Abstract:
A solar tracking system and methods based on passive tracking of solar illumination impinging on solar panels. The system includes a solar panel having cardinal points of the panel provided with piston assemblies. Actuating of pistons in the piston assemblies orients the solar panel to maximize solar illumination impinging on the solar panel. A conduit facilitates flow of a fluid between a solar illumination sensor and piston assembly based on changes in temperature of a canister and fluid contained within the canister. The heating of the fluid causes the fluid to flow toward and activate the piston assembly to rotate the solar panel about a longitudinal axis or lateral axis, which passively orients the solar panel in a position to maximize solar illumination impinging on a front face of the solar panel.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to solar panels and more particularly to a system and methods for collecting solar energy using passive tracking. Specifically, the present invention contemplates a solar panel system and methods based on tracking techniques that facilitate bi-directional tracking of solar energy impinging on solar panels. 
     BACKGROUND OF THE INVENTION 
     Conventional solar panels using passive solar tracking systems employ a frame pivotable about an axis. The systems typically have two canisters at opposing ends that are connected to each other via a conduit. The canisters are filled with a volatile fluid that transfers between canisters based on the temperature in each of the canisters. More specifically, once solar energy heats one of the canisters at a temperature greater than the other canister, the volatile fluid will pass to the other canister and cause passive rotation of the solar panel. 
     U.S. Pat. No. 4,476,854 illustrates a passive solar tracking system as described above that has solar panels mounted on a pipe. The panels rotate about an axis defined by a rod. Canisters are positioned at opposing ends of a frame. A conduit connects the canisters to facilitate transfer of a volatile fluid between the canisters as the canisters are heated to different temperatures. The passive solar tracking system further includes a bracket that may be manually adjusted to improve solar input on the panels. However, since the bracket requires manual adjustment, such a tracking system does not provide bi-directional tracking of a solar panel or group of panels. Moreover, the design of the tracking system makes it vulnerable to wind damage since the pipe provides support for the frame and solar panels. 
     U.S. Pat. No. 4,198,954 provides an alternative solar tracking system that has a reflector pivotable about a horizontal axis. Tubular reservoirs are connected via a conduit and act as sun sensors. A rod and bellows moves a lever, which pivots the reflector upon heating of the tubular reservoirs. The reflector further includes tubular reservoirs that are connected via a conduit. The heating of the tubular reservoirs causes rotation of the reflector. More specifically, a rotary disc is positioned on the base plate. The rotary disc includes a gearwheel and transmission, which is connected to a lever, to rotate the reflector about a vertical axis. Certain disadvantages are associated with this conventional solar tracking system. Specifically, debris may accumulate between the rotary disc and base plate preventing rotation of the rotary disc. 
     An example of a bi-directional solar tracking is provided by U.S. Publication No. 2011/0048406. This solar tracking system has scissor shaped structures or lifters that facilitate pivoting of the solar panel about two perpendicular axes. Certain disadvantages are associated with this known solar tracking system. Specifically, the configuration of the lifters is complicated and susceptible to damage from twisting and torsional movement of the solar panel under wind conditions. 
     Therefore, a need exists for a solar tracking system and methods for passively collecting solar energy that is resistant to environmental factors such as wind, rain, and debris, and otherwise minimizes damage to the solar panel for bi-directional passive tracking. The present invention satisfies this demand. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention include a solar panel system and methods for providing passive solar tracking. Embodiments of the present invention permit bi-directional movement of the solar panel while providing an improved support mechanism to protect the solar panel such as from wind, rain, damage and debris. 
     In certain embodiments, the present invention includes a solar panel and a plurality of lift assemblies. The solar panel may be sized and shaped to have a longitudinal axis and a lateral axis. In certain embodiments, the longitudinal axis is aligned with east and west cardinal points, and a lateral axis is aligned with north and south cardinal points. In such embodiments, the lifting assemblies can cause the solar panel to rotate about one or both of the lateral and longitudinal axes. 
     Embodiments of the solar panel have a front face and a back face. In certain embodiments, the front face is positioned to receive solar illumination from the sun or another light source. In certain embodiments, the back face is connected to the plurality of lift assemblies. The solar panel may be oriented using a passive rotation arrangement to permit a maximum amount of solar illumination to impinge perpendicularly on the front face of the solar panel. Advantageously, the amount of solar energy collected in the solar panel may be improved as more rays of solar illumination impinge perpendicularly on a face of a solar panel, compared to when rays of solar illumination impinge non-perpendicularly. 
     Embodiments of the lift assemblies may include a piston that expands and contracts to raise and lower the solar panel at one of the cardinal points which rotates the solar panel about one of longitudinal and lateral axes. Accordingly, activation of more than one piston may rotate passively and bi-directionally the solar panel about the axes to maximize solar illumination that impinges perpendicularly to the front face of the solar panel. This solar energy captured by the solar panel is increased as compared to conventional passive solar tracking systems. Moreover, the connection of the piston assemblies to the four cardinal points at the back side of the solar panel improves structural support for the solar panel to protect against wind damage. 
     The lift assembly may include a ball and socket assembly connected to the piston that further supports rotational movement of the solar panel. As the piston extends and retracts linearly, the ball and socket assembly can pivot to accommodate the rotational motion of the solar panel about the longitudinal axis and/or the lateral axis. 
     In certain embodiments, a solar illumination sensor and conduit may also be included as part of the lift assemblies. The conduit connects the solar illumination sensor to the piston. Fluid is contained in the solar illumination sensor and conduit which may be heated to activate and extend the piston to rotate the solar panel about one of the axes. The solar illumination sensor may include a canister that receives solar illumination directly and/or indirectly from solar reflectors. The fluid in a heated canister may then be transferred to the piston to activate the piston. In this manner, separate solar illumination sensors may be connected to each of the pistons to facilitate passive rotation of the solar panel about the longitudinal axis and lateral axis to maximize solar illumination impinging perpendicular to the front face of the solar panel as the sun moves throughout the day. 
     In another embodiment of the invention, a method for passively tracking a solar panel in response to the sun&#39;s movement includes a step of providing a solar panel having pistons at each of the cardinal points to rotate the solar panel about a longitudinal axis and a lateral axis. The methods also may include a step of reflecting solar illumination toward one or more canisters to heat a fluid stored in the canister. Each canister is connected to a respective one of the pistons such that one canister may actuate a piston for each cardinal point of the solar panel. Additionally, the method activates each piston assembly upon the heating of the fluid to rotate passively the solar panel about at least one of the longitudinal axis and the lateral axis. Thus, embodiments of the method facilitate passive tracking of the sun to maximize solar illumination impinging perpendicular to the solar panel throughout the day. 
     The present invention and its attributes and advantages will be further understood and appreciated with reference to the detailed description below of presently contemplated embodiments, taken in conjunction with the accompanying drawings. 
     The described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the invention is not limited to the foregoing description. Those of skill in the art will recognize changes, substitutions and other modifications that will nonetheless come within the scope of the invention and range of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the invention will be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which: 
         FIG. 1  is a perspective view of one embodiment of a solar panel system according to the invention; 
         FIG. 2  is a top view of the solar panel system of  FIG. 1  including the north and south lifting assemblies according to the invention; 
         FIG. 3  is a side view of the solar panel system of  FIG. 1  including the east and west lifting assemblies according to the invention; 
         FIG. 4  is a diagram illustrating the position of the sun as it passes from east to west throughout a calendar year; 
         FIG. 5  is a side view of another embodiment of a solar panel system according to the invention; 
         FIG. 6  is a side view of yet another embodiment of a solar panel system according to the invention; 
         FIG. 7A  is a perspective view of another embodiment of a solar panel system according to the invention; 
         FIG. 7B  is a detailed view of the solar panel system of  FIG. 7A  according to the invention; and 
         FIG. 8  is an alternative view of the solar panel system of  FIG. 7A  according to the invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Solar energy processes the sun&#39;s light or solar illumination to transform the solar illumination into electrical energy. Generally, a solar panel is formed by interconnecting a number of photovoltaic or solar cells. Solar illumination has photons that are absorbed by the solar cell to energize the cell. The energized solar cells then provide electricity, which may be used for residential or commercial use. Alternatively, the electricity may be stored until needed. 
     The performance of a solar panel is dependent on a number of factors, but especially on the angle of incidence between the solar illumination and the normal to a front face of the solar panel that receives solar illumination. Other external factors that affect the performance of a solar panel include of amount of rays received from the sun due to interference from clouds, fog, and rain. However, while weather may affect how often solar energy can be collected using a solar panel, many geographical areas have temperate climate zones that provide suitable environments for using solar panels. 
     A perspective view of a solar panel system, generally designated as  10 , according to certain embodiments of the invention is shown in  FIG. 1 . The system  10  includes a solar panel  12  having multiple interconnected photovoltaic cells  14 . The solar panel  12  is arranged to have a longitudinal axis A and a lateral axis B. Solar illumination  16  from the sun impinges on a front surface  18  of the solar panel  12  to energize the photovoltaic cells  14 . The energized photovoltaic cells  14  convert the solar illumination  16  into electrical energy as is known to those skilled in the art of solar energy capture. 
     The solar panel  12  is supported above a base surface  20 , for example the ground, by a plurality of lifting mechanisms  22 . In the illustrated embodiment, four lifting mechanisms  22   a ,  22   b ,  22   c ,  22   d  are provided at each of the cardinal points (i.e., north, south, east, and west, respectively) as best seen in  FIG. 2 . The lifting mechanisms  22   a ,  22   b ,  22   c ,  22   d  may attach to a back surface  24  of the solar panel  12 . 
     Each of the lifting mechanisms  22   a ,  22   b ,  22   c ,  22   d  may include a ball and socket assembly  26 , piston  28 , and solar illumination sensor  30 . A conduit  32  connects the solar illumination sensor  30  to the piston  28 . The piston  28  is connected to the ball and socket assembly  26 . The ball and socket assembly  26  is attached to the back surface  24  of the solar panel  12 . The pistons  28  are configured to extend and retract to rotate the solar panel  12  about the longitudinal axis A and/or the lateral axis B. 
     The solar illumination sensors  30  are configured to receive the solar illumination  16 . The sensors  30  each have a canister  34  and reflector  36 , as best seen in  FIG. 1  and  FIG. 3 . The reflectors  36  are arranged to direct the solar illumination  16  toward the canisters  34 . Depending on the location of the sun, different solar illumination  16  impinges on each of the canisters  34  resulting in temperature differentials between each of the canisters  34 . A fluid  38  is provided in each of the lifting mechanisms  22   a ,  22   b ,  22   c ,  22   d  and travels from the canisters  34  through the conduits  32  and toward the pistons  28  in response to the temperature of the canisters as they are heated to activate the pistons. In this manner, the changing temperature of the canisters  34  throughout the day changes the extensions of the pistons  28  and hence the position of the solar panel  12  Thus, a passive tracking system  10  is provided that maximizes solar illumination  16  impinging on the front face  18  of the solar panel  12 . 
       FIG. 4  is a diagram illustrating the position of the sun as it passes from east to west throughout a calendar year. As can be seen in the figure, the latitude of the sun varies throughout the year in the different hemispheres. Accordingly, it is contemplated that a length of a north piston  28  is greater than a length of a south piston  28  in the northern hemisphere. The reverse occurs for a solar panel system  10  designed for the southern hemisphere. Furthermore, the system  10  has an eastern piston  28  that is shorter than a western piston  28 . 
       FIG. 5  is a side view of solar panel system  100  according to another embodiment of the invention. In this embodiment, a pole  102  supports a base  104  that secures the pistons  28  and hence the solar panel  12 . The solar illumination sensors  30  have arm portions  106  that extend from the pistons  28 . The reflectors  36  of the solar illumination sensors  30  face away from the pistons  28  so that solar illumination is reflected toward the canisters  34 . The conduit  32  attaches a canister  34  at one cardinal point (e.g., east) to a piston  28  at the opposing cardinal point (i.e., west). 
       FIG. 6  is a side view of a solar panel system  200  according to another embodiment of the invention. One difference between the embodiment of the solar panel system  200  and the system  100  of  FIG. 5  is that the sensors  30  are connected to ends of the solar panel  12 . Another difference is the solar reflectors  36  are reversed, so that solar illumination  16  is reflected toward the solar panel  12  instead of away from the solar panel. Similar to the system  100 , the reflectors  36  reflect solar illumination  16  toward the canisters  34  to heat fluid in the canisters  34  and conduits  32 . Another difference between the embodiment of the solar panel system  200  and the system  100  is the arrangement of the conduits  32 . Solar panel system  200  has conduits  32  that secure to pistons  28  at the same cardinal point. Thus, a sensor  30  at the east cardinal point is connected via the conduit  32  to the piston  28  at the east cardinal point. 
     In an alternative embodiment shown in  FIG. 7A ,  FIG. 7B  and  FIG. 8 , the solar panel system  300  includes a solar panel  12  of a spherical configuration  306  that is rotatable about pivot point “P” using a linkage system  312 . The solar panel  12  includes a front surface  18  with photovoltaic cells  14  (see  FIG. 1 ) that convert the solar illumination into electrical energy. In this embodiment, lifting mechanisms  22   a ,  22   b ,  22   c ,  22   d  may or may not be used along with the linkage system  312 . 
     Linkage system  312  includes at least links  308 ,  310  attached to solar panel  12 . More specifically, links  308 ,  310  each include piston  28  that facilitates links  308 ,  310  to extend and retract linearly as can be seen in  FIG. 8 . 
     As shown, a pole  102  extends from base surface  20  to base  104 . More specifically, base  104  includes support stand element  302 . Pivot element  304  connects support stand element  302  with links  308 ,  310  and solar illumination sensor  30 . In particular, pivot element  304  connects to conduit  32  of the solar illumination sensor  30 . 
     As described above, each sensor  30  includes a canister  34  and a reflector  36 . Reflectors  36  are arranged to direct solar illumination toward the canisters  34 . Depending on the location of the sun, different solar illumination impinges on each of the canisters  34  resulting in temperature differentials between each of the canisters  34 . As an example, in response to an increase in temperature of the canisters  34 , pistons  28  are activated to extend and thereby rotate the solar panel  12  about pivot point “P” as shown in  FIG. 8 . 
     One advantage of the invention is that the solar energy captured by a solar panel is maximized by using a passive tracking system that does not require an external energy source to move the solar panel in response to movement of the sun throughout the day. Another advantage of the invention is that movement of the solar panel is bi-directional such that longitudinal and latitude changes in the location of the sun each day may be accounted for without any external user adjustments to the solar panel. Furthermore, the solar panel system may use multiple pistons to facilitate rotation of the solar panel. Each of the pistons additionally assists with maintaining the solar panel in position to prevent excessive movement of and damage to the solar panel due to excess wind, rain, debris or other environmental factors. 
     While this disclosure is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and have herein been described in detail. It should be understood, however, that there is no intent to limit the disclosure to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.