MXPA06003696A - Evacuable flat panel solar collector - Google Patents

Abstract

The present invention relates to an evacuable flat panel solar collector (1) wherein the transparent planar wall (4) and the housing (2) are sealed by a soft metal ribbon (32) which is soft soldered at least with a first portion (34) to the housing (2) and at least with a second portion (36) to a metallized area of the transparent planar wall (4). The present invention also relates to a method for the preparation of said flat panel solar collectors (1) as well as to a flat panel solar collector system (56) comprising said flat panel solar collector (1) and at least one external mirror (54).

Description

SOLAR COLLECTOR OF FLAT PANELS EVACUABLE DESCRIPTION OF THE INVENTION The present invention relates to an evacuable flat panel solar collector comprising at least one absorber, at least one duct, a retaining structure and at least one transparent wall. The invention also relates to a system of flat panel solar collectors comprising at least one solar collector of flat panels according to the invention and at least one mirror, and also to an arrangement of flat panel solar collectors. Finally, the invention relates to a method for the preparation of a evacuable flat panel solar collector according to the invention. Solar collectors, particularly flat panel solar collectors, are well-known devices that are commonly used to absorb and transfer solar energy within a collection fluid. Mainly, the solar collectors consist of a cylinder or blackened absorption plate contained in a housing that is frontally closed by a transparent window sheet. Due to the diluted nature of sunlight, to increase the operating temperature by reducing thermal losses, the solar collectors can be evacuated during their use to eliminate gas convection and conduction REF: 169856 molecular. Very high temperatures could also be achieved when focusing light. However, only direct light can be focused, while diffused light is lost. Therefore, this solution is not very attractive for regions, such as in central Europe, where approximately 50% of sunlight is diffuse. Since the evacuation of solar collectors from flat panels is problematic due to the need for a structure that is capable of maintaining a high vacuum even under the large forces resulting from atmospheric pressure, the focus has been on solar collectors that 'are based on a cylindrical glass envelope containing a cylindrical or flat absorber. This design can, for example, be found in US 4,002,160 where a multi-tube solar energy collector having a diffuse reflection surface positioned behind a collector pipe arrangement is described which includes a plurality of double-walled tubular elements in those that the outer wall is made of a glass material that is transparent around its entire circumference. According to US 4,579,107, a tubular collector is described which has very suitable characteristics that are achieved by a method that is used to create both solar-selective surfaces or coatings and reflective surfaces or coatings on glass by depositing, by spray, molten metal on its surface in such a manner that the glass melts after contact with the molten metal, resulting in good adhesion and thermal contact. Also, the solar energy collection system according to US 3,960,136 is based on the use of a double-walled glass tube whose outer wall is transparent about substantially its entire circumference. The separation between the double walls is sealed at a sub-atmospheric pressure. Although it is well known that against an arrangement of tubular collectors, such as those described in US 4,002,160, flat panel collectors allow a maximum availability of energy for absorption, tubular solar collectors are still considered very commonly suitable thanks to the manufacture more easy seal glass to metal, as required to maintain a high vacuum. In US 4,084,576 there is disclosed a bulb-type solar collector comprising a blackened solar absorber that is inserted into a flat-lamp envelope thus making use of a reliable sealing technique known, for example, from television cathodic tubes.

From US 3,916,871 it is possible to derive a solar collector module with flat panels comprising a housing with an evacuated chamber defined therein., a transparent flat wall forming one side of the chamber and a radiant energy absorber with flow conduits therein that is thermally insulated from the housing. In one embodiment, a vacuum pump is connected through suitable conduits to the collector module to evacuate it from time to time as necessary. According to US 3,916,871 a vacuum in the area of a Torr (1 mm Hg) is considered sufficient to eliminate convective losses. However, in this document it is admitted that very low pressures that essentially also eliminate driving losses would require a technology not commercially available. US Pat. No. 5,563,222 discloses a flat panel solar collector with which an attempt is made to provide an evacuated flat panel collector having sufficient structures to withstand the forces applied by the atmosphere to an evacuated enclosure. The heat losses that come from the absorber plate due to convection, conduction and thermal infrared emissions, commonly called radiation, will be overcome by a flat panel solar collector comprising a rear housing that is configured to provide a series of parallel cells, preferably of semicircular cross section, whereby each of these cells is adapted to support the primary glaze and to receive a finned tube absorber. These finned tubes occupy at least 90% of the open area between the side walls of the cells so that most of the radiation is absorbed and very little radiation passes between the finned tube absorbers and the side walls. It is indicated that the circular cross section of the individual cells provides the best resistance to the forces of deformation of the internal vacuum. A flat panel solar collector according to US 5,653,222 produces a multitude of components whose dimensions have to be precisely determined and which must also be arranged in a predetermined and complex manner. Accordingly, flat panel solar collectors of US 5,653,222 are very expensive and also quite difficult to manufacture. US 4,455,998 makes use of a solar collector consisting of at least one evacuated and sealed transparent tube or envelope containing a reversible and heatable hydrogen degasser consisting of one or more of the metals titanium, zirconium, hafnium, scandium, yttrium, lanthanum, rare earths, strontium, barium, vanadium, niobium, tantalum, thorium and alloys thereof in a partially hydrogenated condition. The hydrogen pressure is increased by heating the reversible hydrogen degasser which then releases oxygen, while the hydrogen is picked up again when the reversible hydrogen degasser is cooled. This mechanism ensures that the solar collector maintains its normal high efficiency since the losses of the solar collector can be increased by increasing the hydrogen pressure when the heat production of the solar collector exceeds the storage capacity of the rest of the installation, so the temperature of the absorber tends to become too high. As an envelope for the solar collector only a glass tube having a round cross section and enclosing a plate-shaped absorber which is connected in a thermally conductive manner to the evaporating section of a heat pipe is described. Despite the merits of the solar collectors designed to date, the evacuated tubular collectors still present certain important inconveniences. Each tube requires a glass to metal seal at each end with bellows to • reduce heat conduction and to compensate for the differential thermal expansion of the cooling tube with respect to the ambient temperature envelope. In addition, the tubes must be separated apart to avoid overshadowing that results in a loss of absorbent capacity. Likewise, the maintenance and cleaning of the structures of several tubes is quite problematic. Therefore, quite commonly, an additional front glass needs to be added to alleviate this problem, however, resulting in additional loss of transmitted light. Although the above disadvantages of tubular solar collectors can be at least partially overcome by a flat evacuated solar panel, the main disadvantage of these flat systems is still that a large flat surface is less adequate to withstand atmospheric pressure. In addition, the glass to metal peripheral seal still causes major problems. Probably due to these difficulties, the flat solar collector of US 3,916,871 is based on a housing made of plastic that also has a transparent plastic front. As a consequence, this flat solar collector is evacuated only at 1 Torr, a pressure that may be sufficient to eliminate air convection, but not molecular conduction. Against this background, it has been an object of the present invention to provide a flat panel solar collector that can also be used at very high temperatures, which has an increased efficiency and which maintains a very high vacuum over a very long period. Another object of the invention is to provide a flat panel solar collector which also comprises large flat surfaces and which can withstand atmospheric pressure and ensures high safety of operation. Furthermore, it has been an object of the invention to provide a reliable manufacturing process that produces highly vacuum-sealed flat panel solar collectors. This objective has been achieved by a flat panel solar collector comprising at least one absorber, in particular a plate absorber, at least one conduit that is at least partly thermally associated with at least one absorber, a retaining structure, in particular made of metal, comprising a perimeter frame, and at least one first transparent, in particular flat, wall, in particular a glass sheet, wherein, in particular the perimeter of the first transparent wall and the retaining structure, in in particular a first support surface of the frame, they have an overlapping area, in particular perimeter, wherein at least one side of the first transparent wall comprises at least partially, in particular on at least part of the overlap area and / or the perimeter of the first side of the first transparent wall, a metal lining, comprising in particular a first metal layer, in particular a copper layer e spreaded with plasma, and a second metal layer, in particular a tin cover layer, thus creating at least one metallized area on the transparent wall, the flat panel solar collector further comprises in particular a first soft metal ribbon, in particular a lead and / or copper tape, which is adapted to seal the joint between the first transparent wall and the retaining structure and which is adapted to be welded, in particular welded in soft, to the retaining structure, in particular to the perimeter frame, and to the metallic area of the first transparent wall. In another aspect of the invention the flat panel solar collector further comprises a lower part attached to the retaining structure, thereby forming a housing which is adapted to be vacuum-tight. It is particularly preferred when at least one soft metal strip is aligned at least partially parallel to the metal retaining structure. Thus, the metal tape is very conveniently aligned to the underlying surface of the retaining structure on which it rests. According to one embodiment of the present invention, the perimeter of the transparent wall and the frame and / or the lower part attached to the retaining structure are fixed together by the use of a soft metal tape.which is adapted to be welded in soft by means of at least a first portion welded in soft to the retaining structure, in particular to the frame and / or lower part of the retaining structure, and / or by means of at least a second portion welded in soft to the transparent wall, in particular to the metallized area of the transparent wall. The present invention also provides a solar collector of flat panels further comprising at least one second transparent wall, particularly flat, in particular a glass sheet, separated from the first transparent wall by the retaining structure, wherein in particular the perimeter of the second transparent wall and in particular the second supporting surface of the frame have an overlapping area, particularly perimeter, wherein at least one side of the second transparent wall comprises at least partially, in particular over at least part of the area that overlapping and / or the perimeter of the side of the second transparent wall, a metallic coating, in particular comprising a first layer of metal, in particular a layer of copper spread by plasma, and a second layer of metal, in particular a layer of tin cover, thereby providing at least one metallized area on the second transparent wall; and in particular a second soft metal strip which is in particular a lead and / or copper tape, which is adapted to seal the junction between the second transparent wall and the retaining structure, and particularly the frame, and which is adapted to be welded, particularly welded in soft, to the retaining structure, in particular to the perimeter frame, and to the metallized area of the second flat transparent wall. According to a preferred embodiment, the flat panel solar collector also comprises at least one separator, particularly in the form of a separating arrangement, particularly of metal bars. Spacers are used to adequately support the transparent flat wall of the flat panel solar collector, particularly when a glass sheet covers a very large surface. Without separators a larger transparent front leaf would collapse under atmospheric pressure. Most preferably, an array of longitudinal and transverse metal bars is used, particularly with a height essentially identical to the depth of the collector housing. It is usually sufficient to provide longitudinal or transverse bars, particularly metal bars, having a width of about 1 to 10 mm. Thus, the dimensions of the elements of the retaining structure, in particular the perimeter frame and the spacers, are designed in such a way that all the support areas of the retaining structure that support the transparent wall tightly rest within a single plane . In this way, the forces applied to the transparent wall are distributed very uniformly. Preferably, at least one protective plate is used, in particular a low emissivity protective plate, which is adapted to be interposed between the absorber and the lower part attached to the retaining structure. With these protective plates the thermal losses can be reduced more, mainly thanks to the reduction of the radiation exchange of the absorber with the metallic part of the collector. Regularly, the distance between the bottom of the housing and the transparent flat wall is approximately 1 to 10 cm. Suitably, the distance between the bottom part when attached to the retaining structure and the front transparent flat wall is in the range of approximately 2 to 6 cm. Moreover, the thickness of the front glass sheet is usually in the range of about 1 to 10 mm. The thickness of the front glass sheet depends mainly on the size of the surface of the glass sheet and the distance between the separators. According to a preferred embodiment at least the retaining structure, in particular at least part of the inner wall of the retaining structure, at least one spacer and / or the lower part, in particular the inner wall of the lower part, they are made of copper, steel or aluminum and / or are coated with a low infrared absorption film, in particular comprising copper and / or aluminum to reduce radiation losses of the absorber. Provisions are made that the material used for the retaining structure, and / or the bottom part is adapted to be resistant to corrosion, in particular on the exterior of the flat panel solar collector. In another embodiment of the present invention there is provided a flat panel solar collector further comprising at least one concentrated degasser and / or at least partially a degassing liner, in particular having an average thickness of less than 1000 nm, on at least part of the absorber and / or the retaining structure. It is preferred to resort to degassing technology. to provide the flat panel solar collector of the invention with an integrated pump. By using this integrated pump it is possible to maintain pressures of less than 10 ~ 4 Torr which are normally necessary to reduce the losses of molecular conduction to a significant degree. In a preferred embodiment a non-evaporable thin film degassing coating is applied, in particular on the rear side of the absorber and / or on the internal surface of the housing or retaining structure. Care must be taken that the thickness of the degassing coating does not impair the emissivity of the underlying copper or aluminum alloy coating. Normally, the thickness of the degassing coating should be maintained at a few hundred nanometers, in particular on the scale of around 100 to 600 nm, and more preferably around 100 nm. The degassing coating technique is described, for example, in US 6,468,043. As a concentrated degassing pump, commercially available degasifiers can be used, such as for example the non-evaporable degasser St 707 produced by SAES Getters. Also, a flat panel solar collector is provided which further comprises between the transparent wall and the absorber at least one additional transparent wall and / or an infrared mirror coating on the inner side of the transparent wall and / or on the inner side or both sides of 'the additional transparent wall. To reduce the radiation losses to the glass-face wall, even glass sheets and / or additional infrared mirror coatings can be used. In one aspect of the invention vacuum-tight connection ports are integrated in the perimeter frame and in particular comprising at least one expansion bellows. Also, provision may be made that at least one connection port in the form of a pumping port is incorporated in the perimeter frame or side wall of the retaining structure for the initial evacuation of the collector. Cooling tubes or ducts which are disposed within the solar collector of flat panels extend through the wall of the solar collector housing of flat panels in a vacuum-tight manner. Due to the different thermal behavior of the conduits and the housing, expansion bellows may be used in the vicinity of the housing connection and the cooling pipe or conduit. The pumping port is preferably designed in such a way that after the conclusion of the evacuation process the connecting tube is closed by valve. That tube can also be detached, especially if it is made of copper. In a very preferred embodiment provisions can be made that the retaining structure, in particular the frame, comprises a side wall and, in particular perpendicular thereto, a support surface connected to the side wall which is adapted to carry, in particular the perimeter of, the transparent wall. It is particularly preferred that the solar collector frame of planar panels comprises a perimetric side wall surrounding the bottom of the housing and which is in particular aligned perpendicular to the bottom of the housing. In a preferred embodiment the support surface which is connected to the side wall is aligned parallel to the bottom of the housing at least where it is opposite to the support surface. This U-shaped profile of the edge portion of the solar collector of flat panels allows a very robust installation of the front transparent flat wall. In another embodiment of the invention it is preferred that at least one strip of soft metal be at least partially placed between the transparent flat wall and the support surface of the frame, and wherein at least a first portion of the metal tape is welded, in particular welded in soft, to the particular metallic area of the transparent flat wall and / or to the housing, in particular to the side wall and / or to the supporting surface, and / or wherein at least a second portion of the metallic tape is welded, in particular welded in soft, to the particular metallic area of the transparent flat wall and / or to the housing, in particular to the side wall and / or to the supporting surface. It has been found that a very effective seal of the flat panel solar collector of the invention can be achieved by the use of a tin-copper metallization of the transparent flat wall, in particular by metallizing the perimeter of one of the two surfaces of the transparent flat wall. A soft metal ribbon can then be welded in soft to both the housing, which is usually made of metal, and the glass wall. It is preferred to place the soft metal tape between the inner side of the glass wall and the supporting surface which is connected to the side wall of the housing, thus minimizing the vacuum dead volume and protecting the glass wall from scratches that could produced by friction against the metal structure of the support surface of the frame. Thus, provisions are made that at least a first portion of a soft metal tape is welded, in particular welded in soft, to the housing, in particular to the frame and / or the support surface of the frame, and wherein a second portion of the soft metal tape is welded, in particular welded in soft, to the transparent wall, in particular to a metallized area of the flat wall.

In another aspect of the invention provisions are made that the absorber comprises at least one copper plate, in particular an OFE and / or OFS copper plate, which is coated with a selective absorbent film, in particular chromium black, at less on the side that is exposed to solar radiation. Absorbers made from copper plates typically exhibit an average thickness of about 1 to 2 mm, for example, when using OFE or OFS copper plates. In general, as a selective absorber film, films that are capable of withstanding long-term heating up to about 350 to 400 ° C are preferred. The back of the absorbent plates is preferably fixed to a conduit, for example, to a cooling tube for the extraction of heat. For applications up to 150 ° C, water can normally be used as a cooling fluid, although oil or air is preferred for higher temperature applications. Likewise, flat panel solar collectors are provided in which at least one, in particular an essentially U-shaped conduit is thermally bonded to at least one absorber, in particular by welding or brazing, and wherein the conduits are arranged so as not to be in direct thermal contact with the retaining structure, in particular the perimetric frame and / or at least one spacer.

Furthermore, in one embodiment of the invention at least one external pump is provided, in particular a turbo-molecular pump station. This external pump can be used to initially set a pressure low enough so that later integrated pumping can be used, for example, based on the degassing technology. The objects of the present invention can also be solved by a solar collector in which also the rear part of the collector comprises a transparent wall. In this way, a flat panel solar collector is provided comprising at least one absorber, in particular a plate absorber, at least one conduit which is at least partially associated in thermal form with at least one absorber, a perimeter frame, in particular a metal frame, a transparent front wall and a transparent rear wall wherein, in particular the perimeter of the front transparent wall and the upper side of the frame and, in particular the perimeter of the rear transparent wall and the lower side of the Each frame has a perimetral area that overlaps, wherein at least a part of the area overlapping the side of the front transparent flat wall faces the upper side, in particular a supporting surface, of the frame and at least part of the area that overlaps the side of the rear transparent wall facing the rear side, in particular a supporting surface of the frame, are coated each with at least one first metallic layer, in particular they are metallized with a copper layer scattered by plasma, and wherein each first metallic layer is protected with at least one second metallic layer, in particular a tin covering layer, and in where in particular the perimeter of the front transparent wall and the frame and in particular the perimeter of the rear transparent wall and the frame are fixed together each by the use of a first and second soft metal ribbons in particular perimeter, in particular a ribbon metal lead and / or copper, the first metallic strip being adapted to be welded in soft, in particular by means of at least a first portion, to the metallized area of the front transparent flat wall and by means of at least a second portion, in particular on its opposite side, to the frame, in particular through defined welding portions, and where, in particular the perimeter of the wall transforms The rear spacer and the frame are fixed together by the use of a second, particularly perimeter, soft metal tape, in particular a metallic lead and / or copper tape, which is adapted to be welded in soft, in particular by means of at least a first portion, to the metallized area of the rear transparent flat wall and by means of at least one second portion, in particular on its opposite side, to the frame, in particular through defined welding portions. The first and second soft metal ribbons are preferably aligned at least partially parallel to the retaining structure. Special benefits can be achieved by a flat panel solar collector system in which combined use is made of a flat panel solar collector of the present invention and a mirror that is suitable to reflect sunlight on the rear transparent flat wall, allowing thus increase the incident solar flux on the absorber more effectively. Thus, a flat panel solar collector system comprising at least one flat panel solar collector according to one of the preceding claims and at least one mirror, in particular an essentially cylindrical mirror, is provided, the mirror being adapted to reflect light on at least one transparent wall of the flat panel solar collector. In a preferred embodiment, the solar collector of flat panels can be placed on the half-cylindrical mirror, in particular in such a way that even the diffuse component of sunlight entering the mirror can be almost completely reflected on the rear part of the collector solar flat panels. In another embodiment of the invention, for example, if a half-cylindrical mirror is used, the solar collector is aligned essentially along the axis of the half-cylindrical mirror.

Furthermore, it is proposed here that the cross section of the mirror exhibits the shape of a circular arc or a part thereof, in particular being smaller than a semicircle. According to another embodiment of the invention, there is provided a system of flat panel solar collectors in which the solar collector is located on two adjacent half-cylindrical mirrors, or mirrors whose cross-section exhibits the shape of a circular arc. By placing the mirrors adjacent to each other, both will reflect sunlight entering the mirrors on the rear portions of the collector. When a flat panel solar collector is used for the front and rear walls of which are transparent, it is preferred to blacken the front and rear sides of the absorber with a selective absorbent film, in particular with chromium black or any other coating capable of withstanding heating. long term up to approximately 350 to 400 ° C. The degassing of the surface can be greatly reduced if the complete flat panel solar collector of the invention is heated preferably to around or more than 150 ° C, in particular for a few hours, while this collector is evacuated with a pumping station external Accordingly, the flat panel solar collectors of the present invention are preferably made in accordance with the following steps: a) providing at least one retaining structure, in particular at least one perimeter frame and / or at least one spacer, at less an absorber, in particular a plate absorber, at least one conduit, at least one first transparent wall, at least one lower part and / or at least one second transparent wall, wherein in particular the perimeter of the first and / or or second transparent wall comprises at least partially a metallic coating, in particular comprising a first metallic layer, in particular a copper layer spread with plasma, and a second metallic layer, in particular a tin covering layer, b) adjusting the spacers in the perimeter frame, c) adjusting at least one duct that is thermally associated with an absorber, in particular by welding or brazing, on the l or less a separator, in particular by at least one snap-fit element, and in connection ports in the perimeter frame, d) welding the ends of the conduit to the connection ports, e) adjusting the first transparent wall on the cladding metal from which a soft metal tape has been welded in soft on the retaining structure, f) welding the soft metal tape to the retaining structure, thereby aligning in particular by at least part of the soft metal tape essentially parallel to the holding structure, g) evacuate the solar panel, in particular by means of a pumping port, by using at least one external pump, h) heating the solar collector of flat panels from about 120 ° C to about 170 ° C, in particular up to about 150 ° C for a period of time, in particular for at least 30 minutes, sufficient to provide sufficient degassing of the collector, i) ca to flatten the flat panel solar collector, in particular those parts of the flat panel solar collector comprising a concentrated degasser and / or a degassing liner, at temperatures above 170 ° C, in particular up to about 180 ° C or more, to activate the degasser, and j) to isolate the solar collector from flat panels, in particular when closing a valve or to dismantle the connection of conduits in the pumping port. As part of this method or separately the degassing pump or the degassing coating can be thermally activated before closing the pumping port by keeping the panel at an elevated temperature for a sufficient period of time. For example, if a TiZrV coating is used as a degassing material, heating is preferably continued to about 180 to 200 ° C for about two hours. By this method a pressure of less than 10 ~ 8 Torr can be obtained. The flat panel solar collector of the invention is then isolated, for example by a valve or preferably by dismantling the connecting tube. If the retaining structure and the lower part are not already aligned together, the step of adjusting the lower part to the retaining structure, in particular to its frame, in a vacuum-tight manner, can be incorporated in the manufacturing process. In case both sides of the retaining structure are provided with a transparent wall instead of adjusting a lower part of the retaining structure, the next stage has to be incorporated in the manufacturing process: adjusting the second transparent wall on the covering metal from which a soft metal tape has been welded in soft on the retaining structure, and weld the soft metal tape to the retaining structure. The invention is then based on the surprising perception that a flat panel solar collector can be obtained with which very low pressures are accessible, thus providing a highly sufficient glass to peripheral metal seal. The flat panel solar collector of the invention is then well suited to withstand the thermal constraints resulting from the differential expansion of different solar collector materials without damaging the seal. These flat panel solar collectors can therefore be used for very long periods without the need to evacuate the housing by the use of an external pumping station. Also, the flat panel solar collectors of the invention can be used under various climatic conditions and for a multitude of different applications. Likewise, the full temperature range of about 30 ° C to about 300 ° C and still higher can be covered. With the flat panel solar collectors of the present invention, even those which are being exposed to solar radiation from one side only, equilibrium temperatures of about 350 ° C and more have been obtained. Apart from the domestic heating that can already be achieved by the non-evacuated collectors, the solar collectors of the present invention can also be used for the generation of electrical energy, for example, by means of collector fields, for cooling and air conditioning. Moreover, the flat panel solar collectors of the invention can be used for the generation of hydrogen from water, the desalination of seawater and the generation of hot oil for commercial or residential kitchens. Likewise, the maintenance of these solar collectors is quite easy and the time that is required for maintenance work is reduced. Another advantage of the present invention is that a solar collector is described which can be assembled very easily and which, therefore, allows an economical mass production. It is also of great advantage that a very reliable glass-to-glass seal is provided. Since very large transparent panels can also be used, a wide variety of technical applications are accessible with the flat panel solar collector of the present invention. Further features and advantages of the invention can be derived from the following description, in which the preferred embodiments of the invention are explained in detail by way of an example based on schematic drawings. The figure illustrates a schematic top view of a flat solar panel structure according to the invention. Figure Ib illustrates an exploded perspective view of a flat panel solar collector according to the invention. The figure illustrates another exploded perspective view of the flat panel solar collector according to the invention.

Figure 1d illustrates a schematic sectional view of the side portion of the solar collector of flat panels according to FIG. Figure 2 illustrates a schematic cross-sectional view of a peripheral seal configuration of a flat panel solar collector according to the invention. Figure 3 illustrates a schematic cross-sectional view of a peripheral seal configuration of a flat panel solar collector according to the invention. Figure 4 illustrates a schematic cross-sectional view of a peripheral seal configuration of a flat panel solar collector according to the invention. Figure 5 illustrates a schematic cross-sectional view of a peripheral seal configuration of a flat panel solar collector according to the invention. Figure 6 shows a cross-sectional view of a peripheral seal configuration of a flat panel solar collector of the invention also comprising a cooling tube. Figure 7 shows a schematic cross-sectional view of a peripheral seal configuration of a flat panel solar collector of the invention which also comprises a lateral connection for evacuation. Figure 8 shows another embodiment of a flat panel solar collector of the invention.

Figure 9 shows another embodiment of a flat panel solar collector of the invention and Figure 10 shows another embodiment of a flat panel solar collector system of the invention. In the figure is shown a solar collector of flat panels 1 having a rectangular shape and comprising a housing 2 in the form of a metal box and an upper transparent flat wall 4. The housing 2 comprises a substantially flat lower part 6 and a perimetric side frame 8. The upper transparent flat wall 4 is placed along its perimeter on the frame 8. Longitudinal and transverse metal bars 10 and 12 are used as spacers to support the transparent flat wall 4. The low pressure inside the flat panel solar collector 1 can be accumulated by means of the connection port 14 which exhibits a lateral connection by means of the frame 8 to the interior of the housing 2. Conduits or cooling tubes 16 and 18 are placed inside the housing, preferably between the lower part 6 and absorbent plates 20 (shown in dotted lines to thereby reveal the underlying cooling pipe system). The surface of the absorber 20 that is subject to sunlight is preferably coated with a black film. In addition, the cooling tubes 16 and 18 are thermally connected to the rear part of the absorber plate 20. The flat panel solar collector 1 according to the figure further comprises a concentrated degassing pump (not shown), for example, adjacent to frame 8, with which very low pressures can be obtained and also maintained for very long periods. It has been found to be suitable to provide cooling tubes 16 and 18 having expansion bellows 24 and 26 outside the housing 2 to thereby handle the differential thermal expansion. Figure Ib shows a solar collector of flat panels 1 with its individual components separated artificially from their integrated positions. The retaining structure 2 has a rectangular shape with a perimeter frame 8 and a longitudinal and transverse spacer metal bar 10 and 12, respectively, forming a cross-type configuration. The height of these spacer bars and the perimetric frame is adjusted in such a way that a cooling tube 16, 18 and absorber plates 20 can be received inside the solar collector housing of flat panels 1, when the transparent flat wall is placed on them . The individual absorber plates 20 are dimensioned in such a way that they fit in the compartments generated by the separator bars and the perimetric frame 8. The cooling tube 1618 is attached to the individual absorber plates, for example having a U-shape, then making contact with all four absorber plates 20. Very conveniently, the spacer bars 10 and 12 are provided with respective cuts, for example in form of fasteners, so as to receive and fix the cooling tube 16, 18. Care must be taken that there is essentially no thermal contact between the cooling tube 16, 18 and the separator bars 10 and 12. This can be achieved for example by using fasteners or other distant pieces. The end portions of the cooling tube 16, 18 inside the retaining structure 2 are joined at the connection ports 17 and 19, respectively, which are integrated into the perimeter frame 8. From the figure you can derive an exploded view of the flat panel solar collector according to figure Ib seen from below. As shown in the figure, the cooling tube 16, 18 is attached to the entire lower part of each individual absorber plate 20 to ensure a maximum transfer of thermal energy from the absorber plate 20 to the fluid transferred in the cooling tube. In an alternative embodiment, not only the cover plate of the flat panel solar collector can be provided with a transparent flat wall 4, but also its rear part, thus replacing the lower part 6 of the housing with another transparent flat wall. In this embodiment, the absorbent plates 20 'are blackened on both sides. Alternatively, another set of absorbent plates 20 is placed between the second transparent flat wall and the cooling tube 16, 18. In this embodiment the cooling tube 16, 18 is sandwiched between two sets of absorber plates and is then thermally associated on opposite sides of their tubes with the opposite absorbing plates. However, it is also possible to provide the second set of absorber plates with a separate cooling tube system, so that at least two separate cooling tubes are disposed between the first and second sets of absorber plates. In Figure 1 a section of the solar collector of flat panels 1 according to Figure Ib can be seen in an enlarged form. The connection ports 17 and 19 receiving the end portions of the cooling tube 16, 18 are each provided with expansion bellows 24 and 26 to thereby handle a thermally induced dimension change. The pumping port is shown after being closed and destacked to thereby ensure a highly vacuum-tight housing of the solar collector of flat panels 1. Figures 2 to 5 illustrate different sealing modes that can be used to connect the upper transparent flat wall 4 to a housing 2. In figure 2 a cross-sectional view of the edge portion of the solar collector of flat panels 1 of the invention is shown in a schematic manner. The frame 8 comprises a side wall segment 28 which is essentially perpendicular to the lower part 6, and on the outer edge of the side wall 28 is provided a support surface 30 which preferably extends parallel to the lower part 6, being thus oriented essentially perpendicular to the side wall 28. The sealing of the flat panel solar collector 1 is achieved according to the embodiment of figure 2 by arranging a soft metallic ribbon 32 between the perimeter of the flat wall 4 and the surface 30. In this embodiment, at least the lower surface of the flat wall 4 is coated by means of tin-copper metallization along its perimeter, preferably where the portions of the soft metal tape to be welded are placed. in soft form to the flat wall 4. In the present example, the soft metal ribbon 32 has a first portion 34 that is welded in soft to the upper support surface 30., which is usually made of metal, as is the entire accommodation 2. Moreover, the soft metallic ribbon 32 is fixed to the transparent wall 4 by means of a second portion welded in soft 36, in this way achieving a very hermetic seal which is also very suitable to minimize the dead volume to the vacuum. Since there is no direct contact between the transparent wall 4 and the frame 8, the transparent wall is protected from scratches that could be produced by friction against the metal structure of the frame. As a common feature of a preferred bonding mode between the glass plate and the metal retaining structure, the soft metal tape is at least partially placed substantially parallel to the metal retaining structure, for example, the frame. Similarly, Fig. 5 provides an alternative sealing mode for a flat panel solar collector of the invention which also avoids a direct contact between the flat wall 4 and the supporting surface 30. Unlike Fig. 1, the tape soft metal 32 is welded in soft with a first portion 34 to the support surface 30, preferably located at one end of the soft metal ribbon 32, and to the upper transparent flat wall 4 by means of a second portion welded in soft 36, which is fixed to the metallized front perimeter of the flat wall 4. Alternatively, an airtight seal can also be obtained by the use of a soft metal tape 32 which is joined to the side wall 28 by means of a first portion welded in soft 34 and to the upper surface on the perimeter of the transparent flat wall 4 by means of a second soft welded portion 36. The soft metallic ribbon 32 then seals the union of the pair. ed flat 4 and the support surface 30, figure 3. Another sealing mode can be derived from figure 4, according to which the soft metal tape 32 is joined to the side wall 28 by means of a first portion welded in soft 34 and to the lower surface of the transparent flat wall 4 by means of a second welded portion in soft 36. In this case, the lower surface of the transparent flat wall 4 is covered with a metallic layer as described above along its perimeter. Unlike the embodiments shown in Figures 2, 3 and 5, the flat panel solar collector 1 of Figure 4 uses a transparent flat wall 4 which is slightly larger in size than the housing 2, thus extending over the side wall 28 along its perimeter. In Figure 6 schematically illustrates the connection of the cooling tube 38. Expansion bellows 40, which are connected to an opening in the side frame 8 on one side and, for example, to thermal insulation on the other, are used to handle the differential thermal expansion of different materials used within the solar collector of flat panels 1. Also, as can be seen in figure 7, a lateral connection 42 can be provided as a connection means for an external pumping station. The connection port 44 can be provided, for example, with a valve for sealing the solar collector of flat panels 1. Preferably, the lateral connection is offset to provide a suitable seal. From Figure 8 a solar collector 1 'of alternative flat panels 1' can be derived comprising an upper transparent flat wall 46, a lower transparent flat wall 48 and a peripheral circumferential wall or frame 50 which is preferably made of metal. Most preferably, the frame 50 is provided with a side wall 68 and with peripheral support surfaces 70 and 72 on its upper and lower parts in which the upper and lower transparent flat walls 46 and 48 can be placed, respectively. As with the flat panel solar collector 1, also the flat panel solar collector 1 'can be provided with metal bars 52 which function as spacers and which support both upper and lower flat walls 48 and 46. Again, an airtight connection between the upper flat wall 46 and the surface 70, and between the lower flat wall 48 and the support surface 72 can be achieved by means of individual soft metal tapes 74 and 76, respectively, each comprising welded portions at soft 78, 80 and 82, 84. At least the portions of the flat walls 46, 48 which are softly welded into the soft metal strips have been metallized, in particular by a double metal layer system, for example, a layer double tin / copper. It is also possible to use a single soft metal ribbon that extends from the upper support surface along the side wall to the lower support surface (not shown). In a preferred embodiment of the invention, the flat panel solar collector 1 'is used in combination with a half-cylindrical or duct-type mirror 54, thus offering a solar collector system of flat panels 56-. In one embodiment shown in Figure 9, the flat panel solar collector 1 'is located along the axis of a half-cylindrical mirror 54 that covers essentially one half of the mirror opening. The sunlight can then enter the portion of the half cylinder that is not covered by the solar collector 1 ', and can then be reflected on the rear part of the collector. In this way, the solar flux incident on the absorber can be increased more effectively. Preferably, the absorber is coated with a black surface on its upper part as well as on its rear part. The concept below the solar collector system of flat panels 56 can also be exploited with an arrangement as shown in Fig. 10. The flat panel solar collector system 56 'of Fig. 10 makes use of two adjacent half-cylindrical mirrors which they are attached or fixed or at least are in close proximity in respective edge portions, thus essentially having a W-shape. On this junction of both half-cylindrical mirrors 58, 60 the solar collector of flat panels 1 'is placed, covering thus a portion of the half-cylindrical mirror 58 as well as a portion of the half-cylindrical mirror 60. The sunlight can then enter both half-cylindrical mirrors 58, 60 by means of the portions that are not covered by the solar collector of flat panels 1 '. . Although the invention is illustrated and described in detail in the figures and the foregoing description, it should be considered as illustrative and not restrictive, it being understood that only the preferred embodiment has been shown and described, and that it is changes and modifications that come within the scope of the invention are protected. Reference list 1, 1 'flat panel solar collector 2 retaining structure 4 transparent flat wall 6 housing bottom 8 housing side frame 10 metal longitudinal separator bar 12 metal transverse separator bar 14 pumping port 16 cooling tube 17 port connection 18 cooling tube 19 connection port 20 absorber plate 24 expansion bellows 26 expansion bellows 28 frame side wall segment 8 30 support surface 32 soft metal belt 34 first welded portion in soft 36 second portion welded in soft 38 cooling tube 40 expansion bellows 42 side connection 44 connection port 46 flat top transparent wall 48 flat bottom transparent wall 50 perimeter frame 52 metal stripper bar 54 half cylindrical mirror 56, 56 'flat panel solar collector system 58 half cylindrical mirror 60 half cylindrical mirror 68 side wall 70 support surface 72 support surface 74 soft metal band 76 soft metal band 78 soft welded portion 80 soft welded portion 82 soft welded portion 84 soft welded portion that in relation to this date, the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (26)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A flat-panel solar collector that is adapted to be evacuatable and vacuum-tight, characterized in that it comprises at least one absorber, in particular an absorber of plate, at least one duct that is at least partially thermally associated with at least one absorber, a retaining structure, in particular made of metal, comprising a perimeter frame, and at least one first transparent, in particular flat, wall in particularly a glass sheet, wherein, in particular, the perimeter of the first transparent wall and the retaining structure, in particular a first support surface of the frame, have an overlapping area, in particular perimeter, wherein at least one side of the first transparent wall comprises at least partially, in particular on at least part of the overlapping area and / or the perimeter of the side of the first transparent wall, a metal coating, comprising in particular a first layer of metal, in particular a layer of copper spread with plasma, and a second layer of metal, in particular a cover layer of tin, thus creating at least one. metallic area on the transparent wall, the flat panel solar collector further comprises in particular a first soft metal tape, in particular a lead and / or copper tape, which is adapted to seal the junction between the first transparent wall and the retaining structure, and which is adapted to be welded, in particular welded in soft, to the retaining structure, in particular to the perimeter frame, and to the metallized area of the first transparent wall.
2. 2. The flat panel solar collector according to claim 1, characterized in that it also comprises a lower part joined to the retaining structure, thus forming a housing that is adapted to be vacuum-tight.
3. 3. The solar collector of flat panels according to claim 1, characterized in that it also comprises at least one second transparent wall, particularly flat, in particular a glass sheet, separated from the first transparent wall by the retaining structure, where in particular the perimeter of the second transparent wall and in particular the second supporting surface of the frame have an overlapping area, particularly perimetral, in which at least one side of the second transparent wall comprises at least partially, in particular over at least less part of the overlapping area and / or the perimeter of the side of the second transparent wall, a metallic coating, in particular comprising a first layer of metal, in particular a layer of copper spread by plasma, and a second layer of metal , in particular a tin covering layer, thus providing at least one metallized area on the second wall of the wall. spacer; and in particular a second soft metal tape which is in particular a lead and / or copper tape, which is adapted to seal the junction between the second transparent wall and the retaining structure, in particular the frame, and which is adapted to be welded, in particular welded in soft, to the retaining structure, in particular to the perimeter frame, and to the metallized area of the second flat transparent wall.
4. The flat panel solar collector according to one of the preceding claims, further characterized in that at least one soft metal strip is aligned at least partially substantially parallel to the metal retaining structure.
5. The flat panel solar collector according to one of the preceding claims, characterized in that the perimeter of the transparent wall and the frame and / or the lower part of the retaining structure are fixed together by the use of a soft metal tape, which is adapted to be welded in soft by means of at least a first portion welded in soft to the retaining structure, in particular to the merco and / or lower part of the retaining structure, and / or by means of at least a second portion welded in soft to the transparent wall, in particular to the metallized area of the transparent wall.
6. 6. The flat panel solar collector according to one of the preceding claims, characterized in that the retaining structure further comprises at least one spacer, particularly in the form of a spacer arrangement, in particular metal rods.
7. The flat panel solar collector according to one of the preceding claims, characterized in that it further comprises at least one protective plate, in particular a low emissivity protective plate, which is adapted to be interposed between the absorber and the lower part attached to the retention structure.
8. The flat panel solar collector according to one of the preceding claims, characterized in that the distance between the lower part when it is connected to the retaining structure or between the second transparent wall and the first transparent wall is about 1. to 10 cm.
9. 9. The flat panel solar collector according to one of the preceding claims, characterized in that at least one retaining structure, in particular at least part of the inner wall of the retaining structure, at least one spacer and / or part The lower part, in particular the inner wall of the lower part, are made of copper, steel or aluminum and / or are coated with a film of low infrared absorption, in particular comprising copper and / or aluminum.
10. The flat panel solar collector according to one of the preceding claims, characterized in that the material used for the retaining structure and / or the lower part is adapted to be resistant to corrosion, in particular on the outside of the solar collector of flat panels.
11. The flat panel solar collector according to one of the preceding claims, characterized in that it further comprises at least one concentrated degasser and / or at least partially a degassing coating, in particular having an average thickness of less than 1000 nm, on at least part of the absorber and / or the retaining structure.
12. The flat panel solar collector according to one of the preceding claims, characterized in that it further comprises between the transparent wall and the absorber, at least one additional transparent wall and / or an infrared mirror coating on the inner side of the wall transparent and / or on the inner side or on both sides of the additional transparent wall.
13. 13. The flat panel solar collector according to one of the preceding claims, characterized in that the conduits comprise vacuum-tight connection ports which are integrated in the perimeter frame and in particular comprising at least one expansion bellows.
14. The flat panel solar collector according to one of the preceding claims, characterized in that it further comprises at least one connection port in the form of a pumping port which is incorporated in the perimetric frame or side wall of the retaining structure and / or at least one pump that is adapted to be connectable to the pumping port.
15. The flat panel solar collector according to one of the preceding claims, characterized in that the retaining structure, in particular the frame, comprises a side wall and, in particular perpendicular to it, a supporting surface connected to the side wall which is adapted to carry, in particular the perimeter of, the transparent wall.
16. 16. The flat panel solar collector according to one of the preceding claims, characterized in that at least a first portion of a soft metal strip is welded, in particular welded in soft, to the housing, in particular to the frame and / or the surface of support of the frame, and wherein a second portion of the soft metal tape is soldered, in particular it is welded in soft, to the transparent wall, in particular to a metallized area of the flat wall.
17. 17. The flat panel solar collector according to one of the preceding claims, characterized in that the absorber comprises at least one copper plate, in particular a copper plate .OFE and / or OFS, which is coated with an absorbent film. selective, in particular chromium black, at least on the side that is exposed to solar radiation.
18. 18. The flat panel solar collector according to one of the preceding claims, characterized in that at least one duct, in particular essentially U-shaped, is thermally bonded to at least one absorber, in particular by welding or brazing, and / or wherein the conduits are arranged so as not to be in direct thermal contact with the retaining structure, in particular the perimeter frame and / or at least one spacer.
19. 19. A system of flat panel solar collectors characterized in that it comprises at least one solar collector with flat panels according to one of the preceding claims and at least one mirror, in particular an essentially cylindrical mirror, the mirror being adapted to reflect light on at least one transparent wall of the flat panel solar collector.
20. 20. The flat panel solar collector system according to claim 19, characterized in that the solar collector is aligned substantially along the axis of a half-cylindrical mirror.
21. 21. The flat panel solar collector system according to claim 19 or 20, characterized in that the cross section of the mirror exhibits the shape of a circular arc or a part thereof, in particular being smaller than a semicircle.
22. 22. The flat panel solar collector system according to one of claims 19 to 21, characterized in that the solar collector is located on two adjacent half-cylindrical mirrors, or mirrors whose cross section is in the form of a circular arc or a part of it.
23. 23. A solar collector arrangement characterized in that it comprises at least two flat panel solar collectors according to one of claims 1 to 18 and / or flat panel solar collector systems according to one of claims 19 to 22.
24. 24 A method for the preparation of the flat panel solar collector according to one of claims 1 to 18, characterized in that it comprises a) providing at least one holding structure, in particular at least one perimeter frame and / or at least one spacer, at least one absorber, in particular a plate absorber, at least one conduit, at least one first transparent wall, at least one lower part and / or minus a second transparent wall, wherein in particular the perimeter of the first and / or second transparent wall comprises at least partially a metallic coating, in particular comprising a first metallic layer, in particular a copper layer spread with plasma, and a second metallic layer, in particular a tin covering layer, b) adjusting the spacers in the perimeter frame, c) adjusting at least one conduit that is thermally associated with an absorber, in particular by welding or brazing, on at least one spacer, in particular by at least one snap-fit element, and in connection ports in the perimeter frame, d) welding the ends of the conduit to the connection ports, e) adjusting the first transparent wall on the metal cladding from which a soft metal strip has been welded in soft on the retaining structure, f) welding the soft metal strip to the retaining structure, thereby aligning in particular at least part of the soft metal strip essentially parallel to the retaining structure, g) evacuate the solar panel, in particular by means of a pumping port, by using at least one external pump, h) heating the solar panel collector flat from about 120 ° C to about 170 ° C, in particular up to about 150 ° C for a period of time, in particular for at least 30 minutes, sufficient to provide sufficient degassing of the collector, i) heating the solar collector of flat panels, in particular those parts of the solar collector of flat panels comprising a concentrated degasser and / or a degassing liner, to temper atures above 170 ° C, in particular up to about 180 ° C or more, to activate the degasser, and j) isolating the solar collector from flat panels, in particular when closing a valve or when undoing the connection of conduits in the pumping port.
25. 25. The method according to claim 24, characterized in that it further comprises the step of adjusting the lower part to the retaining structure, in particular to its frame, in a vacuum-tight manner.
26. 26. The method according to claim 24, characterized in that it further comprises the step of adjusting the second transparent wall on the metal cladding from which a soft metal strip has been softly welded onto the retaining structure, and welding the soft metal strip to the retention structure.