Patent Application
20100139645
1. Field of the Invention
The present invention is in the field of support and tracking systems for an array of photovoltaic cells. More particularly, the present invention relates to a support and tracking system for an array of photovoltaic cells that is well balanced in the North-South declination sense and has numerous additional improvements over the state-of-the-art.
2. Brief Description of the Prior Art
The need to obtain reliable and renewable energy sources alternative to fossil fuels is greater at the present time than perhaps in any previous time in history. Electrical power generated from solar irradiation is a well known alternative and renewable energy source and the technology to exploit this source has been advancing rapidly during the last few decades. In the present state of the art photovoltaic cells are available that are capable of supplying very substantial electrical energy. Because photovoltaic cells are typically arranged in substantially flat panels, the terms “photovoltaic cells” and “solar panels” can be used interchangeably for the purposes of describing the state-of-the-art pertinent to the present invention, and for describing the invention itself.
Photovoltaic cells or solar panels are typically permanently mounted on flat surfaces such as roofs, or on stands, poles, frames or other mounting apparatus or mechanism. It is well known in the art, that better performance is obtained from solar panels when the panels continuously face the sun, that is, when they follow the Sun on its East to West daily track in the sky. This type of movement of the panels is commonly known as East-West movement or adjustment. It is also known in the art that still further improved performance is obtained from solar panels if the panels are inclined or tilted relative to the horizontal as a function of the geographical latitude of the location where the panels are, and still further if periodic adjustment of the panels' inclination or tilt is made during the seasons when the position of the Sun in the sky changes. This type of adjustment of the position of the solar panels is referred to as a North-South adjustment.
Photoelectric devices and associated electronic circuitry are available in the state-of-the-art to detect the position of the Sun in the sky and to control an electric motor or like device to cause the panels to move East-West to follow the daily track of the Sun in the sky, provided the mounting apparatus or mechanism allows such movement.
When the mounting apparatus allows adjustment of the North-South inclination or tilt of the panels, then this is typically performed periodically, but not necessarily daily, as the seasons change. A good practical rule to be followed in this regard is that during the summer the panels should be declined relative to the horizontal at an angle that is approximately 15 degrees less than the latitude-in-degrees of the location where the panels are, and during winter at an angle of 15 degrees greater than the latitude-in-degrees of the location where the panels are. Optimally, the declination of the panels can also be periodically changed between the above-noted two extremes as the seasons change.
The solar panels have substantial weight and because they are typically arranged in arrays of multiple panels, their combined weight can amount to several hundred or with wind loads to even several thousand pounds. It should already be apparent from the foregoing that the mounting mechanism that is capable of supporting this much weight and is also capable of reliably allowing the North-South adjustment of panels and reliably performing or allowing the East-West daily movement of the panels is relatively complex itself. In fact, the prior art has produced a large number of such mounting and tracking mechanisms as evidenced by the numerous United States and foreign patents, published patent applications and catalogs and advertisements in this field of technology.
More specifically, such mounting devices or mechanisms are described, for example, in U.S. Pat. Nos. 6,046,400; 4,280,853; 4,457,297; 6,563,040; 6,848,442; 6,302,099; 6,239,353; 7,240,674; 7,202,457; 4,225,781; 4,266,530; 4,302,710; 4,476,854; 4,202,321; 6,248,968; and in 4,172,739; in Published Patent Applications Nos. US 2004/0238025; US 2007/0227574; EP 1 241 416 A2; WO 92/11496; and WO 2005/026628.
Additional disclosures of interest to the present invention and pertaining to mounting mechanisms of various devices such as panels, solar cameras, weathering test apparatus and the like are found in U.S. Pat. Nos. 3,889,531; 70,09; 931,692; 6,572,061; 6,305,653; 4,378,100; 6,766,623; and 6,563,040.
In spite of the relatively large number of such disclosures of mounting and tracking apparatus for solar panels the mounting apparatus known in the present state-of-the-art still have some serious disadvantages in terms of the cost of installing them to a permanent location, their durability, particularly the durability of their East-West tracking and North-South tilting mechanism, and their ability to withstand wind pressures which can be very substantial. The present invention provides improvements in terms of all these problems of the prior art.
Another serious problem in the prior art relates to the weight of the solar panels when a North-South declination or tilting is adjusted or maintained. More specifically, whenever North-South declination or tilting and its periodic adjustment are enabled, the array of panels is mounted on an axis that allows such tilting relative to the horizontal. In all prior art mounting apparatus known to the present inventors whenever such North South tilting is enabled, the weight of the panels would normally cause the array to precipitously drop or fall relative to the horizontal axis until the maximum angle allowed is reached. This uncontrolled drop or can seriously injure or even kill a person who may be hit by the combined weight of the panels and the may damage the entire mounting device and the panels themselves. The state-of-the-art is aware that seriousness of this problem increases with the size and therefore with the weight of the array of panels. Because such rapid uncontrolled drop of the array of panels must be prevented to avoid injury and damage in the present state-of-the art usually at least two persons are needed to install the solar tracking apparatus. Usually two persons are needed also when the periodic adjustment of the North-South declination is performed. Even then, the installing persons are not free of danger, and sometimes other mechanical assistance is needed to avoid the damage or injury. One principal feature of the present invention is to eliminate the just-described serious problem.
It is an object of the present invention to provide a solar tracking mechanism and mounting platform that can be installed on a concrete foundation instead of attached to a pole affixed in the ground.
It is another object of the present invention to provide a solar tracking mechanism and mounting platform having an array of panels that is less subject to wind pressure than similar size panels mounted in accordance with the prior art.
It is still another object of the present invention to provide a solar tracking mechanism and mounting platform that has long useful life and requires a minimum of repairs or maintenance procedures.
It is a further advantage of the present invention to provide a solar tracking mechanism and mounting platform that is completely or substantially completely balanced relative to a horizontal axis of declination or tilting whereby the danger of damage and injury to persons is eliminated or minimized during installation and during adjustment of the North-South declination of panels.
These and other objects and advantages are attained by a solar tracking mechanism and mounting platform for solar panels that is mounted with three or four legs attachable to a concrete pad and includes a substantially vertically disposed axle and a substantially horizontally disposed axle to which a plurality of panel support members are mounted to form a panel support assembly. The vertically disposed axle allows at least approximately 240 degree rotation of the panel support assembly to follow the daily East-West travel of the Sun in the sky. The substantially horizontally disposed axle allows declining or tilting of the panel support assembly for the North-South adjustment of the panel support assembly to correspond to the geographic latitude of the location where the solar tracking mechanism and platform is used.
The substantially horizontally disposed axle is placed on the centroid or substantially on the centroid location relative to the panel support members, including solar panels so that, as a result, the assembly is completely or substantially balanced and can be placed horizontally or in any inclined position without the weight of the assembly, including solar panels mounted thereon, causing it to precipitously drop or fall.
The objects and features of the present invention are set forth with particularity in the appended claims. The invention may be best understood by reference to the following description, taken in connection with the accompanying drawings wherein like numerals indicate like parts.
The following specification, taken in conjunction with the drawings, sets forth the preferred embodiments of the present invention. The embodiments of the invention disclosed herein are the best modes contemplated by the inventors for carrying out their invention in a commercial environment, although it should be understood that various modifications can be accomplished within the parameters of the present invention.
A perspective view of a preferred embodiment of the solar tracking assembly and mounting platform 40 is provided in
It should be noted at the outset that photosensor apparatus and associated electronic or electric circuitry, electric motors capable of performing the East-West tracking of the Sun when controlled by the photosensor apparatus and electrically powered actuators per se are well known in the art, are commercially available, and need not be described here further.
Referring still primarily to
Before describing several of the principal novel features of the present invention the solar panel mounting subassembly 52 of the solar tacking apparatus is described briefly. This description is provided for the purpose of providing a complete description and enabling disclosure and in order to be able to refer to and identify certain components of the subassembly 52 when novel features of the invention are described. The solar panel mounting subassembly 52 is shown in perspective view in
Referring still primarily to
Continuing to describe the solar panel mounting subassembly 52, primary reference is made to
The cross-sectional view of
It should be readily apparent to those skilled in the art that numerous modifications can be made to the above described solar panel mounting subassembly 52 in terms of the number of main support members, such as 54 and 56, in terms of the number of main cross support members 58, 60, 62 and 64, in the manner of affixing these to one another, and further in the manner of affixing the solar panels 78 to the subassembly 52. Such modifications in terms of the number of the respective support members and the mechanical means, including welding, using nuts, bolts, carriage bolts or like means should be considered equivalent to the above described presently preferred construction and structure of the solar panel mounting subassembly 52 and of the attachment of the solar panels 78 to it.
Having described the solar panel mounting subassembly 52 to which the plurality of solar panels 78 are mounted, reference is now made primarily to
As is shown in
Referring still primarily to
The vertical axle 92 has a fixedly attached gear 132 with cogwheel type teeth 136 on its periphery that is in meshing engagement with an output gear 138 of the electric motor 122. The housing 126 is mounted to the legs 42 with plates 140 and bolts 142, as is best shown in
In the just described preferred embodiment a battery 144 is mounted to the legs 42 and provides or contributes to the electric power needed to rotate the solar panel mounting subassembly 52 with the solar panels 78. The battery 144 is shown only in
An arm 158 is affixed on one side of the member 148 to hold an actuator 160 the output rod 162 of which is attached to the one of the main cross support members 60 of the solar panel mounting subassembly 52, as is best shown in
The location of the substantially horizontally disposed axle 146 in such a manner that it causes the solar panel mounting subassembly 52, together with the assembled solar panels 78 to be weight-balanced against precipitous and dangerous drop is a highly important feature of the invention and is described below in detail.
It was found in accordance with the present invention that the desired weight balancing of the solar panel mounting subassembly 52 can be accomplished only when the axis of horizontal pivoting movement or rotation represented by the axles 146a and 146b is in the centroid or substantially in the centroid of the combined weight solar panel mounting subassembly 52 and solar panels 78. The concept of centroid per se is well known in mathematics and engineering and is described here for the sake of completeness only by including description from readily available sources, such that may readily accessed by searching on the Internet. Thus, as it can be found by searching for “centroids” in GOOGLE, the free encyclopedia, Wikipedia, describes centroid as follows:
In geometry, the centroid or barycenter of an object X in n-dimensional space is the intersection of all hyperplaness that divide X into two parts of equal moment about the hyperplane. Informally, it is the “averagee” of all points of X. The centroid of an object coincides with its center of mass if the object has uniform density, or if the object's shape and density have a symmetry which fully determines the centroid. These conditions are sufficient but not necessary. The centroid of a finite set of points can be computed as the arithmetic mean of each coordinate of the points. The centroid of a convex object always lies in the object. A non-convex object might have a centroid that is outside the figure itself. The centroid of a ring or a bowl, for example, lies in the object's central void.
More specifically with regard to “center of gravity” and “moment of inertia” as is well known and can be found by searching on the Internet the following is noted for the sake of complete description of the present invention. The centroid, or center of gravity, of any object is the point within that object from which the force of gravity appears to act. An object will remain at rest if it is balanced on any point along a vertical line passing through its center of gravity. In terms of moments, the center of gravity of any object is the point around which the moments of the gravitational forces completely cancel one another.
The center of gravity of a rock (or any other three dimensional object) can be found by hanging it from a string. The line of action of the string will always pass through the center of gravity of the rock. The precise location of the center of gravity could be determined if one would tie the string around the rock a number of times and note each time the line of action of the string. Since a rock is a three dimensional object, the point of intersection would most likely lie somewhere within the rock and out of sight. The centroid of a two dimensional surface (such as the cross-section of a structural shape) is a point that corresponds to the center of gravity of a very thin homogeneous plate of the same area and shape. The planar surface (or figure) may represent an actual area (like a tributary floor area or the cross-section of a beam) or a figurative diagram (like a load or a bending moment diagram). It is often useful for the centroid of the area to be determined in either case. Symmetry can be very useful to help determine the location of the centroid of an area. If the area (or section or body) has one line of symmetry, the centroid will lie somewhere along the line of symmetry. This means that if it were required to balance the area (or body or section) in a horizontal position by placing a pencil or edge underneath it, the pencil would be best laid directly under the line of symmetry.
If a body (or area or section) has two (or more) lines of symmetry, the centroid must lie somewhere along each of the lines. Thus, the centroid is at the point where the lines intersect. This means that if it were required to balance the area (or body or section) in a horizontal position by placing a nail underneath it, the point of the nail would best be placed directly below the point where the lines of symmetry meet. This might seem obvious, but the concept of the centroid is very important to understand both graphically and numerically. The position of the center of gravity for some simple shapes is easily determined by inspection. One knows that the centroid of a circle is at its center and that of a square is at the intersection of two lines drawn connecting the midpoints of the parallel sides.
For further description and explanation of the concept of centroid and how to find it on a given object, reference is made to standard handbooks of mathematics, geometry and engineering.
Solar panels are usually of rectangular shape and therefore have a symmetry of the type described above that would render the determination of the centroid of each panel easy. Each of the solar panels used in the same assembly have practically the same weight and density distribution on their respective surfaces. Moreover, in accordance with the present invention the plurality of solar panels are preferably placed in a symmetrical pattern on the solar panel mounting subassembly 52. It is important that it was found in accordance with the present invention that the centroid is usually high in, or relative to the solar panel mounting subassembly 52, and can be found by routine experimentation that is sufficiently simple so as not to constitute undue experimentation. For this reason a mathematical or geometrical determination of the centroid is usually not necessary in the practice of the invention, although it can be performed. As noted before, the axis of rotation, namely the axle 144 (or as in the preferred embodiment of the axles 146a and 146b) is placed in the centroid, or substantially in the centroid in accordance with the present invention.
The herein shown preferred embodiments of the invention accomplish well the goal of weight balancing by utilizing the described mechanical construction. It should be noted that in the preferred embodiments the position of the horizontal axle 146 is as specifically shown in
Thus, the just noted preferred embodiment may lack the photosensor 124 of the first preferred embodiment. It lacks the electric motor 122 and lacks the electrically powered actuator 160 of the first preferred embodiment. Nevertheless, to enable manual tracking of the Sun, or to place the solar panel mounting subassembly 52 together with the assembled solar panels 78 into a desired East-West position a disk 164 is fixedly attached to the vertical axle 92 above the non-adjustable bearings 128. The disk 164 has a plurality of apertures or holes 166 close to its periphery. Similarly to the teeth 136 of the gear 132 of the first preferred embodiment, in this embodiment the apertures 166 are placed at least approximately 240, preferably at approximately 270 degrees around the periphery of the disk 164. Optionally, and as is shown for the presently described preferred embodiment, the disk 164 may have the apertures 166 around its entire periphery. A plate 168 is affixed to the axle housing 94 below the disk 164. The plate 168 includes an aperture that can be aligned with one of the plurality of apertures 166 on the disk 164. A bolt and nut combination 170 is normally used to secure the vertical axle 92, together with the solar panel mounting subassembly 52 and assembled solar panels 78 to remain stationary in any desired East-West position. When the bolt 170 is removed, then the vertical axle 92, the subassembly 52 with the solar panels 78 can be manually rotated to any desired new position.
Exemplary dimensions of the solar tracking assembly and mounting platform 40 of the present invention, designed and constructed to mount state-of-the-art commercially available solar panels are as follows. The solar panel mounting subassembly 52 (that can also be called “the frame”) is approximately 10×12 feet when designed to hold eight (8) solar panels of 3 feet by 5 feet. A frame that is designed to hold up to thirty (30) solar panels is 18×25 feet. Thirty state-of-the-art panels may provide up to 5 KW power.
In summary, several advantages of the above-described solar tracking assembly and mounting platform 40 of the present invention include the advantage of being weight balanced whereby the tilting of the subassembly 52 and solar panels 78 can be readily accomplished manually without major hazard to workmen and substantially decreased chance of property damage due to precipitous drop of the subassembly 52 and panels 78 around the horizontal axis. Having the subassembly 52 and the panels 78 weight balanced renders it easier for the electric motor 122 of the first preferred embodiment to function and prolongs the useful life of the equipment. Having the subassembly 52 and the panels 78 weight balanced also renders manual East-West rotation or adjustment easier.
Another important advantage is the ability to mount the solar tracking assembly and mounting platform 40 on a concrete pad 44 at a substantially lesser cost and effort than the usual mounting on poles as in the prior art. Still another advantage is that by utilizing three or four legs the solar panels can be at a relatively low height above the ground 50 whereby exposure of the solar panels 78 to wind pressure is substantially decreased. All of the foregoing contributes to the prolonged useful life and less requirement for maintenance and repair.
As a practical example the following is noted. At a latitude of approximately 37 degrees North (where Cedar City, Utah) is located an exemplary solar tracking assembly and mounting platform 40 that has 24 panels (each panel being 3 feet by 5 feet) the horizontal axis of the subsassembly 52 is at approximately eight (8) feet above the ground. At this latitude the practical maximum inclination for the winter is about 55 degrees relative to the horizontal. The same height is also appropriate when thirty (30) such solar panels are included.
Referring now primarily to
In order to accomplish the North-South declination or tilting of the solar panel mounting subassembly 52 an electric motor or tilt motor 216 is mounted to a plate 218 that is itself mounted to an arm 220 (shown at an approximately 45 degree angle in
In the presently most preferred embodiment also, like in the previously described embodiments, the horizontally disposed axle 146 (shown only schematically in
The applicants claims priority of provisional application Ser. No. 61/200,550, filed on Dec. 1, 2008.
| Number | Date | Country | |
|---|---|---|---|
| 61200550 | Dec 2008 | US |
