SOLAR PANEL UNIT AND SOLAR LAMP INCLUDING SAME

Abstract: A solar panel unit includes a solar panel (10) supported for rotation about a frame (13) and driven around the frame (13) by an electric motor (14). Radiation sensors (22) and (23) have their planar axes equally and oppositely off-set from the planar axis of the panel (10). Signals from the sensors (22) and (23) are monitored and used to control the operation of the motor (14) such that the panel (10) moves as the sun moves during daylight hours and the panel remains with its planar axis at right angles to rays of the sun throughout the day.

Description: SOLAR PANEL UNIT AND SOLAR LAMP INCLUDING SAME." The invention relates to solar 'lamps. The invention relates more particularly to a solar panel unit for a solar lamp. Normally, the solar panel converts solar energy during the day time into electrical power to charge up or to maintain a charge in a battery power pack which supplies the lamp during the night as required. Customarily, the panel is oriented to be directly facing the sun, that is a with its planar surface at least approximately perpendicular to the direction of the sun at say noon each day. The conversion of solar energy by a solar panel is most efficient in this position but as the sun moves throughout the daylight hours, the panel is for most of the day operating at considerably less than its optimum efficiency. It is an object of the invention to overcome or at least reduce this problem. According to the invention there is provided a panel arrangement support carriage and a drive motor for moving the carriage to orient the panel arrangement relative to the sunlight into optimum orientations for receiving solar energy, including means for sensing the intensity of solar TE SHEET energy received by the panel arrangement and controlling operation of the motor to move the panel arrangement towards the optimum orientations as the sun moves relative to the unit. The carriage may be pivotably supported about an axis and the motor arranged to move the carriage about the axis, which axis in use is positioned generally perpendicular to the radius of the arc of daily movements of the sun. The sensing means may comprise two sensors equally and opposingly off-set to respond to the intensity of solar energy at angles at either side of the optimum orientation of the panel arrangement arranged to control the motor to move the panel arrangement when the intensity of solar energy received by the two sensors is significantly unequal . The panel arrangement may comprise two panels which are somewhat angularly off-set from one another and from a central mean optimum orientation of the panel arrangement, in which the sensing means comprises means for responding to the solar energies converted by each respective panel to control movement of the motor when the two converted energies are significantly unequal. A solar panel unit according to the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a sectional front view of the unit; Figure 2 is a sectional side view of the unit; and Figure 3 shows an electrical circuit arrangement for the unit. Referring to the drawings, in Figures 1 and 2 the unit includes a solar panel 10 formed by an array of solar cells in conventional fashion mounted behind a window 11 to receive solar energy. The panel is mounted on a carriage 12 which is rotatably supported on a frame 13 to turn about the frame. The panel is supported in use with its window facing the sun. When the front plane of the window is generally perpendicular to the rays of the sun, the panel is in its optimum orientation for receiving solar energy. A motor 14 is provided for moving the carriage in either direction around the frame 13. A fluorescent lamp 15 is supported in the frame 13 behind a transparent lamp cover 16 and in front of a reflector 17. Two auxiliary solar cell panels 22 and 23 are mounted at the top of the panel 10 (see Figure 2) which their planar axes off-set from another and a printed circuit board 18 is mounted under the panel 10. A battery pack 19 is mounted on the frame 13. Referring to Figure 3, two small auxiliary solar cell panels 20 ahd 21 are mounted on the carriage with their windows 22 and 23 equally off-set from the plane of the surface of the window of the main solar panel. The panels 20 and 21 are electrically connected to a comparator 24 which responds to differences in the currents generated by the solar cells when they convert solar energy. When the difference in currents exceeds a value corresponding to a voltage D/2 as compared to a reference voltage, the output of the comparator 24 is fed to bias parallel coupled amplifiers 25 and 26, also supplied with the reference voltage. This causes a supply current to flow in a drive motor 27 in one or other direction according to the polarity of the bias applied to the amplifiers. The drive motor will run forwards or backwards according to the direction of the supply current until the bias returns to equal the reference voltage as the carriage is moved by the motor. This is when the panels 20 and 21, turning together with the main panel, have moved until they receive substantial the same amount of solar energy. The circuit is arranged so that the motor is only energised when the solar energy converted by the cells 20 and 21 is significantly unequal. In this way the motor is only energised say every five minutes. Alternatively, or additionally, a timer circuit may be provided to constrain, or prevent, the motor being energised in intervals of less than five minutes. This has the effect of conserving the electrical energy required to move the solar panel and reduces the overall efficiency of the solar energy conversion only marginally in practice. In an alternative arrangement, the solar panel is formed with two arrays of cells in panels which are angularly off¬ set, say 1° or 2°, to one another and at either side of a mean optimum orientation. In other words, the two panels are positioned side by side facing the direction of the sun and, in the mean optimum orientation, each panel is off-set from its own optimum orientation by, say, ° or 1° respectively. In this arrangement, the output of each panel, that is the solar energy converted to electrical power, is sensed and used to provide a control signal to initiate and control the operation of the drive motor. Again, the small reduction in efficiency caused by off¬ setting the solar panels is compensated for in practice by there being no need to provide the auxiliary solar panels 20 and 21, or other radiation sensors. The unit may be arranged to be generally stationary except during the hours of say 9 a.m. to 3 p.m. Generally, movement of the panel or panels to follow the movement of the sun during a central part of each day is sufficient to significan ly increase the overall conversion of solar energy, as compared to using normal permanently fixed or stationary panels. Thus the motor is inhibited so as not SUBSTITUTE SHEET to be operative before, say, 9 a.m. and after 3 p.m. The circuit is provided with a time-of-day clock to provide suitable control signals for the motor and to cause the motor to move the carriage from a 3 p.m. position to a 9 a.m. position during the night. The clock may be provided with and selectable different settings as may be required for generally different conditions applicable between seasonal variations of the relative movement of the sun.

Claims: C l a ims 1. A solar panel unit comprising a movable solar panel arrangement support carriage and a drive motor for moving the carriage to orient the panel arrangement relative to the sunlight into optimum orientations for receiving solar energy, including means for sensing the intensity of solar energy received by the panel arrangement and controlling operation of themotor to move the panel arrangement towards the optimum orientations as the sun moves relative to the unit. 2. A unit according to claim 1, in which the carriage is pivotably supported about an axis and the motor is arranged to move the carriage about the axis, which axis in use is positioned generally perpendicular to the radius of the arc of daily movements of the sun. 3. A unit according to claim 1 or 2, in which the sensing means comprises two sensors equally and opposingly off-set to respond to the intensity of solar energy at angles at either side of the optimum orientation of the panel arrangement arranged to control the motor to move the panel arrangement when the intensity of solar energy received by the two sensors is significantly unequal. 4. A unit according to any one of claims 1 to 3. in whi the panel arrangement comprises two panels which ar somewhat angularly off-set from one another and from central mean optimum orientation of the panel arrangemen panels, in which the sensing means comprise means fo responding to the solar energies converted by eac respective panel to control movement of the motor when th two converted energies are s gnificantly unequal. 5. An unit according to any one of claims 1 to 4 including means to constrain motor to move the carriag intermittently at intervals of a few minutes or more. 6. An unit according to any one of claims 1 to 5, in which the motor is powered by a battery. 7. A solar lamp having a housing including a solar panel according to any one of claims 1 to 6.

Inventors: SHALVI RAM, SHALVI, RAM
Applicants: SOLAR WIDE IND LTD, SOLAR WIDE INDUSTRIAL LTD.
Application year: 1992
Main classification: F21S9
IPC codes: F21S9, F24J2, G05D3, H01L31