Patent Publication Number: US-2011048407-A1

Title: Solar Collectors

Description:
This invention relates to solar collectors and methods of constructing them. 
     Solar collectors are used to collect the energy of incident solar radiation and convert it to a form in which it can conveniently be used, transmitted and/or stored. For example, solar energy can be directly converted to electricity by photovoltaic cells; it can be used to heat water which can then be used directly, for example to bathe in; or it can be used to heat a thermal transfer fluid which can in turn be used to heat water for consumption or can be supplied to a space heating system. 
     One form of solar collector is described in patent document EP1332322A and is made up from sections of metal pipe on a longitudinal metal fin. The sections are joined together in runs between battens extending along a roof, and at the end of each run the pipe is plumbed to the pipe in the next run or to a header or manifold. Once the sections have been installed, the roof is tiled over the sections with tiles having a high transmissivity to solar radiation. In use, the pipework is filled with water or some other thermal transfer fluid which is heated by solar radiation. The thermal transfer fluid can then be drawn off as hot water or can be circulated around a heating system or to a heat exchanger and back to the solar collector. 
     Installation of the collector of EP1332322A entails a large amount of plumbing work with a consequent risk of leaks, and is laborious and therefore expensive. Also, the majority of the solar radiation is collected by the fin and needs to be conducted through the fin to the pipe and thence to the thermal transfer fluid. As a result, the efficiency of energy collection leaves room for improvement. 
     An aim of a first aspect of the present invention, or at least of specific embodiments of it, is to provide a method of construction of a solar collector which is quick and simple and results in a highly efficient solar collector. 
     In accordance with the first aspect of the invention, there is provided a method of construction of a solar collector on a support structure (such as a roof) that has a plurality of side-by-side channels (for example formed between roof battens). The method employs a length of an elongate web of flexible material that is formed with a plurality of generally parallel passageways for a thermal transfer fluid extending in the longitudinal direction of the web and spaced apart across the width of the web. The method comprises the steps of: laying a first run of the web along a fust of the channels of the support structure so that one face of the web faces out of said first channel; splitting the web longitudinally between at least one adjacent pair of the passageways adjacent and beyond the end of said first run; curving the split web so that the web enters a second of the channels of the support structure; and laying a second run of the web along the second channel so that said one face of the web faces into said second channel. This aspect of the invention alternatively extends to the cases where the channels are formed at the same time as or after the web has been laid. 
     The solar collector of the first aspect of the invention is far easier to install and less likely to leak than the collector of EP1332322A because the only plumbing work that is required is at the ends of the web, and a single web, if sufficiently long, can be used for a complete roof face. The provision of a plurality of passageways for the thermal transfer fluid along each run, rather than a single pipe as in EP1332322A, improves the efficiency of energy collection. The thickness of the battens that are typically used for solar collectors of this general type, and therefore the depth of the channels is relatively small, typically 25 mm, and therefore the space available for turning the multi-passageway web at the end of a run is restricted. However, the splitting of the web between passageways at the curve at the end of a run enables the passageways to be curved smoothly without kinking in the space available, as will be appreciated from the following detailed description. Meanwhile, the formation of the passageways as a web along the runs facilitates a neat and effective arrangement of the passageways and simplifies installation. 
     It may be remarked that patent document CA 1172532 describes a solar collector employing an elongate web of flexible material that is formed with a plurality of generally parallel passageways for a thermal transfer fluid extending in the longitudinal direction of the web and spaced apart across the width of the web. The web is laid out as a plurality of runs within a frame. At the turns between adjacent runs, the web is split longitudinally between adjacent pairs of the passageways. However, the web is laid out so that each face of the web faces in the same direction for all of its runs. As a result, at each turn, the passageways have different curvatures, and the passageway that lies closest to itself between adjacent runs is bent extremely tightly at the turn, with a consequent risk that it will kink and therefore block or considerably restrict the flow of the thermal transfer fluid. 
     It may also be remarked that patent document U.S. Pat. No. 4,823,771 describes a solar collector for heating a pool or spa employing a number of multi-passageway webs. Each web has first and second generally parallel runs that extend over the ground from and to first and second manifolds respectively. At the other end of each run (i.e. at a region half-way long the web), the passageways are not connected together as a web so that the passageways can be curved. Since the curved region is always half-way along the web, the web is apparently manufactured in this form, rather than splits being formed in the web during laying of the solar collector on the ground. By contrast, in accordance with the first aspect of the invention, the web may be provided without the splits being pre-formed, and the split or splits are formed during installation of the solar collector on the support structure. The web can therefore be used with any length of run and with runs that vary in length from one run to the next. Indeed, it is a preferred feature of the first aspect of the invention that the splitting step is performed after at least the majority of the first run has been laid. Accordingly, the installer can readily see where they need to split the web, without needing to take measurements of the length of the run. 
     In order to take up little space at the curve, in the splitting step, the web is preferably also split longitudinally between at least one other adjacent pair of the passageways adjacent and beyond the end of said first run, and more preferably between each adjacent pair of the passageways adjacent and beyond the end of said first run. Preferably, the splits have similar lengths. 
     The web is preferably formed to facilitate splitting of the web longitudinally between adjacent pairs of the passageways, for example with grooves to produce lines of weakness. 
     The first and second channels of the supporting structure accommodating the first and second runs of the web would typically be adjacent each other. In this case, in order to facilitate a smooth curve between the runs, the length of each longitudinal split is at least about one-and-a-half times the pitch of the channels. 
     Preferably, an edge of the web has a protruding formation, and the method further includes the step of fixing the protruding formation to the support structure. The protruding formation may be a simple flange which can be stapled or nailed to the supporting structure. Alternatively, the protruding formation may be shaped to interlock with a complementary formation of the support structure. It will be appreciated from the following description that if the edge with the protruding formation is laid uppermost on one run of the web (so that the web hangs from it), it will also be uppermost on the next run of the web. Therefore, there is no need to provide a similar protruding formation on the opposite edge of the web. Indeed for reasons of cost, the opposite edge of the web is preferably devoid of a symmetrical, interlocking, protruding formation. The protruding formation may be formed with an elongate ridge arranged, along the first run of the web, to face out of said first channel and to contact and seal with glazing tiles overlying the web and the support structure. In this case, the web is preferably also formed with a further elongate ridge symmetrically disposed with respect to the first-mentioned ridge and arranged, along the second run of the web, to face out of said second channel to contact and seal with the glazing tiles. 
     In the case where the channels of the support structure are substantially narrower than the width of the web, the method may further include the step of splitting the web to remove at least one of the passageways from the web. It is therefore unnecessary to manufacture a large range of sizes of the web. Instead, one or a few sizes may be manufactured, and a particular size can then be adjusted at the time of installation. Furthermore, in the case where one of the first and second channels is substantially narrower than the other of the first and second channels and is substantially narrower than the width of the web, the method may further include the step of splitting the web to remove at least one of the passageways from the run of the web that extends along said one channel. A single web can therefore be used with different width channels on the same support structure. In both these cases, if the web has the protruding formation described above, the removed passageway or passageways are preferably removed from the edge of the web opposite the edge having the protruding formation. 
     Of course, the web may be formed into more than two runs, and the method may therefore further include the steps of: splitting the web between at least one adjacent pair of the passageways adjacent and beyond the end of said second run; curving the split web so that the web enters a third of the channels of the support structure; laying a third run of the web along the third channel so that said one face of the web faces out of said third channel. Indeed, the web may be formed into sufficient runs so as to cover substantially the whole of a face of the support structure. 
     The method preferably further comprises the step of connecting the opposite ends of each passageway to an inlet manifold and an outlet manifold for the thermal transfer fluid. 
     A second aspect of the invention provides a solar collector constructed by the method of the first aspect of the invention. 
     A third aspect of the invention provides a building having a roof provided with a solar collector according to the second aspect of the invention. 
     A fourth aspect of the invention provides an elongate web for use in the method of the first aspect of the invention, wherein the web is made of flexible material, the web is formed with a plurality of generally parallel passageways for a thermal transfer fluid extending in the longitudinal direction of the web and spaced apart across the width of the web, one edge of the web has a protruding formation for affixing the web to a support structure, and the opposite edge of the web is devoid of a symmetrical, protruding formation. Preferably, the protruding formation is shaped to interlock with a complementary formation of the support structure, and the opposite edge of the web is devoid of a symmetrical, interlocking, protruding formation. 
     A fifth aspect of the present invention provides a solar collector system comprising a support structure and elongate web of flexible material (for example extruded from plastics or synthetic rubber material) that is supported by the support structure and has a plurality of runs, which may be of different lengths, extending across the support structure, the web being formed with a plurality of generally parallel passageways for a thermal transfer fluid extending in the longitudinal direction of the web and spaced apart across the width of the web so that solar energy incident on the structure can be absorbed by the web to heat the thermal transfer fluid in the web, the web extending integrally from one to another of the runs of the web at a return portion, and at the return portion at least one longitudinal split being formed between an adjacent pair of the passageways. 
     The solar collector system of the fifth aspect of the invention may be provided with many of the features of the other aspects of the invention described above. 
    
    
     
       Specific examples and embodiments of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an isometric view of a building, to which the embodiments of the invention may be installed, with a portion of the tiling of the roof removed; 
         FIG. 2  is an isometric view of one form of web that may be used in the embodiments of the invention; 
         FIG. 3  is an isometric view of another form of web that may be used in the embodiments of the invention; 
         FIG. 4  is a face view of a roof in the direction  4  shown in  FIG. 5 , before fitting of its tiles, to which an embodiment of solar collector is fitted; 
         FIG. 5  is a sectioned side view, taken along the section line  5 - 5  shown in  FIG. 4 ; 
         FIG. 6  is a sectioned side view of a roof fitted with another embodiment of solar collector; 
         FIG. 7  is a sectioned side view of a roof fitted with a further embodiment of solar collector; and 
         FIG. 8  is a sectioned side view showing a modification to the embodiment of  FIG. 6 . 
     
    
    
     Referring to  FIG. 1 , a building  10  has a pitched roof  12 , and, in the Northern Hemisphere, solar collectors are installed in the roof faces  14  that face generally southerly between about south-east and south-west. The roof faces  14  are formed in a conventional way from rafters (not shown) covered by a layer or layers  16  of weatherproofing and thermally-insulating material. Spaced-apart wooden counterbattens  18  extending in the direction of slope of the roof faces  14  are fixed over the layer  16 , and spaced-apart horizontal wooden battens  20  are fixed over the counterbattens  18 . A solar collector system (not shown in  FIG. 1 ) is then installed in the horizontal channels  22  formed between adjacent battens  20 . The roof faces  14  are then tiled with tiles  24  made of a material with a high transmissivity to solar radiation, such as glass. It should be noted from  FIG. 1  that, due to the inclined join between the roof faces  14 , the lengths of the channels  22  formed in each roof face  14  vary. 
     The solar collector system that is installed in the roof faces  14  employs a web  26 , examples of short lengths of which are shown in  FIGS. 2 and 3 . Each web  26  is extruded from a flexible synthetic rubber material such as ethylene propylene diene monomer (EPDM) rubber. Each web  26  is formed as a series of cylinders  28  interlinked side-by-side so as to provide a series of parallel passageways  30 . In the examples, each web  26  has ten cylinders  28  and ten passageways  30 , but webs  26  with other numbers (two or more, more preferably three or more, and even more preferably several) of cylinders  28  and passageways  30  may be employed. In the examples, the cylinders are shown as being circular, but they may be of other shapes such a square or oval. In the example of  FIG. 2 , the cylinders  28  slightly overlap so that they are interlinked by thin portions  32  of the synthetic rubber material, along which the material can readily be cut or even torn so as to separate one cylinder from the next, as shown. In the example of  FIG. 3 , the cylinders  28  are spaced apart slightly and interconnected by thin sub-web portions  34 , each formed with a groove  36  to provide a line of weakness along which the synthetic rubber material can likewise readily be cut or even torn so as to separate one cylinder from the next. Along one edge of each web  26 , an integral protruding flange  38  is formed, whereas the opposite edge  40  is devoid of any such flange. The web  26  is preferably supplied to an installation site in long lengths of, for example, 50 or 100 metres wound on a drum or reel. 
     One example of installation of the web  26  on a simple rectangular roof face  14  will now be described with reference to  FIGS. 4 and 5 . The web  26  may be installed at the same time as, or after, fitting of the battens  20 , the latter method requiring threading of the web  26  beneath the battens  20 . The former method will be described. 
     First, the uppermost batten  20   a  is secured to the counterbattens  18 . Then a run  26   a  of the web  26  is laid extending upwardly from its end  26   b  below the lowermost batten  20   j  and in the channel  40   a  between the rightmost pair of counterbattens  18   a , 18   b , with the web flange  38  to the left. Shortly before the run  26   a  reaches the uppermost batten  20   a , splits  42  are formed in the web  26  between each of the adjacent pairs of cylinders  28 , and the web  26  is folded over itself to the left. The splits  42  enable each cylinder  28  to follow a smooth quarter-circular path at the fold without kinking, and the web flange  38  becomes uppermost. The web  26  is then laid as a run  26   c  to the left below the uppermost batten  20   a , and the web flange  38  is secured to the uppermost batten  20   a  by suitable means, such as staples  44 . Shortly before the run  26   b  reaches the leftmost counterbatten  18   g , splits  46  are formed in the web  26  between each of the adjacent pairs of cylinders  28 , and the web  26  is folded under itself, downwardly and to the right. The splits  46  enable each cylinder  28  to follow a smooth semi-circular path at the fold without kinking, and the web flange  38  again becomes uppermost. The uppermost-but-one batten  20   b  is then secured to the counterbattens  18 , and the web  26  is then laid as a run  26   d  to the left below the uppermost-but-one batten  20   b , and the web flange  38  is secured to the uppermost-but-one batten  20   b . The procedure is continued until the last main run  26   k  of the web  26  is laid under the lowermost-but-one batten  20   i  and secured to it. Shortly before the last main run  26   k  reaches the leftmost counterbatten  18   g , splits  42  are formed in the web  26  between each of the adjacent pairs of cylinders  28 , and the web  26  is folded under itself and downwardly. The splits  42  enable each cylinder  28  to follow a smooth quarter-circular path at the fold without kinking. The web  26  then extends downwardly as a short run  26   l  and is cut from the remainder of the supply of web  26  to form an end  26   m , and the lowermost batten  20   j  is then secured to the counterbattens  18 . 
     The end runs  26   b , 26   l  of the web  26  are then connected to inlet and outlet pipes  48 , 50  at manifolds  52 . Various connection schemes may be employed. In the example shown, at each end of the web  26 , the cylinders  28  are split from each other for a short distance; the passageways  30  are alternately connected to the inlet pipe  48  and the outlet pipe  50 ; and each passageway  30  is connected at one end to the inlet pipe  48  and at the other end to the outlet pipe  50 . 
     Once the web  26  has been installed, the roof face  14  is tiled using glass tiles  54  held in place by tile hanger brackets  56  secured to the battens  20 . Each tile  54  has a length of about 2½ times the pitch of the battens  20 . 
     Various modifications may be made to the example of the invention described above with reference to  FIGS. 4 and 5 . For example, instead of using the web  26  for the runs  26   a ,  26   l , the inlet and/or outlet pipes  48 , 50  may be arranged to be connected by manifolds directly to the ends of the first and last horizontal runs  26   c , 26   k  of the web  26 . Although  FIG. 4  shows a rectangular roof face  14 , the web  26  may be fitted to a non-rectangular roof face, as shown in  FIG. 1 , with each run of the web  26  being sized to fit the space available. The web flange may be left in place along the whole length of the web, or, as shown in  FIG. 4 , it may be trimmed off except along the horizontal runs  26   c - 26   k  of the web  26 . 
     A modified embodiment will now be described with reference to  FIG. 6 , in which features in common with the embodiment of  FIGS. 4 and 5  have been given identical reference numerals. 
     Instead of the wooden battens  20  described above, battens  58  are used that are pressed from sheet metal. Each batten  58  provides upper and lower flanges  60 , 62  extending along the batten  58  and pointing upwardly in the direction of the roof slope. The glass tiles  54  are held in place by elongate link members  64 . Each link member  64  is fitted to the upper flange  60  of one batten  58  and extends upwardly to rest on the next batten  58  in the upwards direction. Each link member  64  is positioned underneath the gap between two adjacent glass tiles  54  in the same course and provides a rain-guiding channel so that any rain passing through the gap is guided to exit above a tile  54  in the course below. The lower corners of the tiles  54  are held by clips  66  at the lower ends of the link members. The rain guiding channels enable the length of the glass tiles  54  to be reduced to about 1¼ times the pitch of the battens  58 . Apart from the lower flanges  62 , this batten  58  and link member  64  system is known and marketed under the mark Nu-Lok® by Nu-lok Roofing Systems Pty Ltd, AU-5000, and Nu-lok Roofing Systems (UK) Ltd, GB-HA4 7TL. 
     The lower flanges  62  on the battens  58  are provided as a means for attaching the web  26  without the need to use staples or the like. Accordingly, instead of having a plain flange  38 , one edge of the web  26  is formed in cross-section in the shape of a letter “E” with the web extending away from the centre limb of the E. Accordingly, two channels  68 , 70  are formed between the centre limb and the upper and lower limbs of the E. Along one run of the web  26 , the flange  62  of one batten  58  engages in one  68  of the channels  68 , 70 , and along the next adjacent run of the web  26  the flange  62  of the next batten  58  engages in the other  70  of the channels  68 , 70 . Again, the web  26  is devoid of any corresponding formation along the opposite edge  40  of the web. 
     Another modified embodiment will now be described with reference to  FIG. 7 , again in which features in common with the previously-described embodiments have been given identical reference numerals. 
     In the case of  FIG. 7 , the glass tiles  54  are held in place by short glass hanger brackets  72  that are secured to wooden battens  20  by screws  74 . Each bracket  72  engages the lower edge of a first tile  54  about half-way across its width, and its screw  74  (a) passes through a hole in the bracket  72 , (b) passes through the gap between second and third tiles  54  beneath the first tile  54 , (c) passes over the top edge of a fourth tile  54  beneath the second and third tiles  54 , (d) passes through the flange  38  of the web  26  immediately beneath the fourth tile  54  and (e) is screwed into the batten  20  from which the web  26  hangs. The screws  74  therefore serve not only to hold the tiles  54  in place but also to secure the web  26  to the battens  20 . The web flange  38  is formed with integral ridges  76 , 78  on its two faces. Along one run of the web  26 , one  76  of the ridges  76 , 78  engages the glass tiles  54  to seal to them, whilst along the next run of the web  26 , the other  78  of the ridges engages the glass tiles  54  to seal to them. The web flange  38  is also formed at its distal end as a “T” shape, and the arms  80 , 82  of the T engage the tiles in the next course up also to seal to them. The seals provided by the ridges  76 , 78  and arms  80 , 82  of the T shape serve to trap the air that is beneath the tiles  54  so that heat is not lost by convection. The seals also cushion the tiles  54  so as to reduce the risk of damage to the tiles  54  during installation. Yet again, the web  26  is devoid of any corresponding formations along the opposite edge  40  of the web. 
     A modification to the arrangement of  FIG. 6  is shown in  FIG. 8 . In this case, one edge of the web  26  is formed with a wide plain flange  38  which is fitted underneath the lower portion  84  of the metal batten  58  and fixed in place by the same fixing means (such as nails or screws  86 ) that are used to fix the metal battens  58  to the counterbattens  18 . The other edge  40  of the web  26  is devoid of such a flange  38 . 
     It should be noted that the embodiments of the invention has been described above purely by way of example and that many modifications and developments may be made thereto within the scope of the present invention.