WO2007109900A1

WO2007109900A1 - Solar collector

Info

Publication number: WO2007109900A1
Application number: PCT/CA2007/000505
Authority: WO
Inventors: David Gerwing; Steven Tennant; Leonard Winn; Terry Graham
Original assignee: Menova Energy Inc.
Priority date: 2006-03-28
Filing date: 2007-03-28
Publication date: 2007-10-04

Abstract

A solar collector comprises a trough-like reflector having opposed front and rear longitudinal sidles, each defining an air-to-solid interface, and an absorber for receiving solar radiation from the reflector, the absorber being disposed at a position that is offset towards one of the front and rear edges from a central position between the edges of the reflector. The reflector includes first and second opposed spaced apart panels, the first panel having a concave profile transverse to its length for concentrating solar radiation towards the offset absorber, and spacer means are provided for holding the first and second panels in a fixed, spaced apart relationship to form a monacoque structure.

Description

SOLAR COLLECTOR

Field of the Invention

The present invention relates to solar collectors, and in particular to concentrating solar collectors.

Background of the Invention

Solar collectors for collecting solar energy generally fall into one of two categories: concentrating and non-concentrating. Concentrating solar collectors typically comprise a reflector for reflecting and concentrating received solar radiation towards an absorber. The absorber may include a conduit for carrying a heat transfer fluid for absorbing solar thermal energy and/or an array of photovoltaic cells for converting solar energy into electrical energy. The reflector is either in the form of a circular dish with the focal position above the center of the dish, or a trough-like, parabolic reflector which produces a line focus along the length of the reflector. in the latter case, the absorber typically comprises a radiation absorbing tube positioned centrally above the reflector and extending along its length.

Focussing or concentrating solar collectors typically require some type of sun tracking mechanism and tracking control system to vary the orientation of the collector to maintain the focal position of the solar radiation of the absorber surface. Non-focusing solar collectors generally comprise flat, solar absorbing panels which are fixed in position and do not actively track the sun.

An example of a trough-like solar collector system is disclosed in WO 2005/090873. The solar collector comprises a parabolic trough-like reflector having a longitudinal absorber positioned above the reflector ar,d mounted thereon by means of a central support upstanding from the reflector. The reflector includes spaced apart ribs fixed to the underside of the reflector panel to help maintain the shape of the reflective surface. The absorber comprises a longitudinal plate having a radiation absorbing surface which may include an array of solar cells mounted thereon. A conduit is positioned adjacent the back of the plate for transferring solar thermal energy into a heat transfer fluid. Transparent panels extend from each side of the absorber to opposed longitudinal edges of the reflector to protect the reflective surface from weathering and to provide additional structural rigidity.

Summary of the Invention

According to one aspect of the present invention, there is provided a solar collector comprising a trough- like reflector having opposed front and rear longitudinal tdges, each defining an air to solid interface, and an absorber for receiving solar radiation from the reflector, the absorber being disposed at a position that is offset towards one of the front and rear edges from a central position between the edges .

In this arrangement, the absorber is offset towarda one of the longitudinal edges of the reflector, and the reflective surface has a profile which concentrates the solar radiation towards the absorber. This asymmetric arrangement allows βhadowing of the reflective surface by the absorber to be avoided so that the whole reflector surface between opposed edges thereof can be used to reflect solar radiation towards the absorber. In addition, the asymmetric profile of the reflector which may, for example, comprise a portion of a parabolic curve can be flatter than a traditional symmetric parabolic trough-like reflector, thereby reducing the tendency and propensity of the collector co collect and hold elements such as water, .mow and ice on the surface of the reflector. Additionally, this asymmetric arrangement allows one of the edges of the reflector to be ac the lowest point of the reflective surface when the reflector is positioned to receive solar radiation directly overhead, again so that moisture and other elements can readily run off the reflective surface. In addition, this asymmetric arrangement may reduce the tilt angle required to remove moisture from the reflective surface .

In some embodiments, the absorber is mounted to the reflector by means of a support which is connected adjacent an edge of the reflector. This arrangement also assists in preventing the support producing a shadow or interfering with the path of solar radiation between t:h,; reflector surface and the absorber.

In some embodiments, the profile of the reflective surface of the reflector is asymmetric between εhe opposed front and rear edges to concentrate substantially all of the direct solar radiation towards the absorber.

In some embodiments, the reflector comprises opposed -spaced apart first and second panels, with the first panel supporting the reflective surface, and the second panel being positioned below the first panel.

In some embodiments, the panels are spaced apart by front and rear edge portions. In some embodiments, one or more rib members in provided for at least partially defining the profile of the reflector surface.

In some embodiments, one or more rib members are provided between spaced apart panels of the reflector.

Tn some embodiments, the reflector comprises a monocoque structure.

In some embodiments, the collector comprises one or more arms extending from a position adjacent at least one of a front and rear edge of the reflector for supporting the absorber. ϊn some embodiments, an inner edge of the or each arm curves outwardly away from the edge of the reflector adjacent which the arm is attached.

In some embodiments, the absorber comprises an absorbing surface for absorbing solar radiation, the absorbing surface having a width transverse to the longitudinal direction of the reflector, and a solar energy to electrical energy conversion device having a width in a direction trnasverse to the longitudinal direction of the reflector, the solar energy to electrical energy conversion device being disposed on the absorbing surface, wherein the width of the device is less than that of the absorbing surface. In some embodiments, the width of the absorber is equal to or greater than the maximum spread of solar radiation at the absorber surface, so that the absorber is able to receive all of the concentrated solar radiation as the spread varies with the position of the sun.

In some embodiments, the absorber includes means defining an aperture for admitting solar radiation onto the absorbing surface, the aperture having a width transverse to the longitudinal direction of the absorber which is less than the width of the absorbing surface. The reflector may be adapted to concentrate the solar radiation towards a focal position which is spaced from and is in front of the absorber surface. This arrangement assists in distributing the solar radiation across the width of the absorber, while allowing the radiation to pass through the aperture. rhe focal position, i.e., the most narrow portion of the concentrated radiation may be positioned near the aperture. Reflector (s) may be provided between the aperture and the absorber to reflect radiation that may be reflected or emitted from the absorber, back to the absorber.

In some embodiments, the absorber comprises a plurality of conduits for carrying fluid for absorbing heat from the absorber and wherein the conduits are positioned in side-by-side relationship across the width of the absorber for absorbing thermal energy across the width of the absorber. This arrangement helps to provide a more uniform temperature distribution across the absorber.

In some embodiments, thermal insulation is provided to thermally insulate the conduits.

In some embodiments, two adjacent support arms form an enclosure for enclosing at least one of electrical cables and/or connectors and/or fluid carrying conduits to/from the absorber.

According to another aspect of the present invention, there is provided a solar collector comprising a reflector assembly for supporting a reflective surface for receiving solar radiation and an absorber positioned for receiving solar radiation reflected from the reflective surface, the reflector assembly comprising first and second opposed spaced apart panels, the second panel being positioned below the firat panel and each having opposed longitudinal edges extending along the length thereof and a width between the opposed longitudinal edges, and wherein the first panel has a concave profile transverse to its length for concentrating solar radiation towards the absorber, and spacer means for holding the first and second panels in a fixed, spaced apart relationship.

In this arrangement, the upper and lower panels of the reflector assembly, which are firmly held in a spaced apart relationship, with the upper panel having a concave profile, provide a reflector with considerably enhance-d structural rigidity in comparison to single sheet reflectors, and removes the need for a translucent cover above the reflector, thereby simplifying the deaign and removing the problem of condensation and the ingress of moisture in the space between the translucent cover and the reflector.

In some embodiments, the spacer means comprises one or more rib members positioned between the first and second panels.

in some embodiments, the spacer means comprises a plurality of rib members spaced apart in a direction along the length of the firat and second panels.

In some embodiments, at least one rib member has an upper surface which at least partially defines the profile for directing and concentrating the solar radiation towards the absorber, and the first panel is firmly held against the profile forming upper surface of the rib member. In some embodiments, the upper surface of at lϋast one rib member is substantially continuous along the length of the rib member and the first panel is held against the upper surface over a major portion of the length of the rib member .

In some embodiments, the second panel has a non-linear transverse profile between its opposed longitudinal edges. The profile may for example be curved and/or convex. The non-linear profile may increase this structural rigidity of the reflector assembly.

In some embodiments, the rib member has a lower surface, and the second panel is held against the lower surface of the rib member. The lower surface of the rib member may have a non-linear profile, for example a convex profile which may correspond to the profile of the second panel .

in some embodiments, the rib has one or more apertures formed therein. This reduces the weight of the rib, saves material and reduces cost. In some embodiments, one or more ribs may be formed by stamping a sheet material.

In some embodiments, the spacer means comprises at least one of (1) a web extending between the first and second panels and extending along one of the longitudinal edges, and (2) first and second webs extending between, the first and second panels and each extending along a respective opposed longitudinal edge of the first and second panels .

In some embodiments, the upper surface of the first panel provides a reflective surface for reflecting and concentrating solar radiation towards the absorber. In some embodiments, the solar collector further comprises fastening means for fastening a reflective panol for reflecting solar radiation towards the absorber above and against the first panel.

In some embodiments, the fastening means comprises at least one of (1) a longitudinal member extending in a direction along the length of the first: panel and adjacent an edge of the first panel for holding the reflector panel against the first panel, and (2) first and second longitudinal members each extending in a direction along the length of the first panel and being disposed adjacent a respective longitudinal edge of the first panel and each for holding the reflective panel against or towards the first panel .

in some embodiments, the fastening means is adapted to releaaably fasten the reflective panel against the first panel to enable the reflective panel to be removed from the assembly. This allows the reflective surface to be renewed when required, e.g. once the performance of the present reflective surface falls below an acceptable level.

In some embodiments, the solar collector further includes sealing means for sealing against ingress of the ambient between the reflective panel and the first panel .

In some embodiments, each of the longitudinal edges of the reflector assembly define an air to solid interface, and the absorber is disposed at a position that is offset towards one of the edges from a central position between the edgee . In some embodiments, the profile of the reflective surface of the reflector is asymmetric between the opposed edges of the reflector assembly.

In some embodiments, the aolar collector furcher comprises one or more arms extending from a position adjacent a longitudinal edge of the reflector assembly for supporting the absorber - One or more of the arms may De positioned at or outside the longitudinal edge so that it does not overlap or encroach upon the reflective surface. In some embodiments, each arm extends from a position adjacent the rear longitudinal edge of the reflector assembly.

In some embodiments, the or each arm curves outwardly away from the edge adjacent which the arm is attached. This arrangement assists in avoiding shadowing of the reflective surface by the absorber support. In some embodiments, the arms may be curved on one or both aides- This may assist in strengthening the arm or making the arm more rigid.

In some embodiments, one or more arms have one or more apertures formed therethrough. Advantageously, this reduces the weight of the arms, and saves material and cost.

In some embodiments, the absorber is mounted to at least one arm in a manner which allows relative movement between the absorber and the arm in a longitudinal direction. This arrangement allows the absorber to expand and contract longitudinally due to variations in temperature independently of the arms, i.e. without causing longitudinal displacement of the arms. In some embodiments, the absorber comprises a housing, and the housing is mounted to the arm in a manner which allows relative movement between the arm and the housing in the longitudinal direction. This arrangement allows the housing to expand and contract longitudinally, for example, due to temperature variations independently of the arm.

In some embodiments, the absorber comprises .an absorber member for absorbing aolar radiation and the absorber ia mounted to an least one arm in a manner which allows relative movement between the arm and the absorber member in the longitudinal direction. Advantageously, this arrangement allows the absorber member to expand and contract longitudinally, for example, due to variations in temperature, independently of the arm.

in some embodiments, two adjacent arms form the aides of an enclosure for enclosing at least one of an electrical cable, a connector and a fluid carrying conduit coupled to the absorber. In some embodiments, the enclosure further comprises at least one of (1) a panel extending between the adjacent arms, and (2) opposed first and second panels extending between the adjacent arms and forming the enclosure therebetween.

In some embodiments, the absorber comprises a plurality of conduits for carrying fluid for absorbing heat from the absorber, and wherein the conduits are positioned in side-by-aide relationship across the width of the absorber for absorbing thermal energy across the width of the absorber. Advantageously, this arrangement helps to reduce temperature gradients across the absorber surface-.

Maintaining a uniform temperature across the surface may be beneficial for the performance and efficiency of solar to electrical energy conversion devices which may be mounted on the absorber surface .

In some embodiments, the conduits are collectively arranged to cause fluid to flow across a major part of trie width of the absorber.

In øome embodiments, the absorber comprises a plurality of conduits, for example, two or three or more, wherein the conduits are interconnected to provide a continuous fluid path. A plurality of conduits may share a common inlet and/or a common fluid outlet. The fluid inlet and fluid outlet may be positioned adjacent one another. In acme embodiments, the fluid inlet and fluid outlet may be positioned between the same aupport arms and/or positioned adjacent the same arms. Xn some embodiments, the inlet and outlet are formed in the same conduit .

In some embodiments, the absorber comprises a receiving surface for receiving solar radiation reflected from the reflector, the reflector being arranged to reflect solar radiation onto the receiving surface over a widuh of the receiving surface which decreases from a predetermined width as the angle of incidence of solar radiation on the reflector moves away from 90° to the longitudinal axia of the reflector, and wherein the receiving surface inclαdss means for converting solar radiation into electrical energy and has a width which is less than the predetermined width. Advantageously, this arrangement assists in reducing the time, if any, over which Bolar radiation is incident on part of the energy converter surface but not on all of the surface of the converter. Avoiding the presence of dark regions on the surface of the solar to electrical energy converter may assist in preventing a deterioration in performance .

In some embodiments , the absorber comprises .in absorbing surface for absorbing solar radiation, the absorbing surface having a width transverse to the longitudinal direction Qf the reflector and a solar energy to electrical energy conversion device having a width in a direction transverse to the longitudinal direction of the reflector, the solar energy to electrical energy conversion device being disposed on the absorbing surface, and wherein the width of the device ia less than that of the absorbing surface.

In some embodiments, the absorber comprises a plurality of spaced apart solar radiation to electrical energy conversion devices and a plurality of translucent panels spaced from and positioned above the solar radiation to electrical energy conversion devices, and wherein the; junction between the two adjacent panels is positioned within the gap between two adjacent solar radiation to electrical energy conversion devices. This arrangement avoids the junction between two adjacent translucent panels being positioned above a solar radiation to electrical energy conversion device, thereby avoiding any effect of. the junction on the device in reducing the amount of solar radiation transmitted wherethrough.

in some embodiments, the solar collector further includes mounting means for rotatably mounting the soLac collector about a longitudinal axis. This arrangement allows the position of the reflector to vary as the height of the εun changes over a daily period. In some embodiments, the solar collector further comprises mounting means for rotatably mounting the solar collector about an axis substantially perpendicular to the longitudinal axis, for example about a substantially vertical axis. This arrangement allows the position or the solar collector to vary as the sun moves from east to west (azimuthal variation) , so that the direction of solar rays incident on the solar collector can be maintained orthogonal to the longitudinal axis of the reflector as the sun changes position over a daily period.

In some embodiments, the solar collector may be mounted on a one axis tiling system or a two axis tilting and rotating system.

Brief Description of the Drawings

Examples of embodiments of the present invention will now be described with reference to the drawings, in which:

Figure 1 shows a perspective front and right end view of a solar collector and mounting system, according to an embodiment of the invention;

Figure 2 shows a cross-sectional view of the solar collector shown in Figure l;

Figure 3 shows a perspective view of part of a solar collector according to an embodiment of the present invention;

Figure 4 shows a perspective view of a solar collector from the rear thereof according to an embodiment of the present invention, with fluid conduits housed between two support arms ; Figure 5 shows a partial perspective cut-away view of an absorber according to an embodiment of the present invention,-

Figure 6 shows a cross-sectional view of an absorber according to an embodiment of the present invention;

Figure 7 shows a fluid conduit arrangement £or an absorber according no an embodiment of the present invention,-

Figure 8A shows a cross-sectional view through an absorber according to an embodiment of the present invention, with a narrow reflected light pattern;

Figure 8B shows a cross-sectional view through the absorber of Figure 8A with a wider reflected light patte-rn incident thereon;

Figure SC shows a plan view of the absorber shown in Figures 8A and 8B;

Figure 8D shows a front view of the absorber £3hown in Figure 8C;

Figure 9 shows an example of the curvature of a solar collector and relative position of an absorber according to an embodiment of the present invention;

Figure 10 shows an array of solar collectors each with a ground mounting and anchoring system according to an embodiment of the present invention;

Figure 11 shows an array of solar collectors mounted on a ground anchored two axis cracking system according to an embodiment of the present invention; Figure 12 shows an array of solar collectors on a roof mounted two axis tracking system according to an embodiment of the present invention,- and

Figure 13 shows a graph of the available solar energy from various tracking configurations ao a function of time .

Description of Embodiments

Referring to Figures 1 and 2, a solar collector 1 according to an embodiment of the present invention comprises a reflector assembly 3 for supporting a reflective surface 5 for receiving solar radiation 7, and an absorber 9 positioned for receiving solar radiation reflected from the reflective surface 5, The reflector assembly 3 has front and rear longitudinal edges 11, 13 and a first panel 15 extending along the reflector assembly 3 and having a concave profile transverse to its length for concentrating the solar radiation towards the absorber 9 as for example indicated by the solar ray lines 17. The absorber is positioned asymmetrically above the reflective surface, i.e. at a position which is offset from a central position between the longitudinal edges of the reflector assembly which define a solid to air interface. in this embodimant , the absorber 9 is positioned substantially directly above the rear edge 13 when the reflector is oriented to receive vertically incident solar rays 7. The concave profile of the reflector is shaped to concentrate and direct the solar radiation towards the rear edge of the reflector assembly and onto the absorber. The profile of the reflective surface is relatively shallow, reducing the ability of the reflector surface to accumulate moisture, water, ice and snow. The rear edge in the orientation of the reflector shown in Figure 2 is the lowest point of the reflector surface allowing water and other elements to readily drain from the surface, over the rear edge. An example of the calculated surface profile of the reflector is described below with reference to Figure 9. The reflector assembly further comprises a second panel 19 positioned below the first panel 15, and the panels 15, 19 are held in a spacad apart relationship by means of one or more spacer members. In this embodiment, the spacer members comprise transverse rib members 21 which are spaced apart in a direction along the length of the reflector assembly, as for example shown in Figure 3, and positioned between the first and second panels 15, 19. Each rib has an upper surface 23 which supports the first panel 15 and defines the curved profile for reflecting and concentrating solar radiation towards the absorber 9. The panel is securely held against and fastened to the upper surface of the rib 21 by any suitable means, for example adhesive. The rib has a lower surface 25 for supporting the second panel 19, and which, in this embodiment , has a convex profile which corresponds to the profile of the lower panel 19. The lower panel 19 is firmly held against: the lower surface 25 of the rib 21 and securely fastened thereto by any suitable means, such as adhesive.

The ribs 21 may be formed from sheet material and cut from the sheet material by stamping. The sheet material may comprise a metal such as aluminum, a plastic or polymeric material, a composite material, a laminate, or a combination of any of these.

The upper and/or lower edges of the rib may include a flange 24, 26 (Figure 3) to increase the support/contact area between the rib and the respective

IS panel. If the rib is formed of a sheet material, the flamge may be formed by bending a portion of the sheet.

In this embodiment, the upper surface 23 of i.h« rib 21 is continuous and the first panel is supported against the continuous upper surface of the rib. In ochi≥r embodiments, the upper surface of the rxb may be discontinuous and the panel may be supported by the ric .at spaced intervals. Similarly, in the present embodiment, the lower surface 25 of the rib is continuous and the lower panel 19 is held against the continuous lower surface. In other embodiments, the lower surface of the rib may be discontinuous and the second panel held at spaced intervals against the rib .

In this embodiment, the rib has a plurality of apertures 27 formed therethrough to reduce weight and material used.

The reflector assembly 3 further includes front and rear edge members 29, 31 which extend longitudinally along the front and rear edges between upper and lower portions 33, 35 of the reflector assembly. The longitudinal front and rear edge members 29, 31 may each comprise discrete members and may conveniently be formed as an extrusion or from sheet material. Alternatively, one or both of the longitudinal edge members may comprise an integral part of one or both of the upper and lower panels 15, 19. One or both ends of the rib may include a flange 30, 32 (Figures 3 and 4) to increase the support/contact area between the rib and the respective longitudinal edge member 29, 31. If the rib is formed of a sheet material, the or each flange may be formed by bending a portion of the sheet . The combination of the first and second panels and longitudinal front and rear edge members may be arranged to provide an enclosed apace therebetween, which may be sealed either fully or partially by any suitable means to prevent the ingress of moisture and other atmospheric elements. The reflector assembly thus formed effectively constitutes a. monocoque structure with substantially increased rigidity and stiffness in both torsion about the longitudinal axis of the assembly and normal to the reflector surface, in comparison to other structures formed of a single upper reflective panel. Although in some embodiments, the lower panel 19 may be flat, providing the lower panel with a non- linear profile, such as a convex profile, as for example, shown in Figures 1 and 2, assists in increasing the rigidity and stiffness of the reflector assembly for both torsion and in a direction perpendicular to the longitudinal axis. The longitudinal edge members 29, 31 also assist in increasing the rigidity and stiffness for both torsion about the longitudinal axis and in a direction perpendicular to the longitudinal axis.

The rib members assist in stiffening the re elector assembly in torsion, and in a direction normal to the reflector surface, and assist m preserving the curvature of the upper panel 15. in other embodiments, the rib members 21 may be omitted altogether and the spacer members for holding the first and second panels in a fixed spaced apart relationship may comprise the longitudinal edge members 29, 31. In other embodiments, one or more rib members may be provided which is fastened against only one of the panels 15, 19 but which does not extend fully across the gap between the two panels.

IS The upper surface 16 of the first panel 15 may provide the reflective surface for reflecting solar radiation towards the absorber 9. Alternatively, or in addition, the reflective surface may be provided by a separate panel which ia .supported on the first panel 15.

Fastening means may be provided for releasably fastening the separate reflective panel above the firsc panel. Referring to Figures 2 and 3, the fastening system comprises a fastening member 39 positioned adjacent the rear edge 31 of the reflector assembly which provides a receptacle or gap above the first panel 15 for receiving an edge of the separate reflector panel 40. The fastening system further comprises a releasable clip or clamping member 43 having a clamping portion 45 for placing over the opposite longitudinal edge of the separate reflective panel 40 and holding the longitudinal edge against or towards the first panel 15. The clamping member 43 may include a releauable fastener 47 which engages a complementary fastener 49 of the reflector assembly, A seal 51, 53 may be provided for sealing against the ingress of moisture between the first panel 15 and the separate reflective panel 40 along the opposed longitudinal edges of the reflector. The clamping members 39, 43 may extend continuously along the lengch of the reflector assembly or may comprise discrete members which are spaced apart along the reflector assembly. The clamping members may conveniently be formed by extrusion.

Referring to Figures 2 and 3 , to mount a separate reflector panel 40 to the reflector assembly, the rear longitudinal edge of the panel is inserted in the receptacle 41 of the rear edge clamping member 39 and the front edge clip or clamping member 43 is then placed over the opposite longitudinal edge of the separate reflector panel and secured co the reflector assembly. To assisc in ensuring that the separate reflector panel achieves tile correct transverse profile for concentrating solar radiation towards the absorber 9, the reflective panel may be preformed with a transverse curvature before being mounted to the reflector assembly, and in one embodiment, the transverse curvature may be tighter than the required curvature to assist in urging portions of the reflector panel between its opposed longitudinal edgeø against ch.≥ first panel 15.

The releasable panel fastener allows reflector panels to be replaced, as required when the performance of the reflector surface deteriorates to an unacceptable level. Tn other embodiments, the fastener 39 may be positioned along the front edge, and the fastener 43 may be positioned along the rear edge. In other embodiments, any other form of releasable fastening system may be used to secure a separate panel to the reflector assembly or provision ol: a fastener may be omitted altogether.

The absorber 9 comprises a longitudinal member which extends along the length of the reflector assembly and which is supported above the reflector assembly by a plurality of spaced apart support arms or stanchions E.7. Referring to Figures 1 to 3 , the support arma each have upper and lower ends 59, 61 with the absorber 9 being coupled to the upper end and the lower end 61 being connected to or at a position adjacent the rear edge 31 of the reflector assembly. Mounting the support arms at ox outside a longitudinal edge of the reflector prevents the absorber support interfering with the path of solar raya 17 between the reflector surface and the absorber, and allows the whole dimension between opposed edges of the reflector assembly to be used to reflect solar energy to the absorber. This allows che distance between opposed edges of the reflector assembly to be reduced in comparison to other configurations in which che support structure upstands from a position intermediate between the longitudinal edges of the reflector, allowing the reflector assembly to be more compact .

In this embodiment, each arm 57 has an inside edge 63 which curves outwardly, away from the edge 31 of the reflector assembly to assist in ensuring that no part of the arm interferes with che path of the solar radiation reflected from the reflector surface. The outer edge 55 of each arm is also curved in a similar manner to the inside edge S3. The curved inside and/or outside edges of each arm may assist in strengthening the arm and increasing its rigidity or stiffness. Each arm comprises a plurality of apertures 67 formed therethrough to reduce wind loading on the arm, to reduce weight and save material. Each arm may be formed from aheet material and may be formed by stamping. The material may comprise a metal, plastic or other polymeric material, a composite material, a laminate or any combination of these. Each arm may include a flange 69, 71 along its inside and/or outside edge at an angle to the plane of the arm to increase its strength and rigidity, for example, in a direction transverse to the plane of the arm. The upper and/or lower ends 59, 61 of the arm may include a flange 73, 74 extending at an angle to the plane of the arm, for example at substantially 90° thereto and conveniently provides a mounting point and attachment surface for attaching the absorber to the arm and the arm to the reflector assembly.

Referring to Figures 2 to 7, the absorber 9 comprises a longitudinal absorber member 75 having a front, radiation absorbing surface 77 and a plurality of conduits 77, 79, 81 positioned behind and in thermal communication with the solar absorbing surface 77. The absorber member 75 is mounted within an absorber housing 83 which is mounted on and coupled to the end of each arm or stanchion 57. The housing includes opposed side members 85, 87 which extend forward of the front surface 77 of ths absorber member 75 and whose opposed ends 89, 91 define an aperture S3 therebetween for receiving solar radiation reflected from the reflector. The aperture 93 thus formed comprises a longitudinal slot which extends along the length of the absorber and has a width which is leas than this width of the absorber member 75.

The opposed side members 85, 87 may include a reflective internal surface 95, 97 for reflecting solar radiation that may be reflected from the absorber member 75 back to the absorber member, thereby increasing the efficiency of the absorber. In this embodiment, the reflective surfaces 95, 97 taper inwardly towards the aperture 93 and are angled relative to the absorber froriC surface 77.

The absorber housing S3 may be connected to one or more support arms in a manner which prevents relative movement between the housing and the arm in the z-direct: ion, and also in the x and y directions. In some embodiments, the absorber housing 83 may be coupled to one or more other arms 57 in a manner which allows relative movement between the arm and the housing in the longitudinal (i.e. z) direction with movement restricted in the x and y directions. This arrangement may be advantageous in allowing the housing 83 to expand longitudinally with increasing temperature without causing corresponding longitudinal displacement of the arms. The coupling may comprise any suitable arrangement, for example, the coupling may include one or more protrusions 94 (Figure 6) , extending from the housing (or arm) and one or more receptacles 9ά in the arm (or housing) for accommodating the protrusion, and which allows the protrusion to slide relative to the receptacles in the longitudinal direction but which restricts movement in the x and y directions.

In some embodiments, the absorber member 75 is; mounted to the housing 83 in a manner which allows the absorber member to move relative to the housing in the! longitudinal direction to allow for thermal expansion and contraction of the absorber member 75 relative to the housing and vice versa. Referring to Figure 6, the mounting may comprise a slidable mounting, in which an «:dge or other portion 99 of the absorber member 75 is received within a longitudinally extending groove 101 of the housing 83, or vice versa, In other embodiments, any other form of mounting may be used which allows relative movement between the housing and absorber member 75, examples of which may include wheels or ball bearings or other coupling arrangements .

Referring to Figures 4 and 5, fluid lines 107, 109 are provided for carrying heat transfer fluid to and from the absorber, respectively. Both fluid lines may be connected to the absorber at positions which are proximate one another as shown for example in Figure 5. The junctions or points of connection between the absorber and both fluid lines may both be positioned between the same two support arms 57A, 57B as for example shown in Figure 5. An enclosure ill may be formed between the adjacent support: arms 57A, 57B for enclosing the fluid lines 107, 109 and optionally electrical cable (s) for solar σell(s). The enclosure may be formed at least partially by the adj acent support arms 57A, 57B and by a rear and/or front pane L member 113, 115 extending between the arms. The enclosure may include thermal insulation for thermally insulating one or both fluid lines.

Referring to Figure 5, the absorber housing 8:3 may be attached to one or both the support arms 57A, 57B in a manner which prevents relative longitudinal movement between the support arms and the housing for example by one or more bolts 116. One or more other arms may be connected to the housing to allow relative longitudinal movement: therebetween.

Referring in particular to Figures 5 and 7, the absorber member 75 comprises three longitudinally extending conduits 77, 79, 81 positioned side-by-side across th«; width 82 of the absorber member. The middle conduit 79 has a fluid inlet 121 and a fluid outlet 123 formed therein. An end cap 125 is provided for connecting the end of the middle conduit 79 to the ends of each of the outer conduits 77, 81. The ingress fluid supply line 107 is coupled to the fluid inlet 121 and the egress fluid line 109 is coupled to the fluid outlet 123. A common connector block 127 may be: used to connect both fluid lines 107, 109 to the respective- inlet and outlet ports 121, 123, or a separate coupling may be provided for each fluid line. In use, fluid from the ingress line 107 is introduced into the middle conduit 79 via the fluid inlet 121 and is caused, by means of a flew blocker 126 between the inlet and outlet ports 121, 123 to f low r.nws rrin nnp

cap 125 directs the fluid back along the outer conduits 77, 81 towards the opposite end. The opposite end includes an end cap which is similar to end cap 125 which directs the fluid flows from Che outer conduits 77, 81 through the middle conduit 79 cowards the end 129. The fluid leaves the middle conduit 79 through the outlet port 123 to the fluid egress line 109.

Although in this embodiment the fluid inlet and outlet porta are formed in the middle conduit, in other embodiments, the inlet and outlet ports may both be formed in one of the other conduits. In other embodiments, one or more conduits may each have a fluid inlet and/or a fluid outlet.

In some embodiments, the conduits may be arranged so that the flow of heat transfer fluid therethrough provides a relatively uniform temperature across the width of the absorber. Advantageously, this may assist in optimizing the performance of solar energy to electrical converters mounted on the absorber which may be adversely affected by too high a temperature or temperature gradients.

Figures SA to 8D show various views of an absorber according to an embodiment of the present invention. The absorber 201 comprises a longitudinally extending member 203 having a generally planar front absorbing surface 205 and having a plurality of solar to electrical converters 207, 209 mounted thereon and which are spaced apart in the longitudinal direction, z. A plurality of translucent plates or panels 211, 213 are positioned above the converters and spaced apart therefrom to provide a gap 215 therebetween to reduce thermal loss from the absorber cΞiused by convection or conduction of heat that may otherwise result from a free airflow adjacent the absorber surface.

The translucent plates 211, 213 have opposed ends 215, 217 and opposed ends of adjacent plates are positioned adjacent one another and may abut each other as for example shown in Figures SC and SD. The adjacent ends are positioned within the gap 219 between adjacent solar converters so that any reduced transmissivity caused by the ends do not affect propagation of solar radiation to the solar converters. A plurality of conduits 221, 223, 225 extend longitudinally along the absorber and are positioned side by side and in thermal communication with the front surface of the absorber member 203. The conduits may be arranged to provide a relatively uniform temperature distribution across the width of the absorber to avoid local hot spots or temperature spikes which might adversely affect the performance of the solar converters. The longitudinal member and conduit may be formed separately or integrally, for example by an extrusion process.

In some embodiments, the solar collector may be arranged so that the angle between the incident solar rays and the longitudinal axis of the reflector varies over a daily period as the sun moves through the sky. For example, the sun's rays may be at 90° to the longitudinal axis at noon and at 45° to the longitudinal axis in che morning and evening, as for example shown in Figure 8D . Thus, in the morning and evening the transverse curvature of the reflector is less than at noon, in which case the focal position moves away from the reflector towards the absorber causing the width of the reflected light pattern at the absorber to be less than the width when the solar radiation is normal to the longitudinal axis, at noon for example, as shown in Figures 8A and 8B. The solar to electric ensr^gy conversion device, which may for example comprise an array of solar cells is arranged so that all of the cells capcure light, even when the sun is not normal to the absorber face, such as in the morning and the evening. Thia prevents some solar to electric energy conversion devices being positioned in the "dark", while others are still illuminated, which may deteriorate the performance of the solar to electric conversion system.

In some embodiments, the solar collector ia arranged such that when the reflected light pattern expands from the photoelectric acceptance width 227, due to changes in the angle of the sun from normal to the absorber surface (with a one axis tracking system) , the thermal acceptance width 229 ia wide enough to receive the expanded portion of the reflected light pattern. Thus, in this embodiment:, the absorber optical acceptance surface extends beyond the photoelectric acceptance width on one or both sides thereof. In some embodiments, the thermal acceptance width is wide enough so as not to lose any solar radiation collected by the reflector when the reflected light pattern extends beyond the photoelectric acceptance width.

Figure 9 shows a non-limiting example of a transverse profile of the reflective surface of the reflector according to an embodiment of the present invention and the geometric placement of a non- limiting example of an absorber relative to the reflective suri:ac:e, according to an embodiment of the present invention.

The equation defining the transverse curvatures of the reflector, with the origin at the center C of the absorber surface is

, where R = -58.003643

k = -0.79358593

a4 = -5.6637866e-8

aS = 7.87343B4e-ll

a8 = -8.97S6772e-15

alO = -2.3560559e-18

al2 = 6.43973S7e-22

zθ = 30.9488581 yO = 2.10371901

It is to be noted that dimensions ahown in

Figure 9 of the width, w_a, of the aperture 93 of the absorber 5 and the distance d₃ between the absorber surface 205 and bhe aperture 93 are not critical and c:ari be varied, aø required. It is to be noted that the accuracy of each constant may be to the first decimal place or any one or more decimal places thereafter.

Other embodiments of the reflector may have any other suitable curvature and geometrical configuration with the abaorber.

Mounting System

Embodiments of the solar collector may be mounted on either a one or two axis tracking system to change the position of the solar collector with movement of the ti:urι. A one axis tracking system generally rotates the solar collector about an axis extending longitudinally of the reflector, e.g. in the vertical plane and a two axis tracking system additionally tracka in the azimuthal direction, i.e. rotates the solar collector in the horizontal plane. Referring again to Figure I , the sol.ar collector 1 is mounted on a one-axis tracking system. The tracking system comprises a surface mounting system which comprises structural sections 10 which may be interconnected using any suitable technique, including, for example, connections that do not require welding or metal fusing . For example, the structural sections may be connected together using clamps, or other mechanical means, connectors or couplers. The mounting system shown in Figure 1 may be suitable for supporting the solar collector on a surface such as a building roof 12 with limited point load support capability.

in some embodiments, one or more of the structural sections may comprise a tubular section. The tubular sections 10 may have any desired cross- sectional geometry such as circular or square or rectangular.

The mounting system may include one or more pads 14 having an area which is greater than that of t.hss structural sections 10, and for example which may serve to spread the load to more uniformly distribute weight and wind load to the support structure below, which may comprisie the membrane of a building roof. In this embodiment, the mounting system includes a plurality of spaced apart upright: members 16 which rotacably support the solar collector about a longitudinal pivotal axis 18. An actuator arm 20 is: coupled between the mounting system (e.g. upright member 16, or other part of the mounting system) and a point on the collector displaced from the pivotal axis 18, In this. embodiment:, the actuator arm ia pivotally connected adjacent a front edge 11 of the reflector assembly 3. In operation, the actuator arm rotates the solar collector about the longitudinal axis 18 to maintain the direction of the reflected solar radiation on the absorber surface with movement of the sun.

Referring to Figure 10, an embodiment of a ground mounting system 301 for mounting a solar collector according to an embodiment of the present invention comprises an anchor post 302 having opposed ends, one end of which iis for insertion into the ground to form a support for pivotiil^'Ly mounting the solar collector thereon, and also may provide a support for an actuator 303 for tiling the solar collector.

In some embodiments, the mounting system further includes a lateral force support assembly 305 coupled to the post and capable of being positioned above the lower «nd of the post to provide an anchor for resisting lateral force. In one embodiment, the lateral force support assembly 305 comprises one or more flanges, vaneβ or other structure extending transversely away from the longitudinal axisj of the post for engaging the ground material, for example positioned below, e.g. just below the ground surface _iO7 to reduce or prevent lateral motion of the post. The support assembly 305 may be connected to the post in such a wciy that the connection prevents relative vertical motion between the support assembly 305 and the post. in some embodiments, the post may be provided with an auger or similar device 309 at the lower end thereof and which may be rigidly affixed to the anchor post. The anger tip may have a relatively low pitch. The anchor post may be augured into the ground 311 and/or a hole dug and the post assembly buried and back filled. The anchor post may be formed of any suitable material and may have any suitable cross-sectional geometry. In some embodiments, the psac 302 comprises solid wood and has a square or round structαϊ.al section which may be solid or hollow. In other emb0di.rn.2nts, the post may comprise a tubular construction formed of .any suitable material such as a metal, e.g. aluminum or sceel or other similar structural material.

A plurality of solar collectors may be arranged together in an array either back to back, as shown in Figure 10 and/or end to end, and each may be mounted m a similar manner. The solar collectors may be similar to the solar collector described above, for example with reference to any one or more of Figures 1 to 9.

Referring to Figure 11, a mounting system 401 is provided for mounting a plurality of collectors 403 in .1 stacked angled array. The mounting system may be arranged such that the collectors are stacked at an angle approximately equal to the latitude location on the p Laπet and track the sun vertically in the sky and m addition also track azimuth. This may have the effect of capturing up to 35% more direct solar radiation than an east -west axii; single axis tracking system, as for example shown in th(. graph of Figure 13.

The stacked angular mounting system may comprise a rotary support 411 for enabling the mounting system 4Ul to rotate about the vertical axis 407 (i.e. the azimuth axis shown in the figure) . The support also enables one; or more reflectorβ of the solar collectors to rotate to different angles of inclination, e.g. about: the longitudinal axis 409.

In some embodiments, the azimuth rotation system 411 comprises a windlass winch 414, cable 415, an extrusion track, support and guide wheels, a motor 417 and a gear box 419. Other embodiments may comprise any otlnar suitable rotation system.

In some embodiments, the azimuth angle is si≥noed by a sensor, e.g. by an electric compass or other means, and fed back to a system controller.

In some embodiments, the azimuth angle is fed back to a system controller via a rotary position inducer,

In some embodiments, the mounting system includes a roller channel track which may be suitably secured to a lower support . The lower support may for example comprise a concrete or other structural slab, or any other support substrate .

In some embodiments, the rolled channel track is attached to one or more posts for a ground mounted system, for example as shown in Figure 11. The ground mounting posts may include any one or more features of the anchoring posts described above.

In some embodiments, one or more clamps 421 may be provided to join Support sections 423 (e.g. round or rectangular or square hollow tubes) , to form the support structure for the inclined collectors, as for example shown in Figure 11.

In some embodiments, a bracket 425 may be provided and may serve both to provide ths pivot support and actuator attachment means, and the bracket may be clamped or otherwise connected to the structural support sections 423 (e.g. tubes). A stamped or molded bracket may allow the actuator to be mounted beside rather than through the structural member. Aspects and embodiments of the present invent Lσn provide any one or more of the following features.

A solar collector having a trough-like reflector for focusing solar radiation on a receiving absorber wh.ich is asymmetrically positioned above the collector over at least the length of the reflector, the reflector forming a monocoque structure to stiffen the structure in torsion and to strengthen the structure in directions normal and transverse to the reflector surface.

In some embodiments, the receiving absorber extends beyond one or both ends of the reflector to absorb solar radiation when for example the sun's rays are not orthogonal to the longitudinal axis of the reflector.

The reflector structure may comprise at leasit two panels.

In some embodiments, the structure comprises; first and second opposed panels, which are spaced apart in a direction transverse to the longitudinal axis of the collector to form a space therebetween which extends the* longitudinal axis.

In some embodiments, the panels include one or more transverse stiffening members. The stiffening r.bs: may be firmly affixed to the opposed panels so as to form a monocoque structure. One or more stiffening ribs may be: formed of stamped metal, molded metal plastic, and may control the shape of the reflector surface.

The reflective surface may be provided by the upper panel facing the absorber. In other embodiments, the reflector may be clamped or otherwise rigidly held against the upper panel facing the absorber so as to assume substantially the exact curve specified by the upper panel.

In some embodiments, longitudinal extrusion** form the front and rear of the monocoque structure and are rigidly anchored to the opposed upper and lower panels and/or to the stiffening ribs.

In some embodiments, the solar collector includes a reflective surface that can easily be replaced in longitudinal sections by removing clamping extrusions and reaffixed using bolts, screws or captive features.

In some embodiments, the surface captivation system includes removable extrusions to provide a transverse clamping force to force the reflective surface to assume: the shape of the top curve generating sheet which may be rigidly attached to transverse stiffening ribs. In some embodiments, flexible seals are provided to assist in fractionally, removably clamping the reflective surface in place and assist in preventing moisture from rain or imow to enter the space between the curved generating sheet and the reflector. In some embodiments, the absorber is fixed rigidly in space in the x and y directions by support arms or stanchions and is enclosed by a housing, with a relatively narrow aperture facing the reflective surface;. The housing may be permitted to move in the longitudinal (i.e. a direction) . The support arms or stanchions may be stamped or formed with perforations to allow wind to paε.s therethrough.

In some embodiments, two support arms or stanchions may be kept front and rear with light gauge; .sheet metal, for example to provide a guide volume for electrical and/or heat transfer fluid conduit (a) and/or respective connections.

In some embodiments, the absorber enclosure is rigidly fixed in the x and y directions to one or more support arms or stanchions, but free to move longitudinally in the z direction by way of wheels, bearings, bushings or other sliding means, but fixed in the 2 direction at least one of the fluid inlet and outlet. Thermal insulation may be provided surrounding some or all surfaces of the absorber except the optical acceptance surface.

In some embodiments, the optical acceptance surface may be fitted with solar cells, thermionic diodes, electrical generation polymers or other photoelectric devices that generate electricity.

In some embodiments, the convective and conductive heat transfer from the optical acceptance surface may be minimized by translucent material placed over the surface such as low ion glass, translucent insulation, with an air gap between the material and optical acceptance surface or optionally evacuating the gap to increase the thermal insulation effect.

In some embodiments, longitudinal joints in the translucent material coincide with gaps or joints between photoelectric devices so that the joint shadow does not degrade the performance of the photoelectric device.

In some embodiments, the solar collector absorber includes a fluid path which allows a substantially colocated fluid entrance and exit from the absorber along the longitudinal direction of the absorber. In some embodiments, the fluid path substancially covers the optical acceptance area to reduce the temperature gradient across one or more photoelectric devices mounted thereon.

In some embodiments, the solar collector includes photoelectric cells positioned on the absorber optical acceptance surface such that with a one-axis tracking system, the illuminated portion of the cells is always covered, even when the sun is not normal to tha absoroer face, such ae morning and evening,

In some embodiments, when the reflected light, pattern expands from the photoelectric acceptance width due to changes in the angle of the sun from normal to the absorber surface with a one-axis tracking øystem, the thermal acceptance width is wide enough ao as not to lose any solar radiation collected by the reflector.

Other aspects and embodiments of the present invention comprise any one or more features disclosed herein in combination with any one or more other features disclosed herein, an equivalent or variant thereof. In any aspect or embodiment of the invention disclosed herein, any one or more features may be omitted altogether or substituted for another feature or element which may or may not comprise an equivalent or variant thereof. Numerous modifications and changes to the embodiments described above will be apparent to those skilled in the art.

Claims

CLAIMS :

1. A solar collector comprising a trough-like reflector having opposed front and rear longitudinal .=dges, each defining an air-to-solid interface, and an absorber for receiving solar radiation from the reflector, the abBorber being disposed at a position that is offset towards one of the front and rear edges from a central position between the edges .

2. A solar collector as claimed in claim 1, wherein the profile of the reflective surface of the reflector :Ls asymmetric between the opposed front and rear edges to concentrate and direct the reflected aolar radiation towards the absorber.

3. A solar collector as claimed in claim 1 or :> , further comprising a first panel supporting the reflective surface, a second panel positioned below the first panel and spaced therefrom by spacer means for- holding the first: and second panels in a fixed, spaced apart relationship.

4. A solar collector comprising a reflector asi.eiαbly for supporting a reflective surface for receiving solar radiation and an absorber positioned for receiving solar radiation reflected from the reflective surface, the reflector assembly comprising first and second opposed spaced apart panels, the second panel being positioned below the first panel and each having opposed longitudinal (≥dtjes extending along the length thereof and a width between the opposed longitudinal edges, and wherein the first panel has a concave profile transverse to its length for concentrating said solar radiation towards said absorber, and spacer means for holding the first and second panels in a fixed, spaced apart relationship.

5. A solar collector ae claimed in claim 3 or Λ , wherein said spacer means comprises one or more rib members positioned between che first and second panels.

6. A solar collector as claimed in claim 5, whι_r(_in said spacer means comprises a plurality of rib members spaced apart in a direction along the length of said first and second panels .

7. A solar collector as claimed in claim 5 or 6, wherein at least one rib member has an upper surface which at least partially defines the profile for directing and concentrating said solar radiation towards said absorber, and said first panel is firmly held against the profile forming upper surface of said rib member.

8. A solar collector as claimed in claim 6, wherein the upper surface of at least one rib member is substantially continuous along the length of the rib member , and the first panel is held against said upper surface over a major portion of the length of the rib member.

9. A solar collector as claimed in any one of claims 6 to 8 , wherein the rib member has a lower surface, and the second panel is held against the lower surface of the rib member.

10. A solar collector as claimed in claim 9, wherein the lower surface of the rib member has a non- linear profile.

11. A solar collector as claimed in any one of claims 6 to 10, wherein at least one rib has one or more apertures formed therein.

12. A solar collector aa claimed in any one of claims 6 to 11, wherein at least one rib is formed, by stamping a sheet material .

13. A solar collector as claimed in any one of claims 3 to 12, wherein the second, panel has a non-linear transverse profile between its opposed longitudinal edg«;e.

14. A solar collector as claimed in claim 13, wherein said second panel has at least one of a curved and convex transverse profile,

15. A solar collector as claimed m any one of claims 3 to 14, wherein said spacer means comprises at least one of (1) a web extending between said first and second panels and extending along one of said longitudinal edg«s and (2) first and second webs extending between the

and second panels and each extending along a respective opposed longitudinal edge of said first and second panels.

16. A solar collector as claimed in any one of claims 3 to 15, further comprising one or more members «ach defining the transverse profile of the first panel .

17. A solar collector as claimed in any one of claims 3 to 16, wherein the upper surface of the firsi: panel provides a reflective surface for reflecting and concentrating solar radiation towards said absorber.

18. A solar collector as claimed in any one of claims 3 to 17, further comprising fastening means fo:: fastening a re flective panel for reflecting solar radiation towards aaid absorber above and against said first panel.

19. A solar collector as claimed in claim 18, wherein said fastening means comprises at least one of (1) a longitudinal member extending in a direction along the length of the first panel and adjacent an edge of the f.rst panel for holding the reflector panel against the fir»t panel and (2) first and second longitudinal members each extending in a direction along the length of said fir.st panel and being disposed adjacent a respective longitudinal edge of the first panel and each for holding said reflector panel against said first panel.

20. A solar collector as claimed in claim 18 or 19, wherein said fastening meana is adapted to releasably fasten said reflective panel against said first panel to enable: said reflective panel to be removed from said assembly.

21. A solar collector as claimed in claim 19 or 20, further including sealing meana for sealing against ingress of the ambient between the reflective panel and the first panel.

22. A solar collector as claimed in any one of claims 4 to 21, wherein each of the longitudinal edges of the reflector assembly define an air to solid interface, and said absorber is disposed at a position that is offset towards one of the edges from a central position between the edges .

23. A solar collector as claimed in claim 22, wherein the profile of the reflective surface of the reflectoi is asymmetric between the opposed edges of the reflector assembly.

24. A solar collector as claimed in any one of claims 1 to 23, further comprising one or more arms extending from a position adjacent a longitudinal edge; of the reflector assembly for supporting the absorber.

25. A solar collector as claimed in claim 24, wherein each arm extends from a position adjacent the rear longitudinal edge of the reflector assembly.

26. A solar collector as claimed in claim 24 or 2ϊ>, wherein the or each arm curves outwardly away from the- edge adjacent which the arm is attached.

27. A solar collector as claimed in claim 25 or 2€, , wherein one or more arms have one or more apertures therethrough .

28. A solar collector as claimed in any one of claims 24 to 27, wherein at least one arm is formed by stamping sheet material .

29. A solar collector as claimed in any one of claims 24 to 2S, wherein said absorber is mounted to &t least one arm in a manner which allows relative movement between said absorber and said arm in the longitudinal direction.

30. A solar collector as claimed in claim 29, whetein said absorber comprises a housing, and said housing is mounted to said arm in a manner which allows relative movement between said arm and aaid housing in said longitudinal direction.

31. A solar collector as claimed in claim 29 or 3C, wherein said absorber comprises an absorber member foi absorbing solar radiation and said absorber is mounted to at leaat one arm in a manner which allows relative movemom; between said arm and said absorber member in said longitudinal direction.

32. A solar collector aa claimed in any one of claims 24 to 31, wherein two adjacent arms form the sides of an enclosure for enclosing at least one of an electrical cable, a connector and a fluid carrying conduit couplud to said absorber.

33. A solar collector as claimed in claim 32, wherein said enclosure further comprises at least one of (1) .a panel extending between said adjacent arms and (2) opposed first and second panels extending between said adjacent arms .and forming said enclosure therebetween.

34. A solar collector as claimed in any one of claims 1 to 33, wherein the absorber comprises a plurality of conduits for carrying fluid for absorbing heat from the absorber, and wherein the conduits are positioned in side by side relationship across the width of the absorber for absorbing thermal energy across the width of the absorbsr.

35. A solar collector as claimed in claim 34, wherein the conduits are collectively arranged to cause fluid to flow across a major part of the width of the absorber.

36. A solar collector as claimed in any one of claims 1 to 35, wherein said absorber comprises a receiving surface for receiving solar radiation reflected from the reflector, the reflector being arranged to reflect solar radiation onto the receiving surface over a width of che receiving surface which decreases from a predetermined width aa the angle of incidence of solar radiation on said reflector moves away from 90° to the longitudinal axis of the reflector, and wherein the receiving surface includes means for converting solar radiation into electrical energy and has a width which is less than said predetermined width.

37. A solar collector as claimed in claim 36, wherein the converter means has a width which is less than or equal to the width of received radiation at an angle of 30° from the orthogonal direction.

38. An apparatus as claimed in any one of claims 35 to 37, wherein said receiving surface has a width which is equal to or greater than said predetermined width.

39. A solar collector as claimed in any preceding claim, wherein the absorber comprises an absorbing surface for absorbing solar radiation, the absorbing surface having a width transverse to the longitudinal direction of the reflector, and a solar energy to electrical energy conversion device having a width in a direction transverse to the longitudinal direction of the reflector, the solar energy to electrical energy conversion device being disposed on the absorbing surface, wherein the width of the device is less than that of the absorbing surface.

40. A solar collector as claimed in any preceding claim, wherein the absorber comprises a plurality of .ip.iced apart solar radiation to electrical energy conversion devices and a plurality of translucent panels spaced from and positioned above said solar radiation to electrical energy conversion devices, and wherein the junction between two adjacent panels is positioned within the gap between two adjacent solar radiation to electrical energy conversion devices .

41. A solar collector as claimed in any preceding claim, further comprising mounting means for rotatably mounting said solar collector about a longitudinal axis ,

42. A solar collector as claimed in any preceding claim, further comprising mounting means for rotatably mounting said solar collector about a substantially vertical axis .

43. A solar collector comprising any two or more* features claimed in any preceding claim or disclosed herein.

44. A reflector for a solar collector comprising ciny combination of features of the reflector disclosed or claimed herein.

45. An absorber for a solar collector comprising jiny combination of features of the absorber disclosed or described herein.