Roof covering comprising a waterproofing membrane covered with thin-film solar cells

<u>The invention</u>

The present invention relates to the technical field of sealing covers laying in the construction sector (industrial, residential, offices, etc.). It particularly concerns a functional roof cover, capable of producing electrical energy.

<u>PRIOR ART</u>

Traditional roofing cover known standing seam, generally made of long noble metal bands such as zinc or copper, or by sheet metal or metal cladding (steel, aluminum, etc.). These strips have longitudinal tabs which are taken in the standing seam which is doubly crimped, which seals (<figref idrefs="f0001">figure 1</figref>).

This type of coverage is particularly attractive, durable, and easily adapts to the architectural form of the building. For example, it may conform to the circular shape of a roof by a gironnage (cutting triangle or trapezium metal strips).

In return, the traditional coverage is expensive by a number of factors such as the current high metal prices, the necessary operations of cutting and bending, the need to ask a previously sheathing underlying wood, etc. Moreover, these covers expand and resent the temperature extremes and require ventilation to delay aging.

To overcome these disadvantages, the Applicant has proposed a very simple cover system involving a waterproofing membrane 1 made of plastic, for example PVC, stretched over a roof support underlying 2 (see Patent <patcit id="pcit0001" dnum="EP0964968B1"><text>EP 0964968 B1</text></patcit>, <figref idrefs="f0001">2</figref>). On this membrane are fixed sections 3 (sole 3A, 3B soul) that restore the aesthetic character of the traditional coverage of zinc or copper, while offering a number of technical functions such as:<ul><li>through a parallel arrangement of sections between them in the direction of the slope, ensure optimum guidance of the flow of water, especially in the case of gentle slopes;</li><li>hide junction areas with any piercing fasteners, between two adjacent membrane strip which sealing of the cover;</li><li>mechanically subdivide the membrane surfaces exposed to wind and thereby improve the anchoring of the cover.</li></ul>In addition, if they are made of the same thermoplastic material as the membranes, the sections may be attached thereto by cold solvent welding, gluing and also welding (air) hot, which allows the avoid condensation problems by providing a warm roof.

Finally, the execution of the coverage is easier and faster in the case of blankets zinc standing seam, especially for roofing complicated forms where the exposure time gain is appreciable.

Moreover, currently, considerable efforts are made to promote renewable forms of energy in order to drastically reduce fossil fuel use and greenhouse emissions, or to produce "green" electricity. In the industrial building sector but also offices and residential, many solutions are proposed to take advantage of the available solar energy which can be captured particularly at the large roof surfaces of buildings.

In particular, the photovoltaic field has seen some development and some evolution. Currently research is moving towards semiconductor products polycrystalline thin film deposited on flexible surfaces, which should show a higher return and be much cheaper than rigid panels using first generation of monocrystalline silicon wafers. In addition, the popularity of photovoltaic technology constantly shortage threatens the supply of these. Recent market research amounts to nearly 25% from photovoltaic thin film market. It could even be 50% in 2015.

Thus, in order of increasing efficiency in thin film technology, has emerged successively flexible panels covered with amorphous silicon (a-Si), cadmium telluride (CdTe) of copper indium siléniure (CIS) and of copper-indium-gallium disiléniure (CIGS - CuIn_xga_(1-x)himself₂). This recovery would be the most promising with a yield of about 20%. CIGS cells are generally manufactured by technology in vacuo by co-evaporation on a heated substrate or co-evaporation / co-sputtering. However, an alternative manufacturing technology and very competitive in terms of cost has been developed and is in the form of a rotary printing on flexible substrate by means of an ink containing nanoparticles (CIGS<nplcit id="ncit0001" npl-type="b"><text>"Solarzellen - einfach gedruckt" Bild der Wissenschaft (Scientific American) 2 2007</text></nplcit> ; <patcit id="pcit0002" dnum="US7306823B2"><text>US 7306823 B2</text></patcit>).

The document <patcit id="pcit0003" dnum="WO2009011790A2"><text>WO 2009/011790 A2</text></patcit> proposes a photovoltaic roofing member comprising a substrate, a photovoltaic module disposed on the substrate member and an inverter for converting AC the direct current produced by the photovoltaic module. According to a particular embodiment, the system may include active elements comprising one or more photovoltaic modules, which can be configured in the form of shingles to give the appearance of a roofing and inactive elements also having the appearance a roof covering. The substrate may be in the form of a roll or a ribbon and the photovoltaic module is flexible and includes photovoltaic cells arranged in a thin layer (semiconductor material pn homojunction or heterojunction).

The document <patcit id="pcit0004" dnum="US20040173255A1"><text>US 2004/0173255 A1</text></patcit> offers a roof mounting method of flexible strips carriers of photovoltaic cells, where two adjacent strips are secured longitudinally by staples to their non-active edges, forming a seal raised triangle. The seals are protected by the subsequent stapling a curve shaped latte that matches the shape of triangle and seal ensures the sealing function. A similar joints edging statement and stapling system is proposed by the document<patcit id="pcit0005" dnum="WO9314525A1"><text>WO 93/14525 A1</text></patcit>.

In the document <patcit id="pcit0006" dnum="WO02073704A1"><text>WO 02/073704 A1</text></patcit>, The edge joints between two strips are flat and secured to the underlying support by a longitudinal strip which is stapled on a protection curve slat.

<u>Aims of the invention</u>

The present invention aims to provide, in the field of roofing, a solution that provides at least one additional function of producing energy in the form of electricity in addition to the primary sealing function and which allows, when pose, to take charge of simple and inexpensive way increased the technical constraints of the presence of the photovoltaic material.

The invention is particularly intended to provide a multifunctional roofing that optimizes the flow of water and therefore the longevity of the photovoltaic material.

The invention also aims to provide a multifunctional roofing which offers rigidity and resistance to sufficient wind.

The invention also aims to provide a multifunctional roofing having an aesthetic or architectural appearance similar to traditional roof coverings in zinc or copper standing seam sheets or blankets and metal cladding (steel or others).

<u>Main characteristic elements of the invention</u>

The present invention relates to a roofing system comprising:<ul><li>a flexible sealing membrane laid in contiguous tape edge seals flat and fixed on an underlying support;</li><li>a plurality of sections or bars, in one piece in cross section, fixed at regular intervals on said sealing membrane so as to form a rigid unit; <b>characterized in that</b> the sealing membrane comprises at least on part of its outer surface a plurality of photovoltaic semiconductor cells in the form of a thin film or monojonction heterojunction.</li></ul>

According to preferred embodiments of the invention, the roofing system above further comprises, in combination, one or more of the following:<ul><li>the profiles are also covered, at least over part of their surface exposed after fixing said semiconductor photovoltaic cells in the form of a thin film;</li><li>the flexible sealing membrane (10) is a synthetic membrane;</li><li>the synthetic membrane is selected from the group consisting of membrane of copolymer of ethylene, propylene and vulcanized diene-monomer (EPDM), isoprene isobutylene copolymer and vulcanized (IIR Butil), vulcanized polychloroprene (CR), polyethylene chlorosulfonated partially vulcanized (CSPE), vulcanized nitrile rubber (NBR), epichlorohydrin (ECH), vulcanized thermoplastic elastomer (TPV), thermoplastic polyolefin (TPO), interpolymer ethylene (EIP), butadiene nitrile polymer (NBP), polyvinyl chloride polymer (PVC) with plasticizer, uncured polymer polyisobutylene (PIB), vinyl acetate copolymer unvulcanized ethylene (EVA), polyvinyl acetate copolymer and unvulcanized ethylene and bitumen (ECB) and polymer uncured chlorinated polyethylene and plasticizer-free (CPE); </li><li>the membrane comprises a woven, a reinforcement or a backing layer incorporated to reinforcing purposes or for improving the adhesion of an adhesive used;</li><li>the material of the woven fabric, the reinforcing or backing layer incorporated is selected from the group consisting of polyester, polyamide and glass mat;</li><li>the flexible sealing membrane (10) is a bituminous membrane;</li><li>the bituminous membrane comprises at least one layer and is improved by the addition of atactic polypropylene (APP) or of styrene-butadiene-styrene (SBS);</li><li>the bituminous membrane comprises a reinforcement in the form of a glass mat or polyester or as an aluminum foil;</li><li>the flexible sealing membrane includes in its composition the compounds selected from the group consisting of plasticizers, pigments, biocides, flame retardants, UV absorbers and antioxidants;</li><li>the semiconductor material of the photovoltaic cells in the thin film is selected from the group consisting of amorphous silicon, nanocrystalline silicon, with or without addition of SiGe, CdTe, CdS, GaAs, CuInSe₂ (CIS) and CuIn_xga_(1-x)himself₂ (CIGS);</li><li>the semiconductor thin film was formed on the membrane by spraying under vacuum or by printing by means of a roller of an ink containing semiconductor nanoparticles;</li><li>the underlying support on which the membrane is fixed covered with photovoltaic cells is selected from the group consisting of an insulator, a concrete base, a sheet or a metal casing, another membrane sealing, structure and / or a natural wood panel or roof sheathing or composition and assembly of any of these;</li><li>the coated membrane of photovoltaic cells is separated from the underlying support by interposing a geotextile;</li><li>the underlying support is provided with ventilation means of photovoltaic cells;</li><li>the thin film photovoltaic semiconductor cells deposited on the waterproofing membrane is covered by a protective layer vis-a-vis the elements;</li><li>the profiles are fixed to the membrane by gluing, cold welding, hot air welding or mechanically;</li><li>each shaped in one piece in cross section is formed of a sole and a projecting web surmounted by a portion having a cross section of essentially triangular, square, round, cylindrical or sagging.</li></ul>

The invention also relates to a building having a roof cladding system according to any preceding claim.

<u>BRIEF DESCRIPTION OF FIGURES</u>

The <figref idrefs="f0001">figure 1</figref>, Mentioned above, shows, in a sectional view, the steps of realization of standing crimped joints in the case of traditional metal roofing (source: documentation Ugine &amp; ALZ Arcelor).

The <figref idrefs="f0001">2</figref>, Mentioned above, shows, in a sectional view, a roofing with synthetic sealing membrane gaskets and profiles glued or welded with hot air according to the prior art.

The <figref idrefs="f0002 f0003 f0004 f0005 f0006">Figures 3 to 7</figref> represent, in a sectional view, examples of embodiments of the invention particularly adapted to an existing roof covering.

<u>Description of preferred embodiments of the invention</u>

The present invention provides a roof covering system comprising a flexible sealing membrane intended to be tensioned and fixed to an underlying roof structure, and on which are fixed on a regular basis or rigid section bars, made or not in the same material as the sealing membrane.

According to the invention, the sections are advantageously made in one piece in cross-section.

The flexible sealing membrane is preferably a membrane that is resistant to aging caused by solar radiation, as well as mechanical, thermal and chemical.

The flexible sealing membrane may be a synthetic membrane, usually in monolayer form.

Synthetic membranes can be of three types:<ul><li>synthetic elastomers (thermosetting);</li><li>thermoplastic elastomers;</li><li>plastomers.</li></ul>

Amongst thermosetting elastomers, there are in particular the ethylene, propylene and vulcanized diene-monomer (EPDM), currently the most widely used of the elastomeric high polymers, especially in the USA, isoprene copolymer and vulcanized isobutylene (IIR Butil) vulcanized polychloroprene (CR) or neoprene^®The partially vulcanized chlorosulfonated polyethylene (CSPE), the cured nitrile rubber (NBR), epichlorohydrin (ECH).

Among thermoplastic elastomers, one finds in particular the vulcanized thermoplastic elastomer (TPV) consisting of a blend of elastomeric polymers and vulcanized plastomers, thermoplastic polyolefin (TPO) consisting of polypropylene copolymers without plasticizer, ethylene interpolymer (EIP) PVC compound and interpolymers of ethylene stabilizers, the polymer nitrile butadiene (NBP), composed of PVC and butadiene-acrylonitrile copolymers.

Among plastomers, there are polyvinyl chloride polymer (PVC) with plasticizer, the unvulcanized polymer polyisobutylene (PIB), vinyl acetate copolymer unvulcanized ethylene (EVA), the acetate copolymer polyvinyl and unvulcanized ethylene and bitumen (ECB), chlorinated polyethylene polymer unvulcanized and plasticizer-free (CPE).

Synthetic membranes may optionally have a woven, a reinforcement or a backing layer incorporating, for example polyester, polyamide, glass cloth, etc., reinforcement purposes or to improve the adhesion of the adhesive.

Synthetic membranes can be, as appropriate, mechanically fastened, put in full or partial adhesion or by weighted free installation. The adhesion to the support is obtained by heat-bonding, by means of bitumen, or cold (contact adhesive). Adjoining sheets can often be done with hot air or by using a solvent.

The membrane may also be a bituminous membrane consisting of a bitumen coated reinforcement. In this case, the membrane may be monolayer or multilayer. The bitumen can be improved by the addition of polymers, which may include two types: plastomers (APP to atactic polypropylene) which impart plastic properties to the bitumen and elastomers (SBS styrene-butadiene-styrene) which impart elastic properties bitumen. Any sub-layers are made of blown bitumen. The frame of the bitumen may be in the form of a glass mat or polyester or in the form of an aluminum foil.

The waterproofing membranes of the invention may also comprise, besides their base composition and without this list being exhaustive, plasticizers, pigments, fungicides and algaecides, flame retardants, UV absorbers or antioxidants.

According to the invention, the outer surface of the membrane, that is to say the surface which will be exposed to daylight, once laid on the roof, is covered in whole or in part of semiconductor photovoltaic solar cells obtained by depositing thin film technology, monojonction or multijunction. A multijunction cell is formed by stacking a plurality of cells, usually two or three, one on the other. The semiconductor material used in these cells may include, for example:<ul><li>amorphous silicon, nanocrystalline (or microcrystalline), with or without the addition of SiGe;</li><li>a semiconductor II-VI such as CdTe or CdS,</li><li>a semiconductor III-V such as GaAs and / or </li><li>a semiconductor I-III-VI such as CuInSe₂ (CIS) or CuIn_xga_(1-x)himself₂ (CIGS).</li></ul>

Organic photovoltaic cells may also be used in the context of the present invention, such cells polymers made from mixtures of two conjugated polymers or conjugated polymer with a molecular sensitizer (PPV Poly (p-phenylene vinylene ), polyfluorene or polythiophene). However, at present, the performance of these cells is significantly lower than inorganic cells as listed above.

The prior sale of the thin film on the membrane may for example include the screening vacuum or printing ink containing semiconductor nanoparticles.

The sole of each profile is fixed to the sealing membrane by any method, for example by welding to the hot air, cold welding or by solvent bonding.

In a preferred embodiment, each profile is formed with a base and a projecting web, optionally terminated in its outermost part by a profile section of generally triangular shape, square, round, arrow, etc., having the possibly a rounded ridge. The profile may also advantageously have a cylindrical shape. Still according to the invention, the exposed surface of the profile is advantageously covered, in whole or in part of the same semiconductor photovoltaic cells made of thin film as covering the aforementioned membrane.

A wide range of underlying supports of roof covering is compatible with the invention.

Thus, according to an exemplary embodiment of the invention, on the surface of an element of a roof, for example an insulator, a sheathing, a concrete base, a wooden board, chipboard, plywood, multiplex OSB, etc., a sheet, etc., or a combination of several of these elements is fixed, by any mechanical means (screws, nails, glue, etc.) a homogeneous sealing membrane made of for example sheets PVC covered with photovoltaic cells in thin film as specified above. The<figref idrefs="f0002">3</figref> shows an embodiment adapted to an existing roof, comprising, arranged in successive layers, a roof support in the form of a steel tray 2A, a vapor barrier existing 2B, an existing insulation 2C, a sealing membrane existing one, an interposer geotextile 6 and finally a membrane covered with photovoltaic cells 10. The thin film <figref idrefs="f0003">4</figref> shows a similar embodiment to that of <figref idrefs="f0002">3</figref>Wherein the interposer geotextile 6 is replaced by a 4 wooden structure covered with panels or wooden battens 5. <figref idrefs="f0004">5</figref> shows a similar assembly to that of <figref idrefs="f0003">4</figref>, Where additional insulation is inserted into the wooden structure 4. The <figref idrefs="f0005">6</figref> shows a similar assembly to that of <figref idrefs="f0003">4</figref>Where a geotextile interposer 6 has been inserted between the wooden panels 5 and the photovoltaic membrane 10. The <figref idrefs="f0006">7</figref> shows a similar assembly to that of <figref idrefs="f0004">5</figref>Where a geotextile interposition 6 was inserted between the 5 wood panels and photovoltaic membrane 10.

On this membrane 10 are placed (glued) of profiles 3 of a plastic part, for example flexible PVC profiles, arranged parallel to each other, along the greatest slope of the roof, with a regular spacing between them. The profiles are fixed on the membrane by welding, for example by cold welding or bonding using tetrahydrofuran, by welding using hot air or mechanically fastened.

Advantageously be chosen limited height profiles and spaced so as to render negligible their shadow on the surface of photovoltaic cells located on the surface of the sealing membrane.

The profiles can be fixed on the overlapping area of ​​two widths of consecutive PVC, which has the effect of making invisible joints. The appearance of a roofing and done simply and quickly, is similar to that of a roofing zinc or traditional copper.

Another advantage of the invention is to provide a photovoltaic sensor function in very discreet roof, if that can not be distinguished by passers over a roof which does not have this feature.

Still advantageously, the arrangement of parallel profiles them will be selected to optimize the flow of water and thus extend the life of the membrane and especially its semiconductor recovery. The proposed solution is distinguished by its simplicity in terms of installation solutions photovoltaic flexible strips according to the prior art, which on the contrary use complex stapling systems.

The present invention is applicable regardless of the roof slope between 0 and 90 degrees, the two extremes being the horizontal roof and vertical siding.