Patent Application
20090194146
1. Field of Invention
This invention relates generally to solar panels and more specifically to an improved arrangement of multiple reflector facets around solar cells within a solar panel, or alternately around the outside of solar panels.
2. Description of the Prior Art
There is a substantial interest in the commercial application of solar energy. Even as the cost of other energy sources rise, a main obstacle to widespread adoption of solar power is the high cost of solar devices, especially solar photovoltaic cells. This is generally due to the high cost of materials used to convert solar energy into thermal or electrical energy, especially relative to reflector materials. It is well known in the art to use a solar cell for intercepting sunlight and producing energy of a thermal or electrical nature or the combination of both. A solar device or solar cell generally can mean a receiver or thermal absorbing plate (for solar thermal applications) or a solar photovoltaic (PV) cell (for solar electrical applications). Moreover it is fairly common knowledge that if more sunlight reaches a solar cell, one can convert proportionally more solar energy into thermal or electrical energy. Solar cells are frequently connected or joined to other cells either in parallel or in series and once a useful number are assembled they are generally enclosed in what is commonly called a panel.
A panel frequently has a transparent cover, parallel to and above the plane of the solar cells which allows sunlight to enter the panel and strike the solar cells. The panel frequently has a frame with sides and a backing plate that define a weather tight enclosure that shield the solar cell from the elements.
The prior art contains many examples of arrangements of solar cells and reflectors within a panel. Much of the prior art use reflectors on one or at most two sides of each solar cell, as taught in U.S. Pat. Nos. 6,528,716 5,538,563 and 4,316,448. While these arrangements reduce the amount of costly solar cell materials somewhat, they still include the inefficient or wasteful use of expensive materials.
The prior art also contains examples of panels using hard to manufacture circular, conic or parabolic reflectors, to increase the amount of sunlight reaching a solar cell. Some examples include U.S. Pat. Nos. 4,199,376 and 2,904,612 which both utilize complex three dimensional shapes to reflect light onto round solar cells (as they used to be made) from the region in between the round solar cells within a rectangular solar panel. There are numerous prior art example of complex reflector geometries many of which are used to increase sunlight arriving at solar devices, especially for use with solar thermal energy conversion or hybrid electric-thermal systems including U.S. Pat. Nos. 5,419,782 and 4,248,643. Disadvantages of these types of arrangements include complex geometries which are difficult to make and costly to reproduce.
Finally the prior art contains numerous examples of arrangements of multiple reflective facets used for different solar applications, such as solar cooking. Examples of such prior art include U.S. Pat. No. 4,637,376 to Varney and U.S. Pat. No. 4,292,957 to Golder and U.S. Pat. Nos. 4,220,141 and 4,077,391 to Way Jr. The prior art of Varney contains a reflector arrangement with some elements in common with this invention, but his invention has numerous additional elements primarily related to solar cooking that are not required for the manufacture and/or use of solar panels.
It would be advantageous to have a method and apparatus that uses inexpensive flat reflective facets and a simple to implement geometry to increase or concentrate the amount of sunlight falling on a solar cell or panel. Given the much higher cost of solar cells or panels relative to the cost of reflective facets or reflectors, this invention can reduce the average cost of solar power and allow many more people to benefit from clean, abundant, and renewable solar energy.
The present invention relates to a method and apparatus for arranging multiple reflector facets around a solar cell or panel. The present invention in a preferred embodiment uses multiple reflector facets arranged to form an inverted pyramid shell where the apex of the pyramid is removed and replaced by a solar cell or panel. Assuming the solar cell is square, there will be four equal sized isosceles trapezoid shaped flat reflector facets used, each one with the shorter parallel side located adjacent to the solar cell and with the reflective face tilted at a 120 degree angle from the surface of the solar cell. The angle between the solar cell and the reflective facet is important as it ensures uniform illumination of the solar cell provided the length of the solar cell is approximately equal to the length of the reflective facet.
If the solar panel (or cell) is rectangular, the reflective facet faces will have the shorter parallel side located adjacent to the solar panel, with the reflective face tilted at a 120 degree angle from the panel's surface, and the shorter parallel reflector sides ought to be the same length as the panel sides they are placed adjacent to.
While a panel that incorporates this inverted pyramid arrangement of reflector facets will be deeper than a standard panel, this design enables a much stronger panel to be constructed. The regular spaced reflector facets allow uniform support, either by the facets themselves or by adding a top to bottom vertical support midway between each solar cell at the point where the facets meet at the top of the panel. It is well known that regularly spaced vertical support will produce a much stronger structure than one which is primarily supported along the edges. The result is that one can construct a much stronger panel using the materials of standard panel construction, or one may construct an equivalently strong panel using less expensive materials.
Any solar panel generates more power if it is placed on a solar tracking system and solar panels made with the reflector arrangement(s) described above (either inside or outside the panel) will likewise benefit from solar tracking.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.
Several drawings and illustrations have been presented to better explain the construction and functioning of embodiments of the present invention. The scope of the present invention is not limited to what is shown in the figures.
The present invention uses a simple arrangement of flat reflectors or reflective facets arranged around a solar cell or solar panel to increase the amount of light arriving at the solar cell or panel, with the object of reducing the average cost of solar power.
If the solar cell 24 is rectangular, then only the reflective facets 26 on opposite sides of the solar cell 24 may have an equivalent isosceles trapezoid shape, but the shorter parallel side of each pair of equivalent reflective facets 26 will be located adjacent to the corresponding length side of the solar cell 24.
These additional means include but are not limited to: mounting clips which may be attached to the side of the solar panel 32 capable of securing—through friction or a spring force—the reflective facets 26 in place in the desired orientation, mounting slots cut into the frame of a standard solar panel 30 that serve to capture the reflective facets 26 in the desired orientation, or mounting brackets which may be added to the side of the solar panel 32 which serve to hold the reflective facets 26 in the desired orientation.
In all embodiments, the reflective surfaces can optionally be designed to not reflect wavelengths of sunlight, such as infrared or UV, which might overheat or damage the performance of the solar cell. This is especially useful if the cell is a photovoltaic cell that produces less electricity as the cell temperature rises. In this manner, only useful wavelengths can be directed to the cell from the reflectors.
Several descriptions and illustrations have been presented to aid in understanding the present invention. One of skill in the art will realize that numerous changes and variations are possible without departing from the spirit of the invention. For example, a solar cell may be a hybrid cell capable of both generating electricity via photovoltaic effect and transferring thermal energy to a circulating fluid in contact with the cell. Each of these changes and variations is within the scope of the present invention.
