WO2010095012A1 - Photovoltaic modules and process for their production - Google Patents

Photovoltaic modules and process for their production Download PDF

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Publication number
WO2010095012A1
WO2010095012A1 PCT/IB2010/000268 IB2010000268W WO2010095012A1 WO 2010095012 A1 WO2010095012 A1 WO 2010095012A1 IB 2010000268 W IB2010000268 W IB 2010000268W WO 2010095012 A1 WO2010095012 A1 WO 2010095012A1
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WO
WIPO (PCT)
Prior art keywords
resin
cavity
module
photovoltaic
cells
Prior art date
Application number
PCT/IB2010/000268
Other languages
French (fr)
Inventor
Mario Molina
Original Assignee
Gigi Molina Brevetti Plastici S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gigi Molina Brevetti Plastici S.P.A. filed Critical Gigi Molina Brevetti Plastici S.P.A.
Priority to EP10708794A priority Critical patent/EP2399298A1/en
Publication of WO2010095012A1 publication Critical patent/WO2010095012A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S20/00—Supporting structures for PV modules
    • H02S20/20—Supporting structures directly fixed to an immovable object
    • H02S20/22—Supporting structures directly fixed to an immovable object specially adapted for buildings
    • H02S20/23—Supporting structures directly fixed to an immovable object specially adapted for buildings specially adapted for roof structures
    • H02S20/25—Roof tile elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/048—Encapsulation of modules
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/048—Encapsulation of modules
    • H01L31/0488—Double glass encapsulation, e.g. photovoltaic cells arranged between front and rear glass sheets
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S20/00—Supporting structures for PV modules
    • H02S20/20—Supporting structures directly fixed to an immovable object
    • H02S20/22—Supporting structures directly fixed to an immovable object specially adapted for buildings
    • H02S20/23—Supporting structures directly fixed to an immovable object specially adapted for buildings specially adapted for roof structures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B10/00—Integration of renewable energy sources in buildings
    • Y02B10/10—Photovoltaic [PV]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present invention relates in general to the production of solar panels consisting of one or more photovoltaic modules connected to one another and, in particular, a process for the production of photovoltaic modules and the modules thus produced.
  • Background art Currently, the photovoltaic modules most widely marketed are produced using monocrystalline silicon, poly crystalline silicon or amorphous silicon cells. Silicon cells have a very limited thickness, in general of a few microns, and must therefore be placed on a rigid backing and then electrically connected to one another.
  • the conventional production process of a cell type photovoltaic module essentially involves positioning of an encapsulating material on glass, followed by positioning of the cells already connected to one another, and finally positioning of a protective material on the back.
  • the composite thus obtained is subjected to lamination in a press and then mounted in a frame generally made of aluminium.
  • the various layers of the module form a sandwich consisting of:
  • a sealing sheet made of EVA (ethylene vinyl acetate) which allows dielectric isolation of the adjacent surface of the cells.
  • EVA ethylene vinyl acetate
  • This material is used, for example, for its transparency, high electrical resistivity and low water absorption properties,
  • the conventional lamination cycle is a sequence of events empirically refined with the objective of making the process short and of obtaining high quality lamination without negative effects on the components.
  • the lamination operation essentially takes place in two steps:
  • the laminate is placed in a chamber that reaches a temperature of 100°C and in which the vacuum (1 mmHg) is applied for a few minutes.
  • the lamination and polymerization cycles are completed: in fact, heating of the module allows the sheet of EVA to melt around the electric circuits, in order to seal the cells to the lower and upper layers of the module. The temperature is then taken to 160 0 C to complete polymerization of the EVA, and subsequently returned to 100 0 C;
  • US patent n. 4147560 describes a photovoltaic cell module in which the silicon cells, having a thickness of around 0.4 mm, are electrically connected to one another and encapsulated in a plastic material reinforced with glass fibres. The surfaces are then covered with transparent plastic sheets which are pre-treated to allow adhesion thereof to the plastic structure reinforced with glass fibres.
  • the photovoltaic module thus obtained has a thickness of about 1.2 mm.
  • one of the major problems of conventional photovoltaic modules is constituted by the excessive weight of the module, in practice due to the weight of the backing structure thereof, which significantly limits possible applications thereof, and to the rigidity of the backing structure caused by the low ductility of glass.
  • An object of the present invention is therefore to propose an improved photovoltaic module having a much lower weight with respect to that of prior art photovoltaic modules and a wider range of applications.
  • Another object of the present invention is to propose a process that allows photovoltaic modules to be produced in shorter times with respect to prior art production processes.
  • a further object of the present invention is to propose a process that allows photovoltaic modules to be produced at lower costs with respect to prior art production processes.
  • the process for the production of photovoltaic modules includes the steps of: i) applying a plurality of photovoltaic cells to a backing fabric comprising glass fibres and electrically connecting the cells to one another; ii) preparing a mould having a shaped cavity and sized in plan to obtain a module having desired dimensions in width and length; iii) applying a layer of transparent gel coat resin in fluid condition to the surfaces of the cavity; iv) placing the backing fabric with the cells attached thereto in the cavity; v) placing a central core on top of the backing fabric; vi) placing a fabric comprising glass fibres on top of the central core; vii) closing the mould by means of an upper mould to seal the cavity; and viii) saturating the cavity with resin until it is completely filled.
  • the backing structure consists of plastic materials, such as resin reinforced with fibres (or fibreglass), and polyurethane or expanded PVC for the central core, i.e. materials that are undoubtedly lighter with respect to those conventionally used, such as glass and aluminium.
  • Saturation of the cavity with filling resin is preferably performed by injection with a low vacuum technique of the RTM LIGHT type. This technique allows gradual diffusion of the resin throughout the inner space of the cavity without damaging the photovoltaic cells, also simultaneously allowing all the air to be removed from the mould cavity.
  • a fabric comprising glass fibres is preferably placed on the central core, in order to give greater strength to the final glass fibre structure also on the back of the module.
  • Suitable fabrics comprising glass fibres are for example those identified by the trademarks ROVICORETM, CONFORMATTM, or in any case fabrics comprising two layers of glass fibres and one intermediate layer made of plastic material or of other materials made of fibres.
  • a further step can also be included to harden the module in an oven, after it has been removed from the mould.
  • This further step can be useful to obtain complete drying of the outer layer of transparent resin coating the module.
  • the transparent resin, or gel coat is a material that allows a high surface hardness to be given to the module.
  • saturation of the cavity with resin can also be performed by means of an infusion technique.
  • the filling resin can also consist of a resin of self-extinguishing type, in order to allow a wider range of applications for the modules obtained according to the present invention in compliance with any safety regulations of various applications.
  • the resin reinforced with fibres is usually a material used for applications that require limited weight but high mechanical strength.
  • the central core can consist of a plastic material such as polyurethane, expanded PVC, or in any case of materials with similar properties.
  • a photovoltaic module according to the present invention therefore includes at least the following elements:
  • At least one backing fabric comprising glass fibres, on which a plurality of photovoltaic cells electrically connected to one another are applied;
  • a coil can also be incorporated for the circulation of a heat exchange fluid.
  • a heat exchange fluid it is known that the output of photovoltaic cells varies as a function of the temperature and, in particular, the output decreases as the temperature of the cells increases. It may therefore be advantageous to make a heat exchange fluid circulate in the module to remove heat from the photovoltaic cells and utilise the thermal energy of the heated fluid for other uses, for example the production of hot water or the like.
  • the coil is placed in contact with or in proximity of the backing fabric of the cells, on the opposite side with respect to the side on which the cells are attached.
  • FIG. 1 is a perspective view of a photovoltaic module according to the prior art
  • - Fig. 2 is a schematic view showing the typical composition of the photovoltaic module of Fig. 1 ;
  • - Fig. 3 is a partially sectional schematic view showing a mould for implementation of the process according to the present invention;
  • FIG. 4 shows some steps of the process according to the present invention
  • Fig. 5 shows the step to close the mould before saturation with the resin
  • FIG. 6 shows the step of the process according to the invention after saturation with the resin
  • Fig. 7 is a schematic sectional view showing a photovoltaic module according to the present invention after removal thereof from the mould;
  • FIG. 8 is a schematic plan view showing a component of the photovoltaic module according to an alternative embodiment of the present invention.
  • Fig. 9 is a schematic sectional view showing a photovoltaic module including the component represented in Fig. 8;
  • FIG. 10 is a schematic sectional view showing a possible embodiment of a photovoltaic module according to the present invention.
  • FIG. 11 is a schematic sectional view showing a solar panel produced by mutually coupling a plurality of photovoltaic modules such as the one represented in Fig. 10.
  • Figs. 1 and 2 represent by way of example a conventional photovoltaic module 100 including a plurality of photovoltaic cells 110 positioned on a backing structure enclosed by an aluminium frame 130.
  • the conventional module 100 includes a top plate 101 made of high transparency glass, a sealing sheet 102 made of EVA (ethylene vinyl acetate) and then the photovoltaic cells 110 placed on a backing sheet 103 made of MylarTM.
  • another sealing sheet made of EVA and finally a plate 104 which constitutes the back of the module 100, for example made of glass or in an aluminium and Tedlar multilayer composite, are positioned under the cells 110.
  • the sandwich thus produced is then subjected to a lamination step (polymerization of the EVA sheets) and to a compression step to eliminate residual air.
  • a lamination step polymerization of the EVA sheets
  • a compression step to eliminate residual air.
  • the module is enclosed in the aluminium frame 130. It can easily be understood that the weight of a module thus produced is very high, as are the costs of the materials used and the costs for their production.
  • Fig. 3 schematically shows a mould 10 and an upper mould 20 for implementation of the process according to the present invention.
  • express reference will be made to a process in which saturation with resin is performed using the low vacuum (or RTM LIGHT) injection technique, but it should be borne in mind that other similar techniques, for example the infusion technique, can be used, provided that damage to the particularly fragile components, in particular to the photovoltaic cells is avoided.
  • RTM LIGHT low vacuum
  • the mould 10 includes a cavity 11 in which the various components of the photovoltaic module will be placed in succession.
  • the upper mould 20 has a closing portion 21 corresponding in shape and size to the cavity 11 to allow it to be sealed during injection of the resin.
  • the mould 10 and the upper mould 20 can be made of any suitable material, such as aluminium, fibreglass or the like, and can also include a temperature control system to prevent the temperature from dropping below a preset threshold. In fact, is should be borne in mind that below a specific temperature, i.e. 15-16 °C, the process could give somewhat unsatisfactory results as the fluidity of the resin injected could be insufficient to ensure complete and uniform filling of all the empty spaces.
  • the upper mould 20 includes a pair of peripheral seals 22 that allow the mould 10 to be hermetically sealed.
  • a suction connection 23 collects air from the chamber 24 delimited by the seals 22 and by the surfaces of mould and upper mould when these are coupled (Fig. 5), in order to generate a sufficiently high vacuum pressure to maintain the two elements coupled during the subsequent steps of the process.
  • a second suction connection 25 allows a weak vacuum pressure to be generated inside the sealed cavity in order to receive the resin pumped through a connection 26.
  • a reservoir 27 allows the excess resin to be collected at the end of the injection step and confirms that all the empty spaces inside the cavity 11 have been filled.
  • the upper mould 20 is also provided with a plurality of through holes 28 through which the electrical terminals, and any hydraulic terminals, of the module being produced are passed. Appropriate cable clamping devices 29 to constrain the terminals during the steps of the production process can be provided outside the holes 28.
  • a release agent is preferably applied to the walls of the mould 11, in order to facilitate removal of the photovoltaic module from the mould 10 at the end of the process.
  • Fig. 4 shows the first steps of the process for the production of photovoltaic modules according to the present invention.
  • a suitable backing fabric 30 including glass fibres has already been prepared, such as ROVICORETM, CONFORMATTM or the like, on which the photovoltaic cells 40 have been placed and that the necessary electrical connections between these cells have already been made.
  • a layer 50 of transparent gel-coat (or gelcoat) resin in fluid condition is applied to the walls of the cavity 11.
  • the layer 50 is then made to dry until the resin has reached at least its gel condition, or until total hardening thereof.
  • the backing fabric 30 with the cells 40 can be placed in the cavity 11.
  • the layer 50 can also be moistened further with the same transparent gelcoat resin in order to close any porosities in the dried layer 50.
  • the photovoltaic cells 40 are oriented towards the transparent layer 50 which, once hardened at the end of the process, will allow the cells to be protected while simultaneously allowing light radiation to pass through.
  • a central core 60 is placed on top of the backing fabric 30.
  • the central core 60 is preferably produced by a plate made of light plastic material, such as polyurethane or expanded PVC, in order to give properties of high rigidity and strength to the module.
  • the central core 60 generally has a thickness between 0.5 cm and 2 cm, but central cores with greater thicknesses can also be used if it is necessary to satisfy particular requirements of strength in specific installations.
  • a further fabric 70 comprising glass fibres, for example the same fabric of the ROVICORETM, CONFORMATTM type or similar already used for the cell backing, is preferably placed on the core 60.
  • Fig. 5 shows the closing step of the mould 10 on which the upper mould 20 is placed, taking care to pass the terminals 45 for electric connection of the module through the through holes 28 (Fig. 3) and to block the terminals with the cable clamping devices 29.
  • the vacuum pressure generated in the chambers 24 through the suction connection 23 hermetically seals the cavity 11.
  • the vacuum condition that holds the mould closed can, for example, be maintained and released using an appropriate valve 13 positioned on the connection 23 or along the pipe that connects it to the vacuum source.
  • the step to saturate the mould with the resin is then started, using a low vacuum (or RTM LIGHT) technique.
  • a low vacuum or RTM LIGHT
  • the resin substantially "impregnates" all the fabrics with glass fibres and all the spaces not occupied by the components of the module inside the cavity, and the vacuum condition generated inside the cavity also simultaneously ensures that all the air present inside said cavity is evacuated.
  • the process according to the invention includes the use of a low vacuum technique, such as the RTM LIGHT technique, so that the resin flows slowly into all the empty spaces and does not damage the most fragile components, i.e. the photovoltaic cells.
  • a low vacuum technique such as the RTM LIGHT technique
  • vacuum pressures of around -0.5 bar can be used to help the resin to flow in the injection step, i.e. vacuum pressures much lower than those applied, for example, to the connection 23 to maintain the mould closed (from -0.9 to -1.0 bar).
  • the mould 10 is then left closed for a time sufficient to allow the resin to harden and subsequent removal of the module without damage thereto.
  • the module removed from the mould can optionally be subjected to a hardening step in the oven which allows the transparent resin (gel-coat) coating the front wall and the side walls of the module and the filling resin incorporating the components of the module to be given high mechanical strength and surface hardness.
  • a module 80 thus obtained has the configuration represented in Fig. 7, in which the module is overturned with respect to the position inside the mould.
  • the cells 40 are protected frontally by the hardened layer 50 of transparent gel coat, while the filling resin has impregnated the fabrics 30 and 70 containing glass fibres and has also incorporated the central core 60 made of polyurethane or expanded PVC, clamping it between the two fabrics 30 and 70.
  • the module has a thickness generally between around 1 cm and 3 cm, but can also have greater thicknesses for particular applications or installations.
  • an alternative embodiment of the present inventions includes the production of a module 80' in which a coil 61 is incorporated in the central core 60 to allow the circulation of a heat exchange fluid therein.
  • a module 90 such as the one represented in section in Fig. 10 can comprise at the sides thereof shaped portions 91 to allow mutual interlocking between several modules and thus form a single photovoltaic solar panel, such as the one represented in Fig.
  • each module can differ from the number represented herein by way of example, and the module can also take different shapes, as a function of the particular applications.

Abstract

There is described a process for the production of a photovoltaic module in which the photovoltaic cells are incorporated in a resin structure reinforced with fibres (or fibreglass). The cells are applied to a fabric comprising glass fibres and positioned in the cavity of a mould, together with other components, and the cavity is then saturated with the resin in order to incorporate all the components of the module.

Description

"PHOTOVOLTAIC MODULES AND PROCESS FOR THEIR PRODUCTION"
************
DESCRIPTION Field of the invention The present invention relates in general to the production of solar panels consisting of one or more photovoltaic modules connected to one another and, in particular, a process for the production of photovoltaic modules and the modules thus produced. Background art Currently, the photovoltaic modules most widely marketed are produced using monocrystalline silicon, poly crystalline silicon or amorphous silicon cells. Silicon cells have a very limited thickness, in general of a few microns, and must therefore be placed on a rigid backing and then electrically connected to one another. Besides the necessary chemical and physical treatments of the silicon wafers and the electrical connections between the cells, the conventional production process of a cell type photovoltaic module essentially involves positioning of an encapsulating material on glass, followed by positioning of the cells already connected to one another, and finally positioning of a protective material on the back. The composite thus obtained is subjected to lamination in a press and then mounted in a frame generally made of aluminium. In particular, the various layers of the module form a sandwich consisting of:
• a pane of tempered glass with excellent transmittance and mechanical strength;
• a sealing sheet made of EVA (ethylene vinyl acetate) which allows dielectric isolation of the adjacent surface of the cells. This material is used, for example, for its transparency, high electrical resistivity and low water absorption properties,
• the surface of the cells welded to one another, on the back of which a layer of Mylar™ (PET - polyethylene terephthalate), necessary to electrically insulate the connections exiting from the back of the cell, is also placed;
• a second sheet of EVA; • a lower layer of Tedlar™ (alternatively glass or multilayer Al-Tedlar-Al). The Tedlar™, or the Al-Tedlar-Al sandwich, is used as structural backing for the module. The function of the aluminium sheet is to protect the module from moisture. The conventional lamination cycle is a sequence of events empirically refined with the objective of making the process short and of obtaining high quality lamination without negative effects on the components. The lamination operation essentially takes place in two steps:
• in the first step, the laminate is placed in a chamber that reaches a temperature of 100°C and in which the vacuum (1 mmHg) is applied for a few minutes. In these conditions the lamination and polymerization cycles are completed: in fact, heating of the module allows the sheet of EVA to melt around the electric circuits, in order to seal the cells to the lower and upper layers of the module. The temperature is then taken to 1600C to complete polymerization of the EVA, and subsequently returned to 1000C;
• in the second step the module is subjected to pressure in order to eliminate the residual air.
These are followed by various post-treatments steps with strictly mechanical machining operations, such as an operation to finish the edges of the module to remove the excess of EVA that seeped out during the lamination step. The module thus finished is finally ready to be mounted in the conventional aluminium frame. US patent n. 4147560 describes a photovoltaic cell module in which the silicon cells, having a thickness of around 0.4 mm, are electrically connected to one another and encapsulated in a plastic material reinforced with glass fibres. The surfaces are then covered with transparent plastic sheets which are pre-treated to allow adhesion thereof to the plastic structure reinforced with glass fibres. The photovoltaic module thus obtained has a thickness of about 1.2 mm.
The process proposed by this prior art document is somewhat laborious and can cause problems during production in the case in which photovoltaic modules having shapes that are not planar are to be produced. Moreover, although considering the reduced thickness as a positive factor from the viewpoint of lower mechanical stresses determined by the different thermal dilations between the silicon cells and the plastic material in which they are encapsulated, the photovoltaic modules thus obtained have limited mechanical strength and can therefore be easily subject to breakages unless adequately protected by rigid backing structures.
Notwithstanding continuous technological improvements with regard to the production efficiency of silicon cells, one of the major problems of conventional photovoltaic modules is constituted by the excessive weight of the module, in practice due to the weight of the backing structure thereof, which significantly limits possible applications thereof, and to the rigidity of the backing structure caused by the low ductility of glass.
Besides weight, it should also be borne in mind that the cost of the backing structure of the module has a significant influence on the overall cost of the module.
Moreover, it is evident that the process for the production of conventional modules is particularly long and complex, and inevitably influences the costs of the finished product.
Summary of the Invention An object of the present invention is therefore to propose an improved photovoltaic module having a much lower weight with respect to that of prior art photovoltaic modules and a wider range of applications.
Another object of the present invention is to propose a process that allows photovoltaic modules to be produced in shorter times with respect to prior art production processes.
A further object of the present invention is to propose a process that allows photovoltaic modules to be produced at lower costs with respect to prior art production processes.
These and other objects are achieved by the present invention through a process according to claim 1. Further features of the process are indicated in the respective dependent claims.
The process for the production of photovoltaic modules includes the steps of: i) applying a plurality of photovoltaic cells to a backing fabric comprising glass fibres and electrically connecting the cells to one another; ii) preparing a mould having a shaped cavity and sized in plan to obtain a module having desired dimensions in width and length; iii) applying a layer of transparent gel coat resin in fluid condition to the surfaces of the cavity; iv) placing the backing fabric with the cells attached thereto in the cavity; v) placing a central core on top of the backing fabric; vi) placing a fabric comprising glass fibres on top of the central core; vii) closing the mould by means of an upper mould to seal the cavity; and viii) saturating the cavity with resin until it is completely filled. In this way, new photovoltaic modules can be produced, in which the backing structure consists of plastic materials, such as resin reinforced with fibres (or fibreglass), and polyurethane or expanded PVC for the central core, i.e. materials that are undoubtedly lighter with respect to those conventionally used, such as glass and aluminium.
The process is also much faster, with less waste of energy, and with greater production simplicity with respect to the production process of photovoltaic modules currently marketed. In fact, all the components of the' module are incorporated directly in the resin during filling of the cavity.
Saturation of the cavity with filling resin is preferably performed by injection with a low vacuum technique of the RTM LIGHT type. This technique allows gradual diffusion of the resin throughout the inner space of the cavity without damaging the photovoltaic cells, also simultaneously allowing all the air to be removed from the mould cavity.
Before closing the mould and performing the injection, a fabric comprising glass fibres is preferably placed on the central core, in order to give greater strength to the final glass fibre structure also on the back of the module. Suitable fabrics comprising glass fibres, not only for the backing for the cells, but also for the back part of the module, are for example those identified by the trademarks ROVICORE™, CONFORMAT™, or in any case fabrics comprising two layers of glass fibres and one intermediate layer made of plastic material or of other materials made of fibres. After having completed injection, a step is preferably performed to harden the resin with the mould closed before removing the module thus formed.
Moreover, a further step can also be included to harden the module in an oven, after it has been removed from the mould. This further step can be useful to obtain complete drying of the outer layer of transparent resin coating the module. The transparent resin, or gel coat, is a material that allows a high surface hardness to be given to the module. Alternatively to the low vacuum injection technique, saturation of the cavity with resin can also be performed by means of an infusion technique. According to a possible embodiment of the present invention, the filling resin can also consist of a resin of self-extinguishing type, in order to allow a wider range of applications for the modules obtained according to the present invention in compliance with any safety regulations of various applications.
In this way a photovoltaic module is obtained weighing over 50% less with respect to prior art modules. The resin reinforced with fibres (or fibreglass) is usually a material used for applications that require limited weight but high mechanical strength. The central core can consist of a plastic material such as polyurethane, expanded PVC, or in any case of materials with similar properties.
A photovoltaic module according to the present invention therefore includes at least the following elements:
- at least one central core;
- at least one backing fabric, comprising glass fibres, on which a plurality of photovoltaic cells electrically connected to one another are applied;
- at least one fabric comprising glass fibres positioned in contact with the central core on the opposite side with respect to the backing fabric for the photovoltaic cells;
- a resin which incorporates the central core, the backing fabric and the cells applied thereon, and the fabric comprising glass fibres placed in contact with the central core on the opposite side with respect to the backing fabric; and
- at least one layer of transparent gel coat resin applied to the surface of the module, wherein the central core is a separate component from the resin and from the fabrics comprising glass fibres. In a possible embodiment of the module according to the invention, a coil can also be incorporated for the circulation of a heat exchange fluid. In fact, it is known that the output of photovoltaic cells varies as a function of the temperature and, in particular, the output decreases as the temperature of the cells increases. It may therefore be advantageous to make a heat exchange fluid circulate in the module to remove heat from the photovoltaic cells and utilise the thermal energy of the heated fluid for other uses, for example the production of hot water or the like.
In this embodiment, the coil is placed in contact with or in proximity of the backing fabric of the cells, on the opposite side with respect to the side on which the cells are attached.
By connecting a plurality of modules according to the present invention to one another, photovoltaic panels of large dimensions and of particularly limited weight can easily be produced.
Another noteworthy advantage of the present invention is given by the possibility of easily producing panels of any shape, and therefore not only flat but also curved, or of any other shape useful to be adapted to any installation site. Moreover, the modules according to the present invention can be shaped so that they can be mutually interlocked or coupled and be easily installed also on roofs or building coverings in general. Brief description of the drawings Further features and advantages of the present invention will be more apparent from the following description, provided by way of example with reference to the accompanying drawings, wherein:
- Fig. 1 is a perspective view of a photovoltaic module according to the prior art;
- Fig. 2 is a schematic view showing the typical composition of the photovoltaic module of Fig. 1 ; - Fig. 3 is a partially sectional schematic view showing a mould for implementation of the process according to the present invention;
- Fig. 4 shows some steps of the process according to the present invention;
- Fig. 5 shows the step to close the mould before saturation with the resin;
- Fig. 6 shows the step of the process according to the invention after saturation with the resin;
- Fig. 7 is a schematic sectional view showing a photovoltaic module according to the present invention after removal thereof from the mould;
- Fig. 8 is a schematic plan view showing a component of the photovoltaic module according to an alternative embodiment of the present invention;
- Fig. 9 is a schematic sectional view showing a photovoltaic module including the component represented in Fig. 8;
- Fig. 10 is a schematic sectional view showing a possible embodiment of a photovoltaic module according to the present invention; and
- Fig. 11 is a schematic sectional view showing a solar panel produced by mutually coupling a plurality of photovoltaic modules such as the one represented in Fig. 10.
Method of producing the invention
Figs. 1 and 2 represent by way of example a conventional photovoltaic module 100 including a plurality of photovoltaic cells 110 positioned on a backing structure enclosed by an aluminium frame 130. As shown in Fig. 2, the conventional module 100 includes a top plate 101 made of high transparency glass, a sealing sheet 102 made of EVA (ethylene vinyl acetate) and then the photovoltaic cells 110 placed on a backing sheet 103 made of Mylar™. Moreover, another sealing sheet made of EVA and finally a plate 104, which constitutes the back of the module 100, for example made of glass or in an aluminium and Tedlar multilayer composite, are positioned under the cells 110.
As indicated previously, the sandwich thus produced is then subjected to a lamination step (polymerization of the EVA sheets) and to a compression step to eliminate residual air. At the end of these steps, after any finishing to remove the excess material, the module is enclosed in the aluminium frame 130. It can easily be understood that the weight of a module thus produced is very high, as are the costs of the materials used and the costs for their production.
Fig. 3 schematically shows a mould 10 and an upper mould 20 for implementation of the process according to the present invention. Hereafter, express reference will be made to a process in which saturation with resin is performed using the low vacuum (or RTM LIGHT) injection technique, but it should be borne in mind that other similar techniques, for example the infusion technique, can be used, provided that damage to the particularly fragile components, in particular to the photovoltaic cells is avoided.
The mould 10 includes a cavity 11 in which the various components of the photovoltaic module will be placed in succession. The upper mould 20 has a closing portion 21 corresponding in shape and size to the cavity 11 to allow it to be sealed during injection of the resin. The mould 10 and the upper mould 20 can be made of any suitable material, such as aluminium, fibreglass or the like, and can also include a temperature control system to prevent the temperature from dropping below a preset threshold. In fact, is should be borne in mind that below a specific temperature, i.e. 15-16 °C, the process could give somewhat unsatisfactory results as the fluidity of the resin injected could be insufficient to ensure complete and uniform filling of all the empty spaces. The upper mould 20 includes a pair of peripheral seals 22 that allow the mould 10 to be hermetically sealed. A suction connection 23 collects air from the chamber 24 delimited by the seals 22 and by the surfaces of mould and upper mould when these are coupled (Fig. 5), in order to generate a sufficiently high vacuum pressure to maintain the two elements coupled during the subsequent steps of the process. A second suction connection 25 allows a weak vacuum pressure to be generated inside the sealed cavity in order to receive the resin pumped through a connection 26. A reservoir 27 allows the excess resin to be collected at the end of the injection step and confirms that all the empty spaces inside the cavity 11 have been filled. The upper mould 20 is also provided with a plurality of through holes 28 through which the electrical terminals, and any hydraulic terminals, of the module being produced are passed. Appropriate cable clamping devices 29 to constrain the terminals during the steps of the production process can be provided outside the holes 28.
Before placing the various components in the mould 10, a release agent is preferably applied to the walls of the mould 11, in order to facilitate removal of the photovoltaic module from the mould 10 at the end of the process.
Fig. 4 shows the first steps of the process for the production of photovoltaic modules according to the present invention. In this step it is presumed that a suitable backing fabric 30 including glass fibres has already been prepared, such as ROVICORE™, CONFORMAT™ or the like, on which the photovoltaic cells 40 have been placed and that the necessary electrical connections between these cells have already been made.
Firstly, a layer 50 of transparent gel-coat (or gelcoat) resin in fluid condition is applied to the walls of the cavity 11. The layer 50 is then made to dry until the resin has reached at least its gel condition, or until total hardening thereof. At this point the backing fabric 30 with the cells 40 can be placed in the cavity 11. Before performing this operation, if necessary the layer 50 can also be moistened further with the same transparent gelcoat resin in order to close any porosities in the dried layer 50. The photovoltaic cells 40 are oriented towards the transparent layer 50 which, once hardened at the end of the process, will allow the cells to be protected while simultaneously allowing light radiation to pass through. Together with the backing fabric 30, or in the immediately subsequent step, a central core 60 is placed on top of the backing fabric 30. The central core 60 is preferably produced by a plate made of light plastic material, such as polyurethane or expanded PVC, in order to give properties of high rigidity and strength to the module. The central core 60 generally has a thickness between 0.5 cm and 2 cm, but central cores with greater thicknesses can also be used if it is necessary to satisfy particular requirements of strength in specific installations.
To protect the back of the module and give high mechanical resistance to the module as a whole, a further fabric 70 comprising glass fibres, for example the same fabric of the ROVICORE™, CONFORMAT™ type or similar already used for the cell backing, is preferably placed on the core 60.
Fig. 5 shows the closing step of the mould 10 on which the upper mould 20 is placed, taking care to pass the terminals 45 for electric connection of the module through the through holes 28 (Fig. 3) and to block the terminals with the cable clamping devices 29. At this point, the vacuum pressure generated in the chambers 24 through the suction connection 23 hermetically seals the cavity 11. The vacuum condition that holds the mould closed can, for example, be maintained and released using an appropriate valve 13 positioned on the connection 23 or along the pipe that connects it to the vacuum source.
The step to saturate the mould with the resin is then started, using a low vacuum (or RTM LIGHT) technique. This allows all the air remaining in the cavity to be sucked out generating a light vacuum through the connection 25 connected to a vacuum source, while the resin is simultaneously injected through the connection 26 connected to an injection pump. In this way, by creating the necessary vacuum and pumping the resin into the cavity, this ensures that all the empty spaces inside the cavity are saturated with the filling resin. In other words, the resin substantially "impregnates" all the fabrics with glass fibres and all the spaces not occupied by the components of the module inside the cavity, and the vacuum condition generated inside the cavity also simultaneously ensures that all the air present inside said cavity is evacuated. In fact, the process according to the invention includes the use of a low vacuum technique, such as the RTM LIGHT technique, so that the resin flows slowly into all the empty spaces and does not damage the most fragile components, i.e. the photovoltaic cells. According to this technique, vacuum pressures of around -0.5 bar can be used to help the resin to flow in the injection step, i.e. vacuum pressures much lower than those applied, for example, to the connection 23 to maintain the mould closed (from -0.9 to -1.0 bar).
As represented in Fig. 6, complete filling of resin inside the mould is detected when the excess resin collects in the reservoir 27. This determines the end of the injection step.
The mould 10 is then left closed for a time sufficient to allow the resin to harden and subsequent removal of the module without damage thereto. The module removed from the mould can optionally be subjected to a hardening step in the oven which allows the transparent resin (gel-coat) coating the front wall and the side walls of the module and the filling resin incorporating the components of the module to be given high mechanical strength and surface hardness. A module 80 thus obtained has the configuration represented in Fig. 7, in which the module is overturned with respect to the position inside the mould. The cells 40 are protected frontally by the hardened layer 50 of transparent gel coat, while the filling resin has impregnated the fabrics 30 and 70 containing glass fibres and has also incorporated the central core 60 made of polyurethane or expanded PVC, clamping it between the two fabrics 30 and 70. The module has a thickness generally between around 1 cm and 3 cm, but can also have greater thicknesses for particular applications or installations. As represented in Figs. 8 and 9, an alternative embodiment of the present inventions includes the production of a module 80' in which a coil 61 is incorporated in the central core 60 to allow the circulation of a heat exchange fluid therein. This allows any excess heat to be removed from the module 80' to increase the efficiency of the photovoltaic cells 40, and to transfer the heat removed from the module for use in the production of hot water or for other suitable uses. The configuration of the module will therefore be the one represented in Fig. 9, in which the coil 61 is placed in proximity to or in contact with the backing fabric 30 on the opposite side with respect to the side on which the cells 40 are present. A module according to the present invention can easily be produced in various shapes, according to the particular installation requirements. For example, a module 90 such as the one represented in section in Fig. 10 can comprise at the sides thereof shaped portions 91 to allow mutual interlocking between several modules and thus form a single photovoltaic solar panel, such as the one represented in Fig. 11 , which can advantageously be positioned on a roof or on a building covering in general. The limited weight of a module obtained according to the present invention can therefore be adapted in shape and size to a wide variety of installations, for example also for vehicles, watercraft or similar, but without particularly influencing the overall weight thereof or without requiring to strengthen any backing structures of these modules. Various modifications can be made to the embodiments represented herein without departing from the scope of the present invention. For example, although a process for saturation of the cavity with the low vacuum injection technique, or in any case of the RTM LIGHT type, has been described by way of example, it must be stated that saturation of the cavity with resin can also be performed using the infusion
■ technique. In practice, while in the low vacuum injection process the resin is pumped into the cavity of the mould while simultaneously sucking out the air contained therein, in the infusion process it is the vacuum pressure generated inside the cavity that sucks the resin inside it, without requiring to pump the resin.
Moreover, the number of photovoltaic cells of each module can differ from the number represented herein by way of example, and the module can also take different shapes, as a function of the particular applications.

Claims

1. A process for the production of photovoltaic modules, characterised by including the steps of: i) applying a plurality of photovoltaic cells to a backing fabric comprising glass fibres and electrically connecting said cells to one another; ii) preparing a mould having a shaped cavity and sized in plan to obtain a module having desired dimensions in width and length; iii) applying a layer of transparent gel coat resin in fluid condition to the surfaces of said cavity; iv) placing said backing fabric with the cells attached thereto in said cavity; v) placing a central core on top of said backing fabric; vi) placing a fabric comprising glass fibres on top of said central core; vii) closing said mould by means of an upper mould to seal said cavity; and viii) saturating said cavity with resin until it is completely filled.
2. The process according to claim 1, wherein said step viii) to saturate said cavity is performed through the injection of resin with a low vacuum technique of the RTM LIGHT type.
3. The process according to claim 1, wherein said step viii) to saturate said cavity is performed by resin infusion.
4. The process according to claim 1, further including a step to harden said resin with the mould closed before removing the module thus formed.
5. The process according to claim 1, further including a step to harden the module removed from said mould in an oven.
6. The process according to claim 1, wherein a release agent is applied to the surface of said cavity prior to said step iii).
7. The process according to claim 1, wherein said transparent resin applied in said step iii) is left in said cavity until reaching at least the gel condition before performing said step iv).
8. The process according to claim 1, wherein said transparent resin applied in said step iii) is left in said cavity until reaching hardened condition before performing said step iv).
9. The process according to claim 1, wherein a further layer of said transparent resin is applied in fluid condition before performing said step iv).
10. The process according to claim 1, wherein the resin utilised for saturation of said cavity is a self-extinguishing resin.
11. A photovoltaic module obtained with a process according to any one of claims 1 to 10.
12. A photovoltaic module, characterized by including:
- at least one central core;
- at least one backing fabric, comprising glass fibres, on which a plurality of photovoltaic cells electrically connected to one another are applied;
- at least one fabric comprising glass fibres positioned in contact with said central core on the opposite side with respect to the backing fabric for said photovoltaic cells;
- a resin which incorporates said central core, said backing fabric and said cells applied thereon, and said fabric comprising glass fibres placed in contact with said central core on the opposite side with respect to said backing fabric; and
- at least one layer of gel coat transparent resin applied to the surface of said module, wherein said central core is a separate component from said resin and said fabrics comprising glass fibres.
13. The photovoltaic module according to claim 11 or 12, wherein said resin incorporating the components of the module is a self-extinguishing resin.
14. The photovoltaic module according to claim 11 or 12, wherein said central core includes a coil incorporated therein for circulation of a heat exchange fluid.
15. The photovoltaic module according to claim 14, wherein said coil is placed in contact with or in proximity of the backing fabric of said cells on the opposite side with respect to the side on which said cells are attached.
16. A photovoltaic solar panel comprising a plurality of photovoltaic modules electrically connected to one another, characterised by including at least one photovoltaic module according to any one of claims 11 to 15.
PCT/IB2010/000268 2009-02-17 2010-02-12 Photovoltaic modules and process for their production WO2010095012A1 (en)

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