WO2009095275A1

WO2009095275A1 - Photovoltaic modules

Info

Publication number: WO2009095275A1
Application number: PCT/EP2009/000666
Authority: WO
Inventors: François RUMMENS; Jochen Bussuyt
Original assignee: Renolit Belgium NV
Current assignee: Renolit Belgium NV
Priority date: 2008-02-02
Filing date: 2009-02-02
Publication date: 2009-08-06
Anticipated expiration: 2010-08-02
Also published as: EP2243170A1

Abstract

Flexible photovoltaic module (1 ) containing cells on plastic films with excellent fire properties, thanks to a backlayer containing halogen flame retardants.

Description

Photovoltaic modules

[001] The present invention relates to light weight, cost effective, photovoltaic modules with excellent fire resistance, durability and wind resistance and a method and system for attaching photovoltaic modules to a roof structure.

[002] Roofs are an ideal place to install photovoltaic modules. Rigid Si photovoltaic modules are very well known but are difficult to handle (they are rigid) and require expensive frames to install them on the roof.

[003] To make a commercial roof (i.e. especially flat or with low slope) watertight, it is well known to use a polymeric or a bituminous sheet (called waterproofing membrane) as a top layer of the roof (commercial buildings). In the case of a roof having on its top a waterproofing membrane, many penetrations of this sheet will generally be required to install the frames for the rigid Si photovoltaic modules. All these penetrations may lead to leakage and to cold bridges (leading to condensation inside the roof structure). Moreover not all roof structures accept heavy frames.

[004] US 6,729,081 describes a light weight photovoltaic module which is self- adhesive and can in principle be glued onto the waterproofing membranes in a cost effective way and without the use of fasteners which perforate the waterproofing membrane and the insulation panels. Gluing operations are however quite delicate on the roof. The (self-) adhesive may be further not compatible with the existing waterproofing membrane. In the case of gluing of such modules (US 6,729,081) onto monomeric plasticized PVC sheets, the plasticizer will migrate into the glue (self- adhesive), resulting in loss of adhesion and brittleness of the PVC sheet.

[005] Another way to obtain a roof with flexible photovoltaic modules attached onto it is to use, as waterproofing membrane, a waterproofing membrane with factory laminated flexible light weight photovoltaic modules on top of it. Such waterproofing membranes are produced by companies like SIT (Solar Integrated) in the USA or by Alwitra in Germany. They consist of several elongated modukes supplied e.g. United Solar Ovonic (Uni-Solar modules) glued in parallel to the polymeric waterproofing membrane. The several Uni-Solar modules are connected in serial under the waterproofing membrane. The connections / soldering are protected (encapsulated) by cast polyamide or cast epoxy or cast polyurethane resin or by similar system. Such photovoltaic waterproofing membranes and systems are described e.g. in DE 29824045 IM and WO2004066324 A2.

[006] EP 769 818, EP 1 458 035 and "Handbook of Photovoltaic Science and Engineering", Antonio Luque and Steven Hegedus; in particular chapter 12, describe elongated flexible photovoltaic modules containing cells on metal foils. The accuracy of the provided description has been checked on Uni-Solar ® modules (from United Solar Ovonic) by optical and electronic microscopy and IR analysis. A typical composition is a) 50 μm top layer from fluoro polymers, b) < 800 μm layer from ethylene vinyl acetate (EVA) containg a glass fleece or glass fibres or glass beads, c) photovoltaic cells on 120 μm metal foil, d) 150 μm EVA layer, e) 100 μm EVA layer from an EVA with low vinyl acetate (VA) content, f) 50 μm dielectric film like polyethylene terephthalate (PET), g) 100 μm EVA layer with low VA content. The layers from EVA with low VA content are glued with an polyurethane (PUR) based adhesive to the PET layer. Fire resistance is provided by a combination of the metal foil, the glass fleece or fibres or beads and restriction of EVA layer thickness above the cells to a maximum of 800 μm. The PET extends to the edges of the module which increases the risk for delamination as demonstrated by 4 weeks of immersion of the Uni-Solar module into water at 80⁰C.

[007] These photovoltaic modules waterproofing suffer from the drawback that they need a metallic foil under or as support of the photovoltaic cells in order to achieve high mechanical strength necessary to resist wind up-lift forces (heavy storms) and several mechanical stresses (hail, puncturing, ...) which may occur on a roof and to have good external fire performances. Further, internal tensions arise as a result of thermal cycli (sun - night) due to the poor matching of the coefficients of dilatation of the metal foil and the polymeric films, sheets and glues. Gluing of photovoltaic modules directly onto the waterproofing membrane will also block or at least much reduce the water vapor permeability of the waterproofing membrane, leading potentially to condensation problems inside the roof structure and/or to damages to the photovoltaic cells and/or to internal delamination of the encapsulating layers of the photovoltaic modules. [008] Cost effective monolithically interconnected cells on plastic substrates (further designated plastic (PV) cells or modules in the following are today produced by several groups and companies. Such films are described e.g. in WO 98/13882 and in "Handbook of Photovoltaic Science and Engineering" (Antonio Luque and Steven Hegedus; in particular chapter 12). The Plastic PV cell(s) may consist of:

- a base plastic film like typically 20 to 250 μm Kapton ® (polyimide) or PEN (polyethylene naphthalate) or PET (polyethylene terephthalate) film.

- on this film, in a cheap roll to roll process, one makes the deposition or transfer of: a) a back electrode (aluminium, etc.) b) an active PV layer or layers c) a transparent front electrode, like a transparent conductive oxide.

[009] The active layers may be: a-Si cells, tandem cells (a-Si, a-Si or a-Si, microcrystalline silicon, ...), triple junction a-Si/a-SiGe/a-SiGe, Organic Photovoltaic (OPV), CIGS, etc.Oxygen and water vapor Barrier layers may be added under a) and above c) if required. Useful barriers are SiOx or AI2O3 layers with hybrid polymers (Ormocers ®) or layers obtained by Atomic Layer Deposition, etc. The layers a), b) and c) are interconnected e.g. by lift-up, laser scribing, etching and silk printing of Ag paste processes, ... . They form strips of interconnected cells of typically 5 to 25 mm width. Cost effective encapsulation of such plastic PV Cells remain an issue.

[0010] More details about light weight flexible photovoltaic cells and modules (and the process of laminating them in e.g. a vacuum laminator) can be found in numerous patents and patent applications like EP 0769 818 A2, WO 2006/089044, and in the patents from the following companies:

- Konarka (Organic photovoltaic and Graetzel cells and modules).

- VHF - Flexcell (a-Si:H cells and modules)

- Helianthos/AKZO NOBEL (a-Si:H cells and modules)

- Powerfilm (Iowa Thin Film) (a-Si:H cells and modules)

- Canon, (a-Si:H cells and modules)

- Fugi, (a-Si:H cells and modules)

- United Solar Ovonic, (a-Si:H and triple junction cells and modules) [0011] Waterproofing membranes with low flammability are very well known, like PVC based waterproofing membranes. Such membranes often contain migrating plasticizer and are rigid at low temperature. They are questionnable for integration with plastic PV cells because of the risk of plasticizer migration into the adhesives of the PV module and the stiffness at low temperature. Waterprooving membranes based on thermoplastic polyolefins (TPO) are more adequate but generally have lower fire performances, requiring a high loading of fire retardants. An increase of the concentration of fire retardant in such waterproofing sheet is often not acceptable.

[0012] The object of the present invention is to provide photovoltaic modules which enable providing of fire safe, durable and cost effective photovoltaic systems. Especially the modules and systems according to the invention should have one or more of the following properties:

- excellent external fire performance

- acceptable external fire properties even with a thickness of more than 0,8 mm of non flame retarded polymeric layers, meaning that the PV module may achieve improved mechanical, impact, scratch and UV stability

- cost effective encapsulants (low material cost and/or quick encapsulation process)

- optimal adhesion between layers and thus high hydrolysis resistance (delayed internal delamination) as obviously required for safety reasons (avoidance of electrical shocks).

[0013] Surprisingly it was found that it is possible to adapt the composition of the modules so that the metal foil can be omitted and/or the EVA can be exchanged for TPO, which are cheaper and have improved compatibility with usual waterproofing membranes.

[0014] Thus, the above problems are solved by flexible photovoltaic modules with good external fire performance comprising cells on a plastic substrate wherein at least one plastic sheet or adhesive layer under the cell is based on a polyolefin, e.g. TPO, and/or a copolymer of ethylene or propylene with vinyl acetate or (meth)acrylate or neutralized acrylic acids (ionomers), the plastic sheet or adhesive layer contains at least 50 g/m², preferably at least 100 g/m² halogenated preferably brominated flame retardant and the layers above the plastic sheet or adhesive layer ensure the release of the flame poisoning substances coming from the plastic sheet or adhesive layer, when fire is set to the module.

[0015] Such flexible photovoltaic modules can be integrated with waterproofing membranes to waterproof the roof (single-layer system) or be used as panels and installed on top of the membrane (double-layer system). In the latter case the panels may be welded or attached with hooks and loops system. In a preferred variant they are attached with profiles on the existing waterproofing membrane.

[0016] According to the invention the waterproofing membrane is a preferably reinforced flexible TPO waterproofing sheet containing flame retardants. Preferably the upper layer of the TPO membrane or sheet is free from halogenated flame retardants.

[0017] It is also preferred to encapsulate and laminate the plastic PV cell(s) on the TPO waterproofing membrane or sheet in a laminating machine with the following stack of flexible layers: a) A transparent front sheet preferably of fluoropolymer film (typically 20 to 200 μm of ETFE, FEP, PVDF/acrylic ... , containing, if required, stabilizer and possibly long lasting UV absorbers). The film is surface treated to improve its adhesion on layer b) b) A transparent adhesive layer (e.g. based on EVA, ionomers, silicone, silicone-urea block polymers, tie-layer, tie-layer/transparent TPO/tie-layer, etc.; total thickness 200 to 2000 μm) or layers. c) The plastic PV cells, which may be coated beforehand with barrier layers and/or be surface treated to improve adhesion to layer b) and d). d) An adhesive layer (like b)) or a tie-layer or a coextruded layer (tie-layer/TPO), preferably opaque and if required flame retarded to provide better reaction to fire to the PV TPO waterproofing membrane. The TPo of the tie-layer/TPO will improve adhesion with the TPO membrane.

[0018] Suitable lamination machines are vacuum laminators, membrane presses and isobahc double-belt presses, which are well known in the art of lamination. [0019] Suitable EVA films are supplied by Etimex under the trade name Vistasolar 486.10 (thickness = 460 μm). Useful EVA films formulation are e.g. described in WO 99/27588. A typical lamination temperature for EVA films is 155°C (15 minutes).

[0020] Tie layers are preferably on base of polyolefin copolymers with acrylic acid or grafted with maleic anhydride. Useful resins to produce the tie-layers are:

EAA (ethylene acrylic acid) polymers

PO (polyolefins like PE or PP) grafted with maleic anhydride.

[0021] Primacor 1321 and Primacor 1410 are examples of EAA resins and are supplied by Dow Chemical. Orevac C314-2 is an example of PP grafted with maleic anhydride supplied by Arkema. Compoline CO/LA and Compoline CO/LL - CO/UL are examples of PO grafted with maleic anhydride and are supplied by Auserpolimeri. The resins may be mixed and/or films colaminated to adapt the Rheology and melting temperature of the tie-layers, potentially a multi-layer product. To improve transparency and softness of e.g. Primacor 1321 and 1410, copolymers like butyl acrylate, may be added during the polymerization step of such resins. This will anyway reduce the melting temperature. Clarifiers are useful mainly for MAH-PP. They are further stabilized to improve durability.

[0022] Other adhesives may be epoxy glues, PUR glues, etc, and will be chosen by the man skilled in the art to obtain good adhesion between the cell substrate film and the TPO waterproofing membrane, which may require a surface treatment to improve adhesion.

[0023] To improve adhesion between the several layers, they may be treated by known techniques like Corona (under O2/N2 or under N2 or N2/CO2 or N2/NH3, etc.), Flame treatment, Atmospheric plasma activation, Atmospheric or low pressure plasma deposition (aerosol assisted, ...) and/or polymerization, (reactive) Sputtering of metals like Aluminium (AI2O3), Chemical etching (NaOH, ...), ... . Barrier layers may be included.

[0024] A preferred surface treatment technique to improve adhesion with tie-layers of this invention is reactive sputtering of AI2O3. Sputtering is general used to coat the plastic films with the back electrode (aluminium) and to bring the front electrode (a transparent conductive oxide e.g. ITO). During these operations, it is easy to add a nanometric layer of AI2O3 on the back-side of the plastic film and on the top side above the transparent conductive oxide layer (e.g. ITO). In situ Radio Frequence 02 chemical etching of plastic film is usually performed before coating to improve adhesion of the sputtered layer as well known by the man skilled in the art.

[0025] The TPO waterproofing membrane is generally a multi-layer laminated sheet and is reinforced with polyester scrim or fabrics (typically 2 ^* 2, 1100 dTex) and/or glass fleece (typically 50 g/m²) and may have a polyester backing to attach the sheet to the insulation panels (with glue or hook and loop systems). More rigid reinforcement (heavy glass scrims, like 3 ^* 3, 1360 dTex, etc.) may be preferred to reduce the deformation of the PV cells during heavy storms. The upper layer of the TPO membrane may have a lower melting temperature or higher fluidity than the under layer. The total thickness of the sheet is typically between 0,8 mm and 4 mm, preferably between 1 ,2 and 3 mm.

[0026] The transparent TPO layer is preferably a mixture of 30 to 60 % by weight random copolymer of polypropylene and ethylene with 40 to 70 % by weight very low density polyethylene (VLDPE), like Exact 8201 , to reduce the rigidity of the random copolymer and improve impact resistance.

[0027] Altemativaly, the transparent TPO layer may be a mixture of: 60 to 80 % ULDPE (like Attane SL 4102 - from Dow) 20 to 40 % Versify 2400 (Dow).

[0028] Migrating and non migrating Hals and UV absorbers, like Tinuvin 123, Tinuvin 770, Chimasorb, 2020 Benzophenone and other additives known per se are typically added to these mixtures, and/or clarifiers (to improve transparency).

[0029] Useful TPO compositions to produce the opaque TPO layer, including the TPO in contact with the tie-layer, are based on:

- Flexible PP (FPP): PP/EPR reactor blends resins (like Hifax CA 10, Hifax CA 12, Hifax CA 02, Hifax CA 60, ... supplied by Basell)

- elastomeric PP resins (like Versify 2300.01 or 2400.01 , supplied by Dow in mixture with e.g. random PP copolymers)

- TPV (Thermoplastic Vulcanisates) with little amount of extension oil like Santoprene, etc. - LLDPE, VLDPE (like Exact 0201 or 8201 supplied by Dexplastomers), OBC (Infuse from Dow) and the like

- copolymers like EVA (ethylene vinyl acetate), EEA (ethylene ethyl acetate), EBA (ethylene butyl acetate), lonomers, etc. or blends thereof. The TPO of the tie-layer/TPO preferably has a higher MFI and/or a lower melting temperature than (at least the lower layer of) the TPO membrane to optimize adhesion. These layers further contain pigments, UV light and thermal stabilizers and flame retardants.

[0030] The TPO layers and the TPO core-layers preferably contain acid scavengers (like Hydrotalcite, potentially at the nano-scale for transparency). Anti-acids may be added to the tie-layers if they don't neutralize the reactive functionalities.

[0031] To obtain a low flammability photovoltaic flexible module (or waterproofing membrane) containing plastic cells, it is preferred to eliminate the glass fleeces in the transparent adhesive layer (contrary to the teaching of EP 0769 818 A2) while further providing a back layer (i.e. under the plastic cell) containing sheets or films which are flame retarded by halogenated, preferably brominated flame retardants whereby the sheets or films above this layer should have a low tendency to charring or forming fire barrier materials. It is necessary that the flame retardant decomposition products can be released and reach the flame to poison it. Therefore, these sheets or films and the sheets or films above these sheets or films are selected on the base that they have no or little tendency to char or to form a barrier layer for the release of the flame retardants decomposition products into the flame. Therefore, no glass fleeces should be included or at least are required into the transparent adhesive layer and the layers under the cells should contain layers based on TPO resins and/or polyethylene with adequate comonomers (Vinyl acetate, acrylates, neutralized acrylic acids, ...), containing preferably brominated flame retardants, materials which are known for their low charring tendency. It has been discovered that even a 1 mm thick (> 0,8 mm) EVA transparent adhesive may be used for the front sheet, if enough flame retardant is added to the back layer. Sufficient inflammability is achieved with improved mechanical properties (thicker protective EVA transparent adhesive). [0032] The adhesive (EVA, "tie-layer/TPO",...) of the back layer (i.e. layer d) may be formulated with halogenated compounds and catalyst (Sb2O3) and will contain at least 50 g/m², preferably at least 100 g/m², of the halogenated, preferably Brominated flame retardant, in order to be able to release enough (Halogene/Bromine) radicals into the flame (to "poison" the flame propagation) when the module catches fire. It has been surprisingly discovered that, when a plastic cell substrate (cell on plastic) is used, a low flammability can nonetheless be obtained by incorporation of such adhesive layer, even if the sheets/foils/films under the adhesive (EVA, ...) layer are charring type materials like P-PVC or TPO with charring flame retardants. Preferably and contrary to the teaching of EP 0769 818 A2, there is no glass fleece in the EVA transparent adhesive layers above the cell. The glass fleece would limit the access of the Halogene radicals to the flame.

[0033] The halogenated flame retardants are preferably brominated flame retardants, preferably in combination with catalysts like Sb2O3 or Sb2O5. Other flame retardants may be added like Zink Borates, etc.

[0034] According to this invention, the TPO waterproofing membrane may contain halogen flame retardant in its full thickness. As the TPO membrane is generally not fully covered by the PV cells and their encapsulation layers, like ETFE (in order to allow for e.g. weldability of the membrane and or replacement of a damaged PV module), the addition of halogenated flame retardants in the upper layer of the TPO membrane will lead, due to the TPO photooxidation, to release of halogenated compounds into the environment. Halogenated flame retardants are further expensive, especially when UV stability is required. Even with the more stable halogen flame retardants, a decrease of the UV stabilty is expected.

[0035] It has been surprisingly discovered that satisfactory fire performances of the membrane (areas with and without PV cells and encapsulation layers) can be achieved without halogenated flame retardants in the upper layer of the TPO membrane: the flame retardant decomposition products can be released and reach the flame to poison it, even at the level of the plastic PV cell(s). The UV aging of such TPO membrane is therefore not reduced by the halogen flame retardants and its price is reduced. [0036] Further the invention provides a tie-layer/TPO composition (layer d) to improve the fire performances of PV TPO waterproofing membrane with plastic cells, where the TPO waterproofing membrane contains classical mineral flame retardants like Mg(OH)2 or AI(OH)3 charring flame retardants. Such "tie-layer/TPO" layer d) is formulated with halogenated compounds and catalyst (Sb2O3) and will contain at least 50 g/m², preferably at least 100 g/m², of the halogenated, preferably brominated flame retardant.

[0037] It has surprisingly been discovered that, while plastic PV cells and their encapsulants lead to a loss of fire performance of conventional TPO membrane (halogen free flame retardants), the above mentioned tie-layer/TPO composition compensates the loss of fire performance, which is the result of the plastic PV cell(s) with transparent encapsulants.

[0038] Consequently, such tie-layer/TPO composition will allow io increase the thickness of EVA layer b), when superior mechanical properties are required and installation of a PV TPO waterproofing membrane on more critical roof structure (roof structure with lower fire performance).

[0039] In one preferred method for improving fire properties and/or for attaching the modules to the roof they are provided with a rigid sheet as substrate, either a metal sheet or a preferably reinforced plastic sheet. The modules are installed e.g. with the help of soft profiles with rigid, preferably with metallic, insert. To this end, profiles are attached to the roof by one of welding, glueing and mechanically fixing with nails, screws or hook and loop. The soft profiles are preferably welded on the waterproofing membrane. The rigid substrate of the module is preferably mechanically attached to the profiles with the insert. The profiles can also be cup shaped or take the form of strips.

[0040] Preferably, soft profiles with a rigid (e.g. metallic) insert, are welded/glued to a previously installed waterproofing membrane. The profiles are preferably equipped with flaps to ease welding, to improve sealing to the waterproofing membrane and to spread wind up-lift forces. The rigid, metal or preferably glass reinforced plastic sheet of the photovoltaic modules is attached (e.g. with stainless steel screws or with clips or with glues like MS (modified silicone) polymers) on the upper (rigid) part of the profile or to the insert (then preferably with screws drilling through the plastic profile). It will be recognized that these methods consisting of attaching the rigid metal or glass reinforced plastic sheets with the photovoltaic modules to profiles or cups attached to the waterproofing membrane do not require to perforate the waterproofing membrane.

[0041] Metal sheets suitable as rigid substrate of cells for this invention may be typically:

- 0,5 to 2 mm single sheet metal profile, as made from AI55/Zn45 type coated steel (Aluzinc, Galvalume, Galval, Zincalume), AZ185 with e.g. epoxy coating

- 0,5 to 2 mm coated Aluminium sheets

The metal sheet may be partly corrugated to improve its flexural rigidity or equipped with ribs or secondary profiles under the sheet, preferably provided with a slight slope (increasing height of the rib/profile). Coatings to improve the adhesion of the metal sheets with polymeric films may be PVC-Vac, PUR, Epoxy, Acrylic, etc. based coatings.

[0042] Rigid glass reinforced plastic sheets suitable as rigid substrate are preferably glass reinforced flame retarded PP, preferably corona treated and/or with a primer (e.g. chlorinated polyolefin), or flame retarded epoxy or unsaturated polyester glass fiber composites.

[0043] For modules with rigid sheet it is further possible to achieve sufficient flame retardancy by using a thick metal sheet as substrate. Usual metal substrates of cells/modules are about 120 μm steel. Using metal sheets of around 1 mm surprisingly provides sufficient flame retardancy even with modules comprising plastic layers of 1 mm that do not contain any added glass nor flame retardants.

[0044] The tests of external fire performance of roofs, required in Europe, are described in ENV 1187 part 1 to part 4. The most relevant tests are part 1 (Method with burning brand) and part 3 (Method with burning brand, wind and supplementary radiant heat). In these tests a complete roof structure (including roof substrate like corrugated metal sheet, insulation boards and waterproofing membrane is submitted to: part 1 : burning brand and part 3: burning brand, wind and supplementary radiant heat. The fire penetration and propagation are assessed and have to meet qualification criteria defined in EN 13501-5. For the main commercial buildings, the classes Broof (t1) 15 ° slope or Broof (t3) 5 ° slope are required. When the waterproofing membrane is installed on roof with higher slope (typically > 30°), the classes Broof (t1) 45 ° slope or Broof (t3) 30 ° slope are required.

[0045] A typical test structure for the assessment of external fire performances (burning brand, etc, attacking the waterproofing membrane) is: waterproofing membranelOO mm thick on Rockwool Taurox insulation panels which in turn are attached to a steeldeck "106/250/3" (0,75 mm thick and 106 mm high).

[0046] The invention will be illustrated further by reference to the attached drawing(s), by examples and specific embodiments which are not meant to restrict the scope to the specific examples and embodiments shown. Other combinations of the preferred features than those shown are also possible and advantageous.

[0047] List of figures:

Figure 1 : shows a cross section of the PV waterproofing membrane of the invention

[0048] Figure 1 shows a multilayer TPO waterproofing membrane (10), typically 1 ,5 mm thick with a reinforcement (10b), typically a polyester scrim or a glass scrim or a polyester/glass fleece combi-mat and with a top layer (10a), typically 0,25 mm thick, which may be without flame retardants. The TPO membrane (10) is wider that the PV module: a zone (5) is foreseen for welding purpose (installation, repair, ...). The TPO membrane contains further heat and UV stabilizers which may migrate into layer d) to avoid any risk of depletion of stabilizers in the layers b) and d) of the module 1 at its edges 1e.

[0049] On top of the TPO waterproofing membrane, one laminates, e.g. in a classical vacuum laminator or in a membrane press (e.g. WEMHONER VARIOPRESS® - press size 1 ,7 * 6 m²) or in e.g. a double-belt press (semi-continuous process) the following stack of layers: a) A transparent front sheet (1 a) b) A transparent adhesive layer (1 b) c) The plastic PV cells (1c) d) An adhesive layer (1d) [0050] The layer a), b) and d) are wider than c), allowing for edge sealing (1 e) of the plastic PV cell (PET, PEN, ... film) (1c), reducing significantly the risk of internal delamination compared to the previous art where the dielectric PET film is included into the edges of the modules (Uni-Solar modules). The color of the adhesive layer 1d is preferably white or light grey limiting the temperature at the edges (1e) of the plastic PV cells and the risk of excessive temperature and start of fusion of the e.g. tie-layer/TPO adhesive layer.

[0051] Further the color of the TPO waterproofing membrane may be white or light grey.

[0052] The obtained PV TPO waterproofing membrane or flexible photovoltaic module (110) is assessed for the fire performances. According to ENV 1187 part 1 and 3 or according to the laboratory test described hereafter.

[0053] The test equipment comprises a ZIP firelighter being a pressed block of rough pinewood sawdust and paraffin wax (30*30*17mm), a test box with supporting deck made from metal, and for a draught free test enclosure an exhaust hood to evacuate the smoke production, avoiding draught over the specimen. The test specimen is the waterproofing membrane 10 with or without module 1 installed on 5 cm thick rockwool as isolation material, with the following dimension: 150mm in width x 300mm in length. The test procedure is as follows:

- Positioning of the brand (ZIP firelighter) before ignition at a distance of 50 mm from the lower edged of the specimen and centrally between the left and right edge

- Test angle = 45°

- The brand (ZIP firelighter) is ignited

- duration of the test is 20 minutes

- observation and measurement of the burnt surface.

Example 1

[0054] Sample A is a polyester reinforced 1 ,5 mm multi-layer TPO waterproofing membrane (10) with halogenated flame retardants according to this invention. The composition of the multi-layer membrane is:

- 300 μm top layer of Hifax CA 10 A with usual stabilizers and pigments and with 25 % Saytex BT 93 halogenated flame retardant and 10 % Sb2O3. - 600 μm intermediate layer of Hifax CA 10 A with usual stabilizers and pigments and with 17 % Saytex 8010 halogenated flame retardant and 6 % Sb2O3

- 2 ^* 2 1100 dTEx Polyester reinforcement.

- 600 μm lower layer of Hifax CA 10 A with usual stabilizers and pigments and with 17 % Saytex 8010 halogenated flame retardant and 6 % Sb2O3

The measured burnt surface after fire testing is 3200 mm².

[0055] Sample B is the same TPO waterproofing membrane (10) with laminated on top of it the following stack of layers simulating a module 1 according to the art: a) 50 μm ETFE with surface treatment to adhere to b) b) 460 μm Etimex Vistasolar 486.10 c) a simulated Plastic PV cell (a PET film with an aluminium top coat obtained by PVD; back side treated by atmospheric plasma, as well known by the man skilled in the art) d) 460 μm Etimex Vistasolar 486.10

The burnt surface after fire testing is 1700 mm². Surprisingly the simulated module 1 comprsing the stack of layers a) to d) does not reduce the fire performance. It is even improved, although the total thickness of non flame retarded film b), c) and d) is 970 μm.

Comparison example 2

[0056] Sample C is a conventional polyester reinforced TPO waterproofing membrane (10) on base of Hifax CA 10 A with usual additives and pigments, containing a high loading (45%) of Mg(OH)2 fire retardants. This waterproofing membrane needs a polyester reinforcement to compensate for the severe reduction in mechanical properties. The burnt surface after fire testing is 2500 mm². The burnt part of the sample shows a mineral crust (char). Thus sample C shows better fire performance than sample A).

[0057] Sample D is the same TPO waterproofing membrane as C but with laminated on top of it the same stack of layers as B. The burnt surface after fire testing is 5000 mm², ie as expected on base of the teaching of EP 0 769 818 A2, the stack of layers a) to d) with a total thickness of non flame retarded film b), c) and d) of 970 μm reduces significantly the fire performance of the PV waterproofing membrane (1 +10).

Example 3

[0058] Sample E is the same TPO waterproofing membrane as C but with laminated on top of it the following stack of layers simulating a module 1 according to the invention: a) 50 μm ETFE with surface treatment to adhere to b) b) 460 μm Etimex Vistasolar 486.10 c) a simulated Plastic PV cell (a PET film with an aluminium top coat obtained by PVD; back side treated by N2/NH3 atmospheric plasma, as well known by the man skilled in the art, for adhesion to Orevac C314-2) d) a Tie-LayeπTPO:

I. Tie-layer = 100 μm Orevac C314-2 (MAH grafted PP), II. TPO = 500 μm of Hifax CA 60 with usual stabilizers and pigments and containing 25% of Saytex 8010 and 8 % of Sb2O3. The amount of halogenated flame retardant is around 125 g/m².

The burnt surface after fire testing is 1600 mm². Surprisingly the obtainned PV waterproofing membrane (1+10) of this invention shows excellent fire performances.

Example 4

[0059] The following multi-layer membrane is submitted to the the laboratory fire test:

- 300 μm top layer of Hifax CA 10 A with usual stabilizers and pigments and without fire retardants.

- 600 μm intermediate layer of Hifax CA 10 A with usual stabilizers and pigments and with 22 % Saytex 8010 halogenated flame retardant and 7 % Sb2O3

- 2 * 2 1100 dTEx Polyester reinforcement.

- 600 μm lower layer of Hifax CA 10 A with usual stabilizers and pigments and with 22 % Saytex 8010 halogenated flame retardant and 7 % Sb2O3

The burnt surface after fire testing is surprisingly limited to 3300 mm² showing that the upper layer of the membrane can be made without flame retardant. [0060] After lamination with the same layers a) to d) of sample B, the obtained PV TPO waterproofing membrane (or module) 1+10, is tested in the laboratory fire test. The burnt surface after fire testing is surprisingly limited to 1800 mm².

Embodiment 1 : production of a TPO photovoltaic waterproofing membrane (or flexible module) in one step, with excellent reaction to fire, thick (> 0,8 mm) protective encapsulation layers, and good adhesion between layers. [0061] A photovoltaic cell is produced according WO 98/13882 and glued onto a plastic film (PEN or PET), cell substrate. This PEN or PET film with the active photovoltaic layers is encapsulated in a vacuum laminator according to a well known procedure (release films may be used between the TPO membrane - layer e) - and the heating plate system) and comprises the following layers: a) An ETFE film 50 μm from DuPont (supplied for PV applications; with classical atmospheric plasma treatment to adhere to EVA) b) Two EVA Vistasolar 486.10 films of +/- 460 μm c) Several 50 μm aligned in parallel PEN films supporting the active layers (stripes of interconnected TCO/pin/back electrode) and interconnected. The back side of the PEN film is e.g. treated by reactive sputtering (deposition of a nano-layer of AI2O3) to improve adhesion with the Primacor (EAA) film. d) A coextruded multi-layer of:

- i) 50 μm Primacor 1410 or 1321

- ii) 50 μm Exact 0203

- iii) 50 μm Exact 0203/Hifax CA 60/Versify 2400.00 in mixture each layer containing anti-oxidants (e.g. 0,3 % Irganox B225 form Ciba), HALS and UV absorbers (e.g. 0,3 % Tinuvin 770, e.g. 0,3 % Chimassorb 944 and e.g. 0,3 % Chimassor 81), pigments (e.g. 5 % TiO2 Kronos 2220), halogenated flame retardants (e.g. 30 % Saytex 8010) and e.g. 8 % of Sb2O3 as catalyst. The EAA Primacor layer shows excellent adhesion to PEN films with AI2O3 nano-layer. The HALS are not added to the Primacor 1410 or 1321 layer at the extrusion step (compounding stage) but are added to the layers ii) and iii) and migrate from these layers to layer i) during the lamination process and during aging. Tinuvin 123 may be preferred above Tinuvin 770. Other NOR-HALS (less reactive with acids groups) may be used as known by the man skilled in the art. Acid scavengers (Hydrotalcite) are only added to layers ii) and iii). e) A 1.2 mm TPO sheet on base of Hifax CA 10 A with usual stabilizers and pigments and brominated flame retardants, like 25% Saytex 8010 and 7 % Sb2O3). The TPO sheet may contain a reserve of e.g. HALS stabilizers of UV absorbers, which will migrate into layers a), b) and d). The top layer of the TPO sheet may contain softening resins like Exact 0201 (lower melting temperature), Hifax CA 60 (lower viscosity) and/or Versify 2400.00 (lower melting temperature and viscosity), to optimize adhesion with layer d), part iii).

The layers a), b), d) are longer and wider (2 cm on each sides) than the layer c) to seal the edges of the cells efficiently (lower risk of delamination). A velour (a Loop fleece) or a hook may be laminated or glued at the back side of the photovoltaic TPO waterproofing membrane (application as flexible module).

[0062] To illustrate the fire performances, several hereabove described flexible module (although "inactive", i.e. with layer c) without the active layers) are attached side by side (flaps 20 covered by aluminum strips or welded together) on an existing 1.2 mm Alkorplan 35176 waterproofing sheet (substrate = insulation panels: 6 cm commonly used mineral wool). The Alkorplan 35176 waterproofing membrane is equipped with 10 cm width hooks strips (e.g. mushrooms strips stitched on strips of the same P-PVC membrane). 3 strips/meter are welded in parallel on the Alkorplan 35176 membrane. The structure is tested and passes with success the external fire performance tests ENV 1187/1 15°, thanks to the halogenated flame retardants which are released to the flame and poison it.

[0063] It has to be recognized that the flexible modules (the photovoltaic TPO membrane) may be installed in big panels with sealed perimeter and connected to venting profiles to limit water accumulation under the modules.

[0064] The flexibles modules may be installed as mono-layer (as photovoltaic integrated waterproofing membrane; preferably on a roof substrate including an enfficient water vapor barrier) or welded on an existing TPO membrane (double-layer system). Embodiment 2: PV TPO waterproofing membrane (flexible module) with Broof (t3) 5° and Broof (t1) 45° performance

[0065] The flexible photovoltaic module of Embodiment 1 , is adapted to have as layer b) one EVA Vistasolar 486.10 film of +/- 460 μm, instead of 2 films. Layer d) is preferably the same as for embodiment 1) or may be instead an EVA film Vistasolar 486.10 film of +/- 200 μm with 30 % Saytex 8010 and 8 % Sb2O3. Such film is not preferred as it is difficult to produce. The structure of embodiment 1 , with adapted module of embodiment 1 passes the Broof (t1) 45° and Broof (t3) 5° requirements with success.

[0066] The present flexible PV modules/membranes are believed to also meet the Broof (t1) 45° and Broof (t3) 5° requirements on more difficult structure (mono-layer installation on Polystyrene, on foamglass in bitumen bath, etc). The membrane may include a glass fleece (innerlayer of as backing).

[0067] It has to be recognized that the compositions and thicknesses of the several layers of the photovoltaic waterproofing membrane (110) may be varied to achieve most of the required fire classes on common subtrates (insulation boards, etc.).

Embodiment 3: production of a TPO photovoltaic waterproofing membrane (or flexible module) in one step in a semi-continuous process [0068] In a double-belt press (with Teflon ® release treatment of the belts) one laminates (press temperature around 185°C) the following layers: a) a 100 μm ETFE film plasma treated (atmospheric plasma treated - N2/NH3 atmosphere) to adhere with b) a coextruded film (brushed surface) of: i) 25 μm of Orevac C314-2 with usual stabilisers (not reacting during the extrusion step with the MAH functionalities and allowing transparency) ii) 300 μm of a transparent TPO composition like e.g. a mixture of random polypropylene-ethylene copolymer and VLDPE like Exact 8201 (60/40 ratio), containing migrating and non migrating Hals and UV absorbers, like Tinuvin 123, Tinuvin 770, Chimassorb 2020 and Benzophenone, with clarifiers to improve transparency and nanoscale predispersed hydrotalcite or other acid scavengers iii) 25 μm of Orevac C314-2 with usual stabilisers (not reacting during the extrusion step with the MAH functionalities and allowing transparency) c) formats of plastic PV cells (if required with barrier layers and preferably with a sputtered nanolayer of AI2O3 at least on the back side), interconnected in parallel d) a complex produced by in-line co-extrusion - laminating of: i) a 50 μm film of Orevac C314-2 with usual additives and if required flame retardants ii) an Alkortop 35086 waterproofing membrane (on base of Hifax CA 10 A, polyester reinforced).

The plastic cells are fed with interruptions to the double-belt laminator, i.e. in the form of long rectangles (typically 6 m long; if required several elements in parallel). For this purpose, they are laid by robots with sucking device in parallel, serial connected, on the (metallic) preparation zone of the double-belt press (equipped with synchronized electrostatic attraction device), on the complex d), and. Typically 10 cm without cell are foreseen in the length between the parallel formats of plastic PV cells to allow cutting and edge sealing. The layers a) and b) are preferably already laminated during an adequate production process, e.g. by extrusion coating of layer b) on layer a). The films a/b) and d) are fed continuously into the double-belt press. They are wider than the plastic cells to seal the edges. The final laminate is cut into formats. Electrical connections (perforation - contacts - soldering) are done off-line.

[0069] The several layers may be treated before lamination by Corona or by Atmospheric or Low pressure Plasma and Atmospheric plasma deposition (aerosol assisted, ...), and/or polymerization, or by atomic layer deposition, or sputtering, ... to improve adhesion between layers and improve barrier properties, as will be recognized by the person normally skilled in the art (Plato Plasma Technology and surface, Vito, AcXys, Dow Corning Plasma Solution, AS Coating Star atmospheric plasma, Beneq Oy ...).

[0070] A fleece (velour) or hook may be further glued or laminated to the back side of the encapsulated module, i.e. on the backside of the Alkortop 35086 TPO sheet. Embodiment 4: Effect of water

[0071] A piece of a Uni-Solar module PVL-series, model PVL 128 has been aged during 3 months in water at 60 ⁰C and 4 weeks in water 8O⁰C and tested for delamination. The Uni-Solar module shows delamination at the level of the inferior PET film (PUR adhesive hydrolysed).

[0072] In the same test, the module of embodiment 1 , with sealed edges (2 cm), doesn't suffer from delamination, as the adhesion between layer b) and d) is excellent (not senitive to hydrolysis).

Embodiment 5: big size module

[0073] Production of a cost effective big size (+/- 1 ,5 ^* 5,8 m²) module on a rigid metal substrate, with good flexural rigidity, fire performances, end of life recycling properties. On the preparation table of a membrane press (WEMHONER

VARIOPRESS® - press size 1 ,7 ^* 6 m²), one lays the following layers (from bottom to top):

A) A glass reinforced polypropylene sheet (preferably corrugated; containing usual additives), with a 50 μm top-layer based on Orevac C314-2 with usual additives and pigments. The surface of the preparation table is adapted to cope with the corrugations in the PP sheet. The PP sheet improves the flexural properties of the PV module.

B) A typically 0,8 mm Aluminium foil

C) If required an adhesive layer (to be chosen by the man skilled in the art; a primacor 1410 based film may be useful)

D) A commercially available module or modules (Unisolar PVL 136 peal and stick - 4 in parrallel; Iowa thin film modules, Flexcell modules, Nuon modules, Fugi electric modules, etc), if applicable/required with adequate surface treatment to adhere to C).

[0074] The stack of layers are pressed in the membrane Variopress® at the required temperature and pressure as known (e.g. 175°C - 3 bars). Before pressing vacuum may be applied to reduce air entrapment. If the PV modules are heat/pressure sensitive, the modules may be laminated in a second step (first step = production of PP/aluminium sheet). [0075] Layer D) can also be replaced by the module layers (from top to bottom) to achieve a one step process:

1 ) An ETFE film 50 μm from DuPont (with a Modified atmosphere Corona surface treatment to adhere 2)

2) A typically 500 μm transparent adhesive layer with adequate surface treatment to adhere to 3) and 4) (edges).

3) The plastic "cell" film (e.g. 50 μm Kapton or PEN or PET film), supporting the back electrode (aluminium, etc) / active PV layers / front electrode (ITO or other transparent conductive oxide)

4) A stack of layers or a coextruded film of following layers:

- a 50 μm layer based on Orevac C314-2 with usual additives and pigments

- a 50 μm layer based on a mixture 80/20 of Hifax CA 60 and Exact 8201 with usual additives, anti-acids, flame retardants and pigments

- a 400 μm layer based on a mixture 50/50 of Hifax CA 60 and Exact 8201 with usual additives, anti-acids, flame retardants, pigments and with 0,3 phr of Tinuvin 123 and 770

- a 50 μm layer based on a mixture 20/80 of Hifax CA 60 and Exact 8201 with usual additives, anti-acids, flame retardants and pigments

- a 50 μm layer based on Primacor 1410 with usual additives and pigments, to adhere to the 0,8 mm aluminium foil.

[0076] Layer 2) may be e.g. a PDMS-UREA based film or a stack of layers or a coextruded film of following layers: i) 50 μm Orevac C314-2 with usual additives (i.e. no reaction with the MAH functionalities) ii) 500 μm of a Transparent TPO foil (mixture Random polypropylene-ethylene copolymer in mixture with VLDPE like VLDPE Exact 8201 : 60/40 ratio) with migrating and non migrating Hals and UV absorbers, like Tinuvin 770 and 123, Chimassorb 2020 and Benzophenone, with clarifiers to improve transparency and possibly anti-acids (nano-scale hydrotalcite). iii) 50 μm Orevac C314-2 with usual additives (i.e. no reaction with the

MAH functionalities) [0077] Layer 4) has the following advantages: cost effective use of raw material, includes a reserve of stabilizer (edge of the modules), is easily flame retarded, and facilitates a reuse of the aluminium substrate (2). The low melt temperature of Primacor 1410 allows for ease of pealing from the aluminium substrate (2) at e.g. 125⁰C. To improve the heat resistance of the module OREVAC C314-2 may be used as component of the tie-layer.

Embodiment 6: attachment with profiles Embodiment 6.1 :

[0078] For the production of modules 1 according to this invention two photovoltaic cells (2 * 0,4 m * 5,4 m) are produced and transferred onto two plastic films (PEN), as described in WO 98/13882. The PEN film is called the (plastic) cell substrate. The two PEN films (0,4 m *5,4 m), with their photovoltaic active layers are encapsulated in a vacuum laminator according to a procedure well known in the art. The encapsulating layers are 5 cm wider and longer at each edge than the two PEN films and cells. Electrical connections are done as known per se.

[0079] The encapsulated module 1 comprises the following stack of layers: a) An ETFE film 50 μm from DuPont (with surface treatment to adhere to EVA) b) Two EVA Vistasolar 486.10 films of +/- 460 μm c) A 50 μm PEN film supporting the active layers (e.g. TCO/pin/back electrode/adhesion layer/adhesive to PEN) with appropriate surface treatment on both sides like deposition of a nano-scale AI2O3 layer (reative sputtering) d) An EVA Vistasolar 486.10 film (thickness +/- 460 μm) each layer containing anti-oxidants (0,3 % Irganox B225 form Ciba), HALS (0,3 % Tinuvin 770 and 0,3 % Chimassorb 944), pigments (5 % TiO₂ Kronos 2220), 24 % Saytex 8010 and 8 % of Sb₂O₃. e) A 1 ,2 mm TPO laminated steel sheet as supplied by Renolit Belgium N.V.

[0080] As alternative, layer d) is replaced by tie-layer/TPO/tie-layer and e) is a 1 mm thick aluminium plate (showing excellent corrosion resistance). Example of appropriate tie-layer/TPO/tie-layer is a coextruded film of "50 μ EAA Primacor 1410/360 μm VLDPE Exact 0203/50 μm EAA Primacor 1410", containing antioxidants (0,3 % Irganox B225 form Ciba), HALS (0,3 % Tinuvin 770 and 0,3 % Chimassorb 944), UV absorbers (0,3 % Chimassorb 81 from Ciba), ), 24 % Saytex 8010 and 8 % of Sb2O3 and and anti-acids. The reactive additives are only added in the VLDPE TPO layer.

Comparison 6.2:

[0081] For production of Modules 2 according to previous art: DE 298 24 045 U1 a photovoltaic cell (0,8 m ^* 5,4 m) is produced according WO 98/13882 and transferred onto a plastic film (PEN), cell substrate. This PEN film with the active photovoltaic layers is encapsulated in a vacuum laminator according to a procedure well known in the art. The encapsulated module 2 is produced by vacuum lamination as known per se and comprises the following stack of layers: a) An ETFE film 50 μm from DuPont (with surface treatment to adhere to EVA) b) Two EVA Vistasolar 486.10 films of +/- 460 μm c) A 50 μm PEN film (normally supporting the active layers (TCO/pin/back electrode/adhesion layer/adhesive to PEN)), surface treated for adhesion to b) and d). d) an EVA Vistasolar 486.10 film of +/- 460 μm. e) A 1.2 mm PVC-Elvaloy 742 sheet (PVC K71 : 100 phr; Elvaloy 742 ®: 85 phr; DiDP: 10 phr; Ca/Zn stabilizer and lubricants: 5 phr; Talcum: 10 phr; Tiθ₂ Kronos 2220: 10 phr).

Embodiment 6.3:

[0082] For production of alternative modules 3 according to this invention two peel and stick Uni-Solar PVL 136 modules are laminated on a 1 mm AluZink ® metal sheet PVDF pre-painted with pressing rolls and installed on profiles.

Test of external fire properties

[0083] Modules 1 to 3 each without their photoactive layers are tested according to ENV 1187/1. The modules 1 and 3 are mounted on profiles with a venting space between the rigid sheet and the waterproofing membrane. These modules pass the ENV 1187/1 requirement at 15° and 45°. The quality of the waterproofing membrane and substrate is not critical as the thick metal sheet acts as fire barrier. The module 2 is installed on mineral wool insulation boards as usual in the art. These module fails in the test ENV 1187/1 (15°). [0084] To further evaluate (comparative tests) fire performance, modules M1 to M3 are produced (see table), without the photoelectric layers, and are placed in a frame (30 ^* 30 cm²) at an angle of 45° against the horizon and submitted during 2 minutes to a gaz burner flame (760⁰C +/- 40 ⁰C). The upper side of the modules (i.e. the side normally exposed to the sun) is looking to the flame. The time until the modules are estinguished (self-estinguishing time) and the damaged surface area are observed. The module constructions have been assessed versus a well-known construction equivalent to the Kalzip ® AluPlusSolar product (M4) approved for pitched roofs with slopes up to 60°. The table lists the constructions and the results.

^* Peel and Stick module consisting of 50 μm ETFE / 500 μm transparent EVA with glass innerlayers / 120 μm stainlesss steal foil with active layers / back sheet (EVA/PET/EVA) / EPR adhesive.

** Same as layer d) in embodiment 6.1 but thicker (high concentration - g/m² - of halogenated flame retardants)

[0085] The module M1 behaves at the same level as the reference module M4 (used today with success for metal roofs with slope up to 60°). This is surprising as the thickness of the EVA/PEN/EVA organic films above the metal sheet is more than 800 μm. This result is achieved thanks to the heat sink effect and thermal conductivity of the thick metal foil. The module M3 behaves even better than the reference module M4, although the thickness of EVA above the cell is more than 800 μm. This result is achieved thanks to the high concentration - g/m² - of halogenated flame retardants in the tie-layer/TPO/tie-layer. Such modules 1 , 3 and 4, mounted on profiles, fulfill the requirements of the ENV 1187/1 , even at 45° slope.

[0086] The modules M2 are self-estinguishing and will fulfill the requirements of the ENV 1187/1 (15° slope).

[0087] This application claims priority of EP 08001991.2 and EP 08017870.0 the contents of which are hereby incorporated by reference in their entirety.

Claims

1. Flexible photovoltaic module (1) with good external fire performance comprising cells (1c) on a plastic substrate and characterized in that:

• at least one plastic sheet or adhesive layer under the cell is based on a polyolefin, and/or a copolymer of ethylene or propylene with vinyl acetate or (meth)acrylates or neutralized acrylic acids (ionomers)

• the plastic sheet or adhesive layer contains at least 50 g/m², preferably 100 g/m² halogenated preferably brominated flame retardant

• the layers above the plastic sheet or adhesive layer allow the release of the flame poisoning substances coming from the plastic sheet or adhesive layer when fire is set to the module.

2. Flexible photovoltaic module (1) according to claim 1 , where a backlayer element of the module has the composition of a fire retarded TPO waterproofing membrane with or without halogenated preferably brominated flame retardant.

3. Flexible photovoltaic module (1) according to claim 1 , where a backlayer element of the module is a commonly available TPO waterproofing membrane and the adhesive layer compensates the loss of fire performance resulting from front-layers and plastic PV cells.

4. Flexible photovoltaic module (1) according to claim 1 , where the module (1) is attached to waterproofing membrane (10).

5. Flexible photovoltaic module (1) according to claim 4, where the waterproofing membrane (10) contains halogenated, preferably brominated flame retardants except at its toplayer (10a).

6. Flexible photovoltaic module (1) according to claim 1 , characterized in that the adhesive layer above the plastic PV cell(s) is a transparent adhesive layer of more than 800 μm thickness.

7. Flexible photovoltaic module (1) according to claim 1 , characterized in that the plastic PV cells are laminated on a TPO waterproofing membrane (10) in a laminator with a tie-layer/TPO.

8. Flexible photovoltaic module (1) according to claim 1 , characterized in that the plastic PV cells are laminated on a TPO waterproofing membrane (10) in a laminator with a tie-layer/TPO adhesive containing halogen flame retardants, preferably brominated flame retardants.

9. Flexible photovoltaic module (1) according to claim 1 , characterized in that the adhesive layer above the plastic PV cells is a transparent tie-layer/TPO/tie-layer adhesive.

10. Flexible photovoltaic module (1) according to claim 1 , characterized in that:

• the adhesive layer above the plastic PV cells is a transparent tie-layer/TPO/tie- layer adhesive and

• the adhesive layer under the plastic PV cells is a tie-layer/TPO

11. Flexible photovoltaic module (1) according to claim 10 produced in a double-belt press.

12. Flexible photovoltaic module (1) according to at least one of claims 1 to 11 having sealing edges.

13. Flexible photovoltaic module (1) according to claim 12, having light color sealing edges attached to a waterproofing membrane (10) possibly with a light color.

14. Flexible photovoltaic module (1) according to claim 12 or 13, attached to a waterproofing membrane (10) containing migrating UV absorbers and migrating HALS to improve stability of the edges.

15. Flexible photovoltaic module (1 ) according to at least one of claims 7 to 11 , wherein tie-layer(s) contain HALS and/or UV absorbers through migration from adjacent layers during lamination and on site.