Patent Publication Number: US-2012037204-A1

Title: Solar system and solar tracking method for solar system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a solar system and a solar tracking method for a solar system, and in particular, to a solar system with a feedback mechanism and a solar tracking method a solar system. 
     2. Description of the Related Art 
     A solar tracker is a device for orienting a daylighting reflector, solar photovoltaic panel or concentrating solar reflector or lens toward the sun. The suds position in the sky varies both with the seasons and time of day as the sun moves across the sky. Solar powered equipment works best when facing directly towards the sun or being disposed as close as possible to the sun. Thus, a solar tracker, which increases system complexity of solar powered equipment, can increase the effectiveness of solar powered equipment, as compared to if solar powered equipment remained in a fixed position. The conventional solar trackers comprise active trackers and passive trackers. Active solar trackers use motors and gear trains to direct the tracker toward a solar direction according to a controller. Maintenance of active solar trackers, however, is troublesome due to alignment deviations caused by nature. Passive solar trackers use a low boiling point compressed gas fluid that is driven to one side or another (by solar heat creating gas pressure), to cause the tracker to move in response to an imbalance. Passive solar trackers, however, do not track the sun very accurately. 
     Thus, a novel solar system and a solar tracking method are desired. 
     BRIEF SUMMARY OF INVENTION 
     A solar system and a solar tracking method for a solar system having a solar cell array on a substrate are provided. An exemplary embodiment of a solar system comprises a substrate comprising a solar cell array disposed thereon. An optical element array is disposed over the substrate to concentrate sunbeams onto the solar cell array. An actuator is affixed to the substrate, wherein the actuator shifts the substrate along an axis direction. A feedback module electrically is coupled to the substrate and the actuator, wherein the feedback module respectively measures a first, a second and a third voltage of the solar cell array corresponding to the first, the second and the third position, and finds a maximum voltage among the first, second and third voltages, thereby defining a maximum feedback position at witch the maximum voltage occurs. 
     An exemplary embodiment of a solar tracking method for a solar system having a solar cell array on a substrate is provided and comprises the steps of: (a) measuring a first voltage of the solar cell array at a first position on the substrate; (b) shifting the substrate by a first distance positively along an axis direction; (c) measuring a second voltage of the solar cell array at a second position on the substrate; (d) shifting the substrate by a second distance negatively along the axis direction; (e) measuring a third voltage of the solar cell array at a third position on the substrate; (f) finding a maximum voltage among the first, second and third voltages; (g) defining a maximum feedback position at witch the maximum voltage occurs; and (h) shifting the substrate to the maximum feedback position. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a top view of one exemplary embodiment of a solar system of the invention. 
         FIG. 2  is a cross section view taken along line A-A′ of  FIG. 1 . 
         FIG. 3   a  is cross section of one exemplary embodiment of a solar system showing the sunbeams directly concentrated onto the solar cell array. 
         FIGS. 3   b  and  3   c  are feedback voltage diagrams along the X-axis and Y-axis directions of the solar cell array of  FIG. 3   a.    
         FIG. 3   d  is top view of a portion of the substrate comprising a solar cell showing the concentrated sunbeam positions of  FIG. 3   a.    
         FIGS. 4   a  to  4   h  show one exemplary embodiment of a solar tracking method for a solar system with a feedback mechanism. 
         FIGS. 5   a  and  5   b  are feedback voltage diagrams along the X-axis and Y-axis directions of the solar cell array of  FIGS. 4   a  to  4   h.    
         FIG. 6  is top view of a portion of the substrate comprising a solar cell showing the concentrated sunbeam positions of  FIGS. 4   a  to  4   h.    
         FIG. 7  is a flow chart showing the feedback mechanism of the feedback module of one exemplary embodiment of the solar system obtaining the maximum feedback voltage of the solar cell array. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The following description is of a mode for carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. Wherever possible, the same reference numbers are used in the drawings and the descriptions to refer the same or like parts. 
     The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto and is only limited by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual dimensions to practice the invention. 
       FIG. 1  is a top view of one exemplary embodiment of a solar system  500  of the invention.  FIG. 2  is a cross section view taken along line A-A′ of  FIG. 1 . The solar system  500  such as a concentrating photovoltaic (CPV) system  500  may comprise a substrate  200  comprising a solar cell array  212  comprising a plurality of solar cells  202  disposed thereon. In one embodiment, the substrate  200 , serving as a carrier and/or a heat dissipation element for the solar cell array  212 , may comprise dielectric materials such silicon, ceramic or the like, or metal materials such as Al or the like. In one embodiment, the solar cells  202  work with a semiconductor that has been doped to form two different regions separated by a p-n junction. An optical element array  214  comprising a plurality of optical elements  204  is disposed over the substrate  200  for guiding sunbeams  216  to the solar cell array  212 . In one embodiment, a vertical distance d between the solar cell array  212  and the optical element array  214  is fixed. In one embodiment, the optical elements  204  may comprise lenses made from glass or acryl. Alternatively, the optical elements  204  may comprise reflectors. As shown in  FIGS. 1   a  and  1   b , in one embodiment, the solar cells  202  of the solar cell array  212  may have a first pitch P 1 , and the optical elements  204  of the optical element array  214  may have a second pitch P 2  which is the same as the first pitch P 1 . A first actuator  206  and a second actuator  208 , which are affixed to the substrate  200 , to respectively shift the substrate  200  along a first axis direction  220  and a second axis direction  222  to change a relatively position between the solar cell array  212  on the substrate  200  and the optical element array  214 . A feedback module  210  is electrically coupled to the substrate  200 , the first actuator  206  and the second actuator  208  for continuous solar tracking. For example, the feedback module  210  drives the first actuator  206  or the second actuator  208  to shift the substrate  200  along an axis direction and measures a first, a second and a third feedback voltage of the solar cell array  212  when the sunbeams  216  are concentrated on a first, a second and a third position on the substrate  200  by the optical element array  214 . Also, the feedback module  210  finds a maximum feedback voltage among the first, second and third feedback voltages of the solar cell array  212  along the axis direction, thereby defining a maximum feedback position on the substrate  200  at which the maximum feedback voltage occurs, wherein the substrate is shifted  200  until the sunbeams  216  are concentrated on the maximum feedback position on the substrate  200  at which the sunbeams  216  are directly concentrated onto the solar cell array  212 , wherein the first position is between the second and third positions. 
     In one embodiment, the feedback module  210  may be integrated with the substrate  200  to reduce volume of the solar system  500 . In one embodiment, the first axis direction  220  and the second axis direction  222  which is different from the first axis direction  220  may be orthogonal. In this embodiment, the first axis direction  220  is an X-axis direction  220  and the second axis direction  222  is a Y-axis direction  222 , so that the first actuator  206  serves as an X-axis actuator  206  and the second actuator  208  serves as Y-axis actuator  208 . 
       FIG. 3   a  is cross section along a first axis direction  220  of one exemplary embodiment of a solar system  500  showing the sunbeams  216  directly concentrated onto the solar cell array  212 .  FIGS. 3   b  and  3   c  are feedback voltage diagrams along the X-axis and Y-axis directions of the solar cell array  212  of  FIG. 3   a .  FIG. 3   d  is top view of a portion of the substrate comprising a solar cell  202  showing the concentrated sunbeam positions of  FIG. 3   a . As shown in  FIGS. 3   a  to  3   c , when the sunbeams  216  are directly concentrated onto the solar cells  202  of the solar cell array  212  by the optical element array  214 , the sunbeams  216  are concentrated on a position a 0  which is directly on the solar cell  202 . At this time, the feedback module  210  measures a maximum feedback voltage of the solar cell array  212  comprising a maximum X-axis feedback voltage V MX  and a maximum Y-axis feedback voltage V MY  along the X-axis and Y-axis directions. 
     The following description describes how the solar system  500  uses the feedback module  210  as shown in  FIGS. 1   a  and  1   b  to determine the shifting direction and distance between the substrate  200  and the optical element array  214  for solar tracking. 
       FIGS. 4   a  to  4   h  show one exemplary embodiment of a solar tracking method for a solar system  500  with a feedback mechanism.  FIGS. 5   a  and  5   b  are feedback voltage diagrams along the X-axis and Y-axis directions of the solar cell array of  FIGS. 4   a  to  4   h .  FIG. 6  is top view of a portion of the substrate comprising a solar cell showing the concentrated sunbeam positions of  FIGS. 4   a  to  4   h . The solar tracking method using a solar system  500  with a feedback mechanism may first start by finding a maximum X-axis feedback voltage V MX  of the solar cell array  212 , and then finding a maximum Y-axis feedback voltage V MY  of the solar cell array  212 , so that the maximum feedback voltage of the solar cell array  212  between the maximum X-axis feedback voltage V MX  and the maximum Y-axis feedback voltage V MY  is defined. Also, the maximum feedback position on the substrate  200  at which the maximum feedback voltage occurs is defined. Alternatively, the sequence of finding the maximum X-axis feedback voltage V MX  and the maximum Y-axis feedback voltage V MY  may be exchanged and is not limited thereto. 
       FIGS. 4   a  to  4   d ,  5   a  and  6  illustrate a solar tracking method performing along a first axis direction  220  such as an X-axis direction  220  to find the maximum X-axis feedback voltage V MX  by using the feedback module  210 . Referring to  FIGS. 4   a  and  6 , when the sunbeams  216   a  are incident onto the optical element array  214  with an incident angle θ, the sunbeams  216   a  are concentrated onto a positional on the substrate  200 . At this time, the feedback module  210  measures a feedback voltage Va 1  of the solar cell array  212  along a first axis direction  220  such as an X-axis direction  220 . Next, referring to  FIGS. 4   b  and  6 , the substrate  200  is shifted by a unit distance dx positively along a first axis direction  220  such as an X-axis direction  220  by the feedback module  210 , so that the sunbeams  216   a  are concentrated onto a position a 2  on the substrate  200 . At this time, the feedback module  210  measures a feedback voltage Va 2  of the solar cell array  212  as show in  FIG. 5   a . In one embodiment, the unit distance dx may be smaller than or equal to the first pitch P 1  of the solar cell array  212 . Also, the unit distance dx may be smaller or equal to the second pitch P 2  of the optical element array  214 . 
     As shown in  FIG. 5   a , because the measured feedback voltage Va 1  is smaller than the feedback voltage Va 2 , the feedback module  210  performs a step of shifting the substrate  200  by the unit distance dx positively along the first axis direction  220  such as an X-axis direction  220  as shown in  FIGS. 4   c  and  6  and a step of measuring a feedback voltage Va 3  of the solar cell array  212  as shown in  FIG. 5   a  when the sunbeams are concentrated onto a position a 3  on the substrate  200  by the optical element array  214 , wherein a distance between the positions a 1  and a 3  is larger than that between the positions a 1  and a 2 . As shown in  FIG. 5   a , the measured feedback voltage Va 2  is larger than the feedback voltage Va 3 . 
     As shown in  FIG. 5   a , because the feedback voltage Va 2  is larger than the feedback voltage Va 3 , the feedback module  210  performs a step of shifting the substrate  200  negatively along the first axis direction  220  such as an X-axis direction  220  so that the sunbeams  216   a  are concentrated onto a position a 2  of the substrate  200  as shown in  FIGS. 4   d  and  6 . At this time, the feedback voltage Va 2  as shown in  FIG. 5   a  can be defined as the maximum X-axis feedback voltage V MX  among the feedback voltages Va 1 , Va 2  and Va 3 . 
     Before the substrate  200  is shifted as shown in  FIGS. 4   b ,  4   c  and  4   d , the feedback module  210  may check the a horizontal distance Db between an edge  226  of the substrate  200  and a edge  226  of the optical element array  214  adjacent and parallel to the edge  226 , wherein the horizontal distance Db satisfies the boundary condition of Db≦P 1  and Db≦P 2 . When the horizontal distance Db does not satisfy the boundary condition, the substrate  200  is not shifted along a first axis direction  220 . The boundary condition of the horizontal distance Db limits the horizontal distance between the edge  226  of the substrate  200  and the edge  226  of the optical element array  214  to insure that sunbeams are concentrated on all of the solar cells of the solar cell array  212 . 
     Alternatively, when the feedback voltage Va 2  is the same as or smaller than the feedback voltage Va 3 , the feedback module  210  may perform the step of shifting the substrate  200  by the unit distance dx negatively along the first axis direction  220  such as an X-axis direction  220  and measure a feedback voltage of the solar cell array  212  until the maximum X-axis feedback voltage V MX  among the previously measured feedback voltages is found. 
     After finding the maximum X-axis feedback voltage V MX , the feedback module  210  performs the steps of changing the relative position between the substrate  200  and the optical element array  214  for solar tracking along the second axis direction  222  such as a Y-axis direction  222  as shown in  FIGS. 4   e  to  4   h ,  5   b  and  6 . 
     Next, referring to  FIGS. 4   e  and  6 , the feedback module  210  performs a step of shifting the substrate  200  by an unit distance dy positively along the second axis direction  222  such as a Y-axis direction  222  and a step of measuring a feedback voltage Va 4  of the solar cell array  212  as shown in  FIG. 5   b  when the sunbeams are concentrated onto a position a 4  on the substrate  200  by the optical element array  214 . In one embodiment, the magnitude of the unit distance dy is the same as the unit distance dx. 
     As shown in  FIG. 5   b , because the measured feedback voltage Va 2  is larger than the feedback voltage Va 4 , the feedback module  210  then performs a step of shifting the substrate  200  back to the position a 2  by a unit distance dy negatively along the second axis direction  222  such as a Y-axis direction  222  as shown in  FIGS. 4   f  and  6 . 
     Next, referring to  FIGS. 4   g  and  6 , the feedback module  210  performs a step of shifting the substrate  200  by an unit distance dy negatively along the second axis direction  222  such as a Y-axis direction  222  to measure a feedback voltage Va 5  of the solar cell array  212  as shown in  FIG. 5   b  when the sunbeams are concentrated onto a position a 5  on the substrate  200  by the optical element array  214 . As shown in  FIG. 5   b , because the measured feedback voltage Va 2  is larger than the feedback voltage Va 4 , the feedback module  210  then performs a step of shifting the substrate  200  back to the position a 2  by a unit distance dy positively along the second axis direction  222  such as a Y-axis direction  222  as shown in  FIGS. 4   h  and  6 . At this time, the feedback voltage Va 2  as shown in  FIG. 5   b  can also be defined as the maximum Y-axis feedback voltage V MY  among the feedback voltages Va 2 , Va 4  and Va 5 . 
     Before the substrate  200  is shifted as shown in  FIGS. 4   e ,  4   f ,  4   g  and  4   h , the feedback module  210  may check the a horizontal distance Db between an edge  226  of the substrate  200  and a edge  226  of the optical element array  214  adjacent and parallel to the edge  226 , wherein the horizontal distance Db satisfies the boundary condition of Db≦P 1  and Db≦P 2 . When the horizontal distance Db does not satisfy the boundary condition, the substrate  200  is not shifted along a second axis direction  222 . 
     Alternatively, when the feedback voltage Va 2  is the same or smaller than the feedback voltages Va 3  or Va 5 , the feedback module  210  may perform the step of shifting the substrate  200  by the unit distance dy positively or negatively along the second axis direction  222  such as a Y-axis direction  222  and a step of measuring a feedback voltage of the solar cell array  212  until the maximum Y-axis feedback voltage V MY  among the previously measured feedback voltages is found. 
     Because the feedback voltage Va 2  is defined as both the maximum X-axis feedback voltage V MX  and the maximum Y-axis feedback voltage V MY , the feedback voltage Va 2  is defined as the maximum feedback voltage of the solar cell array  212 . After the aforementioned steps are completed, the sunbeams  216   a  are directly concentrated onto the solar cell array  212 . Alternatively, when the maximum X-axis feedback voltage V MX  and the maximum Y-axis feedback voltage V MY  are different, the larger one can be defined as the maximum feedback voltage. Therefore, the position a 2  is defined as a maximum feedback position on the substrate  200 . 
       FIG. 7  is a flow chart showing the feedback mechanism of the feedback module  210  of one exemplary embodiment of the solar system  500  obtaining the maximum feedback voltage of the solar cell array  212  (as shown in  FIGS. 1 and 2 ). Firstly, the feedback module  210  sets two positions, a position i and a position j, on the substrate  200  for the sunbeams to be concentrated thereon, wherein i and j are axis coordinate values, i is an integer number and j=i+1 (step  701 ). Also, a boundary condition of the feedback module  210  is Db≦P 1  and Db≦P 2 , wherein Db is the horizontal distance between the adjacent edges of the substrate  200  and the optical element array  214 , P 1  is a pitch of the solar cell array  212 , and P 2  is a pitch of the optical element array  214  (step  701 ). Next, the feedback module  210  checks whether a distance Dij between the position i and the position j satisfies Dij≦Db (step  703 ). When Dij≦Db, the feedback module  210  measures a feedback voltage V 1  at the position i and a feedback voltage Vj at the position j (step  705 ). When Dij does not satisfy Dij≦Db, the feedback module  210  sets j to satisfy j=i−1 (step  709 ). After the feedback module  210  performs step  705 , the feedback module  210   a  checks whether Vi and Vj satisfy Vi&gt;Vj (step  707 ). When Vi&gt;Vj, the feedback module  210  sets j to satisfy j=i−1 (step  709 ). When Vi and Vj do not satisfy Vi&gt;Vj, the feedback module  210  sets i=j, j=j+1 and Vi=Vj (step  708 ) and then performs step  703  again until the feedback module  210  sets j to satisfy j=i−1 (step  709 ). 
     Additionally, after performing step  709 , the feedback module  210  checks whether a distance Dij between the position i and the position j satisfy Dij≦Db (step  711 ). When Dij≦Db, the feedback module  210  measures a feedback voltage V 1  of the position i and a feedback voltage Vj at the position j (step  713 ). When Dij does not satisfy Dij≦Db, the feedback module  210  determines that the position i is the maximum feedback position, and the feedback voltage V 1  is the maximum feedback voltage (step  717 ). After performing step  713 , the feedback module  210  determines whether Vi and Vj satisfy Vi&gt;Vj (step  715 ). When Vi&gt;Vj, the feedback module  210  determines that the position i is the maximum feedback position, and the feedback voltage V 1  is the maximum feedback voltage (step  717 ). When Vi and Vj do not satisfy Vi&gt;Vj, the feedback module  210  sets i=j, j=j−1 and Vi=Vj (step  716 ) and then performs step  711  again until the feedback module  210  determines that the position i is the maximum feedback position, and the feedback voltage V 1  is the maximum feedback voltage (step  717 ). 
     One exemplary embodiment of a solar system has a feedback mechanism is provided for continuous solar tracking. When the sunbeams from the sun move with time, one exemplary embodiment of the solar system may shift relative positions between a substrate and a optical element array thereof (for example, shifting the substrate) according to the feedback voltage from a solar cell array disposed on the substrate until the sunbeams are directly concentrated onto the solar cell array. One exemplary embodiment of a solar system has the following advantages. The optical elements may comprise lenses or reflectors without limiting the size thereof. The feedback module may be integrated with the substrate to reduce the volume of the solar system. Therefore, one exemplary embodiment of a solar system may have lower maintenance costs than that of conventional solar systems using active solar trackers and higher accuracy for solar tracking than that of conventional solar systems using passive solar trackers. One exemplary embodiment of a solar system without the conventional solar trackers can be especially applied in small-sized concentrating photovoltaic (CPV) systems. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.