ES2232299B1 - ASSEMBLY PROCEDURES FOR PHOTOVOLTAIC CONCENTRATION MODULES. - Google Patents

Abstract

Photovoltaic concentration module and assembly procedure between modules. Concentration photovoltaic module (1) based on solar cells (2) of semiconductor compounds III-V and an optical system, which performs the function of concentrating light on the solar cell, composed of two lenses called POE (3) and SOE ( 4), all housed on a substrate or panel (5 or 5``). The module (1) is manufactured following a series of steps, such as the bonding of the solar cell to the substrate, the connection of the front contact to the outside, the bonding of the SOE lens to the substrate, filling of the SOE lens with an encapsulant and final assembly of the module. The cell and SOE encapsulation is done by the leadframe option or by means of thermally improved PCB's. The fastening of the POE lenses is done by adhering the lenses to the glass with transparent elastomeric adhesive, or by means of a POE fastening piece to the rear panel.

Description

Photovoltaic concentration module and Assembly procedure between modules.

Object of the invention

The present invention relates to a module photovoltaic concentration based on solar cells from III-V semiconductor compounds and a system optical consisting of two lenses manufactured by injection molding of methacrylate or some other plastic of similar properties. Reference is also made to the assembly procedure of said modules describing the different stages of the process and the different options that any of these stages present.

The object of the invention is to reduce the presence of semiconductor in the photovoltaic module (more expensive component of the same) and change it for an optical element that concentrates the light in a smaller semiconductor area. All this, along with a design convenient solar cell, leads to obtaining about significantly higher conversion yields and, therefore therefore, considerable cost savings.

Background of the invention

Given the high demand for energy in the currently new technologies are being researched and developed that allow obtaining new energy sources, which instead of being able to meet this demand, be inexhaustible. Among this group of new sources is the use of sunlight to generate electricity.

The technology of concentration of light in Energy Solar Photovoltaic pursues the reduction of the generation of electric power to, in this way, be able to compete equally price with conventional generation systems. Step last is to implement the manufacturing processes of manufacturing Large-scale modules for later commercialization.

Concentration technology, however, is He has studied before trying different types of optics and different types of receptors (solar cell). Nowadays there are some systems of this type under development or demonstration. The most notable examples are cited to continuation.

Thus, for example, in the USA cells are used silicon solar, which are based on an optical lens Fresnel, which has a lower geometric concentration (of the order of 200-300 X) and greater thickness of the photovoltaic module. In this way, the power generated by semiconductor area is minor and reductions, in terms of production costs, they will also be smaller compared to those proposed by the invention described in this report. This concentration option is presented by the Amonix Company, being interested in its commercialization US power companies such as Arizona Public Service.

In Europe, it is tested with modules capable of concentrate light at 500 X, based on Fresnel lenses and being also little compact. However, to date they have a maximum efficiency at 100 X. On the other hand, only it is an approach that uses modules with all the glass surfaces (walls, base and front), what it does in the difficult and complex practice its transfer to the industry. This type of modules are developed by the Freiburg Solar Energy Institute (Germany) in collaboration with the IOFFE Institute in St. Petersburg  (Russia) and responds to the trade name of FLATCON (Fresnel Lens All  glass module Tandem CONCENTOR).

Finally, the option raised in Japan is the which seems to have a better exit in the market, due to the state of module development and the push of Japanese companies in the photovoltaic market. In this module very cells are used Efficient in performance, but lens-based optics Fresnel that reaches the order of 400 X in concentration. He Toyota Institute of Technology and the company Daido Steel are conducting studies on this type of modules.

Description of the invention

The photovoltaic concentration module, object of this patent, fully resolves the previously stated problem; it is a system of concentration whose philosophy is to reduce the presence of semiconductor in the photovoltaic module, and change it to a optical element that concentrates the light in an area smaller than semiconductor; This optical system has a much more cost reduced. In addition, conveniently designing the solar cell and appropriately choosing the semiconductor material, the Conversion yields increase significantly.

The photovoltaic concentration module presents important differences compared to the traditional photovoltaic module, differences that can be seen in the analysis of the elements that are part of the concentration photovoltaic module that perform below:

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Cell solar: it is a very small cell, around 1 mm2; It is composed of different semiconductor materials to conventional silicon. These are semiconductors composed of Groups III-V of the periodic table, such as GaAs, GaInP, GalnAs, AlGaInP, etc. among others. These solar cells are grow well by means of MOCVD technology (chemical deposition of steam from metalorganic precursors), MBE (epitaxy of molecular beams) or LPE (liquid phase epitaxia). Mainly, Germanium substrates or GaAs (Gallium Arsenide) are used. These cells are found in 2 or 4 inch wafers primarily and after a cutting process they are ready to start the process of encapsulated A very relevant advantage derived from the use of these semiconductors is to be able to include in the same cell solar more than one semiconductor junction, which leads to use more efficiently the spectrum of sunlight with consequent savings of costs.

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Optical system: it is the system that responsible for performing the function of concentrating the light on the cell solar. Said system consists of two lenses called generically POE and SOE attending the consideration of primary and high school. This denomination obeys the path that the light travels from outside the module to reach the solar cell. The lens called SOE will encapsulate directly with the cell and get to form with her a set in the next step of assembly

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Substrate or panel that houses all the set: it is designed to act as the rear panel of the module and as a heat dissipating element.

So, these are the main elements of consisting of the concentration photovoltaic module referred to The present invention. The phases are explained below or processes necessary to carry out the procedure of Module assembly, which is also the subject of the invention:

one.

Glued from the solar cell to the substrate by paste or epoxy, thermal conductive adhesive and electric.

2.

Contact connection process front to the outside by ultrasonic welding or thermosonic

3.

Lens bonding process secondary (SOE) to the substrate with high precision. Process that carried out by automated machines.

Four.

Lens filling process secondary (SOE) with a transparent gel-type encapsulant or silicone. It is about protecting the solar cell and the wires of the frontal contact of any possible thermal alteration that may cause disconnection. In addition, the encapsulant exerts a function of adaptation of refractive indices between the solar cell and the lens.

5.

Finally, the last step is the general assembly of the module whose elements are the front glass, the primary lenses (POE, one per cell, the rear panel, the already encapsulated cell and secondary sets and profiles of aluminum that give the module mechanical rigidity.

As a final result of the realization of stages described above, a photovoltaic module is obtained concentration, consisting of a certain number of cells solar and concentrators.

While the assembly procedure developed for the photovoltaic module is the one described previously, they are presented for some of the stages, such as the encapsulated solar and optical cell and the general assembly of the module, different realization options that are equally innovative and innovative.

The first option refers to the encapsulation cell and SOE, and is based on "Leadframes", that is, on small copper plates, generically named "leadframe" according to the terminology of the microelectronic industry One of the advantages of this system, is that it allows a serial connection of the cells that contains, in this way the number will be greatly reduced of operations to perform.

The next option refers to the encapsulation of solar and optical cell, based on thermally improved PCBs; the PCB's are composed of aluminum, dielectric and copper products commercials that are used especially for the world of automotive and light emitting diodes. This option presents Two advantages that make it very interesting:

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It allows to make a plate layout that contain the serial-parallel connection between cells necessary to realize the photovoltaic module. This feature gives it a great potential savings in cost of Operator and machine.

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Facilitates assembly greatly end of the module by being part of the rear panel of the same.

As for the final assembly process of the module, it is necessary to integrate the constituent elements of the module with the right optical precision. These elements constituents are the rear panel, the front glass and the previously encapsulated cell and concentrator elements.

One of the operations that is carried out in This final assembly stage of the module is lens bonding POE to the glass. The POE lens adheres to the glass by the interior surface to the module by one or several sheets of clear elastomer adhesive. This material (adhesive transparent elastomer) is commonly used for encapsulation of solar cells in conventional photovoltaic modules, but in this case, in concentration modules, it is used to adhere the lenses to the glass, avoiding any air chamber Between lens and glass.

Another option for the positioning process and glued from the POE to the glass is to incorporate a piece by POE that be anchored to the substrate and provide mechanical housing. He transparent elastomeric adhesive is also necessary for adhere the lenses to the front glass in this case the function The main one is to couple refractive indexes.

Description of the drawings

To complement the description that is being performing and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical realization of it, is accompanied as part member of that description, a set of drawings where with illustrative and non-limiting nature, what has been represented next:

Figure 1.- Shows prototypes of modules photovoltaic concentration, composed of a certain number of solar cells and concentrators.

Figure 2.- Shows a section of the system optical concentrator consisting of two lenses. It is appreciated in the center the location of the solar cell.

Figure 3.- Shows an example of how it works The cell + concentrator concept.

Figure 4.- Shows a schematic section of the photovoltaic concentration module. Respond to the design that shown as a prototype in figure 1.

Figure 5.- Shows a prototype of Leadframe for encapsulation of concentration cells.

Figure 6.- Shows a detail of the prototype of Leadframe, where you can see the different holes for allow hosting the SOE as well as favoring the process of filling the secondary SOE lens with a transparent encapsulant.

Figure 7.- Shows another detail of the prototype Expanded leadframe to be located on the rear panel of the module.

Figure 8.- Shows a PCB prototype sized to accommodate 32 solar cells.

Figure 9.- Shows a detail of the cell solar connected electrically and mechanically to the substrate.

Figure 10.- Shows a photograph of the lens Primary or POE.

Figure 11.- Shows a photograph of the lens secondary or SOE.

Figure 12.- Shows an interior view of the concentration module during the final assembly phase. Be you can appreciate the detail of the aluminum profile and the lenses POE adhered to the glass using the elastomeric adhesive transparent.

Preferred Embodiment of the Invention

In view of the figures outlined you can observed as a concentration photovoltaic module (1) (figure 1), which is composed of a certain number of solar cells (2) and concentrators or lens systems (3) and (4) that allow concentration of light on the receiver or solar cell (2). For to obtain it it is necessary to carry out some processes of assembly of the different constituent elements: solar cell (2), optical system and substrate or base (5) on which it houses everything set.

The first stage of the manufacturing process of the photovoltaic module of concentration is the one of stuck of the solar cell (2) to the substrate (5) (see figure 9) by paste or epoxy, thermal and electrical conductive adhesive. This step receives the name of "Die bond" or "Die Attach" according to terminology of microelectronics. In this way, in addition to providing mechanical attachment of the device to the substrate, the rear electrical contact. This process requires a cure. by solder paste or epoxy temperature. The cell solar (2) being a two-terminal device, it needs two contacts with the outside, one front and one rear.

Then the process of connection of the front contact (6) to the outside by welding ultrasonic or thermosonic (see figure 9). This process is done. by gold or aluminum wires of very small diameter, A few tens of microns. This stage is called "Wire Bonding. "

The next operation is to paste the secondary lens (4) SOE (see figure 11) to the substrate (5) with precision below 20 microns, this process is done by automated machines, requires a prior dispensing of a adhesive that fixes the lens to the substrate. Once the lens is stuck, it is necessary to cure it.

Subsequently the filling of the secondary lens SOE (4), with a transparent gel-type encapsulant or silicone This is about protecting the solar cell and the front contact wires of any possible thermal alteration that may cause its disconnection. This process is called "Potting" and is done in turn through machines High productivity automated.

One of the options proposed to carry out The cell and SOE encapsulation stage is the encapsulation based on Leadframes (Figure 2), that is, cell encapsulation and SOE on small copper plates (5 ') that have a design optimized to be used in encapsulation machines of microelectronics, it is intended to take full advantage of the capabilities of said machines, pursuing high productivity.

Figure 5 shows a prototype of leadframe, there is room for seven solar cells, but the number of positions can be higher or lower, it also has the advantage of which allows a serial connection of the seven cells that contains In Figure 6 you can see a detail of the leadframe with the specific place where the solar cell is located. The holes (7) that are appreciated are intended to favor the accommodation of the SOE and to facilitate the "Potting" tasks of filling encapsulating material. The grooves (8) constitute, once cut and stretched, the electrical junction (9) between two cells adjacent lots.

The leadframe as shown in Figure 5, It is designed to cover the phases of the process 1,2,3 and 4. Without However, to deal with phase 5 of the process, the joints or grooves (8) partially so as to allow a deployment of the entire array (figure 6). The distance between cells then it becomes the necessary to place the POE lenses (3) as close as possible. Figure 6 shows the philosophy of this design and the great potential advantage it presents for reduce costs by reducing the number of welding operations. Once the leadframe is expanded (figure 7), it is assembled on the back panel with the proper separation between each pair of elements that leave enough space to house the POEs (3).

Another option presented for the encapsulated solar and optical cell is the use of PCB's special (10) composed of an insulated metal substrate (figure 8). These PCBs (10) are formed by an aluminum laminate, dielectric and copper. Figure 8 shows a PCB prototype adapted to accommodate 32 solar cells, the housing (11) planned for each solar cell has the same characteristics than the one already described in the case of leadframes. It is definitely try to perform the same phases of the process with the same type of automation.

Figure 9 shows the detail of the cell solar (2) electrically and mechanically connected to the substrate (5).

Depending on the desired module size, this one It can be composed of a certain number of boards or PCBs. Each of these plates must be attached to the adjacent ones to be able to Obtain the desired voltage and current characteristics.

Finally, to achieve the final process of assembly, it is necessary to integrate the constituent elements of the module with the appropriate optical precision (figure 12). To the perform this task the module is composed of a cavity that they compose it (from top to bottom following the path of light): front glass with the POEs (3) attached, substrate (5) with the SOEs (4) and solar cells (2) attached and an aluminum profile (12) on the perimeter that confers rigidity to the assembly (see figures 4  and 12).

The aluminum profile (12), therefore, as key element to define the perimeter of the module, host the front glass (13) and the rear panel (14); In the design specific to the profile, a small camera filled with desiccant material (see figure 3). In this way, the contained air inside the module is dry air preventing condensation of water vapor that would be detrimental to proper operation of the module.

Another phase of the final assembly stage is the Glued POE lenses (3) to the front glass (13) (Figures 3 and 12). The lens adheres to the glass on the inside surface of the module (1) by one or several sheets of elastomeric adhesive transparent acting like glue (the elastomeric adhesive transparent is a material commonly used for encapsulation of solar cells in conventional photovoltaic modules). In the case of concentration modules, it is used to adhere the glass lenses avoiding any air chamber between lens and crystal. In addition to mechanical fastening, the elastomeric adhesive transparent provides the coupling of refractive indices that minimizes optical losses due to reflections (loss of Fresnel) To carry out this operation, it is necessary to alter The curing profile of transparent elastomer adhesive e introduce certain modifications in the process.

On the other hand, positioning accuracy it must be high because the POE must be located at a very distance precise against the SOE and the cell since the optical accuracies concentrator derivatives are the ones that need to be taken care of more in this module. In the total set, cell, SOE and POE, the precision in x, and, z must be ± 100 microns.

An intermediate step of the assembly phase, in which POE lenses are appreciated (3) adhered to the front glass (13) and the profile detail of aluminum (12) that provides the closure in the perimeter of the module (one). This profile allows to accommodate both the glass (13) and the PCB's (10) in which is the SOE and the solar cell.

Another option for positioning and pasting the POE to the glass is to incorporate a piece that works as positioner and housing the POE, anchoring to the substrate and providing mechanical housing with the mentioned precision previously. The transparent elastomeric adhesive to adhere to front glass is also necessary but in this case the main function is to couple refractive indexes.

In this way the photovoltaic module of concentration is perfectly assembled, presented the appearance that appears in figure 1, and arranged for installation in followers of the sun.

Claims (8)

1. Concentration photovoltaic module, characterized in that it presents solar cells (2) of compound semiconductors III-V of the periodic table that are grown well by chemical vapor deposition technology from metalorganic precursors, either by molecular beam epitaxy or by epitaxy in liquid phase on substrates (5) or (5 ') of germanium or GaAs mainly. 2. Photovoltaic concentration module, according to claim one, characterized in that it has an optical system consisting of two lenses (3) and (4) that concentrates the light on the solar cell (2). 3. Photovoltaic concentration module, according to claim one, characterized in that it has an optical concentrator system that operates by means of total internal reflection and refraction. 4. Assembly method of photovoltaic concentration modules, of the preceding claims, characterized in that it has the following phases or processes:

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glued from the solar cell (2) to the substrate (5) or (5 ') by paste or thermal and electric conductive adhesive epoxy;

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front contact connection process outside by ultrasonic or thermosonic welding;

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secondary lens bonding process (SOE) (4) to the substrate (5) or (5 ') with high precision;

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lens filling process secondary (SOE) (4) with a transparent gel-type encapsulant or silicone;

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finally, the last step is the general assembly of the module (1) whose elements are glass frontal (13), primary lenses (POE) (3), (one per cell), the rear panel (14), the cell and secondary assemblies already encapsulated (2-4) and aluminum profiles (12) that give the module mechanical rigidity.

5. Assembly procedure of photovoltaic concentration modules, according to claim 4, characterized in that the encapsulation of the solar cell (2) and the SOE lens (4) is carried out by means of the leadframe option (copper plates), allowing according to design the serial connection of the cells it contains. 6. Assembly procedure of photovoltaic concentration modules, according to claim 4, characterized in that the encapsulation of the solar cell (2) and the SOE lens (4) is carried out by means of the option of thermally improved PCB's (10) that are made of aluminum , dielectric and copper. 7. Assembly procedure of photovoltaic concentration modules, according to claim 4, characterized in that the POE lens (3) adheres to the glass (13) by the inner surface of the module by means of one or several sheets of transparent elastomeric adhesive that also prevents any air chamber between the lens and the glass. 8. Assembly procedure of photovoltaic concentration modules, according to claim 4, characterized in that the positioning and gluing of the POE (3) is carried out by incorporating a fastening piece of the POE to the rear panel or element that represents the plane of the solar cell and SOE (4) and that provides mechanical housing.