Patent Application
20050139253
Solar cell panels have been used to generate electricity from sunlight. Further, solar cell and solar cell panels comprising a plurality of solar cells have been used in Earth and non-Earth applications when access to other electrical power sources is limited.
In particular, space satellites, spacecraft, and other devices used in non-Earth applications have utilized solar cell panels to provide power from sunlight for powering devices, such telecommunication devices. For purposes of discussion, the term “outer space” means space outside of the Earth's atmosphere. Further, the term “non-Earth application” means any device or system that is designed to function in outer space or on an extraterrestrial body such as a moon or a planet.
The solar cell assemblies are mounted on a rigid frame, such as an aluminum frame, for holding the remaining components of the assemblies. Thus, the solar cell assemblies are not flexible. Further, the rigid frames are relatively heavy which results in relatively high costs to transport the solar cell assemblies from Earth to an outer space environment or a non-Earth environment. Further, because the rigid solar cell assemblies cannot be rolled-up, a relatively large transport vehicle (e.g., rocket) having a large cargo area must be utilized to transport the known solar cell assemblies from Earth to an outer space environment or a non-Earth environment.
Accordingly, it is desirable to provide a flexible solar cell assembly that can be utilized in a space environment or a non-Earth environment.
A flexible solar cell assembly for use in an outer space environment or a non-Earth environment is provided. The flexible solar cell assembly includes a solar cell having a first side and a second side. The solar cell is configured to produce an electrical current when receiving photons on at least the first side. The flexible solar cell assembly further includes a flexible substrate operably coupled to the second side of the solar cell.
A flexible solar cell assembly for use in an outer space environment or a non-Earth environment is provided. The flexible solar cell assembly includes a plurality of solar cells each having a first side and a second side. Each of the plurality of solar cells is configured to produce an electrical current when receiving photons on at least the first side. The flexible solar cell assembly further includes a flexible substrate operably coupled to the second side of each of said plurality of solar cells.
Other systems and/or methods according to the embodiments will be or become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that at all such additional systems and methods be within the scope of the present invention, and be protected by the accompanying claims.
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As shown, stainless steel substrate 30 is disposed over an aperture 54 extending through flexible substrate 40. In particular, an area of substrate 30 can be greater than an area of aperture 54 so that substrate 30 can be fixedly attached to a surface 41 of flexible substrate 40 over aperture 54. Substrate 30 can be fixedly attached to surface 41 using a high-temperature glue for example. Further, substrate 30 can have a thickness of about 5 millimeters (mm) so as to provide considerable flexibility therein. Substrate 30 could be constructed with a thickness less than or greater than about 5 mm depending upon a desired flexibility or a desired thermal conductivity of substrate 30. The particular configurations illustrated in
The solar cell 32 is provided to generate an electrical current in response to photons contacting solar cell 32. Solar cell 32 is fixedly attached to stainless steel substrate 30. As shown more clearly in
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Emissivity layer 44 can have an emissivity greater than or equal to 0.8. The term “emissivity” means the relative power of a surface to emit heat by radiation, and in particular, the ratio of the radiant energy emitted by a surface to that emitted by a black body having the same area and temperature. Emissivity layer 44 can be constructed from silicon oxides such as SiO2, silicon nitrides such as Si3N4, silicon oxynitrides, silicon oxycarbides, silicon carbides, silicon nitrocarbides, silicon oxynitrocarbides, and the like. Further, emissivity layer 44 can have a thickness of 10 microns or greater and may be disposed over substantially an entire top surface of solar cell array 16. An example of a suitable emissivity layer and a method of making the emissivity layer is found in International Application WO 01/75486 A2.
It should be noted that as space satellites orbit the Earth, the satellites come into contact with electrons floating through space. In particular, solar panel assemblies, e.g., 18, 20, 22, 24, 26, and 28, on the satellites come into contact with the electrons that adhere to an outer surface of the solar panel assemblies. After a significant amount of electrons adhere to the solar panel assemblies, an electro-static discharge can occur through solar cells in the solar panel assemblies that can damage the solar cells therein.
The transparent electrically conductive layer 46 is provided to capture electrons that are traveling in space that contact the solar panel assemblies. The transparent electrically conductive layer 46 conducts the electrons away from the solar cell 32 to prevent electro-static discharge therein. Conductive layer 46 can be constructed from indium tin oxide (ITO) or zinc oxide. Conductive layer 46 is preferably disposed over emissivity layer 44 at a thickness of about 30 to about 100 nanometers (nm) and may be disposed over substantially the entire top surface of the solar cell array 16. Conductive layer 46 also reflects light wavelengths greater than or equal to 5 microns contacting layer 46 away from solar cell 32. Layer 46 is configured to be substantially flexible.
In the illustrated embodiment, self-cleaning layer 48 is provided to remove dust or dirt that can adhere to solar cell array 16 when satellite 10 is at a relatively low Earth orbit. Self-cleaning layer 48 can be disposed over layer 46 and may comprise a layer of titanium dioxide (TiO2) that is substantially flexible. While not wanting to be bound by theory, it is believed that the self-cleaning layer 48 attracts water particles, such as may be present at low Earth orbits, which then moves underneath any dust or dirt contacting layer 48 so that the dust or dirt will no longer bond to layer 48. Thereafter, as satellite 10 moves through space, the dust and dirt floats off of layer 48. It should be noted that in an alternate embodiment of assembly 18 (not shown), self-cleaning layer 48 could be removed from the assembly.
It should be noted that on known solar cell assemblies, the solar cell assemblies are mounted on a rigid frame for holding the various components of the assemblies. Thus, the solar cell assemblies are not flexible. Further, the rigid frames are relatively heavy which results in relatively high costs to transport the solar cell assemblies from Earth to an outer space environment or a non-Earth environment. Further, because the solar cell assemblies cannot be rolled-up, a relatively large transport vehicle (e.g., rocket) having a large cargo area must be utilized to transport the known solar cell assemblies from Earth to an outer space environment or a non-Earth environment.
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Flexible substrate 40 can be constructed from a thermally non-conductive polyimide identified by the trademark “KAPTON H” or the trademark “KAPTON E”, manufactured by DuPont Corporation. Because the KAPTON® product is a thermally non-conductive polyimide, the inventors herein have recognized that the heat radiating layers can be disposed through the KAPTON® layer 40 to radiate excess heat generated in solar cell 32 (and the other solar cells in solar cell array 16) from a backside of solar cell array 16.
In alternate embodiments, substrate 40 can be constructed from films of one or more of the following materials: (i) polyethyleneterephthalate (“PET”), (ii) polyacrylates, (iii) polycarbonate, (iv) silicone, (v) epoxy resins, (vi) silicone-functionalized epoxy resins, (vii) polyester such as polyester identified by the trademark “MYLAR” manufactured by E.I. du Pont de Nemours & Co., (viii) a material identified by the trademark “APICAL AV” manufactured by Kanegafugi Chemical Industry Company, (ix) a material identified by the trademark “UPILEX” manufactured by UBE Industries, Ltd.; (x) polyethersulfones “PES,” manufactured by Sumitomo, (xi) a polyetherimide identified by the trademark “ULTEM” manufactured by General Electric Company, and (xii) polyethylenenaphthalene (“PEN”).
In other alternate embodiments, substrate 40 can be constructed from stainless steel. The stainless steel may have an insulating coating or may not have an insulating coating depending upon desired thermal characteristics of substrate 40. Alternately, flexible substrate 40 can be constructed from a relatively thin glass that is reinforced with a polymeric coating, such as a glass manufactured by Schott Corporation, for example.
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The isolation barriers 50, 52 are provided to electrically isolate contacts 36, 38, respectively, in assembly 18. It should be noted that solar cell assembly 18 includes a plurality of such isolation barriers. In particular, each electrical contact proximate an upper surface of solar cell assembly 18 is coupled to a corresponding isolation barrier. Further, each electrical contact proximate a lower surface of solar cell assembly 18 is coupled to a corresponding isolation barrier.
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As shown, flexible substrate 240 has an aperture 254 including aperture portions 96, 98. Aperture portion 96 is configured to receive at least a portion of stainless steel substrate 30. Aperture portion 96 has a periphery smaller than stainless steel substrate 30 such that substrate 30 rests on a ledge 100 defined by aperture portions 96, 98. Aperture portion 96 is configured to receive heat radiating layer 42.
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As shown, solar cell array 316 has an emissivity layer 344, a conductive layer 346, and a self-cleaning layer 348 that covers the solar cell assemblies (e.g., solar cell assemblies 318 and 322) but leaves a portion of flexible substrate 40 uncovered. As shown, flexible substrate 40 has a region 109 between solar cell assemblies 318, 322 that is not covered by layers 344, 346, 348.
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Plasma ejection device 111 includes a body portion 112, a nozzle portion 114, a cathode member 115, and a voltage supply 118. An aperture 113 extends through body portion 112 and nozzle portion 114. Aperture 113 is provided to allow an argon gas from argon supply device 126 to be communicated therethrough. Cathode member 115 is disposed in aperture 113.
Voltage source 118 is electrically connected between cathode member 115 and nozzle portion 114. When argon supply device 126 supplies argon gas through aperture 113, the argon gas is electrically charged by cathode member 115.
Reagent supply device 120 is provided to supply reagent compound particles that will be subsequently coated on a portion of solar array 16. For example, reagent supply device 120 could supply one or more of: (i) silicon oxides, (ii) silicon nitrides, (iii) silicon oxynitrides, (iv) silicon oxycarbides, (v) silicon carbides, (vi) silicon nitrocarbides, (vii) silicon oxynitrocarbides—that can be used by system 110 to form emissivity layer 44 on a solar cell. Further, for example, reagent supply device 120 could supply indium tin oxide (ITO) or zinc oxide that can be used by system 110 to form transparent electrically conductive layer 46 on a solar cell. Further, for example, reagent supply device 120 could supply titanium dioxide to form self-cleaning layer 48 on a solar cell.
During operation of system 110 when plasma ejection device 111 is disbursing ionized argon particles and reagent supply device 120 is supplying reagent particles, the ionized argon particles attach to the reagent particles and the combined particles are directed toward a surface of solar cell array 16. As the argon particles and reagent particles contact the surface solar cell array 16, the reagent particles adhere to the surface of solar cell array 16. It should be noted that system 110 has a relatively fast rate of applying a desired layer or layers to a solar cell assembly. For example, system 110 can deposit layers at greater than 1 micrometer/minute with a deposition temperature of less than 200 degrees Celsius.
Referring to
At step 130, a plurality of solar cell assemblies are disposed on flexible substrate 40. The solar cell assemblies are electrically coupled together with external grid lines and positioned over corresponding apertures in flexible substrate 40.
At step 132, a heat radiating layer is applied to a bottom surface of each of the plurality of solar cell assemblies through each of the corresponding apertures in flexible substrate 40.
At step 134, an emissivity layer 44 is deposited on the plurality of solar cell assemblies disposed on flexible substrate 40. Emissivity layer 44 can be deposited on the plurality of solar cell assemblies utilizing thermal plasma deposition system 110 or a sputtering system known to those skilled in the art.
At step 136, transparent electrically conductive layer 46 is deposited on emissivity layer 44. Conductive layer 44 can be deposited on the plurality of solar cell assemblies utilizing thermal plasma deposition system 110 or a sputtering system known to those skilled in the art.
At step 138, self-cleaning layer 48 can be deposited on conductive layer 46. Self-cleaning layer 48 can be deposited on the plurality of solar cell assemblies utilizing thermal plasma deposition system 110 or a sputtering system known to those skilled in the art.
The solar cell assemblies and a method for controlling a temperature of the solar cell assemblies described herein represent a substantial advantage over known solar cell assemblies and methods. In particular, the solar cell assemblies are configured to radiate excess heat energy from the solar cell assemblies from the backside of the assemblies. Accordingly, an operating temperature of the solar cell assembly can be maintained within an optimal operating temperature range in a space environment or in a non-Earth environment.
While the invention is described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made an equivalence may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to the teachings of the invention to adapt to a particular situation without departing from the scope thereof. Therefore, is intended that the invention not be limited the embodiment disclosed for carrying out this invention, but that the invention includes all embodiments falling with the scope of the intended claims. Moreover, the use of the term's first, second, etc. does not denote any order of importance, but rather the term's first, second, etc. are us are used to distinguish one element from another.
