Abstract:
A method is provided to track the sun. An omnidirectional sensor is used for acquiring sun&#39;s position. The sensor can track sun&#39;s position in an omnidirectional way. A controller is also provided to control the tracking. When the sun shines strongly, the sensor is controlled to track the sun&#39;s position. When the sun does not shine strongly, the tracking is stopped. Thus, the cost for tracking the sun&#39;s position is reduced and accuracy of the tracking is enhanced.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to sensing sun position; more particularly, relates to combining a plurality of optical sensors and a framework to form a sensing device for tracking the sun with high accuracy through equivalent flux values, where the sensing device is coordinated with a controller to be used in a solar tracker for omnidirectional detection. 
     DESCRIPTION OF THE RELATED ARTS 
     High concentration photovoltaic (HCPV) system has a higher power generation performance than traditional solar cell. But, the HCPV system has to be coordinated with a h-accuracy solar tracker for effectively generating power, since the precision of the solar tracker affects the power generation performance directly. Sun position sensor is a key unit in the solar tracker for tracking position of the sun. Hence, technologies for improving performance of the sun position sensor are developed. 
     A prior art is shown in  FIG. 6 . The prior art has a major disadvantage on visual angle limitation. If the sun is not located within a visual angle range of the sun position sensor (e.g. +/−45° to +/−75°), tracking fails and is ignored. Another problem is on when to track. Even when the sun is positioned within the visual angle range, a sensing value set as a base for tracking is hard to obtain for every optical sensor has its own different sensing value and the sensing value may have a very wide range. Not to mention that the sensing value will not be obtainable if the sun is not positioned within the visual angle range and thus cannot be tracked. 
     As a result, a solution is to use a decoder coordinated with calculation of solar orbit for a tracking controller to acquire position of the sun to be compared with a real-time position of the sun. The solar tracker tracks to turn toward the position of the sun for making the sun located within a visual angle range of the sun position sensor. Then, according to a sensing value obtained by the sun position sensor, a further tracking is done for the solar tracker to focus on the sun if the sensing value obtained is big enough. However, in this case, a decoder, a global positioning system (GPS), a microprocessor capable of floating-point calculation and a complex equation for solar orbit are further required, which adds cost to the whole control system and uses complex components while risk in failure is increased. 
     Hence, the prior arts do not fulfill all users&#39; requests on actual use. 
     SUMMARY OF THE INVENTION 
     The main purpose of the present invention is to combine a plurality of optical sensors and a framework to form a sensing device for tracking the sun with high accuracy through equivalent flux values, where the sensing device is coordinated with a controller to be used in a solar tracker for omnidirectional detection. 
     The second purpose of the present invention is to judge sunlight strength and sun position for tracking in an omnidirectional way. 
     The third purpose of the present invention is to provide a tracking method which uses flux value and position of the sun for tracking with low cost and high accuracy. 
     To achieve the above purposes, the present invention is an omnidirectional sun position sensing method, the method uses an omnidirectional sensing device to sense sunlight luminance for tracking the sun; the sensing device is coordinated with a controller; the controller is connected with a solar tracker; and the method comprises steps of: (a) according to a difference between sunlight luminance at the east direction and the west direction, tracking at the east and the west directions to make the sensing device focus on the sun; and (b) according to a difference between sunlight luminance at the south direction and the north direction, tracking at south direction and the north direction to make the sensing device focus on the sun. Accordingly, a novel omnidirectional sun position sensing method is obtained. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
         FIG. 1  is the view showing the preferred embodiment according to the present invention; 
         FIG. 2  is the sectional view showing the optical sensor in the hole not filled with the glue; 
         FIG. 3  is the sectional view showing the optical sensor in the hole filled with the glue; 
         FIG. 4  is the structural view showing the controller; 
         FIG. 5  is the view showing the current-to-voltage converting circuit; and 
         FIG. 6  is the view of the prior art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
     Please refer to  FIG. 1  to  FIG. 5 , which are a view showing a preferred embodiment according to the present invention; sectional views showing optical sensors in a hole not filled with glue and in a hole filled with glue; a structural view showing a controller; and a view showing a current-to-voltage converting circuit. As shown in the figures, the present invention is an omnidirectional sun position sensing method, where the method uses an omnidirectional sensing device to sense sunlight luminance for tracking the sun while the sensing device is coordinated with a controller and the controller is connected with a solar tracker. The omnidirectional sensing device comprises a framework  1  and a plurality of optical sensors  2 . 
     In  FIG. 1 , the framework  1  comprises five square plates  11 ˜ 15  and a rectangle plate  16 . Therein, the plates are aluminium alloy plates; the rectangle plate  16  has an area twice as big as the square plate  11 ˜ 15 ; a cube is formed by combing the square plates  11 ˜ 15  and the rectangle plate  16  at six directions of the cube; a hole  111 , 121 , 131 , 141 , 151 , 161  is set at each center position of the square plates  11 ˜ 15  and a center position of a region of the rectangle plate  16  corresponding to the five square plates  11 ˜ 15 ; two fixing holes  162  are set at a lower half region of the rectangle plate  16 ; and, the square plate  13  at the south direction has a through hole  132  at a lower left corner for guiding out wires. 
     In  FIG. 2 , each optical sensor  2  has two pins with each pin connected with a wire to form a set of wires  21 ; the set of wires  21  is separately penetrated through the hole  111 ˜ 161  of each plate  11 ˜ 16 ; and, each hole  111 ˜ 161  has an indent  112 ˜ 162  to separately lock the optical sensor  2 . Thus, each optical sensor  2  is separately set on each plate  11 ˜ 16  at the six directions; and, each set of wires  21  is guided to penetrate through the through hole  132  on the square plate  13  at the south direction to be connected with joint. In  FIG. 3 , the indent  112 ˜ 162  installed with the optical sensor  2  on each plate  11 ˜ 16  is filled with a water-proof sealing glue  3 . 
     The present invention has a low-power-consuming micro-process controller  4  connected with a control box of a solar tracker (as shown in  FIG. 4 ) and the controller  4  comprises a current-to-voltage converting circuit  41 , a microprocessor  42  and a direct-current (DC) motor driving circuit  43 . Therein, the current-to-voltage converting circuit  41  (as shown in  FIG. 5 ) comprises two load resistors  411 , a differential amplifier  412  and a LOG amplifier  413 . Two currents of the optical sensor  2  generated by being shone by the sun separately enter into the two load resistors  411 . The load resistors  411  separately output voltages to the differential amplifier  412  and the LOG amplifier  413 . 
     The differential amplifier  412  and the LOG amplifier  413  output signals to an analog-to-digital converter  421  of the microprocessor  42  for calculating a light flux value of each optical sensor  2  for tracking. Since optical strength of the sun in the optical sensor  2  has a range between 1 micro-ampere (μA) and 10 milli-ampere (mA) (having a range about 10 thousand times), the range of output value is reduced to about 5 times through the LOG amplifier  413 . Thus, the analog-to-digital converter  421  will not be saturated. After an equivalent luminance value is obtained through parameter conversion, the equivalent luminance value is used to decide tracking actions of the solar tracker. On tracking the sun, the microprocessor  42  controls a driving motor module with the DC motor driving circuit  43  for turning the solar tracker toward the sun. 
     On using the present invention, an omnidirectional sun position sensing device is coordinated with a low-power-consuming micro-process controller to judge sun-light strength and sun position for tracking. In the beginning, tracking is started at the east and the west directions according to sensing values of optical sensors at the east and the west directions and then is continued at the south and the north directions according to sensing values of optical sensors at the south and the north directions. Thus, the sensing device is turned east or west to be focused on the sun and then is turned south or north to be focused on the sun. In this way, the sensing device is perfectly focused on the sun at the east, the west, the south and the north directions. 
     When the omnidirectional sun position sensing device is installed on a solar tracker, relationships among the sensing device, the sun position and the optical sensors comprises the following conditions:
         (a) When the sensing device is positioned horizontally and faces toward the east direction,
           (i) the optical sensor at the south direction obtains a biggest sensing value of sunlight luminance when the sun is located at the east direction;   (ii) the optical sensor at the west direction or the upward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the upward direction and shines toward the south direction; and   (iii) the optical sensor at the north direction obtains a biggest sensing value of sunlight luminance when the sun is located at the west direction.   
           (b) When the sensing device is positioned vertically and faces toward the east direction,
           (i) the optical sensor at the upward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the east direction;   (ii) the optical sensor at the west direction or the north direction obtains a biggest sensing value of sunlight luminance when the sun is located at the upward direction and shines toward the south direction; and   (iii) the optical sensor at the downward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the west direction.   
           (c) When the sensing device is positioned horizontally and faces toward the south direction,
           (i) the optical sensor at the east direction obtains a biggest sensing value of sunlight luminance when the sun is located at the east direction;   (ii) the optical sensor at the south direction or the upward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the upward direction and shines toward the south direction; and   (iii) the optical sensor at the west direction obtains a biggest sensing value of sunlight luminance when the sun is located at the west direction.   
           (d) When the sensing device is positioned vertically and faces toward the south direction,
           (i) the optical sensor at the east direction obtains a biggest sensing value of sunlight luminance when the sun is located at the east direction;   (ii) the optical sensor at the upward direction or the north direction obtains a biggest sensing value of sunlight luminance when the sun is located at the upward direction and shines toward the south direction; and   (iii) the optical sensor at the west direction obtains a biggest sensing value of sunlight luminance when the sun is located at the west direction.   
           (e) When the sensing device is positioned horizontally and faces toward the west direction,
           (i) the optical sensor at the north direction obtains a biggest sensing value of sunlight luminance when the sun is located at the east direction;   (ii) the optical sensor at the east direction or the upward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the upward direction and shines toward the south direction; and   (iii) the optical sensor at the south direction obtains a biggest sensing value of sunlight luminance when the sun is located at the west direction.   
           (f) When the sensing device is positioned vertically and faces toward the west direction,
           (i) the optical sensor at the downward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the east direction;   (ii) the optical sensor at the east direction or the north direction obtains a biggest sensing value of sunlight luminance when the sun is located at the upward direction and shines toward the south direction; and   (iii) the optical sensor at the upward direction obtains a biggest sensing value of sunlight luminance when the sun is located at the west direction.   
               

     Accordingly, the present invention is an omnidirectional sun position sensing device, which uses a plurality of optical sensors and a framework to accurately track the sun with equivalent flux values. The sensing device is coordinated with a controller for processing a tracking method. The sensing device detects sunlight in an omnidirectional way by sensing optical strength of the sun at any direction. Tracking of the sun is done according to optical strength detected by the sensing device, where tracking is started when the optical strength is strong enough and is stopped when the optical strength is weak. At first, the sensing device obtains a position of the sun related to a solar tracker. Then, a microprocessor controls a driving motor module to turn the solar tracker toward the position of the sun for thus accurately tracking the sun. Hence, the tracking method of the present invention uses flux value and position of the sun for tracking the sun with low cost and high accuracy. 
     To sum up, the present invention is an omnidirectional sun position sensing device, where a plurality of optical sensors and a framework are combined to form a sensing device for tracking the sun with high accuracy through equivalent flux values while the sensing device is coordinated with a controller to be used in a solar tracker for omnidirectional detection. 
     The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.