absorber tube of the absorber 6 are as in the detailed representations of Figures 13a and 13b sketched together. Here, Figure 13a represents a solid welded or glued connection, Figure 13b is a positive connection, for example produced by rolling the absorber sheet. The support of the absorber tubes on the rear wall of the tub housing 26 by means of long springs with or without Pipe holding stackable. The long spring can be glued to the rear wall or positively connected to the rear wall, to the rear wall can be formed accordingly. Alternatively, a pipe support 47 may be used as in Figure 13d.

The back of the collector is thermally insulated.

FIG. 8b shows a structure as in FIG. 8a with the difference that no photovoltaic layer is applied, so that in FIG. 8b it is merely a vacuum collector.

FIGS. 9a and 9b show a slightly modified construction compared to FIGS. 8a and 8b. The tray used in Figure 8a is replaced by a frame profile 33 with a rear wall The seal between the rear wall 10 and frame profile 33 is made by silicone adhesive.

Figures 10a and 10b show two embodiments with a covered with a simple solar glass pane 2 absorber 6, in which the entire collector is designed evacuated. Alternatively, it can be filled with inert gas. FIG. 10a shows a PV-T collector, FIG. 10b shows a vacuum collector. Due to the elimination of the rear insulation and the small distance between the disc 2 and absorber 6, the collector can be made with very low height, for example, only 20 to 40 mm. It is therefore also suitable for other fields of application, e.g. as facade element.

The details in Figures 13c and 13d show 2 possible embodiments: The support of the solar glass pane 2 with respect to the absorber 6 is punctiform by spacers 32, which are pronounced in the absorber sheet, embossed on the absorber plate or glued with intervals of grids of 5 to 15 cm. The distance between glass pane 2 and absorber 6 is 1 to 5 mm, so that a variable heat transfer through the transparent cover 2 is created by the controllable internal pressure in the collector. In the absorber tubes of the absorber 6 is similar to the outer tube contour shaped with a distance of 5 to 15 cm. It is either positively connected to the pipe (13c) or pipe and absorber are fixedly connected to each other and the absorber sheet is provided with an expansion fold (13d) so that the absorber sheet can move between two adjacent pipes by continuing around the pipe around places.

The pipe is supported by a long spring or with a fixed pipe holder against the tub housing. The absorber plate preferably has no lateral contact with the edge seal on the tub housing, so that firstly no thermal bridge is formed, secondly the vacuum seal 3 is not unnecessarily thermally stressed and thirdly no storage of the absorber 6 to the side is necessary. The storage and sealing of the solar glass pane 2 show in detail the figures 1 1 (unclamped embodiment) and 12 (stapled embodiment).

FIG. 11 shows, in three embodiments, an identical structure with the silicone seal 28, the actual vacuum seal 3 and an optional seal 4, which, for example, assumes a holding function of the vacuum seal or can absorb movements of the glass pane during evacuation.

The vacuum seal 3 can be designed flat sealing, as one or preferably a plurality of round cords or as a tooth gasket. Preferably, the elements of the seal 3 are positively fixed in the trough 26, so that they are not sucked during evacuation of the vacuum in the collector or slip. In the previous versions, a controlled via an adjustable vacuum heat transfer of a flat collector has been described. In FIGS. 14 and 15 a PV-T collector is outlined, which is provided with alternative control devices for adjusting the heat transfer via the transparent Solar glass pane 2 is provided. The heat transfer is controlled by egg nen lifting mechanism of the absorber 6, which changes the position of the absorber in the collector box such that a distance in the range of 0 ... 20 mm between the absorber 6 and 2 Solarabdeckscheibe adjusts.

Because there is no vacuum in the intermediate space between the absorber 6 and the glass pane 2 in this case, the control range is limited to 4... 20 W / mK. Several different embodiments of this are outlined in Figures 14a, 14b and 14c and 15. All 3 variants are intrinsically safe designs that ensure a standstill protection of the collector with a heat transfer of 20 W / mK in the event of a power failure. The variant in FIG. 14a shows a pneumatically operated pneumatic lifting mechanism. For collector operation optimized for thermal yield, compressed air is fed into several pistons via a valve 13. As a result, a plurality of stop plugs 38 fastened to the absorber are moved away from the cover disk and a return spring 34 is loaded under pressure. The valve closes at a distance between absorber and disc of about 20 mm. In operation with optimized PV output, the valve opens and the return spring establishes contact between the laminated PV absorber and the glass pane. The valve is normally open, so that an intrinsically safe construction of the PV-T collector is guaranteed.

The variant according to FIG. 14b functions in the same way as the variant in FIG. 14a with the difference that instead of a piston, a hose 36 is filled with compressed air which moves a lifting element 38 fastened to the absorber 6. The hose can be open or consist of several hose elements.

The exclusively self-regulating variant in FIG. 14c shows a thermocouple 37, which is fastened to the absorber at several points. This variant can not be controlled from the outside and is only a standstill protection. When heating the absorber moves through the heating of the inner wax element of the punch of the thermocouple out of this and presses the absorber against the cover. The process path of the absorber can be increased by a lever.

FIG. 15 shows an embodiment with a motor-driven absorber heater, which is designed so that it can be controlled in a controllable manner by means of a collector cover. The electric motor attracts a Bowden cable 39 for the thermally optimized collector operation, which lowers the absorber via several, preferably two counter-rotating cam roller pairs 38. The PV-T collector is by a return spring outside the collector, z. B. executed by a circular guide of the cable preferably on the engine intrinsically safe. The spring is clamped when the absorber is lowered and returns the absorber to the cover plate in the event of a power failure or in PV-optimized operation. A motor can be used to activate the lifting mechanism of several collectors.

FIG. 16 shows a collector characteristic curve for different collector types. Upwards the thermal efficiency is plotted in percent, to the right the ratio (T _m -T _at b) / G. Here, T _{m is} the mean collector temperature in [K], Tamb the ambient temperature in [K] and G the irradiation on the collector in [W / m ² ]. The three curves show different collector characteristics in solar flat collectors, which are simply covered with a glass pane and have an air gap of 20 mm. Curve 1 denotes a PV-T solar flat collector under load, curve 2 a PV-T solar flat collector at idle, and curve 3 a selectively coated standard solar flat collector simply covered with a glass sheet.

The construction of the invention allows an extension of the controllable characteristic field between the curves 1 ^* and 3 ^* in the qualitative representation. The curve 1 ^* arises from the curve 1 by an increased heat conduction in the reduced air gap, for example at atmospheric pressure. The curve 3 ^* arises from the curve 3 by evacuating a reduced air gap. FIG. 17 shows the dependence of the heat transmission coefficient on the pressure in the intermediate space 15 with a pane spacing of a laminated glass of a cover 2 of 1 mm. To the right, the gas pressure in hPa is shown, to the top, the heat transfer coefficient A _gas [W / (m ² K)]. It can be seen that the heat transfer coefficient, which initially increases with increasing pressure, finally strives for a limit value.

LIST OF REFERENCE NUMBERS

1 frame

2 transparent cover, especially glass

3 seal

4 seal

5 PV layer, for example wafers embedded in EVA foil

6 absorbers

7 hollow chamber profile

8 wave profile

9 insulation

10 back wall

1 1 heat transfer tube

12 foil

13 valve

14 valve

15 gap

16 lower room

17 side insulation

18 sheet metal

19 spring

20 spacers

21 wave profile

22 hollow chamber profile

23 honeycomb absorber

24 laminated glass pane

25 plastic absorbers

26 tub housing

27 low-e coating or applied foil with low-e coating

28 silicone seal

29 seal 30 clip

31 Welding or adhesive bonding

32 spacers

33 frame

34 spring

35 Compressed air filler neck or discharge nozzle

36 compressed air hose

37 wax thermocouple

38 lifting device

39 Bowden cable

40 Bowden cable case

41 Bowden cable holder

42 Bowden cable feedthrough

43 absorber guidance

47 pipe support

Claims

claims

Solar collector,

with a transparent cover (2) with a solar radiation facing outside,

with an element receiving the solar radiation and converting it into another form of energy inside the solar collector,

characterized,

that between the solar radiation facing the outside of the cover (2) and the solar radiation in another form of energy converting element (6) an intermediate space (15) is arranged, which has a controllable value for the heat flux.

Solar collector according to claim 1,

characterized,

that the intermediate space (15) is filled with a gas, in particular noble gas, or vacuum, and

the pressure of the gas or the intensity of the vacuum in the intermediate space (15) can be regulated.

Solar collector according to claim 2,

characterized,

that the pressure of the gas between 10 ^"4 hPa and 1000 hPa is adjustable.

Solar collector according to one of the preceding claims,

characterized,

the heat loss coefficient of the solar collector can be regulated by a factor of at least five, in particular from 0.8 W / m ² K to 4 W / m ² K and from 10 W / m ² K to 20 W / m ² K. Solar collector according to one of the preceding claims,

characterized,

that the cover (2) is a laminated glass double disc, and

that the space (15) of the space between the two disks of the

Double glass cover (2) is.

Solar collector according to one of the preceding claims,

characterized,

in that the intermediate space (15) is arranged between the side of the cover (2) which is adjacent to the element receiving the solar radiation and converts into another form of energy, and the element (6) receiving the solar radiation and converting it into another form of energy.

Solar collector according to one of the preceding claims,

characterized,

the distance between the cover (2) and the element (6) receiving the solar radiation and converting into another form of energy is between 1 mm and 10 mm.

Solar collector according to one of the preceding claims,

characterized,

that on the underside of the cover (2) and / or on the upper side of the lower disc of a double glass pane and / or on the top of the solar beam ung receiving and ei ne other energy form converting element (6) and / or on the underside of the Solar radiation receiving and in another form of energy converting element (6) a low-e-layer (27) is arranged.

9. Solar collector according to one of the preceding claims,

characterized,

that the solar radiation receiving and converting into another form of energy element is an absorber (6) and the solar collector is a thermal solar collector, or

that the solar radiation receiving and converting into another form of energy element is a photovoltaic element and the solar collector is a photovoltaic solar collector, or

that the element receiving the solar radiation and converting it into another form of energy carries a photovoltaic element, in particular a PV wafer, arranged on an absorber (6), and

that the solar collector is of the type which generates both electricity and heat.

10. Solar collector according to one of the preceding claims,

characterized,

that in the region between the solar radiation receiving and converting into another form of energy element and a rear wall (10) of the solar collector, a further region is arranged with a controllable value for the heat flow.

1 1. Solar collector according to one of the preceding claims,

characterized,

the intensity of the vacuum or the pressure of the gas, in particular of the noble gas, is adjustable by means of a controllable vacuum pump or a controllable valve (13, 14).

12. Solar collector according to claim 1 1,

characterized,

in that a pressure sensor is arranged in or at the intermediate space (15), and in that a regulating device is provided which, depending on the values of a pressure sensor, the vacuum pump falls below a Set pressure turns on and off when reaching a target pressure again.

13. Solar collector according to claim 1 1 or 12,

characterized,

a thermostatic safety element is provided which, when a nominal temperature is exceeded, causes one or the control device to increase the pressure of the gas in the intermediate space (15) or to reduce the intensity of the vacuum in the intermediate space (15).

14. Solar collector according to one of claims 1 1 to 13,

characterized,

that the controllable valve (13, 14) is normally open, in order to increase the stability of the standstill.

15. Solar collector according to one of claims 1 1 to 14,

characterized,

that the control device is designed

that in a purely thermal operation, the valve (13, 14) is closed and the target pressure is minimal, so the intensity of the vacuum is maximum, and / or

that in a purely photovoltaic operation, the valve (13, 14) is open and the target pressure is set to a maximum, so the atmospheric pressure corresponds, and / or

that in a mixed operation, the control device determines which of the two modes currently gives the greater total yield or the currently preferred performance, and then depending on the position of the valves and the pump controls. 16. Solar collector according to one of the preceding claims,

characterized,

that a control device is provided, which provides a control of the solar collector for defrosting snow and / or ice, and that the control device at manual operation or automatically upon detection of the presence of snow and / or ice and preferably depending on the time of day, the vacuum in the space (15) decreases or increases the pressure and at the same time turns on the solar pump so that warm water from the memory of the solar system Absorber (6) flows through.

17. Solar collector according to one of the preceding claims,

characterized,

in that spacers (20) or springs (19) are provided between the element receiving the solar radiation and converting into another form of energy and the cover (2) and / or the rear wall (10).

18. Solar collector according to claim 17,

characterized,

the spacers (20) are punctiform between the element (6) receiving the solar radiation and converting into another energy form or at least have a contact surface which is at most one toe, in particular at most one hundredth of the surface of the surface Cover (2) occupies.

19. Solar collector according to one of the preceding claims,

characterized,

in that the intermediate space (15) is sealed off from the exterior by a seal (3) running around, in particular by a peripheral Viton vacuum seal.

20. Solar collector according to one of the preceding claims,

characterized,

the element (6) receiving the solar radiation and converting it into another form of energy is decoupled from an edge bond and in particular no lateral support is provided.

21. Solar collector according to one of the preceding claims,

characterized,

a force transmission of the forces occurring in the solar collector takes place directly via the solar radiation receiving and converting into another form of energy element (6) and pipes on the rear wall (10).

22. Solar collector according to one of the preceding claims,

characterized,

the distance between the rear wall (10) and the cover (2) is less than 50 mm, in particular between 20 mm and 40 mm.

23. Solar collector according to one of the preceding claims,

characterized,

that in an insulation on the back of the solar radiation in another form of energy converting element (6) one or more vacuum insulation panels are arranged, preferably interrupted several times by films which reflect infrared radiation, and

the vacuum insulation panels can be evacuated in a time-clocked manner by means of a vacuum pump,

wherein preferably a common use of the pumps and units for the regulation of the vacuum in the intermediate space (15).