Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Patent
1993-07-22
1995-04-25
Weisstuch, Aaron
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
H01L 31052
Patent
active
054095506
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a solar cell module comprising a housing with at least one aperture with an associated concentrator, where light energy, which is propagated along the optical principle axis of the concentrator, passes through the aperture and is concentrated on a photoactive area.
BACKGROUND OF THE INVENTION
In recent years much research work has been devoted to solar cells, and this has i.a. entailed an increased interest in solar cell modules of the above-mentioned type. These modules have a significant advantage, since the active area of the module is determined by the area of the concentrator, and such a concentrator may e.g. be a lens or a mirror. The concentrator is expediently a Fresnel lens, since these can be made of a plastics material, thereby minimizing the manufacturing costs. At the same time, Fresnel lenses have a significant advantage, since the lens thickness is reduced, so that the concentrator is very light in this case. When the optical principal axis of the concentrator is directed to the sun, the latter will be imaged in the focal point of the concentrator. Light energy having a very high intensity level will be concentrated around the focal point, so that the solar cell, which is to convert this light energy into electric energy, must be of a very high quality, e.g. made of monocrystalline silicon or gallium arsenide. For best possible utilization of the area of this solar cell, a second optical element is usually positioned in front of the solar cell, said optical element being constructed such that the light energy is distributed evenly over the active areas of the entire solar cell. A plurality of solar cell modules of this type are then assembled to provide a solar cell panel of matrix shape. Since, owing to the imaging properties of the concentrator, the solar cells only receive light energy which is propagated along the optical principal axis of the concentrator, the panel must be mounted on a device so that the panel can follow the travel of the sun across the sky. This technique is known and described in e.g. "Conference Record of The Twentieth IEEE Photovoltaic Specialists Conference, 1988, Volume II", pages 1138-1143 by Don Carroll.
Solar cell panels of this type operate satisfactorily when the optical principal axis of the concentrator is directed to the sun. In cloudy weather the visual field of the panel does not contain a powerful light source in the form of the sun, since the incident light will be in the form of diffuse light from all directions. The advantages of the concentrator by concentrating light from an area corresponding to e.g. 500 times the area of the solar cell, are thus gone. A solar cell panel of that type is therefore useful only in regions where a reasonable number of sunshine hours per day is certain with some statistical probability, it being thus certain that the solar influx is mainly direct influx. Therefore, it is not attractive to use such a solar cell panel in large parts of the world, since it must be considered unreliable depending upon the light conditions.
OBJECT OF THE INVENTION
The object of the invention is to improve solar cell panels of the above-mentioned type such that they also give a reasonable electric output even if they are not irradiated directly by the sun.
SUMMARY OF THE INVENTION
This object is achieved in that each individual solar cell module is provided with a secondary photoactive area which is arranged in the housing so as to be irradiated with light energy, which is propagated in a direction different from the optical principal axis of the concentrator.
The primary photoactive area is expediently provided on the rear wall of the housing on the optical principal axis of the concentrator, while the secondary photoactive areas can then expediently be provided at least on part of the other inner walls of the housing. Light passing the concentrator in a direction different from its principal axis can then be collected and converted to electric energy by solar cells provided on the wa
REFERENCES:
patent: 4427838 (1984-01-01), Goldman
patent: 4710588 (1987-12-01), Ellion
"Condenser Type Solar Battery Device", abstract of JP 57-2581, Patent Abstracts of Japan, 6(60):E102 (1982).
"Semiconductor Photodetector", abstract of JP 63-161680, Patent Abstracts of Japan, 12(423):E680 (1988).
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