FLAT PLATE SOLAR COLLECTOR

Abstract: A flat plate solar collector unit comprises a bottom plate (5), a frame (1-4) enclosing an absorber placed above the bottom plate and provided with ducts for a flowing heat transport medium, and a cover (17) placed above the absorber of a material transparent to solar radiation. The frame comprises prefabricated frame members (1-4) joined with mechanical devices. The bottom plate (5) is placed in the frame (1-4) and is made of a composite material, Composed of preferably cellular plastic covered with sealing aluminum foil. A solar collector comprises several such adjacent collector units and the frame of adjacent units have a frame member common. A method of producing a solar collector as described above is that prefabricated frame members (1-4) are assembled, preferably on the site, with mechanical devices, to a rigid frame. The bottom plate (5) is then positioned in the frame, and the absorber is placed in the frame above the bottom plate and one of its headers is fixed in few points to the adjacent transverse frame member by fastening means. The cover material (17) is fixed to the edges of the frame to cover and seal the unit.

Description: Flat plate solar collector The present invention relates to a solar collector unit with a flowing heat transport medium, a solar collector consisting of several such units, and a method of manufacturing them. Previously known solar collectors are generally manu¬ factured and assembled to complete units or casings industrially. It is then essential for them to possess such qualities regarding strength, rigidity and resistance as to admit transport as well as installation. Due to the fact that difficulties increase with increased size, solar collectors normally are of limited size. This fact makes it necessary to use a considerable amount of frame details, fittings etc, which draw a considerable portion of the production cost. These factors taken together have the effect that the active parts of the solar collectors normally draw only a moderate portion of the total cost. This is an explanation to the fact that solar heating plants have high installation costs and consequently unsatisfactory profitability. This drawback has been overcome by the present invention, which is a basically different collector. By an unconven¬ tional choice of materials, components and assembly tech¬ nique a quick and simple. installation is obtained, which doesn't require professional skill. By this invention production of solar collector elements and complete collector units ready for operation and with high efficiency has been made possible at considerably lower cost than has been possible so far. This is a very important step forward, as profitability is definitely improved. The characteristic elements of the invention are defined r in the patent claims after the descr iption . Examples of embodiments of the invention will be explained in the ensuing description with reference to the accompanying drawings. Fig 1 is a cross-sectional view ( i.e. parallel to the eaves ) comprising among other things frame construction, insulating bottom, support and cover material. Fig 2 is the corresponding longitudinal sectional -view (perpendicular to the eaves at normal erection on a roof of a house) . Fig 3-4 show alternative embodiments of mechanical fastening device for frame structure. Fig 4 also is an embodiment of fastening of an absorber. Fig 5 is a perspective view of an embodiment of support for free hanging of cover, and its fitting in the frame. Fig 6 is a longitudinal sectional view of alternative embodiment of support for cover material. Fig 7 is a cross-sectional view of support according to fig 6. Fig 8 is a cross-sectional view of embodiment of support for cover material according to a second alternative. Fig 9 is a top plan view of collector elements connected to each other, with an embodiment of parallel connection of absorbers of the exemolified embodiment. The figures show the frame of the solar collector, composed of prefabricated frame members (1,2,3,4) of preferably wood, suitably pressure impregnated or otherwise rot-resistant treated, disposed in such a way that the solar collector out of a supplied prefabricated kit may be easily assembled preferably on the erection site. By this procedure each collector unit need not itself form a complete casing, b t does so together with adjacent units, as will be discussed in more detail subsequently. Upper and lower frame members are made in full length along the solar collector comprising two or more collector units, which also simplifies and cheapens the construction. The solar collector is assembled to units by putting its frame members together, preferably by using 'mechanical assembly devices, such as at least one furniture fitting (12) or one assembling bolt (33) per joint. Furthermore these joints are preferably provided with guiding details e.g. guiding pegs and drill holes (13) or tenons and grooves (14) to improve the measure accuracy of the solar collector units and facilitate the assemblage. The side'frame members of the solar collector are provided with laths (6,7) whose edge sides also serve as support for the long, sides of the bottom plate as below. These laths admit rainwater etc. coming in under the roofing to pass freely under the solar collector without affecting it. Similarly condensation moisture is enabled to air out. The laths are also used for fixing the solar collector to the bedding, either this is an even roof like matched board, plywood or the like, or it is a transverse tile strip constuction, or other bedding of framework. Due to the fact that the bottom plate has high strength it may be completely self-supporting within each unit. If necessary it can be supported by extra bed laths for instance performed and installed like (8) in figure 1. In order to support pipings and sheet metal details etc. if any, and simultaneously facilitate ventilation and waste water passage, the ends of the laths (9,10) protrude preferably outside the upper and/or lower member. The bottom plate of the solar collector consists solely of a special composite material in form of a plate (5) simultanously performing three functions i.e. mechanical bottom, diffusion barrier and insulation. It is composed of rnr-turn a sealing layer against diffusion preferably aluminium foil, an insulating layer preferably cellular plastic, such as polyurethane or polyisocyanurate foam and furthermore one sealing layer preferably of aluminium foil These bottom plates are already at prefabrication given the exact size and are at installation positioned in respective solar collector unit, abutting to all sides of the frame. In doing so they are supported along the edges of their long sides by the laths (6,7) which are joined to the outer long sides respective the partition member of the frame. The bottom plates are preferably positioned in the solar collector unit without any special fixing. In accordance with an alternative embodiment a run of jointing sealing compound (25) e.g. silicone gum keeps the bottom plate (5) in its position and makes a seal between the frame members (1,2,3,4) and the bottom plate. The solar collector contains an absorber furnished with ducts (35) for a flowing heat transport medium. The absorber can be made of sheet materials usually of metals like copper or aluminium, possibly with a surface treatment giving properties suitable for this purpose. A selective absorber coating, such as black nickel or black chrome, gives such properties, as the material has a high absorption of wavelengths within the solar radiation, and a low emissivity of longer wavelengths, i.e. heat radiation The absorber units of the solar collector (29) are usual connected parallel by connecting the two preferably horizontally placed header pipes (22 and 21) for inlet respective outlet of the heat transport medium in such a 5 way that it runs along the whole of the upper and lower frame members of the solar collectors (3,4) and through the partition member of the frame (1,2). These frame members therefore have 'holes or slots in their upper an lower ends (30) to make it possible.to join the headers o , 0 the absorber units to each other.- At installation the absorber units (29) are positioned in the solar collector frame from above and the ends of t headers are put into their holes or slots in the longitudinal frame members. In order to join the header 5 pipes, connection fittings or connection hoses ( 34 ) are fitted. To obtain a simple installation and avoid tensions in the absorber caused by temperature movements, the absorber is fixed in the collector units solely in one point along 0 its longitude - preferably at its upper header or corresponding. This is preferably arranged by attaching a pendulum (23) and a pipe clip alternatively a clamp or correspondingly to the upper frame member (3). The heat transport medium is made to circulate by a drivin pump and by a temperature sensitive control to carry the collected heat away. In some cases self-circulation may be sufficient. In order to obtain favourable circulation conditions with as uniform flow of the heat transport medium as possible, the total absorber area is connected preferably diagonally. The inlet pipe (32) is connected to the bottom left and the outlet tube to the top right or arranged opposite hand. Then the inlet tube can be placed. preferably inside the collector in the lower part parallel to the lower header pipe. Special holes or slots (31) are made for this purpose in the partition frame members (2) . This admits the two pipes to be installed at the same side of the collector, and a more favourable installation is obtained. The inlet pipe (32) is preferably connected by a ϋ-shaped fitting (36) at the end of the lower header pipe (22), which in accordance with examples in figure 9 gives flow direction according to arrows from lower right corner to upper left. Due to the symmetrical design of the solar collector the connection points can be chosen at the installation. As support for the cover of the solar collector (1 ) tranverse profiles (11) e.g. T-shaped profiles are fitted at a suitable distance, which at the installation on the site are positioned in prefabricated slots in the sideframe and which are preferably hanging freely within each solar collector unit. According to an other embodiment of the transverse profiles these are provived with grooves or slots, wherein screws can be fitted and in that way fix the cover material to the profiles. An other alternative embodiment is shown in fig 7. Transverse profiles (15) whose lengths are equal to or shorter than the inner width of the solar collector units, are fixed on the underside of the material e.g. by riveting (16). These profiles are shown trapezium profiled, but can be designed differently. This fact makes the reinforced cover material units completely self-supporting between the frame members. A third examplary embodiment is shown in fig 8. Transverse profiles (26) whose length is equal to the inner width of the solar collector units are fixed between the side frames (1,2) by making one or several drill holes (27) in the two units at each connection point and tenons (28) are put The cover material (17) preferably consists of plastic sheets possibly with insulating ducts. When using single plastic sheets these are fixed to the longitudinal partition walls by overlappirgjoints as shown in fig 1. Then the solar collector is preferably sealed between frame and cover material, and between two layers of cover material with elastic profiles. This is preferably done by using . two continous C-shaped sealing strips (18) to seal • both sides of the upside surfaces of the frame. Preferably these strips are fixed. to the frame at prefabrication with e.g. staples or to the cover material with glue or self adhesive tape. When using plastic materials with insulating ducts as cover material, these are preferably fixed with standarized fitting details. When using one-layer plastic material, preferably sheets of fiber-glass armed polyester in UV-stabilized quality, these are attached to the frame construction of the solar collector with laths (19) placed at least partly over the frame members and are fixed preferably with screws (20) with packings. * B RH4^

Claims: Claims 1. Flat plate solar collector unit, comprising a bottom plate (5), a frame (1-4) enclosing an absorber fitted above the bottom plate and provided with ducts for a flowing heat transport medium, and a cover (17) placed above the absorber and made of a material transparent to solar radiation characterized in that the frame comprises prefabricated members (1-4) joined by mechanical means, and that the. bottom plate (5) is positioned in the frame (1-4) and is made of a composite material, preferably consisting of cellular plastic, such a polyurethane or polyisocyanurate foam, covered with sealing aluminium foil. 2. Solar collector unit in accordance with claim 1, characterized in that the bottom plate (5) is positioned loosely in the frame (1-4) and is supported at least partly along its long side by laths (6,7) joined with the long sides of the frame (1,2). 3. Solar collector unit in accordance with claim 1, characterized in that the bottom plate (5) is supported along its long sides by laths (6,7) joined with the long sides of the fra'me (1,2) and fixed to the frame and sealed to the enclosing frame members with sealant. 4. Solar collector unit in accordance with any of the claims 1-3, characterized in that the prefabricated members (1-4) are joined in their joining points between transverse (3,4) and longitudinal (1,2) members to a mechanical unit with mechanical means such as furniture fittings (12) or assembling bolts (33). 5. Solar collector unit in accordance with claim 4 characterized in that"in the joining points of the frame members (1-4) at least one guiding peg and one hole (1__3_ or one guiding tenon and one groove are arranged. 6. Solar collector unit in accordance with any of the oreceding claims, characterized in that at least one transverse profile (11) running between the longitudinal members of the frame and at least partly inserted in corresponding slots in these, is arranged as supporting bed for the cover material (17). 7. Solar collector unit in accordance with any of the claims 1-5, characterized in that transverse profiles (15), whose length is shorter or equal to the inner width of the frame (1-4), and which are fixed to the transparent cover material (17), are arranged to stiffen it. 8. Solar collector unit in accordance with any of the claims 1-5, characte ized in that at least one transverse profile (26), whose length is equal to the inner distance between the frame members (1,2) , is fixed between these by arranging at least one tenon at each joining point, at which the profile serves as support bed for the cover material (17). 9. Solar collector unit in accordance with any of the preceding ' claims, characterized in that the mentioned lath (6,7) supporting the frame (1,4) and/or the bottom plate (5) fixes the solar collector unit to the bedding. 10. Solar collector unit in accordance ' with any of the above mentioned patent claims, characte ized in that the mentioned lath supporting the frame (1-4) and/or the bottom plate (5) protudes outside upper (9) respectively lower (10) frame, so that its protruding ends make one upper and/or one lower shelf. 11. Solar collector unit in accordance with any of the preceding - claims, characterized in that the absorber is fixed only in few points along its longitude by fastening to the upper frame member (3) a header pipe (23) for inlet or outlet of liquid in the absorber, running along the upper longitudinal edge of the absorber. 12. Solar collector, comprising several adjacent solar collector units in accordance with any of the claims 1-10, in which each unit. comprises one bottom plate (15) one frame (1-4) enclosing an absorber ' , arranged above the bottom plate and provided with ducts for a flowing heat transport medium, and a cover (17) fixed above the absorber and of a material transparent to solar radiation characterized in that the solar collector units are parallel connected by header pipes (21,22) for inlet and outlet of the heat carrying medium running essentially horizontally along the longitudinal frame members of the absorber and that the frames (1-4) of two adjacent solar collector units present a frame member common for the adjacent frame sides. 13. ϊάethod for manufacturing a solar collector unit, comprising a bottom plate (5), a frame (1-4) enclosing an absorber fixed above the bottom plate and provided with ducts for a flowing heat transport medium, and a cover made of a material transparent to solar radiation characterized in that prefabricated frame members (1-4) are assembled, preferably on the site with mechanical fastening means (12-14, 33), at the ends of the frame members to a rigid frame whereupon a bottom plate (5) of a composite material, preferably comprising cellular plastic covered with sealing aluminium foil, is positioned in the frame, above the bottom plate and is fixed with the header pipe (21) running along the upper longitudinal edge of the absorber, in few points to the adjacent transverse frame member (3), whereupon the cover (17) is fixed sealing the edges of the frame in order to cover the unit. 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Inventors: LINDKVIST AXEL K
Applicants: LINDKVIST AXEL K, TRIMCO K LINDKVIST
Application year: 1981
Main classification: F24J3
IPC codes: F24J2, F24J3