WO2003098125A1

WO2003098125A1 - Solar reflector and assembly thereof

Info

Publication number: WO2003098125A1
Application number: PCT/AU2003/000601
Authority: WO
Inventors: David C Edwards
Original assignee: JARRAH COMPUTERS Pty Ltd
Current assignee: JARRAH COMPUTERS Pty Ltd
Priority date: 2002-05-21
Filing date: 2003-05-20
Publication date: 2003-11-27
Anticipated expiration: 2004-11-21
Also published as: AUPS248602A0

Abstract

A solar energy collection system is described having one or more solar collectors (11, 17) to collect solar energy. The solar collectors (17) have two reflector panels (13, 15) mounted on hinges for rotation about axes extending along opposite longitudinal edges of the solar collector (17). The reflector panels (13, 15) are connected to an actuating mechanism (20, 22, 24, 26, and 21, 23, 25, 27), controlled by a control unit (29) to move the reflector panels (13, 15) to track the sun. The control unit (29) also controls the actuating mechanism (20, 22, 24, 26, and 21, 23, 25, 27), to move the reflector panels (13, 15) while tracking the sun, between a fully open position (a heliostatic position) in which maximum solar energy is directed by reflection from the reflector panels (13, 15) to the solar collector (17), and a closed position in which minimum solar energy reaches the solar collector (17), in response to a measured (sensor 30) or calculated parameter of energy derived from the solar collector (17).

Description

"Solar Reflector and Assembly thereof

Field of the Invention

This invention relates to the field of solar energy, and in particular to concentration of solar energy

Background Art

There is a growing interest in solar energy, particularly as awareness of dwindling non-renewable energy resources increases, and the cost of such non-renewable energy increases.

Fixed panels for solar energy collection suffer from the disadvantage that the energy collection potential varies throughout the day, being very low from dawn to mid-morning, and again from mid-afternoon to dusk. This problem is exemplified in solar hot water heaters.

With solar photovoltaics, this problem can be ameliorated by aligning the photovoltaic cells to face the sun, and track the sun as it crosses the sky, however this solution is not suitable for solar hot water heating.

With solar photovoltaics, reflectors have been used, angularly fixed along one or both edges of a photovoltaic cell array, to increase the energy incident on the photovoltaic cells. Such an arrangement exemplified in United States patent specification 6,050,526, also rotates the entire assembly of reflectors and photovoltaic cells to face the sun.

This invention seeks to provide a reliable and effective way to increase the efficiency of solar energy collection at minimal cost. This invention also seeks to provide solar energy collection for multiple uses, not limited to photovoltaic applications. Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Disclosure of the Invention

In accordance with the invention there is provided a solar energy collection system having at least one solar collector to collect solar energy, each said solar collector having two reflector panels each connected by a hinging mechanism for rotation about an axis extending proximal and along opposite longitudinal edges of said solar collector; said reflector panels being connected to an actuating mechanism controlled by a control unit to move said reflector panels to track the sun; wherein said control unit also controls said actuating mechanism to move said reflector panels while tracking the sun, between a fully open position (a heliostatic position) in which maximum solar energy is directed by reflection from said reflector panels to said solar collector, and a closed position in which minimum solar energy reaches said solar collector, in response to a measured or calculated parameter of energy derived from said solar collector. The solar collector unit is intended to be located with the axis running north-south, although in higher latitudes, the axis could be located east-west.

Preferably the reflector panels have a reflective surface which may be selected from a pale coloured surface such as white, a polished metal surface, or a mirror surface.

Preferably the reflector panels are substantially planar.

The solar collector may comprise an array of photovoltaic cells, a solar heater for water, skylights on a building, or racks for produce (eg fruit) drying. Thus measured parameter of energy referred to above could be stored energy in the form of water temperature in a body of water heated by the solar collector, or voltage of storage batteries charged by the photovoltaic cells in the solar collector, the battery voltage being indicative of the charge state of the batteries. In the case of a skylight application the measured parameter could be temperature or light. In the case of apparatus for produce (eg fruit) drying, the measured parameter of energy could comprise temperature and perhaps also relative humidity.

Said control unit may, in one arrangement comprise a microprocessor having a program including an algorithm to calculate the optimum position for said reflector panel for a given date and time, and latitude (and longitude where time is GMT/CUT and uncorrected for longitude). In another arrangement, said control unit may include a sensor to track the position of the sun, said control unit being responsive to said sensor to control said actuating mechanism.

Preferably the solar collector prescribes a horizontal plane or alternatively a flat plane that may be placed in an incline on an inclined roof. Preferably, also when placed in an incline, the plane of the solar collector is normal to the equinoxial declination of the sun.

Preferably said hinging mechanism comprises a rotatable shaft to which said reflector panel is fixed.

Preferably said actuating mechanism is connected to a plurality of solar collectors arranged longitudinally side by side, and connected for synchronised movement of said reflector panels. Preferably, " in this arrangement said actuating mechanism includes a rotatable input shaft extending normal to said rotatable shafts of said solar collectors, connected with said rotatable shafts by transmission gears for synchronised movement of said reflector panels.

Preferably the width of the reflectors lies from 1.2x to 1.75x the width of the solar collector.

Preferably said control unit controls said actuating mechanism to move said reflector panels while tracking the sun, to one of said heliostatic position, said closed position, and a parallel position in which said reflector panels are disposed substantially parallel to each other, in response to said parameter. Brief Description of the Drawings

Three preferred embodiments of the invention will now be described in the following description, made with reference to the drawings, in which:

Figure 1 is a conceptual diagrammatic outline looking along the longitudinal axis of a solar collector showing its reflector panels in a heliostatic position to collect solar energy shortly after sun-rise;

Figure 2 is a conceptual diagrammatic outline looking along the longitudinal axis of the solar collector of figure 1 , showing its reflector panels in the heliostatic position to collect solar energy in mid-morning; Figure 3 is a conceptual diagrammatic outline looking along the longitudinal axis of the solar collector showing its reflector panels in a parallel position to collect solar energy in late-morning;

Figure 4 is a conceptual diagrammatic outline looking along the longitudinal axis of the solar collector showing its reflector panels in a closed position to minimise collection of solar energy shortly after mid-day;

Figure 5 is a conceptual diagrammatic outline looking along the longitudinal axis of the solar collector showing its reflector panels in the parallel position to collect solar energy in early-afternoon;

Figure 6 is a conceptual diagrammatic outline looking along the longitudinal axis of the solar collector showing its reflector panels in the heliostatic position to collect solar energy in late afternoon;

Figure 7 is a plan view from above of a row of solar collector units in an array, according to the first embodiment;

Figure 8 is a side view looking along the longitudinal axes of the solar collector units of figure 7;

Figure 9 is a plan view from above of a row of solar collector units in an array, according to the second embodiment; and

Figure 10 is a plan view from, above of an array of solar collector units, according to the third embodiment. Best Mode(s) for Carrying Out the Invention

The embodiments of the invention are an array of solar collectors 11 for a solar hot water heater, a row of the solar collectors 11 being shown in figures 7 to 9, and an array of solar collectors 11 being shown in figure 10. Referring to figures 7 and 8, the first embodiment is shown. Each solar collector 11 has two reflector panels 13, 15 pivotally mounted along longitudinal axes located one along each longitudinal edge of a target in the form of a solar water heater collector 17. The solar water heater collector 17 has an arrangement of pipes thermally connected with a heat-sink material, so that solar energy incident on the pipes and heat-sink material is transferred to water contained in the pipes, and so causing the water to be heated.

The reflector panels 13, 15 are planar, and are each formed of metallised plastic foil (sold under the trade mark SILVERLUX by 3M) secured to a frame, the frame being rigidly mounted to a hinging mechanism in the form of a rotatable shaft 20, 21. The reflector panels 13 and so secured to rotatable shaft 20, while the reflector panels 15 are so secured to rotatable shaft 21. In figure 7, the reflective side of the reflector panels 15 is shown, indicated by oblique lines; while the non reflective side of reflector panels 13 is shown, indicated by plus "+" signs.

Each rotatable shaft 20, 21 is connected via a gearbox 22, 23 to a respective rotatable input shaft in the form of a worm drive 24, 25; each worm drive 24, 25 being driven by respective stepper motors 26, 27. The worm drives 24, 25 extend "across" the rotatable shafts 20, 21 , so as to drive the respective rotatable shafts 20, 21 in synchronised manner, through the gearboxes 22, 23. The stepper motor 26, worm drive 24 and connected gearboxes 22, and rotatable shafts 20 form an actuating mechanism for the reflector panels 13; while the stepper motor 27, worm drive 25 and connected gearboxes 23, and rotatable shafts 21 form an actuating mechanism for the reflector panels 15.

The stepper motors 26 and 27 are controlled in synchronised manner by control means in the form of a microprocessor 29 which includes in its program, an algorithm which controls the stepper motors 26 and 27 to move the reflector panels 13 and 15 in a manner, based on time of the day and date, and latitude and longitude (hence adjusting for differing sunrise and sunset times), so that the reflector panels 13 and 15 track the sun, and can reflect sunlight optimally onto the solar water heater collector 17.

The microprocessor 29 is interfaced to a sensor 30 which measures a parameter commensurate with energy collected by the solar collector 11. In this embodiment, the sensor is a temperature sensor which measures the temperature of stored water that has been heated by being passed through the pipes in the solar water heater collector 17. In response to the temperature of the water measured by the sensor, the microprocessor 29 can control the stepper motors 26 and 27 to move the reflector panels 13 and 15, in addition to tracking the sun, between the positions of heliostatic, parallel, and closed.

The worm drives 24, 25 are mounted on bearings 31 , spaced therealong, to ensure free rotation of the worm drives 24, 25. Similarly the rotatable shafts 20, 21 are mounted on bearings 33, to ensure free rotation. As shown by the break at the lower end of the worm drives 24, 25, the row can be extended to further solar collectors, up to the maximum permitted load of the stepper motors 26, 27. Furthermore, the rotatable shafts 20, 21 may be extended to further rows of solar collectors, also providing that the maximum permitted load of the stepper motors 26, 27 is not exceeded.

Conceptually the operation of the embodiment and invention is best explained with reference to figures 1 to 6. In figures 1 to 6, the solar collector 11 has its longitudinal axis running in a north-south direction. The solar collector 11 has a western reflector panel 13 located along the western longitudinal edge of the solar water heater collector 17, and an eastern reflector panel 15 located along the eastern longitudinal edge of the solar water heater collector 17. The longitudinal axis of the solar collector 11 runs north-south, so the reflector panel 13 is pivotally attached near the western edge of the solar water heater collector 17.

Figure 1 shows the position of the reflector panels 13 and 15 in a heliostatic position, as positioned by the control means and the actuating mechanism in early-moming, shortly after sun-rise, so that sunlight incident on the reflector panel 13 is reflected to the solar water heater collector 17. At this time the reflector panel 15 also reflects a small amount of sunlight to the solar water heater collector 17. At this time, due to the heliostatic position, the energy collected by the solar water heater collector 17 is maximised.

Figure 2 shows the position of the reflector panels 13 and 15 in a heliostatic position as positioned by the control means and the actuating mechanism in mid- morning. Again, due to the heliostatic position, the energy collected by the solar water heater collector 17 is maximised. The tracking of the sun is achieved by the microprocessor calculating the desired reflector panel positions for the heliostatic position, based on parameters comprising time, date, latitude, longitude, and the slope and azimuth of the plane (ie roof etc) on which the solar water heater collectors 17 are installed.

The reflector panels 13 and 15 continue to be positioned in the heliostatic position as positioned by the control means and the actuating mechanism, until the microprocessor 29 determines from the sensor 30 that the temperature of the heated water has exceeded a first predetermined threshold, which for the purposes of this embodiment can be 75°C, at which point in time the microprocessor 29 controls the position of the reflector panels 13 and 15 to be moved to the parallel position as shown in figure 3, as may be expected to occur in late morning. In the parallel position, the microprocessor continues to control the position of the reflector panels 13 and 15 so that they continue to track the sun.

As time passes, if the microprocessor 29 determines from the sensor 30 that the temperature of the heated water has exceeded a second predetermined threshold, which for the purposes of this embodiment can be 85°C, the microprocessor 29 controls the position of the reflector panels 13 and 15 to be moved to the closed position as shown in figure 4, as may be expected to occur shortly after mid-day. In the closed position, the microprocessor continues to control the position of the reflector panels 13 and 15, so that they continue to track the sun. When the microprocessor 29 determines from the sensor 30 that the temperature of the heated water has fallen to a third predetermined threshold, which for the purposes of this embodiment can be 80°C, as might be expected in early afternoon, the microprocessor 29 controls the position of the reflector panels 13 and 15 to be moved to the parallel position as shown in figure 5. The microprocessor 29 continues to control the position of the reflector panels 13 and 15, so that they continue to track the sun, while in the parallel position.

When the microprocessor 29 determines from the sensor 30 that the temperature of the heated water has fallen to a fourth predetermined threshold, which for the purposes of this embodiment can be 70°C, as might be expected in mid to late afternoon, the microprocessor 29 controls the position of the reflector panels 13 and 15 to be moved to the heliostatic position as shown in figure 6. The microprocessor 29 continues to control the position of the reflector panels 13 and 15, so that they continue to track the sun, while in the heliostatic position.

After the sun has set, the reflector panels 13 and 15 can be moved to a closed position as would be expected at mid-day, pending time for sun-rise, where the cycle begins afresh. This arrangement can assist to insulate solar hot water collectors 17 from heat loss.

The mid-day closed position can also be adopted at times of high wind or hail, where the solar collectors 11 or solar water heater collector 17 components are otherwise unprotected.

The above description assumes a normal hot water demand. If there is higher usage of hot water or lower incident solar radiation due to cloud, the first and second predetermined temperature thresholds may be delayed or not be reached, in which case the reflector panels 13 and 15 will continue to track the sun in heliostatic position or parallel position respectively. Similarly, once the water has been heated, the third and fourth temperature thresholds could be reached early due to an increase in demand for hot water, or due to the onset of cloudy conditions. In any event, as the microprocessor 29 continues to control the position of the reflector panels 13 and 15, so that they continue to track the sun, whether in the heliostatic position, the closed position, or the parallel position, the amount of adjustment and hence energy and time required to move the reflector panels 13 and 15, between the heliostatic position and the parallel position, and between the parallel position and the closed position, is minimised.

The microprocessor 29 comprises a CPU, a real-time-clock (RTC), memory (both ROM & RAM), motor drive circuits to control the stepper motors 26 and 27, and input which will be used to control the control algorithm, such as a sensor or a setting potentiometer etc. The CPU is has its control program located in ROM.

The RTC is a dedicated integrated-circuit (IC) which has its own time-base input using a 32kHz crystal to keep time and date. The registers inside the RTC IC which hold this real-time information can be read by the CPU. The accuracy of the RTC is critical to the accuracy of the overall device as the clock information forms the basis of the computation of the sun's position.

The Motor Drive circuits transform four output lines from the CPU into a form that can drive the motors 26 and 27. Logic circuits are used to generate the waveforms required by the stepper motors and the current drive level is increased to drive the motor circuits.

As discussed above, the position of the sun is calculated from the time and date, and other parameters programmed into the computer, namely, the latitude, the longitude, the time-zone, and the slope and azimuth of the plane on which the system is mounted. First, all parameters set by the day of year are calculated: the Declination of the sun and the Equation of Time offset (real time, time zone and longitude). Then the position of the sun relative to a horizontal plane is calculated, and, if the sun is up (determined from the calculation), the position of the sun relative to the plane on which the array of solar collectors 11 is mounted is calculated. Then the projection of the suns position onto the plane perpendicular to the longitudinal axis and the plane of the target area is calculated (this is the plane of the page on which figures 1 to 6 are illustrated). This is referred to as the "sun angle", and is measured with respect to the eastern horizon. Thus if the plane on which the array of solar collectors 11 is mounted is horizontal and the longitudinal axis runs north-south, then the sun angle at sunrise is 0°.

From the sun angle the required mirror angles are determined for the heliostatic position, and the closed position.

For heliostatic positions, the required mirror angles are calculated as follows: For the East mirror, the Heliostat angles are calculated from the identity:

Sin(Eastlncident)=ML*Sin(EastAperture)

Where: EastAperture is (Sunangle - EastMirrorAngle)

Eastlncident is (EastMirrorAngle - EastAperture) and ML is mirror width as a ratio of the collector 17 width

The West mirror for a given sun angle is calculated from:

Calculate (180-Sunangle)

Calculate the East mirror angle using (180-Sunangle) as the input angle Subtract the result from 180

The result of the final subtraction is the required West Mirror angle

For closed angles, the mirror positions are calculated as follows:

For the East mirror, the Closed angles are calculated from the identity:

Sin(Sunangle)=2^*ML*Sin(EastAperture)

Where: EastAperture is (Sunangle - EastMirrorAngle)

For the West mirror, the Closed angles are calculated from the identity:

Sin(Sunangle)=2*ML*Sin(WestAperture) Where: WestAperture is (WestMirrorAngle-Sunangle) For parallel angles, the sun angle is the required angle for both East and West reflectors.

The following is a detailed example at ML= 1.5 (ie the mirror width is 1.5 x the collector 17 width, being a table of the Heliostat and Closed angles for each of the 180 input sun angles:

Sun Heliostat Closed Sun Heliostat Closed

Angle E W E W Angle E W E W

0 0 42 0 0 1 0 43 1 1

2 1 44 2 2 3 2 45 3 3

4 2 46 5 3 5 3 47 6 4

6 4 48 7 5 7 5 49 9 5

8 5 50 10 6 9 6 51 11 7

10 7 52 13 7 11 7 53 14 8

12 8 54 15 9 13 9 55 17 9

14 10 56 18 10 15 10 57 19 11

16 11 58 21 11 17 12 59 22 12

18 12 60 23 13 19 13 60 25 13

20 14 61 26 14 21 15 62 27 15

22 15 63 29 15 23 16 64 30 16

24 17 65 31 17 25 17 66 33 17

26 18 66 34 18 27 19 67 35 19

28 20 68 37 19 29 20 69 38 20

30 21 70 39 21 31 22 71 40 22

32 22 71 42 22 33 23 72 43 23

34 24 73 44 24 35 25 74 46 24

36 25 75 47 25 37 26 75 48 26

38 27 76 49 27 39 27 77 51 27

40 28 78 52 28 41 29 79 53 29

42 30 79 54 30 43 30 80 56 30

44 31 81 57 31 45 32 82 58 32

46 32 83 59 33 47 33 83 61 33

48 34 84 62 34 49 35 85 63 35

50 35 86 64 36 51 36 86 66 36

52 37 87 67 37 53 37 88 68 38

54 38 89 69 39 55 39 89 70 40

56 40 90 72 40 57 40 91 73 41

58 41 92 74 42 59 42 93 75 43

60 43 93 76 44 61 43 94 77 45

62 44 95 79 45 63 45 96 80 46 (Table of Heliostat and Closed angles - continued...)

Sun Heliostat Closed Sun Heliostat Closed

Angle E W E W Angle E W E

64 45 96 81 47 65 46 97 82 48

66 47 98 83 49 67 48 99 84 50

68 48 99 86 50 69 49 100 87 51

70 50 101 88 52 71 50 102 89 53

72 51 102 90 54 73 52 103 91 55

74 53 104 92 56 75 53 105 93 57

76 54 105 94 58 77 55 106 95 59

78 56 107 97 59 79 56 108 98 60

80 57 108 99 61 81 58 109 100 62

82 58 110 101 63 83 59 111 102 64

84 60 111 103 65 85 61 112 104 66

86 61 113 105 67 87 62 113 106 68

88 63 114 107 69 89 64 115 108 70

90 64 116 109 71 91 65 116 110 72

92 66 117 111 73 93 67 118 112 74

94 67 119 113 75 95 68 119 114 76

96 69 120 115 77 97 69 121 116 78

98 70 122 117 79 99 71 122 118 80

100 72 123 119 81 101 72 124 120 82

102 73 124 121 83 103 74 125 121 85

104 75 126 122 86 105 75 127 123 87

106 76 127 124 88 107 77 128 125 89

108 78 129 126 90 109 78 130 127 91

110 79 130 128 92 111 80 131 129 93

112 81 132 130 94 113 81 132 130 96

114 82 133 131 97 115 83 134 132 98

116 84 135 133 99 117 84 135 134 100

118 85 136 135 101 119 86 137 135 103

120 87 137 136 104 121 87 138 137 105

122 88 139 138 106 123 89 140 139 107

124 90 140 140 108 125 91 141 140 110

126 91 142 141 111 127 92 143 142 112

128 93 143 143 113 129 94 144 144 114

130 94 145 144 116 131 95 145 145 117

132 96 146 146 118 133 97 147 147 119

134 97 148 147 121 135 98 148 148 122

136 99 149 149 123 137 100 150 150 124

138 101 150 150 126 139 101 151 151 127

140 102 152 152 128 141 103 153 153 129

142 104 153 153 131 143 105 154 154 132 (Table of Heliostat and Closed angles - continued...)

Sun Heliostat Closed Sun Heliostat Closed

Angle E W E W Angle E W E W

144 105 155 155 133 145 106 155 156 134

146 107 156 156 136 147 108 157 157 137

148 109 158 158 138 149 109 158 158 140

150 110 159 159 141 151 111 160 160 142

152 112 160 161 143 153 113 161 161 145

154 114 162 162 146 155 114 163 163 147

156 115 163 163 149 157 116 164 164 150

158 117 165 165 151 159 118 165 165 153

160 _.119 166 166 154 161 120 167 167 155

162 120 168 167 157 163 121 168 168 158

164 122 169 169 159 165 123 170 169 161

166 124 170 170 162 167 125 171 171 163

168 126 172 171 165 169 127 173 172 166

170 128 173 173 167 171 129 174 173 169

172 130 175 174 170 173 131 175 175 171

174 132 176 175 173 175 133 177 176 174

176 134 178 177 175 177 135 178 177 177

178 136 179 178 178 179 137 180 179 179

180 138 180 180 180

The second embodiment shown in figure 9 differs from the first embodiment in that the microprocessor 29 also controls additional stepper motors 26a and 27a, which connect to additional worm drives 24a and 25a, to connect to rotatable shafts 20 and 21 via additional gearboxes 22a and 23a, respectively, at the other end of the solar collectors 11 from the existing actuating mechanism formed by stepper motors 26, 27, worm drive 24, 25, and connected gearboxes 22, 23. The stepper motors 26 and 26a are operated in unison by the microprocessor 29, and the stepper motors 27, 27a are operated in unison by the microprocessor 29. As will be appreciated, stepper motors 26 and 26a, worm drives 24, 24a, and connected gearboxes 22, 22a, and rotatable shafts 20 form the actuating mechanism for the reflector panels 13 in this embodiment; while the stepper motors 27, 27a, worm drive 25, 25a and connected gearboxes 23, 23a, and rotatable shafts 21 form the actuating mechanism for the reflector panels 15 in this embodiment. This arrangement allows longer solar collectors to be utilised, with the reflector panels 13, 15 driven from both ends. Such an arrangement may also be utilised in shorter solar collectors that might be subjected to a high wind load.

The third embodiment is similar to the second embodiment, except that additional bearings 35 are provided between adjacent solar collectors 11 and 11', along the shafts 20, 20' and 21 , 21 '. This allows a longer array of solar cells to be provided, each with shorter reflectors than those of the second embodiment. This can overcome problems that might occur with long reflectors where high wind load conditions might be expected. Further additional bearings could be provided, to build up large arrays, in both dimensions.

It will be appreciated that the solar collector of the embodiments lend themselves to applications other than solar water heating. With the target area maintained substantially horizontal, the target area can accommodate photovoltaic panels, or fruit drying trays. With solar water heating and photovoltaic applications, the angle of inclination of the target area may be varied to anywhere between the normal to the angle of declination of the mid-day sun at summer or winter solstice depending upon energy collection requirements, although typically one would choose an angle of declination close to normal to the equinoxial declination of the mid-day sun.

It should be appreciated that the scope of the invention is not limited to the particular embodiment disclosed herein, and that changes may be made by a skilled addressee without departing from the spirit and scope of the invention.

Claims

The Claims Defining the Invention are as Follows

1. A solar energy collection system having at least one solar collector to collect solar energy, each said solar collector having two reflector panels each connected by a hinging mechanism for rotation about an axis extending proximal and along opposite longitudinal edges of said solar collector; said reflector panels being connected to an actuating mechanism controlled by a control unit to move said reflector panels to track the sun; wherein said control unit also controls said actuating mechanism to move said reflector panels while tracking the sun, between a fully open position (a heliostatic position) in which maximum solar energy is directed by reflection from said reflector panels to said solar collector, and a closed position in which minimum solar energy reaches said solar collector, in response to a measured or calculated parameter of energy derived from said solar collector.

2. A solar energy collection system as claimed in claim 1 wherein said reflector panels have a reflective surface which may be selected from a pale coloured surface such as white, a polished metal surface, or a mirror surface.

3. A solar energy collection system as claimed in claim 1 or 2 wherein the reflector panels are substantially planar.

4. A solar energy collection system as claimed in any one of the preceding claims wherein said solar collector comprises an array of photovoltaic cells, and said measured parameter of energy comprises a measure of stored energy in the form of voltage of storage batteries charged by said photovoltaic cells in the solar collector, the battery voltage being indicative of the charge state of the batteries.

5. A solar energy collection system as claimed in any one of claims 1 to 3 wherein said solar collector comprises a solar heater for water, and said measured parameter of energy comprises a measure of stored energy in the form of water temperature in a body of water heated by the solar collector.

6. A solar energy collection system as claimed in any one of claims 1 to 3 wherein said solar collector comprises at least one skylight on a building and said measured parameter of energy comprises temperature or light.

7. A solar energy collection system as claimed in any one of claims 1 to 3 wherein said solar collector comprises apparatus for produce (eg fruit) drying and said measured parameter of energy comprises temperature and relative humidity.

8. A solar energy collection system as claimed in any one of the preceding claims wherein said control unit comprises a microprocessor having a program including an algorithm to calculate the optimum position for said reflector panel for a given date and time, and latitude (and longitude where time is Grenwich Mean Time/Coordinated Universal Time and uncorrected for longitude).

9. A solar energy collection system as claimed in any one of claims 1 to 7 wherein said control unit includes a sensor to track the position of the sun, said sensor being located with said solar collector, said control unit being responsive to said sensor to control said actuating mechanism.

10. A solar energy collection system as claimed in any one of the preceding claims wherein said hinging mechanism comprises a rotatable shaft to which said reflector panel is fixed.

11. A solar energy collection system as claimed in any one of the preceding claims wherein said actuating mechanism is connected to a plurality of solar collectors arranged longitudinally side by side, and connected for synchronised movement of said reflector panels.

12. A solar energy collection system as claimed in claim 11 wherein said actuating mechanism includes at least one further rotatable input shaft extending normal to said rotatable shafts of said solar collectors, connected with said rotatable shafts by transmission gears for synchronised movement of said reflector panels.

13. A solar energy collection system as claimed in any one of the preceding claims wherein the width of the reflectors lies from 1.2x to 1.75x the width of the solar collector.

14. A solar energy collection system as claimed in any one of the preceding claims wherein said control unit controls said actuating mechanism to move said reflector panels while tracking the sun, to one of said heliostatic position, said closed position, and a parallel position in which said reflector panels are disposed substantially parallel to each other, in response to said parameter.

15. A solar energy collection system as claimed in any one of claims 12 to 14 comprising a plurality of said solar collectors arranged in an array

16. A solar energy collection system substantially as herein described with reference to any one of the embodiments as shown in the drawings.