MXPA98004760A - Photovoltaic module that has a encapsulant molded by inyecc - Google Patents

Abstract

A photovoltaic module (1) which includes at least one photovoltaic cell (2) which is encapsulated in an unreacted, injection molded polymer material (3), thus forming an environmental seal around the cell. The cell or photovoltaic cells (2) are incorporated in a photovoltaic panel having front, rear and edge sides forming a perimeter, and also includes means for the external electrical connection to the photovoltaic cell. The unreacted, injection molded polymeric material that encapsulates the panel can form useful structures such as tiles, blocks, frames, or boxes.

Description

POTOVOLTAIC MODULE THAT HAS AN ENCAPSULANT MOLDED BY INJECTION DESCRIPTION OF THE INVENTION: This invention relates generally to photovoltaic modules and more specifically to modules that are encapsulated by an unreacted injection molded polymeric material. The encapsulant acts as much as an environmental shield to protect the voltaic cell from the elements during use as a mechanical support and protection. The conversion of photovoltaic energy (PV), the direct conversion of sunlight to electricity, has long been a source of energy in space. However, it has traditionally been too expensive to be practiced in terrestrial applications except in remote locations. Growing concern and attention to the environmental consequences of conventional and atomic generation and the desire to reduce dependence on imported oil have increased the need for renewable energy technologies available. The nation that succeeds first in the development and commercialization of low cost, practical PV technology that is competitive with conventional fuels will be at the forefront of a revolution in global energy with enormous economic consequences. The global shipment PV modules in 1993 was approximately 60 MW that reached a value in dollars of approximately 300 million, including the balance of systems, the total market was 600 million. US companies hold approximately 20% of the shares in this market. According to the United States Department of Energy (DOE), PV will play an increasingly important role in appliances and other uses of electricity due to the need for new electricity generating capacity coupled with high customer service. environmental impacts associated with the use of energy from conventional sources. The new capacity needed for the devices in the United States only in MW in the 1990s and for more than two thirds of the devices, the additional annual need is less than 100 MW. The modular characteristics of the PV make it ideal for these applications and DOE estimates that for the PV market in the US device market alone, it is 900 MW of the cumulative power installation in the 1990s. Huge opportunities also exist in Latin America, Asia and Africa for remote power applications, the United States Agency for International Aid (USAID) foresees that the market for power generation systems between 1990 and 2010 alone in the developing world will be 914 billion. Distributed energy is the most desirable mode of electric generation in many of these countries, and that makes PV systems very attractive. Therefore DOE estimates that the cumulative demand for PV in these countries for the 1990s is 500 MW. This is a huge export market that the United States can not afford to ignore. In order to face this multimillion dollar PV market, an essential requirement is to lower the cost of the PV modules from the prevailing value of 4 to 5 dollars per watt to less than 1 dollar per watt. This challenge can only be met by an aggressive R &D (research and development) by the PV industries to develop an innovative manufacturing technology producing items that include cost, module efficiency and reliability. During the last three decades many attempts have been made to reduce the cost of PV. In order for the cost of PV to be effective and accepted as a convenient source of alternative energy, the following key requirements must be met: (1) low cost of material, (2) high efficiency with good stability, (3) ) low cost manufacturing process with high performance, and (4) environmental safety. It is important to note that all of these requirements need to be met in order for PV to be accepted for large-scale land applications. An area in which the cost of photovoltaic modules can be reduced is the encapsulation and framing of photovoltaic modules. Although there are methods for the production and framing of photovoltaic panels that have provided important improvements in the technology of the solar cell in these years, it has been desired to simplify the lamination and manufacture of these panels and to provide a stronger module and a more perfect seal to protect the photovoltaic panels. For example, the rolling steps have previously required a considerable labor expense and the metal backing sheets that have been previously used to protect the back of the panel can allow electrical leaks that turn a photovoltaic cell into a capacitor. A specific example of a module / lamination forming process is described in U.S. Patent 4,773,944 issued to Nath and associates, the content of which is incorporated herein. Nath presents that once the photovoltaic cell is formed, then a layer of a low-modulus, easily moldable material, durable, lightweight, is laminated on it. The lower laminate is typically aluminum, although other materials such as galvanized steel or plastic can be used, the lower laminate must be able to withstand harsh environmental conditions, be moldable in a variety of shapes, and be able to maintain the shape rigidly, in the which has been molded. On the upper surface of the lower laminate, a layer of dielectric material, for example a flowable organic resin, such as ethyl vinyl acetate (EVA) is deposited.

After the deposition of the layer of a flowable organic resin, an intermediate layer of insulating material is applied between the photovoltaic cell and the organic resin to electrically isolate the lower laminate of the photogenerated current by the photovoltaic cell. The intermediate layer of insulating material that is deposited on the flowable organic resin layer can be TEDLAR (Trademark of DuPont Corp). In the upper part of the intermediate layer of insulating material, a second layer of flowable organic resin is deposited. The second layer of flowable organic resin can be ethyl vinyl acetate (EVA) and the resin is used as an adhesive to bond the lower laminate to the intermediate layer. Finally, the photovoltaic cell is placed on top of the organic resin. In order to complete the encapsulation process, it is then necessary to deposit a layer of flowable organic resin (for example EVA) on the upper surface of the photovoltaic cell. Finally, a layer of optically transparent, flexible, and relatively hard material is deposited on the top layer of EVA. The relatively hard durable layer can be a TEDLAR layer. After completing the rolling process as described in the preceding paragraphs, it is still necessary to form the laminated photovoltaic module in a suitable shape and size for use in a particular application. Therefore, the laminated modules are cut into flat sheets which can then be formed by folding the peripheral edge portions thereof into a three dimensional volumetric configuration such as a rectangular parallelpipe. In order to be sure that the module will maintain the three-dimensional shape, the peripheral edge portions (edge or skirt portions at 90 ° depending on the flat face of the module) are provided with rivets at all four corners. Although these modules are useful, their application is limited and the method used to form them is expensive with respect to both materials and processing. A less intensive processing method to protect the photovoltaic cells was developed in the late 1980s. I use Reactive Injection Molding (RIM) to mold a polymeric encapsulant around the photovoltaic cell. This polymeric encapsulant acts as much as an environmental shield to protect the photovoltaic cell from the environment as a mechanical support for the photovoltaic cell. The RIM encapsulation module and the method for forming such modules are presented in US Pat. Nos. 4,830,038 and 5,008,062, respectively, issued to Andersosn and asoc. that are added as a reference. In the molding by reactive injection (RIM) a machine RIM measures mix and provides chemical agents reactive to a mold, where a chemical reaction occurs and the desired part is formed. This is the mixing of the reactants occurs in the mixing head and continues after injection into the mold. The mold models the part, directs the reactants to the mold cavity, directs the flow of the reactants, and controls the reaction temperature produced by the molding process by removing the heat. Although this process is more adaptable than those of the prior art, it can not be said that it reduces the cost of the finished photovoltaic panel to an important degree. This is due to the high cost of the reactive chemical agents that are required to form the polymeric encapsulant. For example, the precursors of the RIM polyurethane polymer are based on isocyanates, polyols, extenders, catalysts and blowing agents. The extenders are usually glycols or amines or some combination of the two. Although they are typically expensive many of these chemical agents are very dangerous and even toxic. Even so, Anderson suggests that this is the only means by which an injection-molded encapsulant can be formed around a voltaic cell. Reason as follows: "The RIM process is particularly advantageous for encapsulating photovoltaic cells since RIM is a thermoforming polymer formed by the reaction of liquid polymeric precursors injected at a low temperature (less than 200-F (95-C), thus preventing heat damage to the thin film material that could occur if high temperature injection molding techniques were employed. However, the present inventors have found that contrary to what Anderson says, conventional injection molding (this it is injection molded without reaction) can be used to encapsulate photovoltaic cells without damage to them The present invention consists of a photovoltaic module that includes at least one photovoltaic cell that is encapsulated in an unreacted injection molded material, thus forming a seal The cell or photovoltaic cells are incorporated into a photovoltaic panel that has front and back sides and edges that form a perimeter, and also includes means for the external electrical connection to the photovoltaic cell, preferably the photovoltaic cells are a such thin film amorphous silicon cell as a single union, dual tandem or triple PIN tandem. The unreacted injection molded polymeric material encapsulating the photovoltaic panel is preferably capable of injection molding at a temperature of less than about 500 F (260 C) and is a light polymeric, light transmitting material such as a clear ABS material. If desired, the portion of the unreacted injection molded polymeric material which encapsulates the photovoltaic panel and is adjacent to the side where it does not induce light may include a coloring pigment. The non-reactive injection molded polymeric material that encapsulates the panel can form useful structures, such as tiles, blocks, frames and boxes. DESCRIPTION OF THE DRAWING Figure 1 is a schematic, non-scale presentation of a polymer encapsulated photovoltaic panel according to the present invention. The present invention relates to polymeric framed photovoltaic modules and more specifically to photovoltaic modules framed by injection molded polymeric, unreacted. Referring to Figure 1, the photovoltaic module framed 1 includes a photovoltaic panel 2 and a clear, unreacted light-transmissive polymer material 3 that frames the photovoltaic panel 2. The polymeric material 3 forms a framing or an injection molded box not reacted around the photovoltaic panel 2 protecting it both from the environment and from mechanical abrasion. Additionally the polymeric framing 3 can act as a support for the photovoltaic panel 2 when stiffness is required. However, in some final applications, greater flexibility may be desirable. In these cases the polymer case or frame 3 can be thin enough to allow the required flexibility. The photovoltaic panel 2 is preferably a standard amorphous silicon panel, well known in the art. Such panel is formed of at least one photovoltaic cell. The cell or photovoltaic cells are typically formed by the amorphous silicon photovoltaic cell deposit PIN on a heat-resistant substrate such as a stainless steel grid. The photovoltaic cell can have a single PIN connection or can be dual or triple cell. Each of these cells are well known in the art and will not be discussed further. The photovoltaic panel 2 can be described generically as having a front, an incising side for the light (this is where the photovoltaic cell is deposited) and a back side (where light does not impinge) and edges that form the periphery. The framing or polymeric housing 3 can be clear (light transmitter) everywhere or can have pigments in the back (light non-incident side) of the photovoltaic panel. The addition of the pigment can be useful in some applications that require visual aesthetics. One such case is when the wiring and the interconnections on the back side (where light does not strike) need to be hidden for aesthetic reasons. This is because the wiring and interconnections of the typical photovoltaic panels are on the back side, they can not be hidden from sight by adding a pigment to the polymeric material that covers the back of the panel while the clear polymer on the front side will still allow the light to reach the photovoltaic cell. It should be noted that there will be at least two holes (not shown) in the polymeric material to allow external electrical connection to the photovoltaic module 1. Another application of use in which it would be useful to pigment the rear part of the polymeric housing 3 is when it is desirable to hide the rear base behind the visible panel. This is for example, when the panel is used for construction applications such as roofs, panels, sides etc. The production of the encapsulated photovoltaic module 1 is relatively simple. The prefabricated photovoltaic panel 2 (and any necessary interconnection between the cells) is placed in a mold. The panel can be placed on a backing plate or other support structure within the mold as required. Mold inserts to form external electrical connection openings can be added. The housing or frame 3 is injection molded from molten polymer material. The housing 3 can be molded in a single or multiple stages. When a pigment is added to the polymer at the rear of the panel, it will also be easier to mold the front and back portions of the housing 3, separately. The polymer material presented herein is styrene-butadiene-clear acrylonitrile (ABS) copolymer material. However, any polymer can be used as long as its viscosity is sufficiently low (at a temperature of less than about 500 F) (260 ° C) that it can be injection molded around the photovoltaic panel 2. Other applicable polymers include carbonates, acrylics, Acrylonitriles, styrenes, butadiene acrylates, vinyls, etc. Additionally, a layer of polymeric material may be laminated to the surface where the photovoltaic panel light strikes before encapsulation by the unreacted injection molded polymer. This material can help the binding of the encapsulating polymer to the panel, thus avoiding an optical decoupling by the delamination of the panel and the encapsulant. Optical decoupling can reduce the energy production of the photovoltaic panel and should therefore be avoided as much as possible. Although many polymeric materials may be useful in reducing this optical decoupling, a preferred material is vinyl ethyl acetate (EVA). EXAMPLE A panel formed of a triple-PIN junction tandem of amorphous silica photovoltaic cells deposited on a heat-resistant stainless steel substrate was placed in an injection mold. The pins were inserted into the mold to leave the electrical connection openings in the finished module. The clear ABS material was then injected into the mold to encapsulate the photovoltaic panel. The temperature of the injector nozzle was set at 472 F (245 • C). The injection started at 1000 pounds per square inch or 70 kg / cm2 for 2.5 seconds which filled the mold to 80%. Then the pressure was increased to 3500 pounds or 245 kg / cm2 for 1.5 seconds to fill the mold 100%. Then the pressure was reduced to 3000 pounds or 210kg / cm2 and remained 2 seconds to allow all the small features to fill. Now the injector pressure was discontinued and the molded article was in the mold for 50 seconds to cure, the molded panel was then removed and allowed to cool to room temperature. The electrical characteristics of the molded photovoltaic module were compared with the characteristics of the photovoltaic panel before encapsulation. It was found that the modules could be made without loss of electrical characteristics. This, in comparison to the initial unencapsulated panel and the encapsulated photovoltaic module showed that the open circuit voltage, the short circuit current and the 12 volt current remained constant. Thus, it can be clearly seen that the injection-molded photovoltaic modules, without reaction, of the present invention show tremendous promise for commercial, industrial and consumer uses. In particular they can be useful as construction materials for any applications where integrated power is useful. Specific applications include construction materials, such as ceilings, integration in portable equipment, equipment housed in plastic and any other application where it is useful to provide a physical support structure as well as the generation of electrical energy. Specifically useful structures would include, tiles, blocks, frames or boxes. It is to be understood that the presentation made of the present invention in the form of detailed embodiments is intended as a complete and clear presentation of the present invention, and that the details are not limiting.

Claims (13)

1. R E I V I ND I CA C I ONE S. lt "A photovoltaic module having front and rear sides and edges that form a perimeter and at least one photovoltaic cell capable of converting the incident radiation on the front side of the panel, into electrical energy; and an unreacted, injection molded polymeric material that encapsulates the panel and forms an environmental seal around it.
2. 2. - The photovoltaic module according to claim 1, wherein the panel further includes means for establishing external electrical connection to at least one photovoltaic cell.
3. 3. The photovoltaic module according to claim 1, wherein the photovoltaic cell comprises a thin film silicon cell.
4. 4. The photovoltaic module according to claim 3, wherein the photovoltaic cell is a thin-film amorphous silicon cell of a single PIN junction.
5. 5. The photovoltaic module according to claim 3, wherein the photovoltaic cell is a thin film amorphous silicon cell of a single dual tandem PIN junction.
6. 6. - The photovoltaic module according to claim 3e, wherein the photovoltaic cell is a triple-junction triple-junction amorphous silicon cell PIN.
7. 7. - The photovoltaic module according to claim 1, wherein the unreacted injection molded polymeric material which encapsulates the photovoltaic panel is capable of being injected at a temperature of less than about 260 ° C.
8. 8. The photovoltaic module of according to claim 1, wherein the unreacted, injection molded polymeric material encapsulating the photovoltaic panel is a light transmissive, polymeric material.
9. 9. The photovoltaic module according to claim 7, wherein the unreacted injection molded polymeric material encapsulating the photovoltaic panel comprises a clear styrene-butadiene acrylonitrile material.
10. 10. The photovoltaic module according to claim 7, wherein the portion of the unreacted injection molded polymeric material, which encapsulates the photovoltaic panel and is adjacent to the same side thereof where no light strikes, includes a coloring pigment.
11. 11. The photovoltaic module according to claim 1, wherein a layer of polymeric material is laminated on the front side of the photovoltaic panel, that laminated polymeric material aids an optical coupling of the photovoltaic panel and the molded polymeric material, unreacted , which encapsulates the panel.
12. 12. - The photovoltaic module according to claim 1, wherein the unreacted injection molded polymeric material, which encapsulates the panel, forms a useful structure.
13. 13. - The photovoltaic module according to claim 12, wherein the useful structure is selected from the group of tiles, blocks, frames and boxes.