GB2105838A - Solar energy collection system - Google Patents

Abstract

A solar energy collection system capable of tracking the sun comprises at least one concentrator unit 12, a support assembly 10 for rotatably supporting the unit, and rotation means 16, 18 for rotating the unit. The concentrator unit comprises an elongated hollow tube 38 including lens means 40 forming at least a portion of the tube for concentrating the solar energy transmitted therethrough on to a solar energy conversion means mounted therein. Each unit is supported in bearings 34 about its longitudinal axis by a pair of end members respectively secured to opposite ends of the tube, at least one of the end members beings pulley. The rotation means includes driving means 18 for a flexible cable 16 which is cooperative with the pulley for rotating the tube about the rotation axis so that the tube can be maintained at the predetermined angular position as the sun position changes. In the preferred system, the support assembly is constructed so that (1) no shadows are formed by the support assembly on the concentrator unit while the unit is tracking the sun and (2) forms a protective housing for the driving means 18. <IMAGE>

Description

SPECIFICATION Solar energy collection system The present invention generally relates to solar energy collection systems, and more particularly to an improved solar energy collection system capable of tracking the sun.

Since the advent of the energy crisis, many solar energy collection systems capable of tracking the sun have been developed. For example, see U.S.

Patent No. 4,069,812 issued to O'Neill on January 24, 1978 and U.S. Patent No. 4,144,095 issued to Mlavsky on March 13, 1979. Some of these systems, such as the one described in the O'Neill patent include collection assemblies or units comprising a troughlike concentrator and a prismatic lens mounted on the concentrator, both lens and concentratorfunc- tioning to concentrate solar energy onto a solar cell array positioned near the bottom oftheconcentra- tor. When the trough-like concentrator is of an odd geometrical configuration, such as the trapezoidal cross-sectional configuration shown in the O'Neill patent, the rotatable unit includes edges which can catch on structure which may be in the immediate vicinity.For example, where it is contemplated to use such collection units in arid or cold climates, the presence of sand or snow can impede the rotation of the units as a result of these edges. Additionally, because of the large size of each unit, although precautions can be taken to seal the lens to the trough-like concentrator to provide a weather tight seal, such seals may not be sufficient to hermetically seal each unit so that each unit can be evacuated or filled with an inert gas in order to protect the solar cell array.

Although rotatable solar energy collection assemblies having outer cylindrical geometric configurations have been developed, they have been found to have one or more disadvantages. For example, the assembly shown in the Mlavsky patent includes an outer cylindrical envelope and a solar cell array disposed within the envelope. The envelope is relatively small (i.e., approximately the size of commercially available fluorescent light bulb envelopes) so that the envelope can be evacuated or filled with an inert gas and hermetically sealed in order to protect the solar cell array. In order to insure a proper seal of the envelope, the latter is of relatively small dimensions when compared to the dimensions of the trough-like concentrator of the system shown in the O'Neill patent.Consequently, there is a corresponding reduction in concentration (even when employing reflectors within the envelopes) especially since a concentrating lens is not utilized.

In addition to the above, problems have been encountered with specific supporting structures of various collection systems wherein portions of the structures can cast shadows on the rotatable units at various times during the day, a situation which is obviously undesirable.

Accordingly, it is an object of the present invention to provide an improved solar energy collection system which overcomes or reduces the problems of the prior art systems.

Another object of the present invention is to provide an improved solar energy collection system having one or more rotatable collection unit and an improved tracking mechanism for rotating the units.

And another object of the present invention is to provide an improved solar energy collection system having one or more rotatable collection units, each of a cylindrical cross-sectional configuration and constructed so as to form a portion of the tracking mechanism.

Yet another object of the present invention is to provide a solar energy collection system providing relatively large concentrations of solar energy on a solar cell array and at the same time capable of providing a hermetically sealed environment for the array.

Still another object of the present invention is to provide a solar energy collection system having an improved support structure for rotatably supporting individual rotatable solar energy collection units.

These and other objects of the present invention are achieved by a solar energy collection system comprising, in combinatiion, at least one solar energy concentrator unit, a support assembly for rotatably supporting the unit and rotation means for rotating the unit. The concentrator unit comprises (1) an elongated hollow tube having a rotation axis along its elongated direction and including lens means at least partially transmissive to at least a portion of incident solar energy and extending around and forming at least a portion of the tube for concentrating the solar energy transmitted therethrough, (2) solar energy conversion means disposed within said tube relative to said lens means so that when said tube is positioned art a predetermined angular position relative to the sun about the rotation axis, the solar energy transmitted through the lens means is concentrated on the solar energy conversion means, and (3) a pair of end members respectively secured to opposite ends of the tube. At least one of the end members is formed so as to function as a pulley. The support assembly supports the tube so that the latter is rotatably supported about the rotation axis. The rotation means includes cable pulling means and a flexible cable capable of being moved by the cable pulling means and cooperative with the pulley end member for rotating the tube relative to the support assembly about the rotation axis so that the tube can be maintained at the predetermined angular position as the sun position changes.In the preferred system, the support assembly is constructed so that (1) no shadows are formed by the support assembly on the concentrator unit while the unit is tracking the sun and (2) forms a protective housing for the cable pulling means.

Still other objects of the invention are set forth or rendered obvious by the following detailed descriptiion of the invention which should be considered together with the accompanying drawings, wherein: Figure 1 shows a perspective view of the preferred embodiment of the solar energy collection system of the present invention; Figure 2 shows an exploded perspective view of the concentrator unit of the Figure 1 embodiment; Figure 3 shows a partial side cross-sectional view of the concentrator unit rotatably supported in the support assembly; Figure 4 is a cross-sectional view taken along line 4-4 of Figure 3 of the concentrator unit; Figure 5 is a perspective view of the preferred cable pulling means for moving the cable of the embodiment of Figure 1; Figure 6shows a schematic diagram of a control circuit for controlling the rotation of the concentrator unit;; Figure 7 shows a modification of the concentrator unit of the Figure 1 embodiment; Figure 8shows a second modification ofthe concentrator unit of the Figure 1 embodiment; and Figure 9 shows a third modification of the concentrator unit of the Figure 1 embodiment.

Referring to the drawings, wherein the same numerals designate like parts, in Figure 1, the preferred solar energy collection assembly 8 generally comprises a support assembly 10 for rotatably supporting at least one, and preferably a plurality of solar energy concentrator units 12, each containing solar energy conversion means including a solar cell array assembly 14 (shown best in Figure 3). The units are rotatably driven by driving means comprising cable 16 and cable pulling means 18.

The support assembly 10 includes a base 20, the unit support frame 22, and front and rear legs 24 and 26, respectively supporting the frame 22 to the base 20. The base 20 provides a substantially flat support.

Frame 22 comprises a front horizontal member 28 supported by the front legs 24 and including spaced apart tubular bearing supports 30, each of which rotatably supports one end of a corresponding one ofthe units 12. Frame 22 also comprises a rear horizontal member 32 supported by the rear legs 36 and including spaced apart bearing supports 34 each of which rotatably supports the opposite end of each of the units 12. The bearing supports 30 and 34 are preferably positioned with respect to each other so that the axes of rotation of the units 12 are all perpendicular to both the front and rear horizontal members 28 and 32, respectively and all lie substantially in the same plane. Frame 22 also includes the side members 38 connecting the front and rear horizontal members 28 and 32.The side members 36 are disposed below the plane defined by the rotation axes of the units 12 so that when the assembly 8 is properly positioned with respect to the path of the sun, (i.e., in northern latitudes the front of the assembly 8, defined by the front legs 24, faces south so that units 12 will rotate from east to west when tracking the sun) the side members 36 will not cast shadows on the units 12. The entire support assembly 10 is preferably made of hollow tubing of a suitable light-weight material such as polyviny Ichloride, or a strong material such as steel. The front legs 24 are shorter in length than the rear legs 26 so that the units 12 will be inclined toward the sun.Each of the rear legs 26 preferably but not necessarily comprises two or more telescoping parts which can be locked in two or more positions by any suitable means such as locking parts 37 (one of which is shown in Figure 1) so that the angle of inclination of the units 12 can be periodidcally seasonably adjusted if desired in orderto take into account the changing altitude of the sun.

Each concentrator unit 12, shown in Figure 1 and in detail in Figures 2-5, includes an elongated hollow tube 38, preferably of a right circular cylindrical configuration and open at both ends. Tube 38 includes lens means at least partially transmissive to at least a portion of incident solar radiation and extending around at least a portion of the tube 38 for concentrating the solar radiation transmitted therethrough. The lens means is preferably in the form of prismatic lens 40 having a convex cylindrical outer surface and an inner surface designed so as to define an elongated linear lens segment 42 along the center of the lens and linear prismatic facets 44 extending from each side of the center lens segment 42 out to the edges of the prismatic lens 40.Lens 40 is designed so that when the center segment 42 of the lens 40 is directly facing the sun, incident solar radiation is concentrated on the solar cell array assembly 14 as will be more evident hereinafter. The entire tube 38, including the prismatic lens 40, may be made as an integral piece, by, for example extruding it with a suitable thermoplastic, or alternatively, in two pieces, with the lens 40 being secured to the remaining portion of tube 38 along its edges so as to form the tube. An advantage of forming the tube as an extruded integral piece is that the lens can easily be designed to include a larger number of facets 44 over a larger radial portion of the tube so as to increase the relative size of the lens.

Unit 12 also preferably includes additional concentration means in the form of two reflectors 46 respectively extending from the opposite side edges of lens 40 to the array assembly 14 so as to reflect incident solar radiation which is transmitted through lens 40 but for various reasons such refraction and reflection is not directly concentrated on the array assembly 14. Reflectors 46 are shown in Figures 2 and 4 as self-supporting planar sheets although the sheets can be curved in a manner well known in the art so as to increase the concentration of solar radiation on array assembly 14.The reflectors may be fixed in place in any suitable manner such as (1) by providing reflector support 48 which extends along the bottom of the tube 38 (opposite lens 40) and supports the bottom longitudinal edges of the reflectors 46, and (2) by providing suitable support lips 50 which can be integrally formed with the tube 38 adjacent the longitudinal edges of lens 40 for supporting the upper longitudinal edges of reflectors 46.

As best shown in Figure 3, the preferred solar cell array assembly 14 comprises a solar cell array 52 and is positioned with respect to the reflectors 46 so that when tube 38 is properly positioned relative to the sun (wherein the sun, center lens segment 42 and array assembly 14 are aligned) a maximum amount of incident solar radiation transmitted through lens 40 and reflected by reflectors 46 will be concentrated on the solar cell array 52 of the assembly 14. The assembly 14 preferably is made in accordance with the teachings of U.S. Patent No.

4,078,944 issued to Mlavsky on March 14, 1978 and U.S. Patent No.4,144,095 issued to Mlavsky on March 13, 1979. The preferred assembly also comprises a glass envelope 54, an absorber in the form of conduit 56 and end caps 58 (one of which is shown in Figure 3). Generaily, the structure is similar to the structure depicted in Figure 13 of the 4,144,095 Mlavsky patent, wherein the cooling conduit 56 has a substantially rectangular cross-section so that it can support the solar cell array 52, is made of a heat-conductive material, e.g. aluminum or the like, and is supported at each end by the respective end cap 58.As described in the 4,144,095 Mlavsky patent, the rectangular cross-sectioned conduit 56 can be reduced at each end to one of a circular cross-section so that it can pass through the end cap 58, as shown at 60, in a sealing manner. The fluid flowing through conduit 56 can be conducted through suitable tubing 61 which preferably is used to form in part a fluid loop for circulating the fluid. Electrical terminals are suitably connected to the array 52 in a manner described in Mlavsky patents so that an external electrical connection can be made to the array 52 by means such as wiring 63. The solar cell array 52 can therefore be hermetically sealed in the envelope 54, as described in the cited Mlavsky patents, while being disposed within the concentrator unit 12 to receive large concentrations of solar radiation.The entire solar cell array assembly 14 can be suitably fixedly mounted in the tube 38 by any suitable means, such as U-shaped support 64, one being positioned at each end of assembly 14. The support 64 includes at least two screw threaded adjustment pins 66 extending from opposite arms of the support 64 and engaging diametrically opposite sides of the assembly 14, and in particular the respective end cap 58 such that the solar cell array 52 faces lens 40 and the assembly 14 is adjustable in the plane of the array 52 to insure maximum concentration of solar radiation on the array.

Referring again to tube 38, the opposite sides of the tube are closed off by end members 68. Preferably, the end members are disc-shaped having an annular slot 70 on the inner side of the end member for receiving in a fixed manner an end of the tube 38.

The tube can be fixed in place in any suitable manner such as cementing the end members in place. Each end member 68 further comprises a hollow tubular extension 72 which extends from the outer side of the end member and is coaxially positioned with respect to a suitable aperture provided in the end member. The center axes of the extensions at opposite ends of each unit are aligned and substantially define the axis of rotation of that unit. Preferably, each extension 72 is coaxially positioned with respect to the cylindrical axis of the tube, although it should be appreciated that the aligned axes of extensions 72 can be offset and parallel to the cylindrical axis.The end of each extension 72 is coupled to the support assembly 10 and in particular to the respective bearing supports 30 and 34 by suitable bearing means 74 (shown in Figure 3) so that the unit 12 is fixed along and can easily rotate about the axis of rotation defined by extensions 72.

Preferably, bearing means includes a spherical bearing member 76 suitably fixedly secured to each extension 72, and rotatable in a spherical seat 78 suitably fixedly mounted in the respective hollow bearing support 30 and 34 of support assembly 10.

The rotation axes of the units 12 preferably all lie in a common plane.

At least one of the end members 68A is constructed to also function as a pulley as part of the driving means for rotating each unit. In particular, member 68A includes a groove 80 around its peripheral edge for receiving the cable 16. The groove 80 is preferably helical and extends around the peripheral edge of the end member at least and preferably greater than 360" so that the cable 16 can be wrapped 360 around the end member 68A, frictionally engaging the slot without interferring with itself when the cable moves and the unit rotates. Mechanical fastening means in the form of cable clamping means 81 (shown in Figure 3) is also preferably provided for securing the cable 16 in groove 80 in order to insure that the corresponding unit 12 will rotate with the movement of the cable.

Means 81 comprises two bolts 83 positioned in groove 80 on either side of cable 16 and a clamp 85 secured to the bolts for clamping the cable in the slot. The members 68A of all the units 12 are disposed substantially in the same general plane so that the corresponding helical slots of the units are aligned and can cooperate with the single cable 16.

The driving means for rotating the units 12 also comprises the cable pulling means 18, shown generally in Figure 1 and in detail in Figure 5. The cable pulling means comprises a base support 82 for supporting a reversible motor 84, a cable tensioning bar 86, a guide frame 88 for guiding the bar 86, and pulleys 90. The reversible motor 84 is preferably a relatively low rpm gear motor constructed so as to be capable of rotating the lead screw 92 in either direction. Lead screw 92 rotates within a ball nut 94, the latter being secured to one end of bar 86 so that rotation of the lead screw causes linear movement of the bar along its elongated axis. The guide frame 88 provides a linear slot 96. Specifically, frame 88 comprises two spaced-apart L-shaped brackets secured to the base support 82.The brackets may be secured in any known manner such as welding them to the base support, or alternatively, the brackets and support may be made of a high resistance plastic so that both can be extruded as a single integral piece. Bar 86 includes suitable means such as guide rollers 98 which interact with the guide frame 88 so as to prevent bar 86 from rotating with the lead screw 92 when the latter rotates, and insures that bar 86 moves in slot 96. The bar 86 also includes cable attachment means such as the rod 100 secured to the end of bar 86 opposite ball nut 94.

One end of cable 16 is attached to rod 100, threaded around pulleys 90 and subsequently threaded around the cable slot 80 of the end member 68A of each unit 12. In this regard the entire cable pulling means is mounted within one of the side members 36A, hidden from what might otherwise be a hostile environment. The cable 16 extends from the pulleys 90 through a suitable opening in the side member 36A substantially in the general plane defined by the members 68A of the units 12. The side member 36A is disposed below the plane defined by the rotation axes of units 12 and preferably is such that the cable extends from the opening in the side member 36A tangentially to the end member 68A of the closest unit 12, is wrapped 360 around the end member of the unit and subsequently extended to and wrapped around the end members 68A of each of the remaining units 12.The remaining cable 16 extends through a suitable opening in the opposite side member 36B (the latter also preferably being disposed below the plane defined by the rotation axes of units 12) where it is suitably tensioned with, for example, a tension spring 102, or alternatively a suitable counterweight disposed within the support assembly 10. The general plane defined by members 36A and 36B is substantially tangential to all of the end members 68A.

The collection assembly 8 is assembled by assembling and mounting the units 12 in the respective bearing supports 30 and 34. The tubing 61 and wiring 63 of each unit can be extended through the hollow extension 72 of the corresponding end member 68A, through the bearing support 30, and through the front horizontal member 28 to an appropriate location. Since the assembly 8 is preferably made of hollow tubing or pipe, the assembly thus can easily function as a manifold for both tubing 61 and wiring 63 so as to protect both from a hostile environment. Tubing 61 can be connected to a suitable heat exchanger (not shown) where the heated fluid can be utilized and the fluid cooled, recirculated back through similar tubing to the array assembly 14 and thence recirculated through conduit 56.Thus, in addition to cooling the solar cell array 52, the fluid also serves to collect useful heat energy collected in the concentrator unit. Similarly, wiring 63 of all the units can be electrically connected together and to an appropriate load, such as a storage cell of an electric motor.

In operation the units can be initially rotatably positioned to face in an easterly direction by suitably energizing motor 84 so as to rotate lead screw 92 and thus move bar 86 to a first position in slot 96, (which as shown in the drawings is farthest from the motor 84) so as to extend cable 16 and thus rotated to the units to the desired position. The motor can then be energized at a predetermined speed so that the units will rotate at a predetermined rotational speed so that the units will track the sun while providing maximum concentrated energy on the solar cell array 52 of each array assembly 14. At the end of the day, when the bar 86 is at the near end of slot 96 the motor can be reversed, rotating lead screw 92, so that the bar 86 will return to the first position, extending cable 16 so as to rotate the units back to the easterly directed position.

The above described operation is preferably accomplished automatically. The tracking operation can be performed by a suitable clocking mechanism since the position of the sun can always be predicted at any time. In such a situation a time clock can be suitably connected to the motor 84, so as to synchronize the speed of the motor with the passage of time of day. The units 12 can be easily returned to their easterly direction at the end of each day.

Alternatively, a sensor 104 is positioned at an appropriate location on one of the units 12 so as to provide an electrical output signal representative of the position of the sun. The sensor 104 can be any commercially available type and preferably is adapted to sense infrared radiation so that the sensor will operate on cloudy days. Additionally, two contact switches 1 06A and 1 06B can be disposed on the guide frame 88 at opposite ends of slot 96 so that when the bar 86 is moved to the first position, thereby rotating the unit 12 to an easterly direction, the roller 98B will contact and close switch 106B, and conversely at the end of the day when the bar 86 is at the opposite position in slot 96, roller 98Awill contact and close switch 1 06A.As shown in Figure 6, the sensor 104, switches 106A and 106B and motor 84 are electrically connected to suitable control circuitry 108 (the latter being of a type well known in the art) so that the output of sensor 104 will regulate the speed of motor 84 to insure proper and constant tracking of the sun as the latter moves across the sky. Contact of the roller 98A with switch 1 06A will cause the motor to reverse, automatically rotating lead screw 92 resulting in a return of bar 88 until roller 98B contacts switch 1 06B thereby positioning units 12 in an easterly direction for the next day.

Although the invention has been described in its preferred form, several modifications can be made to the above apparatus without departing from the scope of the invention. For example, as shown in Figure 7 the entire tube 38A, prismatic lens 40 and reflector supports 48A can be formed as an integral structure by extruding the structure in accordance with a three-hole extrusion process. In such a situation a cavity 110 is provided below the reflector supports 48Afor receiving the solar cell array assembly 14. Reflectors can easily be provided by securing a reflective tape 112 on the mutuaily opposing surfaces of the supports 48A so as to provide the identical optical system (provided by the lens 40 and reflectors 46) as the system described in Figures 1-5.Similarly, as shown in Figure 8, the tube is shown as a one hole extrusion with the reflectors 46A being mounted within the tube relative to the absorber similar to that described in Figure 4 except that reflectors 46A are dimensional to extend only part way toward the longitudinal edges of lens 40.

Finally, where it is considered unnecessary to seal the solar cell array 52 within the envelope 54, the envelope 54 and end caps 58 could be eliminated and the conduit 56 mounted at each end directly to the respective end members 68 as shown in Figure 9.

The above described solar collection assembly has several advantages. Since the units 12 are of a cylindrical cross-sectional configuration they are less likely to be impeded by such obstacles as sand or snow, and further can be provided with end members 68A which provide the dual function of closing off an end of each unit and at the same time form a pulley as part of the tracking mechanism.

Further, by enclosing a hermetically sealed assembly 14 within the larger concentrator unit 12, relatively large concentrations of solar energy can be concentrated on a solar cell array 52 and at the same time the array 52 can be adequately sealed within an inert environment within the envelope 54. The support assembly 10 provides an improved support structure for rotatably supporting the individual rotatable solar energy concentrator units 12. By providing the side members 36 below the plane of the rotation axes of units 12, the former will not cast shadows on the latter regardless of the position of the sun, and the cable will be aligned tangentially with the end members 68A. Further, the cable pulling means 18 can be disposed in the side member 36A protecting the former from a hostile environment. The rotation mechanism for rotating each of the units provides a simple yet unique rotation driving mechanism. Still other advantages and possible modifications will be obvious to persons skilled in the art.

Since certain other changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted in an illustrative and not in a limiting sense.

Claims (28)

1. A solar energy collection system comprising, in combination: at least one solar energy concentrator including (1) an elongated hollow tube having a rotation axis and including lens means, at least partially transmissive of at least a portion of incident solar energy and extending around at least a part of said tube for concentrating the solar energy transmitted therethrough, (2) solar energy conversion means disposed within said tube relative to said lens means so that when said tube is positioned at a predetermined angular position about said axis relative to the sun, the solar energy transmitted through said lens means is concentrated on said solar energy conversion means, and (3) a pair of end members respectively secured to opposite ends of said tube, at least one of said end members being a pulley;; a support assembly for supporting said tube so that said tube is rotatably supported about said rotation axis; and rotation means including a flexible cable cooperative with said pulley for rotating said tube relative to said support assembly about said elongated axis so that said tube can be maintained at the predetermined angular position as the sun position changes.

2. A system according to claim 1, wherein said lens means includes a prismatic lens extending along the length of said tube.

3. A system according to claim 1, wherein said tube is a right circular cylinder.

4. A system according to claim 1, wherein said solar energy conversion means comprises a solar cell array and a conduit for supporting said solar cell array and for conducting a fluid therethrough so as to absorb heat from said solar energy conversion means.

5. A system according to claim 4, wherein said conduit is mounted at each end to a respective one of said end members.

6. A system according to claim 1, wherein said solar energy conversion means comprises an envelope, a solar cell array disposed within said envelope, and end caps hermetically sealed to opposite ends of said envelope so as to seal said solar cell array within said envelope.

7. A system according to claim 6, wherein said solar energy conversion means further comprises a conduit for supporting said solar cell array and for conducting a fluid through said envelope in order to absorb heat from said solar energy conversion means.

8. A system according to claim 7, wherein said conduit is mounted on said end caps.

9. A system according to claim 1, wherein said pulley is disc-shaped and has a groove formed around its peripheral edge, said groove being shaped so that said cable engages and will remain in said groove and said cable will rotate said tube about said elongated axis upon movement of said cable along its length.

10. A system according to claim 9, further including means for securing said cable in said groove.

11. A system according to claim 9, wherein said rotation means further includes means for moving said cable along its length.

12. A system according to claim 11, wherein means for moving said cable comprises driving means connected to one end of said cable for moving said cable in one direction and tensioning means for moving said cable in the other direction.

13. A system according to claim 12, wherein said driving means includes a motor, an elongated bar drivingly connected to said motor and being operatively connected to said cable so that operation of said motor moves said bar which in turn moves said cable in said one direction.

14. A system according to claim 13, wherein said driving means further includes lead screw means drivingly connecting said motor to said bar so that rotation of said screw moves said bar in its elongated direction.

15. A system according to claim 14, wherein said bar is moveable in its elongated direction (1) a first position wherein said predetermined angular position is in an easterly direction and (2) a second position wherein said predetermined angular position is in a westerly direction.

16. A system according to claim 15, further including control means for moving said bar between said first and second positions, said control means including a sensor for producing a first signal representative of the position of said sun, means responsive to said first signal for producing a second signal when said the position of the sun changes relative to the predetermined angular position, wherein said motor is responsive to said second signal so as to move said bar and said cable such that said tube rotates about said elongated axis to the new predetermined angular position relative to the new position of the sun.

17. A system according to claim 16, wherein said control means further includes switching means disposed at each of said first and second positions for reversing the direction of rotation of said lead screw.

18. A system according to claim 12, wherein said support assembly includes hollow side members disposed respectively on opposite sides of said tube and said driving means is disposed in one of said side members and said tensioning means is disposed in the other of said side members.

19. A system according to claim 18, wherein said side members are disposed in a substantially common plane below said elongated axis so that said cable extends from said one side member tangential to said pulley, 360 around pulley to said other of said side members.

20. A system according to claim 9, wherein said groove of said pulley is a helical groove.

21. A system according to claim 9, wherein said solar energy conversion means includes a solar cell array and a cooling conduit supporting said solar cell array, transmission meansfortransmitting electricity generated by said solar cell array and transport means for transporting a cooling fluid through said cooling conduit, said one end member further including a hollow extension coupled with said support assembly wherein said transmission and transport means extend through said extension into said support assembly.

22. A system according to claim 1, wherein said support assembly comprises a base, and a support frame coupled to said base so as to be inclined with respect to said base wherein the front of said frame is below the rear of said frame, said frame including bearing supports in the front and rear of said frame for supporting said unit about said rotation axis so that said axis extends from the front to the rear of said frame.

23. A system according to claim 22, wherein said frame includes side members disposed in a common plane below said rotation axis of said tube.

24. A system according to claim 1, wherein said tube and lens means are formed as an integral unit.

25. A system according to claim 1, wherein said solar energy concentrator further includes reflective means disposed within said tube for reflecting solar radiation transmitted by said lens means to said solar energy conversion means.

26. A system according to claim 25, wherein said reflective means includes reflectors and means for supporting said reflectors.

27. A system according to claim 26, wherein said tube, lens means and said means for supporting said reflectors are an integral unit.

28. A solar energy collection system constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.