Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
1998-10-02
2001-03-13
Codd, Bernard (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S248000, C136S251000, C438S066000
Reexamination Certificate
active
06201179
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to a solar collector system and in particular to an array of photovoltaic modules for an integrated solar power collector system.
2. Background and Related Art
Photovoltaic devices made of Selenium have been known since the 19
th
century. The silicon solar cell was the first known photovoltaic device that could convert a sufficient amount of sun's energy to power complex electronic circuits.
A photovoltaic cell is a solid-state device in which a junction is formed between adjacent layers of semiconductor materials doped with specific atoms, in order to create an n-type region and a p-type region. The photons incident on the semiconductor dislodge electrons from the valence band. These electrons, collected by the electric field at the junction, create a voltage which can be put at work in an external circuit.
A basic limit on the performance of these devices is that light photons lacking the energy needed to lift electrons from the valence to the conduction bands can not contribute to photovoltaic current, and also the energy transferred to electrons which exceeds the minimum excitation threshold, can not be recovered as useful electric current. Most of the photon energy not recovered as electricity, is converted to thermal energy in the cell. The overall effect is that the efficiency of solar cells does not exceed 16% in commercial devices.
As the energy collected is proportional with the surface exposed to solar radiation, and also in order to accommodate the electrical characteristics of the solar cells, in most application 36 (4×9) photovoltaic cells are grouped in a module, the cells being connected in series. The wires between the cells are arranged inside the module and not accessible. The only accessible connections are the “+” terminal of the first cell in the series and the “−” terminal of the last cell.
A module usually has an area of 1.5′×3′ or 4′×2′. Larger modules with an area of
16
square feet are also commercially available. A cell generates approximately 0.5 volts, and as a result, a module generates approximately 20 volts open circuit, giving a short-circuit current of 4 to 6 amperes. Still, the power generated by a module is rather low, a fill factor of only 0.5-0.8 can be obtained, depending on the quality of the cells.
Therefore, many applications use arrays of modules which are connected to each other in accordance with current and voltage requirements of the application. There are also various ways for electrically connecting the modules; in general, the positive and negative poles of all modules are wired to two bus-bars, or are wired with conductors placed in channels specifically provided on the back of the modules.
It is known practice to mount solar modules on rooftops where they are most likely to receive a maximum amount of sunlight without interference from trees or nearby constructions. One method for mounting an array of solar modules on a roof is to first assemble the modules on a base, to form the array, and then to secure the array on the existing rooftop. Special consideration should be given to the wind load, the weight of the snow, and the extra weight of the modules, when designing such a roof-over roof assembly.
Another method for mounting an array on the roof is to mount the solar modules individually directly on the roof. In this case, there are a number of operations which must be performed on the roof, such as installing the modules, interlocking the modules to each other, wiring the modules and treating the surface thus obtained to obtain a weather—resistant roof. The modules are fragile and may break if stepped on. As such, walkways must be provided on the roof, which reduce the surface dedicated to the modules.
A photovoltaic roofing assembly is disclosed in U.S. Pat. No. 5,505,788 (issued to Dinwoodie on Apr. 9, 1996), where the modules are disposed as a layer on top of the roof, and separated therefrom by pre-formed spacers, pedestals or supports. Use of spacers enables heat exchange with a convecting fluid flowing between the modules and the roof. Preferably, the cooling fluid is air or other gaseous fluid, or could also be a liquid. Besides the disadvantages listed above, it is difficult to mount the spacers on the roof and then the modules on the spacers as in the system disclosed by this patent.
There is a need to provide a method for installing an array of photovoltaic modules directly on the roof, which is simple, cost-effective and easy to install.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a solar power collector system which alleviates totally or in part the drawbacks of the prior art photovoltaic systems.
It is another object of the present invention to provide an integrated solar power collector system which uses arrays of photovoltaic modules interlocked to form an integrated collecting surface of a desired size.
Still another object of the present invention is to provide a solar power collector system comprising a plurality of photovoltaic modules installed on a corrugated substrate. The substrate provides enhanced resistance to stress and facilitates temperature control of the modules. As such, the solar power collector system according to the invention acts as a combined electrical current generator and hot air collector.
Still another object of the invention is to provide an integrated solar power collector system which is weather resistant and offers improved resistance to water leakage.
Accordingly, the invention provides an integrated solar power collector system comprising a first array of photovoltaic modules including: a first substrate, defining a module support area, an anchoring zone, a first interlocking zone and a second interlocking zone on an opposite side of the first substrate from the first interlocking zone; and a first collecting surface comprising a plurality of photovoltaic modules arranged proximal to each other on the module support area so as to leave a minimal residual space between the modules.
A second corrugated substrate, supports a second collecting surface comprising a plurality of photovoltaic modules arranged proximal to each other so as to leave a minimal residual space between the modules. Means for interlocking the second interlocking zone of the first array and the first interlocking zone of the second array to each other provide an integral collecting area. The solar power collector system may be installed directly on an upholding structure, such as the roof of a building.
The invention also provides for a method for collecting solar power comprising providing a first array of photovoltaic modules on a first substrate so as to leave a minimal residual space between the modules, the first substrate defining a first collecting surface, an anchoring zone, a first interlocking zone and a second interlocking zone on an opposite side of the first substrate from the first interlocking zone, and fixing the first substrate to an upholding structure along the anchoring zone and the first interlocking zone.
A second array of photovoltaic modules is provided on a second substrate, the second substrate defining a second collecting surface, an anchoring zone, a first interlocking zone and a second interlocking zone on an opposite side of the second substrate from the first interlocking zone. The second substrate is fixed to the upholding structure along the anchoring zone, and the first substrate is fixed to the second substrate and to the upholding structure along the second interlocking zone of the first substrate and the second interlocking zone of the second substrate, to provide an integral collecting area.
Advantageously, the solar power collector system of the invention alleviates the need for individual framing of the modules, resulting in a system that is lighter and less expensive than systems of the prior art.
Another advantage of this invention is that the modules are assembled in arrays at the factory, which res
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