WO2015121607A2

WO2015121607A2 - Modular double glazed long narrow solar collector and mounting means

Info

Publication number: WO2015121607A2
Application number: PCT/GB2015/000051
Authority: WO
Inventors: Brendan Ruff
Original assignee: Brendan Ruff
Priority date: 2014-02-16
Filing date: 2015-02-11
Publication date: 2015-08-20
Also published as: GB201502155D0; WO2015121607A3; EP3105513A2; GB2526900A; GB201402698D0

Abstract

A novel design of solar thermal collector is presented which is double glazed and formed substantially from a clear polymer extrusion which simplifies the manufacturing process. The internal gas separation sheets are mounted in a novel sliding arrangement which solves the problem of differential thermal expansion between the clear polymer body of the collector and the internal gas separation sheets which may be at a relatively high temperature. Also a novel thermostatic device allows convective circulation of the internal gas in higher stagnation temperatures to prevent over heating of the internal gas separating sheets and of the device as a whole. Finally a novel mounting arrangement is presented for forming a continuous weather proof roof from a multiplicity of collector modules in an array, and a variant is presented which steps up the across-roof configuration to more optimally mount the modules for winter sun orientation while maintaining a low profile to the roof. Other variations on this design are presented.

Description

TITLE

Modular double glazed long narrow solar collector and mounting means

BACKGROUND

The invention presented here lies in the field of solar thermal fluid, heating, and in particular domestic water heating. The innovation lies particularly in the area of using a clear polymer to form both the body of the collector and the glazing as a single material formed in an extrusion process. The present invention is based upon a double glazed principle with a novel solution to removing the double glazing operation in over-heating conditions.

Whereas typical solar collectors lie in either the category of flat panels which are wide or alternatively vacuum tube which are long and very narrow, there is no category of modular narrow flat panel. Though the aspect ratio of the panel alone does not differentiate the function of the panel, it does however open up the possibility of novel mounting means and improvement in alignment of the panel to the sun while maintaining a low profile to the roof on which it is mounted, and the narro width also allows for the possibility of extruding the frame and glazing as a single piece

Typically polymers such as polycarbonate are not used in solar thermal collector design due to the problem of high stagnation temperature which is the condition that no heat is harvested from the collector combined with high ambient air temperature and noon day full normally incident solar radiation. It will be shown in this invention that careful design of internal gas circulation combined with internal thermostatic redirection of this circulation allows for successful regulation of the internal gas temperature below the heat deflection temperature of the polymer which forms the bulk of the collector device, and in particular if this material is polycarbonate.

There is also a problem of thermal expansion in polymers and in particular differential thermal expansion which can lead to deformation of large devices made from a polymer, and this can lead to severe internal stress in the material as well as dimensional change of the device which can be a problem in mounting such a device. It will be shown that the current invention solves both of these problems. DESCRIPTION

Introduced here is a novel design of double glazed gas filled solar thermal collector whose frame and outside glazing are formed from a single clear extruded polymer, and in particular polycarbonate which has excellent impact resistance and strength combined with a typical heat deflection temperature of over 145°C which defines the upper working temperature limit of the material.

In overview, the long and narrow solar thermal collector of the present invention is intended to be deployed as an array of such identical devices connected in parallel as shown in figure 1 which is a diagram showing by way of example four collector modules (6) connected in parallel and the whole diagram shows a circulation of heat transfer fluid through the collectors from the fluid inlet (11) of the first collector module in the array at the cold end (12) of the collector modules and thence through the array via fluid conduits (1) provided in each collector module which are arranged to be thermally communicating with the heat exchange and solar absorber assembly (3) of each module so that the heat transfer fluid is heated during its passage through the conduit means (1) and thereafter leaves the collector module at the hot end (4) and exits the array at the fluid outlet (7) which outlet is arranged to communicate through external piping to a fluid store or heat exchanger (8) whose purpose is to either form a buffer and store of heat or alternatively to exchange the heat with another fluid (not shown), and thereafter the heat transfer fluid leaving the means (8) is returned to the collector array at inlet (11) through an optional fluid pump (9), noting that a gravity fed arrangement is also possible which excludes the pump (9) in which case the hot end of the collector array is arranged to be higher than the colder inlet end when in mounted operation so that convection of the heated fluid leads to natural circulation of the fluid around the circuit through the array to the means (8) and back again, and in the figure the cold end of each collector module is arranged with a T-manifold adapted so that fluid flowing into the T from the array inlet direction (11) may flow in part through the conduit (1) in the module's solar absorbing and heat exchanging means (3) from the cold end (12) though the conduit means (1) and on to the hot end (4) of each collector module, and in part also flows to the outlet leg of the cold end T manifold to the inlet leg of the next collector module's cold end inlet T manifold, and in this way all inlet T manifolds of each separate collector thereby form an aggregate manifold communicating all of the cold end individual T manifolds, and similarly all hot end T manifolds are arranged to communicate to form an aggregate hot end manifold communicating all hot end T manifolds, and to terminate the aggregate cold end manifold the last individual T outlet is arranged to be blocked by an end cap (10) and similarly the first collector's hot end manifold inlet is arranged to be blocked by an end cap (5) so that the hot and cold end manifolds are sealed against fluid loss. Shown in the figure the collector module has a body (2) which is formed from a clear polymer such as polycarbonate and the individual collectors are mounted together by a means that is not shown but will be introduced later, and this means holds the collector modules for instance along their long edges but not limited thereto and this bracketing means is arranged with means to fix to a mounting surface such as a roof or wall.

Also shown in figure 1 and described in more detail later there is an end cap to close off the body (2) against dust and water ingress and also to substantially prevent gas movement into or out of the collector other than optionally to balance pressure and means may also optionally be provided to limit such balancing air movement so that it passes through a drying means or alternatively is arranged to communicate with a reservoir so that external air is excluded from the collector and excess or deficiency of air is balanced by movement of gas between the reservoir and collector.

In section the body (51) of the collector is typically a rectangular profile with a substantially flat front sunward face and rear face as shown in figure 7 but the profile is not limited to this shape. Figure 12 shows a simplified curving collector body (51) and an example of a curving solar absorber and heat exchange assembly (69) with a single heat transfer fluid pipe (54) and no other details are shown for clarity, for instance internal glazing, ridges, and mounting means are not shown. In particular the profile of the body may be curving from a slight curvature as shown in figure 12 where the body (51) has approximately 90 degrees of curvature, up to an including a semicircle which subtends 180 degrees and typically the curving profile is arranged to match that of typical half-pipe style roof tiles which fit together with one half pipe facing down interlocking or overlapping with the next tile which faces up and such tiles typically have for instance a 90 degree arc. The height of the curving profile which is the perpendicular distance from the front to the rear surface at any point is arranged to be substantially less than the width of the profile so that the curving profile is arranged as curved version of the rectangular profile flat panel collector, that is as if the rectangular profile was warped into a curve across its width. The curving profile version of collector allows for both stylish and water excluding integration with this type of half pipe tiled roof and also has functional benefits. In particular the curving profile compared to the flat front surface profile has a lower maximum solar power absorption for the same total absorber area since a smaller area is exposed to the incident sunlight which has parallel rays and also there is always a higher amount of incident sunlight lost to reflection collector's hot end manifold inlet is arranged to be blocked by an end cap (5) so that the hot and cold end manifolds are sealed against fluid loss. Shown in the figure the collector module has a body (2) which is formed from a clear polymer such as polycarbonate and the individual collectors are mounted together by a means that is not shown but will be introduced later, and this means holds the collector modules for instance along their long edges but not limited thereto and this bracketing means is arranged with means to fix to a mounting surface such as a roof or wall.

In section the body (51) of the collector is typically a rectangular profile with a substantially flat front sunward face and rear face as shown in figure 7 but the profile is not limited to this shape. Figure 12 shows a simplified curving collector body (51) and an example of a curving solar absorber and heat exchange assembly (69) with a single heat transfer fluid pipe (54) and no other details are shown for clarity, for instance internal glazing, ridges, and mounting means are not shown. In particular the profile of the body may be curving from a slight curvature as shown in figure 12 where the body (51) has approximately 90 degrees of curvature, up to an including a semicircle which subtends 180 degrees and typically the curving profile is arranged to match that of typical half-pipe style roof tiles which fit together with one half pipe facing down interlocking or overlapping with the next tile which faces up and such tiles typically have for instance a 90 degree arc. The height of the curving profile which is the perpendicular distance from the front to the rear surface at any point is arranged to be substantially less than the width of the profile so that the curving profile is arranged as curved version of the rectangular profile flat panel collector, that is as if the rectangular profile was warped into a curve across its width. The curving profile version of collector allows for both stylish and water excluding integration with this type of half pipe tiled roof and also has functional benefits. In particular the curving profile compared to the flat front surface profile has a lower maximum solar power absorption for the same total absorber area since a smaller area is exposed to the incident sunlight which has parallel rays and also there is always a higher amount of incident sunlight lost to reflection compared to normal sunlight incidence on a flat surface as reflectivity increases on the glazing with increasing angle of incidence and at all times there is a significant part of the incident sunlight that is not normally incident on the glazing since this glazing is curving. Note that for the same collector footprint area on the roof then the curving collector compared to a flat collector has an increased absorber area which if the curvature is circular is an increased factor of ( 0.5 x theta / sin(theta/2) ) where theta is in radians and is the angle subtended by the collector from the center of curvature. Therefore there is a larger area of absorber and cost for the curving collector compared to the flat collector for the same footprint. However the curved collector maintains its power of solar collection over a larger range of incident sunlight angles which range increases with the subtended angle, and this maintains the power output of the collector at the expense of increase in total absorber area and material used, and this effect is widely known in the public literature as a benefit for instance for circular profile vacuum tube collectors and the effect is used here also for this reason. If the curving collector has a space between collectors which space is typically the same as the collector width then the collectors do not shadow each other significantly during operation. Another benefit of the curving design is increased mechanical strength as the curving profile is highly resistant to bending and this increased strength is an object of the present invention. Note that though the maximum power is less than the flat profile's due to reflective losses this power is maintained over a larger window of sunlight incident angles resulting in a more uniform power output from the collector and a lower maximum operating temperature. This may be beneficial in some installations given local weather conditions and desired period of operation during the day. The flat profile remains the most efficient for noon day operation in low ambient temperatures.

In itself the arrangement of collector modules in fig.l introduces little apparent novelty, however commercially this arrangement is not seen since instead to have multiple small absorbing surfaces packaged into narrow collectors manufacturers make single larger solar absorbing surfaces to which an arrangement of pipes is welded which form a large fluid circuit arranged in manifold or as a serpentine so as to form a single larger collector. This splitting of the collecting surface into a modular array of long narrow collectors has certain advantages.

Firstly each module is smaller and lighter and easier to handle both in manufacture and in final mounting for instance on a roof and allows for novel design shape such as the curving half pipe shape which has a different power curve compared to a standard flat panel collector. Secondly when considering the use of a polymer such as polycarbonate by way of example, then thermal expansion over for instance a 100°C temperature swing of the collector module body (2) could lead to a great change in dimension if a single large collector design were used since both the length and the width of the collector would change by around 7mm per meter of dimension for a typical coefficient of thermal expansion of a polymer of 70 x 10^"6 m/°C. By choosing a long narrow design then the impact of thermal expansion in width is minimised since the width of the body (2) of the collector is relatively small, for instance between 10cm and 50cm though not limited thereto, and typically around 20cm so in the same temperature swing the width dimension changes by l/5th of 7mm, ie 1.4 mm. As will be discussed later, this variation in width of the collector module is accommodated by the fixing means for instance in the case of fixing along the collector module's long edge to the mounting flanges within the mounting rails which have clearance built into the connecting means to allow for the range of width of the collector module over its expected working temperature range and thereby the combined collector module and mounting rails have no overall variation in width over the working temperature range and so no thermal stress ensues even for very wide arrays of tens of collector modules.

Also considering the length of the long narrow collector introduced here, then the length may be as little as lm and as long as 10m or more, but typically the length is arranged to be from 2.5m to 5m, and typically the array comprises only one length of module in its length dimension and its width comprises the aggregate width of all of the individual modules in the array in this case where the modules are connected to each other along their long edges. The thermal expansion of the length of each module is arranged to be accommodated by mounting only the long edges of each module to the mounting rails so that the module may slide along the rails while arranged to be held in place against movement in the plane normal to the rails long dimension so that there is no binding between the long edges of the module and the mounting rails and thereby the modules are free to expand in length arising from thermal expansion, and so no thermal stress ensues. However, since the collector module is desired to be held in place against its own weight and other external forces applied, for instance wind and vibration, then accordingly one point of fixing is arranged to hold the collector module in place against gravity and other forces that might arise for instance by being held at one end of the collector or the other but not limited thereto, and in particular it is preferred that this fixing is an end stop at the lower end of the collector for an up-roof oriented collector arrangement so that the collector is prevented by the end stop from sliding out of the rails in a downward direction but not prevented from sliding up the rails. In any case the top end of the collector may be optionally arranged to seal against water ingress into the roof space below by a flashing arrangement which overhangs it but is not fixed to it and which is further arranged to accommodate the maximal range of length of the collector arising through thermal expansion which could be several centimetres.

The mounting of the collector in the long dimension is not limited to only the long edges, and in general the mounting is arranged in at least two points arranged with discrete brackets or along substantially the whole length of the collector arranged with continuous rails. In particular the discrete brackets may be arranged with a hooking means to the existing roofing materials, for instance tiles, as so-called roof hooks.

So, though not exceptional, the innovation in the long narrow design of the modular collector has profoundly important characteristics which allow a polymer to be used for the body of the device and make the device easy for a single person to handle and fit and allows for thermal expansion. Later it will be introduced that another benefit is low profile on the roof when stepped up for optimal angle to the sun at the installed location.

Looking now in more detail at the internal design of the modular collector in regards to the fluid manifolds and connection of one collector module to the next, then figure 2 shows a single collector in plan view. The clear polymer body (2) houses the solar absorber and heat exchange assembly (3) with thermally communicating heat transfer fluid pipes (1) which may be integral to the assembly (3) or separate, and the ends of the collector module are arranged to be sealed against gas and liquid ingress or egress at each end by an end cap arrangement shown as a dashed rectangle at each end of the body (2) showing the cold end cap arrangement (23) and hot end cap arrangement (16) and optionally the gas sealing may be arranged to allow passage of a small amount of gas so as to allow balancing of external and internal pressure, and in this diagram the arrow alongside the fluid pipe (1) designates that the cold end of the collector module is at the left in the diagram and the hot end at the right, and in this example the fluid conduit (1) passes through the sealing means of the end cap which sealing means is arranged so that the fluid pipe (1) may slide through the sealing means without binding and so accommodate the differential thermal expansion between the solar absorber and heat exchange assembly and the body, and optionally this pipe and hole are further provided with a gasket means between them to substantially prevent or reduce dust and gas and fluid movement through the hole, and the cold and hot end T manifolds (22) and (17) are connected to the fluid conduit (1) by optional flexible pipe means (25) and (13), or alternatively connected directly to the conduit's ends, and in the case of flexible connection then this flexibility is arranged to accommodate part or all of the differential thermal expansion between the body (2) and assembly (3), and the inlet (26) and outlet (20) at the cold end and inlet (14) and outlet (19) at the hot end are optionally connected via a flexible pipe means (24) and (21) at the cold end and (15) and (18) at the hot end so that adjacent collector modules have inlet and outlet T manifolds that are connected together that may move with respect to each other which movement arises from differential thermal expansion between the adjacent connected modules and thereby this thermal expansion arising movement is accommodated safely by this flexible connection, and optionally the end cap arrangements (23) and (16) are arranged to be weatherproof so that rainwater and dust do not enter the end caps internal space and also optionally so that rainwater is prevented from reaching the area underneath the collector module so that the array of modules form a weatherproof surface.

Optionally the T manifolds may lie outside the end caps and so are not internal to the collector.

The overall dimensions and form of the long narrow solar thermal collector described here have useful characteristics for the mounting of the collector and also for arranging the collector to be oriented towards the sun during winter months. Also, the long edges of the collector module may be used to connect to a rail for mounting but not limited thereto and this connection which comprises of the rail shape and the shape of the long edges of the collector may further be arranged so that rain water ingress is prevented and rain water excluded from the area of the mounting surface underneath the collector array, which combined with a flashing arrangement particularly at the top end of the array and sloping sides arranges for the array to be a roof and so replace conventional roofing materials where it is mounted.

Referring to figure 3 this shows a typical gravity aligned "up-roof ¹ arrangement of collector modules (6) on a typical sloping roof (27) and here by way of example of one installation variant the collector modules are mounted so that their lower cold ends (23) form the eves of the roof so that water runs off the ends of the collectors into the roofs gutter, and the upper hot ends (16) of the collector modules are flashed (28) into the roof though alternatively the length of the modules could be arranged to run the full sloping height of the roof up to the peak of the roof as another installation variant for instance for a total collector length of for instance 7m on a typical small roof. The collector modules in this up-roof mounting arrangement are mounted to the roof by rail mounting means (not shown) running along the long edges of each collector module but not limited thereto and these rail mounts are fixed to the roof prior to mounting of the collector modules, and typically an end stop means is provided (not shown) at the lower cold end of each collector to prevent the collector from sliding along and out of the rails in a downwards direction, and typically in this mounting arrangement the mounting rails and end stop and collector module body are arranged so that the collector module may be mounted by sliding in from one end of the rails or alternatively fixed in place by a second piece that fixes in a removable way to the mounting rails and so arranged to capture the collector module long edges so that the module may only slide along the rails but not otherwise move, and by this rail mounting means and end stop means the collector array is fixed in place but arranged to permit sliding along the rails to accommodate thermal expansion along the length of the collector modules, and further the rail mounts distribute the weight of the collector modules and loaded weight for instance with snow on top across the roof very evenly and avoids undue loading at any point on the roof and this is an object of the rail mounting means to so distribute the loading across the roof, and further the mounting means are adapted so that the mating between the mounting means and the collector modules is optionally weather proof so that the collector modules may optionally form a continuous and weatherproof roof, and by the gravity aligned orientation of the long axis of the collector then an object of this installation variant is that optionally a gravity fed circulation is induced without the need of a heat transfer fluid circulation pump.

Optionally the rail mounting means may be discrete brackets rather than a continuous rail, for instance by cutting the continuous rail profile, and fixing these brackets at discrete points along the length of the collectors.

However, notice that in this mounting variant that the angle of the collector modules is the same as the angle of the roof. In some installations if may be preferred that the collector modules are angled at the optimum orientation for winter or spring/autumn sunlight, and this angle depends on the latitude of the installation, and typically this angle is in the region of 70° to the horizontal in Europe whereas typical roofs are closer to 45° to 50°.

A second variant for mounting the collector modules is to "step" these up at an angle from the roof along their short edges and to mount the collector modules horizontally across the roof as shown in figure 4. Accordingly one variant of the mounting arrangement for the collector modules (6) is such that they are angled up from the roof so that the sunward face (29) of each module is at a steeper angle than the roof by use of a mounting means along the long edges of each collector element and thereby the sunward face of the collector module is arranged at a more optimum angle for winter or autumn/spring sunlight while at the same time exposing a smaller total area to noonday summer sun which thereby reduces the maximum temperature experienced in summer stagnation, and further the narrow width of the collector module permits the higher long edge to remain in a low profile on the roof, typically less than 7cm projection normally from the roof plane though not limited thereto, and this narrow width of the collector module when stepped up reduces the visual impact and wind resistance of the collector compared to a wider standard flat panel collector, and at the same time in one version of the step arrangement a gutter (30) is produced by the stepping which is useful to carry away rain water to the sides of the collector array and a shallow or near horizontal surface (31) is produced which is either part of the mounting rail assembly or a separate flat and optionally insulating piece which serves as a snow barrier to prevent snow slipping off all at once from the roof which can be dangerous or destructive.

Optionally the mounting means is a plurality of discrete brackets, for instance arranged with a roof hooking fixing means to the roof material such as tiles or batons, and optionally each bracket fixes to both the long edges of the collector and so the collector is independently held rather than sharing a bracket between neighbouring collectors and so the collectors may be spaced according to the roof tiles spacing in this case.

Optionally the surface (31) may be omitted so that rain water and snow may fall between the mounted collectors to the existing roof surface below.

Another variant of the mounting arrangement in either up-roof or stepped across-roof variants is to mount each collector with a means to swivel the collector angle much like a louvre blind arrangement so that the angle of the collectors as a whole may be changed, for instance provided by a bearing means provided at each end of the collector, and as with a louvre blind each connector is arranged to be connected to its one or more neighbours by a means that arranges to keep the angle of each the same, for instance a double cable arrangement or a stiff connecting rod or ganged rod, and in this case a means may optionally also be provided to affect a change in the angle of the array of collectors using an active motor means or alternatively a manual means, and in this way an up-roof mounted array of collectors may be further arranged to track the sun during the day time or in an across-roof stepped mounted array the collectors may be further arranged to change their mounted angle to track the sun across the yearly seasons to be more optimally oriented for winter and optionally deliberately none optimally oriented during summer or to reduce stagnation temperature or reduce the total absorbed solar power when power is not needed, and optionally a vibration may be applied to the array through the louvre connection means so as to assist snow or ice to release from the collectors.

Looking now at the detail of the mounting means for the mounting variant shown in figure 3, figure 5 shows an example of this mounting means and adaptation of the collector body shape at the long edges but note that this is just one example of how this may be achieved, and accordingly in general for mounting the collector modules in an array then one arrangement for this is to adapt the long edges of the collector module in combination with a suitably adapted mounting rail shape so that either the mounting rail captures the collector module long edges in such a way as to permit sliding so that the collector module may be assembled with the already roof mounted rail by sliding in from one end or the other, or alternatively the rail my consist of two parts, the lower part of which is fixed to the roof and on which rests the collector module which module is then captured by the second separate part of the rail which fits into its lower mating half and is adapted to fix in a removable way to the lower part for easy disassembly for instance by sliding in from one end, and in either case the mating arrangement between the collector module long edge and the rail is optionally adapted to prevent ingress of rain water into the space below the collector module, and for instance this adaption may include provision of a gutter in the mounting rail below the collector module to collect any water that has reached this point and direct this water down and along the gutter to be spilled at the lower end of the mounting rail.

A particular arrangement of a single piece up-roof oriented mounting rail is shown in figure 5 in section as viewed down the long dimension of the collector showing two adjacent collector modules (6) and a single connecting mounting rail (41), and this rail for instance is typically formed from an extruded aluminium alloy or extruded polymer such as a plastic. In this version of the mounting rail arrangement (41) and adaptation of the shape of two adjacent collector modules (6), the collector module is adapted in shape along its long edges to have a lower flange (40) and upper flange (42) on each of the long edges of the collector module and here by way of example of similar shape and size extending above and below the top and lower surfaces of the collector module, and these four flanges per collector module mate with the adjacent pair of mounting rails (41) by sliding the collector module in from one end or the other, and the mating portion of the mounting rails consists of a lower mating arrangement (34) which also forms a gutter (35) for capturing any rain water that arrives below the collector module, and an upper mating arrangement (33) which also serves to direct rain water away from the mounting rail and onto the upper surface (43) of the collector module, and the upper flanges (42) of the collector module also serve as side walls to deflect rain water back onto the upper surface (43) of the collector module so that the upper surface (43) combined with the pair of upper flanges (42) form a shallow gutter to direct rain water down the length of the collector module to flow off the lower short edge of the module, and the mounting rail further comprises an upright section (39) which lifts the collector modules away from the mounting surface or roof (38) so that there is a narrow space between the lower surface of the collector module and the roof or mounting surface thereby forming a clearance so that they are not touching, and further the mounting rail comprises a lower flange (37) that abuts the mounting surface or roof (38) with additional fixings (36) shown by way of example here on each side of the vertical section (39) and many of these fixings are arranged along the length of the mounting rail, and further a gap is arranged between the mounting rail flanges (33) and (34) and the vertical section of the mounting rail so that this gap accommodates both the width of the collector module's flanges (40) and (42) with additional width to accommodate thermal expansion in the width of the collector module, for instance for a 20cm collector module then around a 2mm extra width is built into the width of the gutter (35) in addition to the thickness of the flanges (40) and (42), and by this total arrangement of mounting rail and adaptation to the shape of the long edges of the collector module then the collector module is arranged to be held in place when mounted so that the module may be assembled into the mounting rails by sliding in from one end or the other and the mounted collector modules and mounting rails optionally form a weather proof surface that prevents ingress of rain water from above the collector modules to the roof surface below and this combination directs the rainwater to flow off the lower end of the top surface (43) of the collector modules, and by the whole mounting arrangement then the weight of the collector modules and any snow loading is distributed across the length of each mounting rail to the mounting surface (38).

Instead of a single piece rail then an alternative variant is a plurality of discrete brackets which could for instance follow the same profile design as the single piece rail or alternatively a single bracket is arranged to detachably fix to the collector, for instance a clip on arrangement that holds both long edges of the collector, and for instance this bracket could be located centrally to the width of the collector like a pylon, and the fixing means to the roof could be optionally a roof hook means that permits to attach to a tile roof for instance by hooking onto the tile or batons.

A particular arrangement of a single piece stepped across-roof mounting rail is shown in figure 6 in section as viewed down the long dimension of the collector showing two adjacent collector modules (6) and the mounting rail assembly comprising weather flange (48), connecting leg (49), roof-butting leg (44), and T mating arrangements (47) and (50) which mate with mating flanges (43) which form a T slot along the length of the collector modules long edges, this mating arrangement and shape being by way of example and not limited to this specific arrangement, and in the figure the connecting leg (49) is shown as sloping so as to form gutters (45) and (46) though also for instance the connecting leg (49) could be arranged horizontally or slightly sloping away and downwards from the higher connected collector module so as to direct rain water and snow away and downwards and so not requiring a gutter to collect and drain the rain water, and the roof butting leg (44) is fixed to the roof or mounting surface (38) by a multiplicity of fixings (36) distributed along the length of the mounting rail and whose position on the mounting rail is optionally higher when mounted than the top of the flange (48) so that water in the gutter does not reach the level of the fixing hole and thereby making the mounting rail weather proof and preventing water ingress onto the mounting surface, and by further arranging the length of the mounting leg (49) and its angle to the roof abutting leg (44) then any desired mounted angle of the collector modules (6) may be achieved, and in particular a range of such angles and lengths is intended in this invention so that an appropriate mounting rail arrangement may be chosen to achieve the desired mounted angle of the collector module for the particular mounting surface angle and latitude of the installation on the planet and desired season for optimal operation.

Instead of a single piece rail for the across-roof mounted collector then an alternative mounting means is a plurality of discrete brackets which could for instance follow the same profile design as the single piece rail or alternatively a single bracket is arranged to detachably fix to the collector, for instance a c lip on arrangement that holds both long edges of the collector, and the fixing means to the roof could be optionally a roof hook means that permits to attach to a tile roof for instance by hooking onto the tile or batons. Another variant for the across-roof mounted collector mounting means is a single long rail that fixes both long edges of the collector and includes the connecting leg (49) and roof abutting leg (44) and the fixing means is arranged as either a single long roof hook formed as part of the rail or alternative as a plurality of hooks arranged to fix to the rail or alternatively the rail may fix directly to the roof material by fixings for instance such as screws or nails, and in this case the collector shape and rail may be further arranged to provide a roof-sealing "flashing" function with the roofing material at the lower long edge of the collector so that this edge is arranged to overhang the immediately lower roofing material and the immediately upper roofing material overlaps the leg (44) so as to make the join weather proof.

Note that in any variant of either the up-roof or across-roof mounting collector then if a weather proof roof is to be formed from one or more collectors then the edges of the collector must be separately sealed or "flashed" to prevent rain water ingress and wind ingress.

Thus far the external shape and features and mounting of the long narrow collector module have been described.

Referring to figure 7, the solar collector module of the present invention is shown in section normal to the long length of the collector and a set of 5 arrows represent the sunward side of the collector exposed to incident sunlight. This example shows only a generic version of the body of the collector (51) with no arrangements for mounting and it should be understood that as previously described the long edges may be adapted and arranged for mating with mounting rails as one example. Also though not shown additional internal features may optionally be present to add stiffness to the body (51) and it is an optional object of this invention that such internal features such as ridges are part of the body (51) bulk material on the inside. Optionally these ridges may be further arranged by their shape and dimensions to reduce convection of the gas inside the collector so as to help insulate the absorber assembly and reduce heat loss from the absorber assembly to the outside of the collector. The diagram shows the body (51) of the collector which is a clear polymer sleeve formed by an extrusion process, for instance made from polycarbonate, so that the body is one piece of polymer and may be cut to any length after the extrusion process, and within this body is held in place a solar absorber and heat exchange assembly (69) that runs substantially the whole length of the body (51) and whose sunward face is adapted to be highly solar radiation absorbing for instance by the application of a solar absorbing coating, and this assembly (69) is held in place along its long edges to the body (51) by a bracket means (61) which is either an integral part of the body (51) or preferably a separate arrangement made from a stiff and high temperature polymer with a heat deflection temperature higher than the maximum expected for the absorber and heat exchange assembly (69) for instance at least 170°C and preferably much higher for instance >200°C and made of a material such as polytetrafluoroethylene (PTFE), and for instance though not limited thereto the means is shaped as a hook (59) where it mates with the assembly (69) and which assembly in this case is also shaped as a hook along its long edges, and which bracket means for instance is T shaped where it is arranged to mate with the body (51) and which body is adapted in shape to have a T shaped slot into which the bracket means (61) is fitted by sliding in from one end or the other, and thereby the absorber assembly (69) may be assembled into the body (51) by sliding in from one end or the other onto the bracket means (61) and by this arrangement the body (51) and assembly (69) and bracket means (61) may all slide with respect to each other along the long dimension of the collector module and thereby differential thermal expansion between these is accommodated by the sliding, and the bracket means (61) arranges to have a temperature which is below the heat deflection temperature of the body material at its points where it touches the body (51) by its relatively long heat conducting path from the absorber assembly (69) to the body (51) and for instance the length of this path may be increased as necessary to achieve this temperature by adapting the width of the bracket means (61), and by way of example a conduit (54) is shown in which flows a heat transfer fluid arranged so that solar radiation absorbed by the assembly (69) is in thermal contact with the conduit and thereby the absorbed energy may be transferred to and harvested by the fluid passing through the conduit, and further an internal glazing arrangement is provided on the sunward side of the assembly (69) by an upper clear glazing sheet (65) to create two gas layers (68) in contact with the absorber assembly (69) and layer (66) which is in contact with the front glazing (67), and which sheet (65) is optionally adapted to be none reflective on its sunward surface for instance with the application of an antireflective coating or by texturing the surface to be antireflective for instance with a nano- texture which acts as a continuous refractive index like a moth's eye, and by the placement of this upper glazing sheet between the absorber assembly (69) and the clear front surface (67) of the collector body then two layers of air are separately trapped and so arranged in thickness of the layers as to reduce convection and loss of heat by convection across the gas layers, and the sheet (65) is held in place at least along its long edges by a mating means (64) and for instance this mating means could be a hook shape as shown which mates with a similar hook (63) formed in the glazing sheet (65) along its long edges for instance by rolling the edge over, and thereby the glazing sheet (65) may be assembled into the body (51) by sliding in from one end or the other, and as the sheet may become hotter than the body in operation of the collector then the sheet is free to thermally expand along the long axis and so avoid build up of mechanical stress, and similarly to the front glazing clear sheet (65) a rear sheet (57) optionally is arranged to create two gas layers (56) and (58) arranged to reduce heat loss through convection from the absorber assembly (69) to the rear surface of the body (51), and this sheet (57) may be made of any material with a melting point higher than the maximum expected for the gas layer (58) which it contacts, and in particular this sheet may be either clear or opaque or indeed preferably highly reflective to thermal radiation wavelengths expected to be emitted by the rear surface of the absorber assembly (69) when in typical operation for instance 30°C to 170°C, and which front and rear sheets are attached along their long lengths to the body (51) by means (60) and (64) which are for example integral to the material of the body (51) and here for example form a hook shape which mates with a hook shape (53) and (63) along the long edges of the sheets so that the sheets are held in place but may slide along the long length of the collector module and so allow for differential thermal expansion between the disparate parts and so avoid mechanical stress.

In particular it is very important that the internal sheets (65) and (57) are free to thermally expand along their long edges relative to the body (51) because in stagnation conditions the gas layers (58) and (68) may be heated to over 100°C even when the body (51) is held at sub-zero temperatures in winter, and over a length of several meters, for instance 3m, then this 100°C or more temperature difference typically leads to over 20mm differential expansion which would be highly stressful and destructive to the materials if the body and sheets were rigidly fixed to each other, and this is seen as a key novel feature in this invention. Also, the narrow width of the collector for instance around 20cm leads to very little increase in this dimension even with high temperature, perhaps at most 2 mm, and this is easily accommodated by either slight bending in the sheet material or by allowance and clearance for expansion in the connection means between the sheets and the body.

The rear sheet (57) material could be any suitable material and does not need to be clear so could be opaque, however a polymer such as polycarbonate is the preferred choice as it has a relatively high heat deflection temperature of around 145°C and high strength, though this material could for instance be a glass. The thickness of the material of the sheet may be anything suitable for instance between 0.1mm and 3mm thickness but in practice it is arranged to be thick enough only to support its own weight and in particular the sheet may be in slight tension as it sags between its mountings along its long edges and thereby the material may be very thin and less than that needed for free standing self-support.

The rear sheet (57) may also be omitted and its function replaced by another insulating means for instance a solid thick insulator for instance which fills the cavity (56).

The front glazing sheet (65) material could be any suitable material that is clear, however a polymer such as polycarbonate is the preferred choice as it has a relatively high heat deflection temperature of around 145°C, though actually this material could for instance be a glass. The thickness of the material of the sheet may be anything suitable for instance between 0.1mm and 3mm thickness but in practice it is arranged to be thick enough only to support its own weight and in particular the sheet may be in slight tension as it sags between its mounting along its long edges and thereby the material may be very thin and less than that needed for free standing self support.

The front glazing sheet (65) or rear glazing sheet (57) or both may also be omitted and its function replaced by a means that reduces convection by arranging the internal stiffening ridges of the body (51) suitably for instance by arranging the length and spacing and angle and shape of the ridges so that two gas layers are substantially formed. Accordingly in the case of two gas insulation layers that are arranged either or both for the front or rear insulation means then the two gas layers may be arranged by adaptation of the shape and dimensions and spacing of the ridge features so that the ridges reduce the convection within the outer layer of gas that is in contact with the outside face of the collector, and the inner layer of gas that is in contact with the solar absorber and heat exchange assembly contains only gas with no ridge features but has a layer thickness adapted to reduce convection and reduce conductive heat loss.

By way of example but not limited thereto the ridge features may be arranged as shown in figures 9 and 10 and 11 which show examples of a planar straight ridge (70) perpendicular to the collector body front and back faces in figure 9, an L shaped box ridge (71) in figure 10 with an additional T ridge (72) at one long edge but also all ridges could be T ridges, and a sloping planar straight ridge (74) on the collector front side and sloping ridge (75) on the collector back side in figure 11 where the collector is shown in a typical mounted orientation where the page up direction represents the vertical and so the ridges (74) on the front/top sunward facing side of the collector are angled more horizontally and possibly angled upward so that the end of the ridges may be higher than the base and the rear ridges (75) are steeply angled upward.

A typical ridge spacing that reduces convection is around 15mm for dry air, and a typical ridge length is at least the spacing distance to reduce convection.

For an across-roof mounted collector as shown in figure 11 the ridges may be angled with respect to the front and rear faces of the collector so that in mounted position they are directed upwards and so form pockets which trap cool air (76) on the front of the collector and pockets of cool air (77) on back of the collector and these pockets reduce convective losses since the cooler air in the pockets resists convection of the warmer air inside the collector.

For the case where the ridge shape is a simple planar vane as shown in figures 9 and 1 1 then during operation the end of the ridge is hotter than the base near the where it connects with the collector front and rear faces, and in consequence the ridge is subject to differential thermal expansion which is accommodated by a repetitive curving or "snaking" degree of freedom wherein the ends of the ridges snake the most and the base has no snaking curvature. If the shape of the ridge is not a simple planar vane then the snaking degree of freedom is restricted or prevented and so the planar vane ridge profile is preferred in this invention but not limited thereto.

For the case of an L-shape ridge profile shown in figure 10 the ridge may be arranged in shape and angle to substantially close off the space between neighbouring ridges to form a substantially closed space (73) where the top of the L connects to the body of the collector and the bottom right end of the L is arranged to be close to the next ridge so as to form the substantially closed pocket (73), and this pocket is arranged in width and depth to reduce convection within it in any mounted orientation, though it should be noted that higher internal stresses arise in the ridge from differential thermal expansion between the base of the ridge and the bulk of the ridge particularly the inner end of the ridge which is possibly much hotter, for instance 100 degrees Celsius hotter in stagnation operation. The benefit of this L shaped ridge compared to a completely closed off box space as seen in many extruded roofing materials is both in easier more reliable manufacture since only one internal void space is needed in the extrusion dye and also there is a snaking degree of freedom for thermal stress relief in the bottom leg of the L.

In the case where the ridges are planar vanes at any angle to the faces then preferably the vanes are arranged to be parallel to each other so that light reflected from their surfaces is guided into the collector to be incident on the absorber and in this way eliminate reflective loss of sunlight.

The ridges may be arranged as any combination of shapes and angles and lengths and spacing from all the same to each ridge being uniquely designed and arranged to optimally reduce convective heat loss and optionally reflective light loss.

The thickness of the gas layers (66) and (68) and (58) and (56) is arranged to be any that is suitable to reduce convection and reduce conductive loss for instance between 5mm and 30mm and typically around 16 to 22mm, and optionally the rear gas layers (58) and (56) may be thinner than the front layers to reduce the overall thickness of the body (51) since heat is less likely to be lost through convection downwards when mounted and also the underside of the body is likely to be protected against heat loss by the surface onto which it is mounted. Though the solar absorber and heat exchange assembly (69) here is shown to be a fin and heat transfer pipe type, it could equally be formed from a multi-port extrusion for instance of a polymer or alloy of aluminium, or it could have more than one conduit for the heat transfer fluid to flow through, or the fin and multiplicity of conduits could be formed from a single polymer or aluminium alloy extrusion.

The length of the collector may optionally be between 50cm and 10m, and typically around 2.5m to 5m.

The sheets (65) and (57) may optionally further be fixed to the front (67) and rear (55) surfaces of the body (51) respectively at one or more points to assist in supporting these sheets and in which case the fixing means is adapted to allow relative sliding along the long dimension of the collector module.

The front (67) and rear (55) surfaces of the body (51) are optionally further adapted with one or more internal ridge features spaced across their inner surface and integral in material with the body for the purpose of improving the stiffness of the body to bending along the long dimension.

In operation in situ on a mounting surface such as a roof the collector module is exposed to rain water and extremes of temperature and humidity. It is desirable that the inside gas, typically dry air, is not contaminated with moisture as this may lead to both condensation in certain dynamic conditions or degradation of the internal materials, particularly reflective and anti-reflective coatings. However, it is not desirable in general to completely seal the air inside the body as this would lead to pressure build up at extreme high temperatures, perhaps l/3rd of an atmosphere above the outside ambient pressure and this pressure increase could stress the body of the collector destructively. One solution for this problem is to provide gaskets and sealing at the end caps of the collector module to prevent gas exchange from the inside to the outside ambient air and further provide a conduit from the outside ambient air to the inside air which outside air is arranged to pass through an air drying device either external to the collector module or integral inside one or the other end cap and thereby at high temperatures the internal air expands out through the conduit and air drying device and is vented to the outside, and in cold temperatures the outside air is drawn inside the collector module via the air drying device and so maintaining the dry conditions desired inside the collector module. The external drying device could be provided as one per collector module or a single large device could be arranged to communicate by gas conduits to all collector modules in an array. An alternative solution is to simply provide an expansion vessel, for instance a bag, which is sealed to avoid contamination from ambient air and which communicates via gas conduits to one or more collector modules internal air via the conduit, and this bag may further contain an air drying agent, and for instance one such vessel may be provided per collector and may for instance be contained within one or both end caps or internally or externally to the collector on the rear side so that this vessel is ergonomically arranged with the collector.

The gas inside the collector modules is optionally a gas with a lower conductivity than standard air, for instance argon.

In extreme summer stagnation it is possible that the temperature inside the inner gas layers (58) and (68) shown in figure 8 may be so high as to be destructive at least to the front glazing sheet (65) for instance if it is a polycarbonate material with a maximum working temperature of around 145°C. The extreme temperature high is less likely with the across-roof mounted variant that is stepped up to a high angle as the sunlight strikes at a relatively low angle in summer midday. However in the up-roof mounting configuration the solar radiation may strike normally at some times close to midday leading to high stagnation temperatures. One solution is provide a thermostatically controlled internal means for permitting the gas in the internal layers (58) and (68) to circulate to the layers (56) and (66) by natural convection. Such thermostatic means could be located for instance in one or both of the end caps and preferably just the higher end cap in the mounted position of the collector module, and this is shown in figure 8 which is a side elevation of the up-roof configuration collector module mounted on a sloping roof or mounting surface (38) showing the upper hot-end end cap (4) and lower end end -cap (12), the rear sheet (57) and solar absorber and heat exchange assembly (69) and front clear sheet (65) all inside the collector module body (51), and within the hot end cap assembly two thermostatic valve devices (71) and (72) are provided whose operation is arranged such that within normal operating temperatures for instance up but not limited to 120°C the valves are shut and prevent air movement between the gas layers (56) and (58) by the shut valve (71) and between the gas layers (68) and (66) but the shut valve (72). The novel feature here is that the operation of the double glazing is removed when the internal gas layers (58) and (68) exceed a pre-set maximum by arranging for the automatic opening of the gas valves and allowing convection from the internal layers to the layers in contact with the outside shell of the body (51) whose outer surface then dissipates heat to the outside ambient air above and below the body. The gas valves (71) and (72) are by way of example simple flaps that are operated by bi-metallic strips or coiled bi-metallic strips or any other suitable thermostatic mechanical operation means suitable for controlling the gas valve mechanisms (71 ) and (72). Accordingly, gas valves (71) and (72) are optionally provided within the collector module and preferably at only the hot end of the collector module within the hot-end end-cap (4) but optionally also provided within the cold-end end-cap (12), these valves arranged to communicate the gas layers (56) and (58) through valve (71) and layers (68) and (66) through valve (72) so that below a pre-set temperature the valves are shut and above this temperature the valves open in such a way that the higher the temperature the more the valves are open, and the operation of these valves is controlled by the gas temperature within the respective layers (58) and (68) so that the thermostatic mechanism is in thermal contact with the respective gas layer, and by this means then above a higher pre-set temperature the valves are completely open and by this thermostatic valve operation the gas within the internal layers (58) and (68) are allowed to communicate with the outer gas layers (56) and (66) respectively, and thereby allowing natural convection in the mounted position of the collector module to circulate the gas internally within the collector so that the rate of heat loss from the solar absorber and heat exchange assembly (69) is higher than it would be without the thermostatic arrangement and in particular arranged so that the temperature of the sheets (57) and (65) do not exceed their maximum safe operating temperature.

The valves are optionally flap valves with their point or rotation at one end or located near the middle of the flap.

The thermostatic mechanism is optionally a bi-metallic strip or coiled bi-metallic strip.

In the case where the body (51) of the collector is curving such as is shown in figure 12 then the mounting means may optionally comprise either a rail or discrete brackets centrally located underneath the collector arranged to detachably fix either to the long edges of the collector or to some shaped means formed from the collector body (51) underneath the collector.

In the case where the body (51) of the collector is curving such as is shown in figure 12 then the mounting means may optionally be further arranged to fix to a separate gutter arranged so that the long edges and the two gutters to either side of the collector form a weather proof seal against rain water ingress and so an array of such arranged collectors and gutters forms a continuous weatherproof surface.

In the case where the insulation means at either or both the front and rear of the solar absorber and heat exchange assembly is two gas layers arranged by a separating sheet then the mounting means for the sheet is a separate bracket assembly into which the sheet is assembled either before or after assembling the bracket into the body of the collector by sliding in from one end and the bracket is so arranged in shape to slide into mating means arranged in the shape of the collector body.

Also in this case of either or both front and rear insulation is provided by the separating sheet means then the mounting bracket means for the sheet may be integral to the mounting bracket means for the solar absorber and heat exchange assembly.

To better illustrate the aspect ratio of the long narrow collector, then for instance but not limited thereto the ratio of the length of the collector to its width is at least 6 and thereby the collector is narrow compared to its length.

To better illustrate the aspect ratio of the profile of the collector body then for instance but not limited thereto the ratio of the width to the height of the profile of the body is at least 2.

Claims

1. A solar thermal collector comprising a long and narrow frame and outside glazing formed as a single piece from a clear extruded polymer so providing a sleeve-like body surrounding an internal cavity, and whereby the body is one piece of polymer with a uniform profile which may be cut to any length after the extrusion process, and further the cavity within the body is arranged to contain a gas for instance ambient air or dry air or a lower conductivity gas such as argon but not limited thereto, and within this body is provided a . solar absorber and heat exchange means which is an assembly that runs substantially the whole length of the body and substantially fills the width of the cavity within the body, and further the sunward face of the assembly is adapted to be highly solar radiation absorbing for instance by the application of a solar absorbing coating but not limited thereto, and this assembly is arranged in location within the body so that there is provided one or more gas layers in the gap between the front surface of the assembly and the front inner surface of the body and further the thickness of the one or more gas layers is arranged to be any that is suitable to reduce convection and reduce conductive heat loss within each gas layer and which arrangement of one or more gas layers thereby provides transparent insulation means between the front surface of the assembly and the front inner surface of the body through which sunlight enters the collector, and preferably the front gas gap is arranged to contain two gas layers but not limited thereto, and further an insulation means that is arranged between the rear surface of the assembly and the rear inner surface of the collector body which means for instance is provided as one or more gas layers but not limited thereto and in which case the thickness of the one or more gas layers is arranged to be any that is suitable to reduce convection and reduce conductive heat loss within each layer, and further the solar absorber and heat exchange assembly is arranged to be held in place within the cavity of the body by a fixing means that permits sliding movement along the long axis of the body so permitting differential thermal expansion between these, and optionally but not limited thereto this fixing means for the assembly is arranged to be along its long edges to the body by a bracket means which is either an integral part of the body or preferably a separate arrangement made from a stiff and high temperature polymer with a heat deflection temperature higher than the maximum expected for the solar absorber and heat exchange assembly, which bracket means is adapted if separate to the body to be assembled into the body by sliding in from one end of the body for instance by a hooking shape which mates with a corresponding shape arranged in the profile of the body but not limited thereto, and so as a result of the sliding fixing means the solar absorber and heat exchange assembly is further arranged to be assembled into the body by sliding in from one end or the other, and the fixing means is arranged to have a temperature which is below the heat deflection temperature of the body material at its points where it meets the body by its relatively long heat conducting path from the assembly to the body and for instance the length of this path may be increased as necessary to achieve this temperature by adapting the width of the fixing means, and further the solar absorber and heat exchange assembly is arranged with one or more thermally communicating heat transfer fluid pipes which may be integral to the assembly or separate, and the ends of the collector body are arranged to be closed by end caps that either completely seal against gas ingress or egress or alternatively are arranged with means to permit sufficient gas movement to balance the pressure external and internal to the collector, and through at least one end cap the heat transfer fluid is arranged to pass by a communicating means to enter and exit the collector device and preferably the heat transfer fluid enters through a conduit means at one end cap and exits at the other but not limited thereto, and optionally either or both the front and rear surfaces of the body are further adapted with one or more internal ridge features spaced across their inner surface and integral in material with the body and thereby the body is arranged to be stiff against bending along its long dimension.

2.. A solar collector device according to claim 1 wherein the polymer material of the body is polycarbonate.

3. A solar collector device according to claim any previous claim wherein the length of the collector is between 50cm and 10m, and preferably between 2.5m to 5m but not limited thereto.

4. A solar collector device according to any previous claim wherein the width of the collector is between 10cm and 50cm, and preferably around 20cm but not limited thereto.

5. A solar collector device according to any previous claim wherein the one or more gas layers are each between 5mm and 30mm in thickness.

6. A solar collector device according to any previous claim wherein the ratio of the length of the collector to its width is at least 6 and thereby the collector is narrow compared to its length.

7. A solar collector device according to any previous claim wherein the ratio of the width to the height of the profile of the body is at least 2.

8. A solar collector device according to any previous claim in which the profile is substantially rectangular wherein the width is greater than the height.

9. A solar collector device according to any previous claim in which the profile is curving and preferably the curvature is approximately circular but not limited thereto and the subtended angle is up to and including 180 degrees which is semi-circular.

10. A solar collector device according to any previous claim wherein the means to form two insulating gas layers in the sunward gas gap is a clear glazing sheet arranged to separate the gas gap into two layers of gas and the thickness of these two layers is further arranged to reduce convection and reduce conductive loss across them.

11. A solar collector device according to claim 10 wherein the sheet is arranged to be held in place at least along its long edges by a mating means with the body of the collector which means is further arranged to permit the glazing sheet to be assembled into the body by sliding in from one end or the other and thereby as the sheet may become hotter than the body in operation of the collector then the sheet is free to thermally expand along the long axis and so avoid build-up of mechanical stress, and further the thickness of the sheet is arranged to be either thick enough to support its own weight or alternatively the thickness is arranged to support the weight of the sheet in conjunction with the sheet being in slight tension as it sags between its mounting along its long edges and thereby the material may be very thin and less than that needed for free standing self-support.

12. A solar collector device according to claim 10 or 11 in which the glazing sheet is between 0.1 mm and 3mm thick.

13. A solar collector device according to claim 10 or 1 1 or 12 in which the glazing sheet is further adapted to be none reflective on its sunward surface for instance with the application of an antireflective coating or by texturing the surface to be antireflective for instance with a nano- texture which acts as a continuous refractive index like a moth's eye.

14. A solar collector device according to claim 10 or 1 1 or 12 or 13 wherein the material of the glazing sheet is a clear polymer and in particular polycarbonate but not limited thereto and which material is arranged with a heat deflection temperature that is higher than the expected highest temperature expected to be experience by the material during collector operation.

15. A solar collector device according to claim 10 or 1 1 or 12 or 13 wherein the material of the glazing sheet is a clear glass.

16. A solar collector device according to any previous claim wherein the means to form two insulating gas layers between the solar absorber and heat exchange assembly and the rear inner surface of the body of the collector is a sheet arranged to separate the gas gap into two layers of gas and the thickness of these two layers is further arranged to reduce convection and reduce conductive loss across them, and further the sheet is arranged to be held in place at least along its long edges by a mating means with the body of the collector which means is further arranged to permit the sheet to be assembled into the body by sliding in from one end or the other and thereby as the sheet may become hotter than the body in operation of the collector then the sheet is free to thermally expand along the long axis and so avoid build-up of mechanical stress, and further the thickness of the sheet is arranged to be either thick enough to support its own weight or alternatively the thickness is arranged to support the weight of the sheet in conjunction with the sheet being in slight tension as it sags between its mounting along its long edges and thereby the material may be very thin and less than that needed for free standing self-support.

17. A solar collector device according to claim 16 in which the sheet material could be any suitable material for the operating temperature experienced within the collector and the material does not need to be clear so could be opaque, however a polymer such as polycarbonate is the preferred choice but not limited thereto.

18. A solar collector device according to any claim 10 to 17 inclusive wherein the mounting means for the sheet is a separate bracket assembly into which the sheet is assembled either before or after assembling the bracket into the body of the collector by sliding in from one end and the bracket is so arranged in shape to slide into mating means arranged in the shape of the collector body.

19. A solar collector device according to claim 18 wherein the mounting bracket means for the sheet may be integral to the mounting bracket means for the solar absorber and heat exchange assembly.

20. A solar collector device according to any claim 1 to 9 inclusive wherein in the case of two gas insulation layers that are arranged either or both for the front or rear insulation means then the two layers are arranged by adaptation of the shape and dimensions and spacing of the ridge features so that the ridges reduce the convection within the outer layer of gas that is in contact with the outside face of the collector, and the inner layer of gas that is in contact with the solar absorber and heat exchange assembly contains only gas with no ridge features but has a layer thickness adapted to reduce convection and reduce conductive heat loss.

21. A solar collector device according to claim 20 in which the ridges are planar and straight arranged perpendicular to the surface of the collector body.

22. A solar collector device according to claim 20 in which the ridges are planar and straight and arranged to project at a sloping angle from the face of the body all substantially at the same angle.

23. A solar collector device according to claim 22 in which the angle is arranged so that in mounted position the ridges are sloping upwards and so form pockets which trap cool air.

24. A solar collector device according to claim 20 in which the ridge is arranged as an L shape where the top of the L connects to the body of the collector and the bottom right end of the L is arranged to be close to the next ridge so as to form a substantially closed pocket, and this pocket is arranged in width and depth to reduce convection within it in any mounted orientation.

25. A solar collector device according to any previous claim in which an additional insulation material is placed between the rear inner surface of the body and the solar absorber and heat exchange assembly and preferably place in contact with the rear inner surface of the body and preferably arranged with a gas gap between the insulation material and the assembly but not limited thereto.

26. A solar collector device according to any previous claim in which the communicating means for the heat transfer fluid to pass through the end cap sealing means for the body is a pipe that passes through the sealing means of the end cap which sealing means is arranged so that the pipe may slide through the sealing means without binding and so accommodate the differential thermal expansion between the solar absorber and heat exchange assembly and the body.

27. A solar collector device according to claim 26 wherein the pipe and hole are further provided with gaskets and sealing at the end caps of the collector module to prevent gas exchange from the inside to the outside ambient air.

28. A solar collector device according to claim 27 in which is further provided a conduit from the outside ambient air to the inside air which outside air is arranged to pass through an air drying device either external to the collector module or integral inside one or the other end cap and thereby at high temperatures the internal air expands out through the conduit and air drying device and is vented to the outside, and in cold temperatures the outside air is drawn inside the collector module via the air drying device and so maintaining the dry conditions desired inside the collector module.

29. A solar collector device according to claim 27 in which is further provided a gas conduit that communicates the internal gas within the collector with a gas expansion vessel which is located externally to the gas cavity within the body of the collector.

30. A solar collector device according to claim 29 in which the gas expansion vessel is located within one or both of the end caps of collector.

31. A solar collector device according to claim 29 in which the gas expansion vessel is located separately to the collector, and which vessel for instance may be connected to more than one collector.

32. A solar collector device according to claim 26 wherein the pipe and hole are further provided with gaskets and sealing at the end caps of the collector module arranged to allow passage of a small amount of gas so as to allow balancing of external and internal pressure.

33. A solar collector device according to any previous claim in which one or both end caps are arranged to contain a T manifold means provided to permit detachable connection and communication of the heat transfer fluid between connected collector devices so that the outlets for the heat transfer fluid of each collector are communicating by an outlet T manifold and equally the inlets for the heat transfer fluid of each collector are communicating by an inlet T manifold.

34. A solar collector device according to claim 33 in which the T manifolds lie outside the end caps and so are not internal to the collector.

35. A solar collector device according to claim 33 or 34 in which the T manifolds are connected directly to the end of the inlet and outlet fluid conduits.

36. A solar collector device according to claim 33 or 34 in which the T manifolds are connected via flexible pipe means to the end of the inlet and outlet fluid conduits so arranged to accommodate part or all of the differential thermal expansion between the body and solar absorber and heat transfer assembly.

37. A solar collector device according to claim 33 or 34 or 35 or 36 in which and the inlet and outlet of the communicating T manifolds of adjacent collector modules are connected via a flexible pipe means so that adjacent collector modules have inlet and outlet T manifolds that are connected together so that they may move with respect to each other which movement arises from differential thermal expansion between the adjacent connected modules and thereby this thermal expansion arising movement is accommodated safely by this flexible connection.

38. A solar collector device according to any previous claim in which the end cap arrangements are further arranged to be weatherproof so that rainwater and dust do not enter the end caps internal space.

39. A solar collector device according to any previous claim in which means is arranged to mount the collector to a surface such as a roof comprising an adaptation of the long edges of the collector module but not limited thereto in combination with a suitably adapted mounting rail shape so that either the mounting rail captures the collector module long edges of two neighbouring collectors in such a way as to permit sliding long the long dimension so that a collector module may be assembled with the already roof mounted rail by sliding in from one end or the other, or alternatively the rail my consist of two parts, the lower part of which is fixed to the roof and on which rests the collector module which module is then captured by the second separate part of the rail which fits into its lower mating half and is adapted to fix in a removable way to the lower part for easy disassembly, and thereby the collector may slide along the mounting means while arranged to be held in place against movement in the plane normal to the mounting means long dimension so that there is no binding between the long edges of the module and the mounting rail and thereby the collector is free to expand in length arising from thermal expansion, and further optionally one point of fixing is arranged to hold the collector in place against gravity and other forces that might arise for instance by being held at one end of the collector or the other but not limited thereto, and in particular it is preferred that this optional fixing is an end stop at the lower end of the collector for the case of an up-roof oriented collector arrangement so that the collector is prevented in this case by the end stop from sliding out of the mounting means in a downward direction but not prevented from sliding up.

40. A solar collector device according to claim 39 in which the solar collector is arranged to be mounted flat to the roof so that each collector in the array is arranged to be mounted in the same orientation and at the same vertical angle as the roof.

41. A solar collector device according to claim 39 in which the solar collector is arranged to be mounted stepped up from the roof plane in an across-roof mounted orientation so that each collector in the array is arranged to be mounted in the same orientation and at a different and more vertical angle than the roof.

42. A solar collector device according to claim 41 in which the stepped mounting means comprises a weather flange, connecting leg, and roof-butting leg, and further the connecting leg may be arranged to slope so as to form a gutter or alternatively the connecting leg may be arranged horizontally or slightly sloping away and downwards from the higher connected collector module so as to direct rain water and snow away and downwards and so not requiring a gutter to collect and drain the rain water, and the roof butting leg is arranged to fix to the roof or mounting surface by a multiplicity of fixings distributed along the length of the mounting rail and whose position on the mounting rail is optionally higher when mounted than the top of the flange so that water in the gutter does not reach the level of the fixing hole and thereby making the mounting rail weather proof and preventing water ingress onto the mounting surface, and by further arranging the length of the mounting leg and its angle to the roof abutting leg then any desired mounted angle of the collector modules may be achieved, and in particular a range of such angles and lengths is intended in this invention so that an appropriate mounting rail arrangement may be chosen to achieve the desired mounted angle of the collector module for the particular mounting surface angle and latitude of the installation on the planet and desired season for optimal operation.

43. A solar collector device according to claim 39 or 40 or 41 or 42 in which the mounting means are adapted so that the mating between the mounting means and the collector is optionally weather proof so that the array of mounted collectors may optionally form a continuous and weatherproof roof.

44. A solar collector device according to claim 39 or 40 or 41 or 42 in which instead of a long rail the mounting means is provided by two or more discrete brackets fixing at discrete points along the length of the collector.

45. A solar collector device according to claim 44 wherein the discrete bracket fixes to both the long edges of a collector and so the collector is independently held rather than sharing a bracket between neighbouring collectors and so the collectors may be spaced according to the roof tiles spacing in this case.

46. A solar collector device according to claim 44 or 45 wherein the discrete bracket mounting means fixes to the roof material such as tiles or batons by arranging a roof hooking fixing means.

47. A solar collector device according to any claim 39 to 46 inclusive in which a gap is further arranged in the mounting means to accommodate thermal expansion in the width of the collector module.

48. A solar collector device according to any claim 1 to 38 inclusive in which a mounting means is provided that arranges to swivel the collector angle much like a louvre blind arrangement so that the angle of the collectors as a whole may be changed, for instance provided by a bearing means provided at each end of the collector, and as with a louvre blind each collector is arranged to be connected to its one or more neighbours by a means that arranges to keep the angle of each the same, for instance a double cable arrangement or a stiff connecting rod or ganged rod, and in this case a means may optionally also be provided to affect a change in the angle of the array of collectors using an active motor means or alternatively a manual means, and in this way an up-roof mounted array of collectors may be further arranged to track the sun during the day time or in an across-roof stepped mounted array the collectors may be further arranged to change their mounted angle to track the sun across the yearly seasons to be more optimally oriented for winter and optionally deliberately none optimally oriented during summer or to reduce stagnation temperature or reduce the total absorbed solar power when power is not needed, and optionally a vibration may be applied to the array through the louvre connection means so as to assist snow or ice to release from the collectors.

49. A solar collector device according to any previous claim in which the solar absorber and heat exchange assembly is a fin and heat transfer pipe type with one or more conduits for the heat transfer fluid to flow through.

50. A solar collector device according to claim 49 wherein the material of the fin and multiplicity of conduits is a polymer.

51. A solar collector device according to claim 49 wherein the material of the fin and multiplicity of conduits is an aluminium alloy.

52. A solar collector device according to any claim 1 to 48 inclusive in which the solar absorber and heat exchange assembly is a multi-port extrusion.

53. A solar collector device according to claim 52 wherein the material of the multi-port extrusion is a polymer.

54. A solar collector device according to claim 52 wherein the material of the multi-port extrusion is an alloy of aluminium.

55. A solar collector device according to any previous claim in which the two insulating gas layers either in front of or behind the solar absorber and heat exchange assembly are formed by a sheet separating means, wherein a gas temperature regulation means is further provided to reduce the maximum stagnation temperature within the collector comprising gas valves provided within the collector module and preferably at only the hot end of the collector module within the hot-end end-cap but optionally also provided within the cold-end end-cap, these valves arranged to communicate the two gas layers through the valves so that below a pre-set temperature the valves are shut and above this temperature the valves open in such a way that the higher the temperature the more the valves are open, and the operation of these valves is controlled by the gas temperature within the respective layers so that the thermostatic mechanism is in thermal contact with the respective gas layer, and by this means then above a higher pre-set temperature the valves are completely open and by this thermostatic valve operation the gas within the internal layers are allowed to communicate with the outer gas layers respectively, and thereby allowing natural convection in the up-roof mounted position of the collector module to circulate the gas internally within the collector so that the rate of heat loss from the solar absorber and heat exchange assembly is higher than it would be without the thermostatic arrangement and in particular arranged so that the temperature of the sheets do not exceed their maximum safe operating temperature.

56. A solar collector device according to claim 55 in which the valves are optionally flap valves with their point or rotation at one end or located near the middle of the flap.

57. A solar collector device according to claim 55 or 56 in which the thermostatic mechanism is optionally a bi-metallic strip or coiled bi-metallic strip.