Photovoltaic module

Abstract

Disclosed is a photovoltaic module (1) comprising a front sheet (2) having a front face and a back face, at least one first encapsulant layer (3), at least one solar cell (4), at least one second encapsulant layer (5) and a back sheet (6) having a front face and a back face. The front face of the front sheet (2) is covered by a protective layer (7), which protective layer (7) comprises an intumescent material.

Description

[0001] Photovoltaic Module

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a photovoltaic module, to a method for manufacturing a photovoltaic module as well as to a use of a photovoltaic module according to the independent claims.

[0004] BACKGROUND OF THE INVENTION

[0005] Building-integrated photovoltaic (BIPV) systems have revolutionized the integration of solar energy generation into architectural design, offering both energy efficiency and aesthetic appeal. However, the proliferation of BIPV installations has underscored the critical need for ensuring fire safety in these solar panel applications, particularly in the context of buildings and structures.

[0006] Solar panels (also referred to as photovoltaic modules), central to BIPV, consist of silicon solar cells, protective encapsulants, and glass surfaces. While BIPV systems offer clean energy solutions, the potential fire risks associated with conventional solar panels have become a significant concern, especially in regions susceptible to wildfires and where stringent fire safety standards are mandated.

[0007] Traditional solar panels commonly use encapsulant materials, such as ethylene vinyl acetate (EVA), to protect and stabilize the solar cells. While EVA is effective as an encapsulant, its inherent fire resistance may fall short in high-temperature scenarios and preventing the spread of flames. US20060201545A1 proposes a photovoltaic module with a fire resistant laminate on its front side. The fire resistant laminate comprises an adhesive material having a fire resistant additive, such as glass spheres or other solid phase material dispersed therein. The adhesive material may be selected from polymers, partic- ularly fluoropolymers, ethylenevinylacetate (EVA), silicon, urethane, a sodium ionomer or a zinc ionomer.

[0008] It is a problem underlying the present invention to elevate the fire resistance of photovoltaic modules, in order to enhance their safety and viability in building- integrated applications. SUMMARY OF THE INVENTION

[0009] In a first aspect, the present invention relates to a photovoltaic module. The photovoltaic module comprises:

[0010] - A front sheet having a front face and a back face;

[0011] - At least one first encapsulant layer; - At least one solar cell;

[0012] - At least one second encapsulant layer;

[0013] A back sheet having a front face and a back face; The front face of the front sheet is covered by a protective layer. The protective layer comprises an intumescent material.

[0014] In the context of the present invention, the terms “at least one first encapsulant layer” and “at least one second encapsulant layer” refer to an arrangement in which the at least one solar cell is fully enveloped or enclosed by the encapsulant material. Such an encapsulant arrangement can be present as one single layer on the front face of the least one solar cell and one single layer on the back face of the least one solar cell. However, there can also be a plurality of encapsulant layers on each side of the least one solar cell.

[0015] If the intumescent material is exposed to the heat of fire, the protective layer swells and the material is converted into a porous opaque mass which is very effective as a thermal barrier. This is particularly important, since even if all the structural plies of the panel are cracked or broken by thermal shock, the panel may retain its effectiveness as a barrier against heat and fumes, since the fragments of the plies may remain in position bonded together by the converted intumescent material. Also during such heat-conversion of the layer, its temperature remains substantially constant so that excessive heating of the structures remote from the fire is delayed.

[0016] This innovative fire-resistant solar panel design offers a host of benefits and advantages that set it apart from traditional industrial building-integrated silicon solar cell systems. The development and integration of a protective layer comprising an intumescent material in building-integrated silicon solar cell panels represent a crucial advancement in addressing fire hazards associated with BIPV systems. This not only advances the cause of sustainable energy production but also aligns with established fire safety regulations and standards, rendering BIPV installations safer and more resilient in the face of fire risks.

[0017] Improved Fire Resistance:

[0018] The primary and most significant advantage of this invention is its exceptional fire resistance. The use of a protective layer comprising an intumescent material on the front face of the front sheet provides a robust defense against the spread of flames and extreme heat. This property greatly reduces the risk of fire damage, which is especially crucial for solar panels integrated into buildings. In the event of a fire, the photovoltaic module can resist heat and maintain structural integrity, minimizing fire-related risks.

[0019] Enhanced Safety:

[0020] The improved fire resistance contributes to enhanced safety, a paramount consideration for building-integrated solar systems. By reducing the risk of fire propagation and mitigating the threat of damage or failure during a fire incident, the present invention prioritizes the safety of both occupants and property.

[0021] The protective layer comprising an intumescent material primarily protects the underlying solar cells and helps to maintain the structural integrity of the panel during a fire event. It reduces the risk of fire propagation and limits the extent of damage, which is especially important for safety and minimizing the spread of fire in a building-integrated solar panel system. Applicability to Building-Integrated Solar Systems:

[0022] The design of this fire-resistant solar panel is well-suited for building-integrated solar systems. Its innovative approach ensures that the solar panel is not just an energy source but also a structural component. The described structure allows seamless integration into building facades, roofs, and other architectural elements. This enhances the aesthetic appeal of the structure while generating renewable energy.

[0023] The back face of the front sheet can be in contact with the first encapsulant layer or one of the first encapsulant layers, respectively. The least one solar cell can be situated between and encapsulated by the at least one first encapsulant layer and the at least one second encapsulant layer. The front face of the back sheet can be in contact with the second encapsulant layer or one of the second encapsulant layers, respectively.

[0024] The back face of the back sheet can also be covered by a protective layer, which protective layer comprises an intumescent material. This feature has a particular advantage as regards fire resistance. If a panel incorporating two protective layers is exposed to fire, the layer which is nearer the fire intumesces. As this layer is heated, the other intumescent layer is kept at a somewhat lower temperature until conversion of the first layer is completed. This prolongs the time taken for the second protective layer to become heated to a given temperature, and also reduces any tendency for the other components of the photovoltaic module to become nonuniform ly heated. This in turn reduces the possibility that they will be broken as a result of thermal shock. The protective layer on the front sheet and the protective layer on the back sheet can be different or identical. The front sheet and / or the back sheet can be a glass sheet, in particular - and usually - a tempered glass sheet. A tempered glass sheet is able to withstand considerable thermal shocks.

[0025] In an alternative embodiment, only the front sheet can be a glass sheet. The back sheet can then for instance be a single layer, moisture-resistant, fire-retardant membrane. This fire-retardant membrane can comprise a material selected from the group consisting of thermoplastic polyolefins (TPO), polyvinyl chloride (PVC) and ethylene propylene diene monomer (EPDM) rubber. The membrane can further comprise a flame retardant additive. In some embodiments, the flame retardant additive may be clays, nano-clays, silicas, carbon black, metal hydroxides such as aluminum hydroxide, metal foils, graphite, and combinations thereof. The back sheet may also include a plurality of plies, such as a first ply and a second ply.

[0026] The protective layer can form a translucent, preferably transparent, solid layer up to a temperature of 100 °C, preferably 120 °C, more preferably 150 °C.

[0027] The intumescent material can have a swelling temperature of 150 °C, 200 °C or 250 °C, depending on the specific application. The swelling temperature is the minimum temperature at which the intumescent material begins to swell. When the temperature reaches between 150°C to 250°C, the intumescent material becomes soft and tumescent. The material expands and becomes 10-20 times thicker than its initial thickness. It hardens again at temperatures above 250°C, while keeping its cellular structure. It can stand against fire up to 600-800 °C for specific duration (e.g. 30 minutes, 45 minutes, 60 minutes, etc.) according the type of glass, its thickness, thickness of the protective layer, and the design of the fire-rated assembly.

[0028] The intumescent material can be an alkali silicate. The alkali silicate can be a hydrated alkali silicate. Such substances have very suitable properties for use in protective layers according to the present invention. They are capable of forming transparent layers which adhere well to glass. On being sufficiently heated, the combined water evaporates and the layers foams, so that the hydrated metal salt is converted into an opaque solid, porous or cellular form in which it is highly thermally insulating and remains adherent to the glass. The use of a glass sheet, usually tempered through a specialized thermal tempering process, in combination with an alkali silicate coating, thus provides a particularly robust defense against the spread of flames and heat.

[0029] Furthermore, the use of a glass sheet in combination with an alkali silicate coating provides efficient heat management. It prevents overheating of the solar panel during intense sunlight exposure, optimizing its performance. The ability to resist extreme temperatures not only ensures the safety of the solar panel but also enhances its energy production efficiency.

[0030] Durability is another advantage of the present invention. The described photovoltaic modules maintain their integrity over time, resulting in a durable and long- lasting solution. The alkali silicate can be selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, and combinations thereof, preferably sodium silicate.

[0031] Alternatively, also other silicates can be used, such as ammonium silicate or calcium silicate.

[0032] The protective layer can comprise a bonding agent, in particular selected from the group consisting of glycidoxypropyl trimethoxysilane, 3-aminopropyl tri-eth- oxysilane and silane / siloxane mixtures. The bonding agent can be present in the protective layer in a weight ratio of 0.1 to 3.0 wt.-%.

[0033] The protective layer composition can comprise a UV stabilizer, in particular selected from the group consisting of hindered amine light stabilizers (HALS), especially a 2, 2, 6, 6, -tetramethylpiperidine derivative, in particular bis(2, 2,6,6, -tetra- methyl-4-piperidyl)sebaceate, bis(1 ,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl-1 ,2,2,6,6-pentamethyl-4-piperidylsebacate, poly(4-hydroxy-2,2,6,6-tetra- methyl-1 -piperidineethanol-alt-1 ,4-butanedioic acid) and poly-{6-[(1 , 1 ,3,3-tetra- methylbutyl)amino-1 ,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)im ino]- 1 ,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidyl)imino)}.

[0034] Alternatively, the UV stabilizer can be a benzophenone derivative, a benzotriazole derivative or a triazine derivative, such as 2-(2-hydroxyphenyl)-benzotria- zole, 2-(2H-benzotriazol-2-yl)-4,6-bis(1 -methyl-1 -phenylethyl)phenol, |3-[3-(2-H- benzotriazole-2-yl)-4-hydorxy-5-tert.butylphenyl]-propionic acid-poly(eth- yleneglycol) 300 ester, bis{[3-[3-(2-H-benzotriazole-2-yl)-4-hydroxy-5-tert-bu- tylphenyl]-propionic acid}-poly(ethylene glycol) 300 ester or 2-(4,6-bis-(2,4-dime- thylphenyl)-1 ,3,5-triazin-2-yl)-5-(octyloxy)-phenol.Such UV stabilizers have been commercialized under the following trade names of BASF SE or Solvay SA, respectively: Tinuvin 234, Tinuvin 292, Tinuvin 770, Tinuvin 783, Tinuvin 1130, Tinuvin 5151 and Cyasorb UV-1164.

[0035] The UV stabilizer can be present in the protective layer in a weight ratio of 0.5 to 5.0 wt.-%.

[0036] It has been found that, depending on the composition, protective layers comprising an intumescent material can tend to degrade with age when exposed to the sun, which results in reduced effectiveness of heat-conversion when the panel is exposed to fire, and for transparent panels, results in a loss of overall transparency. The use of a UV stabilizer addresses this problem.

[0037] The protective layer composition can comprise an antioxidant, in particular selected from the group consisting of hindered phenol antioxidants, especially pen- taerythritol-tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 1 ,3,5-tris(3,5-di- tert-butyl-4-hydroxybenzyl)-1 , 3, 5-triazinane-2, 4, 6-trione and bis(2,4-di-tert-bu- tylphenyl)pentaerythritol diphosphate. Such antioxidants have been commercialized under the following trade names of BASF SE or SI Group Inc., respectively: Irganox 1010, Irganox 3114 or Ultranox 626. The antioxidant can be present in the protective layer in a weight ratio of 0.3 to 2.0 wt.-%. The protective layer can comprise a hydrophobic agent, in particular selected from the group consisting of fluoropolymers and siloxanes, especially polydimethylsiloxane, 3-aminopropyltrimethoxysilane, polytetrafluoroethylene and amino functional polysiloxanes. The hydrophobic agent can be present in the protective layer in a weight ratio of 0.1 to 2.0 wt.-%.

[0038] The protective layer can comprise a filler, in particular a nano-material, especially selected from the group consisting of nano-SiO2, nano-TiO2 and nano-MnO2. The filler can be present in the protective layer in a weight ratio of 1 to 10 wt.-%. The use of a filler can provide to the protective layer enhanced durability. Furthermore, multilayer antireflective coatings can be created by using interference effects.

[0039] In particular, for using SiO2 as one important additive, silicate solutions with high silica content dry quickly when exposed to air and are highly resistant to heat and acids due to their high melting temperature. However, they tend to shrink more during curing compared to solutions with higher alkali content. Alkali-rich solutions with low sil icate-to-alkal i ratio are more elastic and less brittle, but dry more slowly and may not be as effective against corrosion therefore the precise amount of this additive must be added to the gel.

[0040] The first and / or second encapsulant layer(s) can comprise a material selected from the group consisting of polyolefins, ethyl vinyl acetates, ionomers, silicones, polyvinylbutyral, epoxides, polyurethanes and combinations thereof.

[0041] The thickness of the protective layer can be 0.02 to 20 mm, preferably 0.1 to 10 mm, more preferably 1 to 5 mm. The thickness of the front sheet can be 1 to 20 mm, preferably 2 to 15 mm, more preferably 3 to 12 mm.

[0042] The thickness of the first and / or second encapsulant layer(s) can be 0.1 to 5 mm, preferably 0.2 to 4 mm, more preferably 0.4 to 2 mm. The thickness of the least one solar cell can be 0.01 to 3.0 mm, preferably 0.05 to 2.0 mm, more preferably 0.1 to 1 .0 mm.

[0043] The thickness of the back sheet can be 0.1 to 20 mm, preferably 0.5 to 15 mm, more preferably 1 to 12 mm.

[0044] The photovoltaic module as described herein above can comprise a plurality of solar cells. The solar cells can be connected to each other in series or parallel.

[0045] The present invention also relates to a photovoltaic module, in particular a photovoltaic module as described herein above, wherein an edge, preferably two edges, even more preferably all four edges, of the photovoltaic module is / are sealed by a sealant. In order to elevate the fire resistance of the photovoltaic module, it is beneficial to extend the protective strategy of the present invention also to the edges of the module. The sealant may be in the form of gel, paste, glue or strip. Preferably, it can withstand temperatures over 500 °C.

[0046] Typically all four edges of the module, which is usually rectangular, are sealed by a sealant. The sealant can comprise an intumescent material, preferably as described herein above, i.e. especially an alkali silicate, and / or selected from the group consisting of ammonium polyphosphate intumescents, acrylic intumescents and graphite-based intumescents. Intumescent sealants are of particular value, due to their ability to expand and form an insulating barrier when exposed to high temperatures.

[0047] The sealant can be a silicone-based sealant. Such sealants are particularly suitable for environments demanding high thermal stability.

[0048] The silicone-based sealant can comprise a silicone copolymer, such as those combined with phenolic resins or polyurethanes. They offer improved thermal resistance and maintain flexibility under extreme conditions.

[0049] Additionally or alternatively, the silicone-based sealant can comprise a filler, in particular selected form the group consisting of ceramic fillers, such as alumina, silica, titanium dioxide or silicate fillers, such as zirconium silicate or calcium silicate, boron nitride or silicon carbide, and expandable graphite. Such fillers can be added to the silicone formulations to boost their temperature tolerance and mechanical strength, making them suitable for sealing the edges of solar modules where exposure to high temperatures is likely.

[0050] The sealant may also be a water-releasing sealant, in particular aluminum trihydroxide. This material releases water vapor when exposed to high heat, aiding in the cooling and fire resistance of the sealant. This mechanism not only slows down the heat transfer but also helps in reducing the temperature of the immediate environment, protecting the module edges from fire damage.

[0051] An edge, preferably two edges, even more preferably all four edges, of the photovoltaic module can be sealed by a first sealant and optionally additionally a second sealant. When considering fire protection for the edges of solar modules, three strategic approaches may be employed: A single-sealant strategy, a dualsealant strategy or an integrated frame sealing strategy.

[0052] The single-sealant strategy involves applying a single layer of sealant directly to the edges of the solar modules after the lamination process by both manual or automated injection. In this approach, the selected sealant serves as a sole barrier for edge protection, providing both thermal resistance and environmental sealing. This strategy eliminates the need for additional internal sealing materials, simplifying the process while offering robust fire protection.

[0053] In contrast, the dual-sealant strategy combines the use of a standard internal sealant, such as butyl rubber, with an external fire-resistant sealant applied postlamination by both manual or automated injection. The internal sealant, integrated during the lamination process, provides primary sealing and moisture resistance, while the external layer of fire-resistant sealant adds a secondary layer of protection against fire and environmental stress. This dual-layer approach enhances the overall durability and safety of the solar module edges, leveraging the strengths of both materials. In addition to employing single or dual-sealant strategies for edge protection, a further solution involves the use of an aluminum frame specifically designed to support and secure the edges of the solar module. This method entails the application of a sealant as a bonding agent between the solar module and the aluminum frame. The aluminum frame, serving as both a structural support and a thermal barrier, is engineered with a groove or channel where the edges of the solar module fit snugly.

[0054] A sealant is applied within this groove before the solar module is inserted, ensuring a secure and robust bond. This sealant not only acts to affix the module within the frame but also fills any gaps, providing a continuous fire-resistant barrier around the entire perimeter of the module. The choice of sealant can be tailored from the aforementioned categories - intumescent, silicone-based, or water-re- leasing - depending on the specific thermal and environmental resilience required.

[0055] This framing method enhances the structural integrity and fire safety of the installation by creating a sealed unit that minimizes the exposure of module edges to environmental elements and potential fire sources. The application of the sealant can be conducted manually or through automated injection, ensuring consistency and depth of the sealant layer within the frame's groove.

[0056] In a second aspect, the present invention relates to a method for manufacturing a photovoltaic module, in particular a photovoltaic module as described herein above. The method comprises the steps of: a. Providing a front sheet having a front face and a back face; b. Applying to the front face of the front sheet a protective layer, which protective layer comprises an intumescent material; c. Providing a back sheet having a front face and a back face, at least one solar cell and an encapsulant; d. Encapsulating the at least one solar cell in the encapsulant between the front sheet and the back sheet.

[0057] The front sheet and / or the back sheet can be a glass sheet. After step a. and before step b. the front sheet can be subjected to a thermal treatment to obtain a tempered glass sheet.

[0058] In step b. application of the protective layer can be effected by spray coating. Spray coating allows to disperse of the protective layer on the front and / or back sheet uniformly and with controlled thickness. Alternatively, screen printing, inkjet printing or roll coating can be used. Step c. can additionally comprise:

[0059] Applying to the back face of the back sheet a protective layer, which protective layer comprises an intumescent material.

[0060] Step c. can additionally comprise: Subjecting the back sheet to a thermal treatment to obtain a tempered glass sheet.

[0061] The method as described herein above can further comprise a step e. after step d.: Sealing at least one edge, preferably two edges, even more preferably all four edges, of the photovoltaic module with a sealant.

[0062] A third aspect of the present invention relates to a use of a photovoltaic module as described herein above in a building-integrated solar system, in particular in a facade or a roof. The European standard that is concerned with the fire classification of building elements and construction products, including photovoltaic systems, is EN 13501. This standard outlines various performance criteria used to evaluate the fire properties of building products.

[0063] 1 . Fire Behavior The reaction to fire classification determines how much a material contributes to fire behavior.

[0064] - A1 = non-combustible

[0065] A2 = limited combustibility - B1 : High fire resistance.

[0066] - B2: Normally flammable.

[0067] - C, D = ranges from limited to medium contribution to fire

[0068] - E, F = high contribution to fire Preferably, a photovoltaic module according to the present invention has a reaction to fire classification of at least B1 , more preferably A2, even more preferably A1.

[0069] 2. Smoke Development

[0070] This part of the classification refers to the total smoke emitted during the first 10 minutes of exposure to fire:

[0071] - S1 = little or no smoke

[0072] - S2 = quite a lot of smoke

[0073] - S3 = substantial / heavy smoke

[0074] Preferably, a photovoltaic module according to the present invention has a smoke emission classification of ate least S2, more preferably S1 .

[0075] 3. Formation of Flaming Droplets / Particles This part of the classification relates to the number of flaming droplets and particles produced within the first 10 minutes of fire exposure.

[0076] - dO: No droplets; No droplets within 600 seconds.

[0077] - d1 : Some droplets; Droplet form within 600 seconds but do not burn for more than 10 seconds.

[0078] - d2: Quite a lot; Droplets form and bum for more than 10 seconds.

[0079] Preferably, a photovoltaic module according to the present invention has a flaming droplets and particles classification of at least d1 , more preferably dO.

[0080] It is worth noting that EN 50583 is a standard that is applicable to photovoltaic systems that are integrated into buildings as construction products, with photovoltaic modules being used as building components. However, for fire resistance requirements, EN 50583 refers to local building codes and does not provide detailed fire resistance requirements specific to photovoltaic systems.

[0081] In a yet another preferred embodiment, a photovoltaic module according to the present invention conforms to the standards under US norm UL 790 / ASTM E 108. Preferably, the module has a Class A rating when tested in accordance with UL 790 / ASTM E 108.

[0082] It is to be understood that both the foregoing general description and the following detailed description present embodiments are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.

[0083] BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings are showing:

[0085] Fig. 1 schematic sectional view of a photovoltaic module according to a first embodiment of the present invention;

[0086] Fig. 2 schematic sectional view of a photovoltaic module according to a second embodiment of the present invention;

[0087] Fig. 3 schematic sectional view of a photovoltaic module according to a third embodiment of the present invention;

[0088] Fig. 4 schematic sectional view of a photovoltaic module according to a fourth embodiment of the present invention;

[0089] Fig. 5 schematic sectional view of a photovoltaic module according to a fifth embodiment of the present invention. DESCRIPTION OF THE EMBODIMENTS

[0090] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

[0091] Figure 1 shows a photovoltaic module 1 according to a first embodiment of the present invention. The photovoltaic module 1 is a so-called glass-glass module, meaning that the solar cells 4 are arranged between a front sheet 2 and a back sheet 6, which are both glass sheets. The solar cells 4 are encapsulated by an encapsulant, which is present between the solar cells 4 and the front sheet 2 as well as the back sheet 6 as first a encapsulant layer 3 and second encapsulant layer 5. The front face of the front sheet 2 as well as the back face of the back sheet 6 are both covered by a protective layer 7. The protective layer 7 comprises an intumescent material. In the present example, the intumescent material is a hydrated alkali silicate.

[0092] Figure 2 shows a photovoltaic module 1 according to a second embodiment of the present invention, which is related to the module 1 according to Figure 1 . However, in this second embodiment the back sheet is a single layer moisture- resistant fire-retardant membrane. Thus, only the glass front sheet 2 is covered by a protective layer 7 comprising an intumescent material which is a hydrated alkali silicate. Figure 3 shows a photovoltaic module 1 according to a third embodiment of the present invention, which is related to the module 1 according to Figure 1 . However, on the edges of the module, a first sealant 8 has been applied. The sealant is made of an intumescent material with the ability to expand and form an insulating barrier when exposed to high temperatures. Fire protection can therefore also be provided at the edges of the module.

[0093] For ease of understanding, only one edge of the module is shown in Figure 3, on the left side. To avoid any misunderstanding, in the shown embodiment, a first sealant 8 has been applied to all four edges of the rectangular module.

[0094] Figure 4 shows a photovoltaic module 1 according to a fourth embodiment of the present invention, which is related to the module 1 according to Figure 3. However, instead of a single-sealant strategy, a dual-sealant strategy is applied. A second sealant 9 is thus present between the front sheet 2 and the back sheet 6. The second sealant 9 is made of a butyl rubber. The second sealant 9, integrated during the lamination process, provides primary sealing and moisture resistance, while the first sealant 8 adds a secondary layer of protection against fire and environmental stress.

[0095] For ease of understanding, only one edge of the module is shown in Figure 4, on the left side. To avoid any misunderstanding, in the shown embodiment, a first sealant 8 and a second sealant 9 have been applied to all four edges of the rectangular module. Figure 5 shows a photovoltaic module 1 according to a third embodiment of the present invention, which is related to the module 1 according to Figure 1 . However, the edges of the module are encompassed by a frame 10 made of aluminum. In the gaps between the front sheet 2 or the back sheet 6, respectively, and the frame 10, a first sealant 8 of an intumescent material is applied as a bonding agent and for fire protection. The aluminum frame 10 serves both as a structural support and a thermal barrier.

[0096] For ease of understanding, only one edge of the module is shown in Figure 5, on the left side. To avoid any misunderstanding, in the shown embodiment, all four edges of the rectangular module are encompassed by the frame 10.

[0097] In the following, the assembly of a photovoltaic module according to the present invention shall be briefly described.

[0098] Glass Sheets

[0099] The glass sheets are normally subjected to a thermal tempering process, enhancing their mechanical strength and durability. This process known to the person skilled in the art and subjects the glass to precise heating and rapid cooling, creating tempered glass known for its structural integrity even under extreme conditions. The thermal tempering process is an important step in enhancing the mechanical strength and durability of glass substrates, particularly those used in high-performance applications like building-integrated solar cell panels. This process begins with the selection of high-quality glass, for instance low-iron glass, known for its excellent light transmittance and robustness. The glass sheets are cut to the required dimensions, ensuring precision and uniformity.

[0100] Prior to tempering, the glass surfaces undergo rigorous cleaning to eliminate any contaminants, such as dust, dirt, or oils, which could otherwise interfere with the tempering process and the subsequent application of coatings. A pristine glass surface is essential for achieving optimal results.

[0101] The thermal tempering process relies in controlled heating and rapid cooling of the glass sheets. To this ends, the glass sheets are placed into a tempering furnace, where they are subjected to temperatures exceeding their softening point but below their melting point.

[0102] The product of the thermal tempering process is glass that shows enhanced mechanical strength and resistance to thermal stress. It can withstand significant mechanical loads, resist temperature fluctuations, and maintain its structural integrity. Furthermore, tempered glass is engineered to shatter into small, relatively harmless pieces in the event of breakage, enhancing safety.

[0103] Alkali-Silicate Coating Following the thermal tempering, a key step in the assembly is the application of an alkali silicate gel coating onto the glass surface. This gel layer adds an extra dimension of fire resistance by providing thermal insulation and protection against direct flame exposure. The application of the alkali silicate gel is conducted with precision to ensure uniform thickness and distribution, a vital aspect of its effectiveness.

[0104] In order to form the protective layers, hydrated sodium silicate is applied to the tempered glass sheets. The sodium silicate is applied by spray coating as an aqueous solution having the following properties:

[0105] Proportion by weight: (SiO21 Na2O) = 3 / 7

[0106] Viscosity: 0.1 Pa ■ s at a shear rate of 1000 s-1

[0107] Average transmittance: > 90 % in the visible region

[0108] The solution comprises 20-30 wt.-% of solid material (SiO2 1 Na2O). The solvent comprises 80-100 vol.-% of water and 0-20 vol.-% of co-solvents, such as alcohols (e.g. ethanol or isopropanol) or glycols.

[0109] Spray coating is a precise technique used to apply alkali silicate gel onto the surface of glass after it has undergone the thermal tempering process. This method is particularly well suited for coating glass pieces of various shapes and sizes, providing an advantage in terms of controlling both the thickness and uniformity of the coating. A thicker alkali-silicate gel layer can provide better insulation against heat transfer, which can help protect the glass from shattering or warping due to high temperatures during a fire. However, as the gel layer becomes thicker, it can affect the transparency and optical quality of the glass. Controlling thickness of alkalisilicate gel layer is thus an essential step.

[0110] The glass surfaces, which have undergone thermal tempering, are positioned horizontally within a spray booth. The coating process begins with applying the alkali silicate solution evenly across the glass surface. The spray gun or nozzles, which are set at an appropriate distance from the glass, ensure that the solution is distributed uniformly. The goal is to create a consistent and even distribution of the gel solution. The glass sheets are sprayed from above, while they are hated from the bottom side, usually to a temperature of 80 to 100 °C.

[0111] Following the application of the coating, the glass panels are allowed to air dry or undergo a curing process. This curing process can involve exposure to ambient air or controlled conditions that facilitate the formation of the alkali silicate gel layer. The gel will gradually harden and adhere to the glass. Subsequently, the glass sheets are placed into a furnace with controlled temperature settings to gradually increase the temperature to a level where the alkali silicate gel solidifies and forms a heat-resistant layer on the glass.

[0112] To make alkali silicate materials resistant to moisture and relatively insoluble, the water in the solution must be almost completely removed after deposition on top of tempered glass. Preferably, the alkali silicate layer is cured at a temperature of 100 to 140 °C for a period of 300 minutes to eliminate the water. Normally, the temperature is kept below 200 °C.

[0113] Solar Cells

[0114] Preferably, high-efficiency silicon solar cells are integrated into the photovoltaic modules using the so-called glass-glass method. This glass-glass configuration not only maximizes the durability of the solar panel but also enhances its overall performance.

[0115] Encapsulant

[0116] A preferred encapsulant is ethylene vinyl acetate (EVA). EVA, known for its exceptional thermal and electrical properties, assumes a critical role in ensuring the photovoltaic module’s integrity and performance, even in the face of extreme conditions such as a fire.

[0117] The encapsulation of the solar cells into the EVA is executed following established industry practices for photovoltaic module assembly. The encapsulation process guarantees secure sealing of the solar cells, which, in turn, shields them against external factors, including the threat of fire. The EVA encapsulant assumes an important role in maintaining the electrical connections and overall performance of the solar cells. This assembly process adheres to established industry standards for photovoltaic module construction, ensuring that the solar cells are securely incorporated into the panel structure. This optimizes energy capture while maintaining the structural integrity necessary to withstand external stressors and varying environmental conditions. The final lamination process of the solar panel utilizes EVA encapsulation, further ensuring the integrity and longevity of the entire structure. The result is a fire-resistant solar panel that not only provides a sustainable source of energy but also ensures the safety and integrity of the structure in which it is integrated. This assembly process, combining thermal tempering, alkali silicate gel, high-efficiency solar cells and EVA encapsulation, underscores the commitment to both performance and safety in solar panel design.

[0118] When a photovoltaic module according to the present example is subjected to the action of fire, the layer of hydrated sodium silicate applied to the sheet closest to the fire is converted to an opaque porous fire-screening barrier of anhydrous sodium silicate. This anhydrous barrier is somewhat thicker than the hydrated layer from which it was formed, and is a very effective barrier against infrared radiation. During the course of the conversion, the bound water is driven off and thus contributes to a limitation of the temperature increase in that layer. During this phase, the encapsulant contributes to a tendency to render uniform the temperature across the whole area of the module, and any local "hot-spots" in the protective layer first to be converted are reflected in larger hot zones in the second protective layer. When this first layer is completely dehydrated the other layer of hydrated sodium silicate is in turn converted to form an opaque porous barrier of anhydrous sodium silicate. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the Spirit and scope of the invention.

[0119] LIST OF DESIGNATIONS 1 Photovoltaic module

[0120] 2 Front sheet

[0121] 3 First encapsulant layer

[0122] 4 Solar cell

[0123] 5 Second encapsulant layer 6 Back sheet

[0124] 7 Protective layer

[0125] 8 First sealant (edge)

[0126] 9 Second sealant (edge)

[0127] 10 Frame

Claims

PATENT CLAIMS1 . A photovoltaic module (1 ) comprising:- A front sheet (2) having a front face and a back face;- At least one first encapsulant layer (3); - At least one solar cell (4);- At least one second encapsulant layer (5);- A back sheet (6) having a front face and a back face;Wherein the front face of the front sheet (2) is covered by a protective layer (7), which protective layer (7) comprises an intumescent material.

2. The photovoltaic module (1 ) according to claim 1 , wherein the back face of the front sheet (2) is in contact with the first encapsulant layer (3) or one of the first encapsulant layers, respectively.

3. The photovoltaic module (1 ) according to one of claims 1 or 2, wherein the least one solar cell (4) is situated between and encapsulated by the at least one first encapsulant layer (3) and the at least one second encapsulant layer (5).

4. The photovoltaic module (1 ) according to one of claims 1 to 3, wherein the front face of the back sheet (6) is in contact with the second encapsulant layer (5) or one of the second encapsulant layers, respectively.

5. The photovoltaic module (1 ) according to one of claims 1 to 4, wherein the back face of the back sheet (6) is covered by a protective layer (7), which protective layer (7) comprises an intumescent material.

6. The photovoltaic module (1 ) according to claim 5, wherein the protective layer (7) on the front sheet (2) and the protective layer (7) on the back sheet (6) are different or identical.

7. The photovoltaic module (1 ) according to one of claims 1 to 6, wherein the front sheet (2) and / or the back sheet (6) is a glass sheet, in particular a tempered glass sheet.

8. The photovoltaic module (1 ) according to one of claims 1 to 7, wherein the protective layer (7) forms a translucent, preferably transparent, solid layer up to a temperature of 100 °C, preferably 120 °C, more preferably 150 °C.

9. The photovoltaic module (1 ) according to one of claims 1 to 8, wherein the intumescent material has a swelling temperature of 150 °C, 200 °C or 250 °C.

10. The photovoltaic module (1 ) according to one of claims 1 to 9, wherein the intumescent material is an alkali silicate.11 . The photovoltaic module (1 ) according to claim 10, wherein the alkali silicate is a hydrated alkali silicate.

12. The photovoltaic module (1 ) according to one of claims 10 and 11 , wherein the alkali silicate is selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, and combinations thereof, preferably sodium silicate.

13. The photovoltaic module (1 ) according to one of claims 1 to 12, wherein the protective layer (7) comprises a bonding agent, in particular selected from the group consisting of glycidoxypropyl trimethoxysilane, 3-aminopropyl triethoxysilane and silane / siloxane mixtures.

14. The photovoltaic module (1 ) according to claim 13, wherein the bonding agent is present in the protective layer (7) in a weight ratio of 0.1 to 3.0 wt.- %.

15. The photovoltaic module (1 ) according to one of claims 1 to 14, wherein the protective layer (7) composition comprises an UV stabilizer, in particular selected from the group consisting of hindered amine light stabilizers (HALS), especially a 2, 2, 6, 6, -tetramethylpiperidine derivative, in particular bis(2,2,6,6,-tetramethyl-4-piperidyl)sebaceate, bis(1 , 2,2,6, 6-pentamethyl- 4-piperidyl)sebacate, methyl-1 ,2,2,6,6-pentamethyl-4-piperidylsebacate, poly(4-hydroxy-2,2,6,6-tetramethyl-1 -piperidineethanol-alt-1 ,4-butanedioic acid) and poly-{6-[(1 ,1 ,3,3-tetramethylbutyl)amino-1 ,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)im ino]-1 ,6-hexanediyl[(2,2,6,6-tetra- methyl-4-piperidyl)imino)}.

16. The photovoltaic module (1 ) according to claim 15, wherein the UV stabilizer is present in the protective layer (7) in a weight ratio of 0.5 to 5.0 wt.-%.

17. The photovoltaic module (1 ) according to one of claims 1 to 16, wherein the protective layer (7) composition comprises an antioxidant, in particular selected from the group consisting of hindered phenol antioxidants, especially pentaerythritol-tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 1 ,3,5- tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1 , 3, 5-triazinane-2, 4, 6-trione and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate.

18. The photovoltaic module (1 ) according to claim 17, wherein the antioxidant is present in the protective layer (7) in a weight ratio of 0.3 to 2.0 wt.-%.

19. The photovoltaic module (1 ) according to one of claims 1 to 18, wherein the protective layer (7) comprises a hydrophobic agent, in particular selected from the group consisting of fluoropolymers and siloxanes, especially polydimethylsiloxane, 3-aminopropyltrimethoxysilane, polytetrafluoroethylene and amino functional polysiloxanes.

20. The photovoltaic module (1 ) according to claim 19, wherein the hydrophobic agent is present in the protective layer (7) in a weight ratio of 0.1 to 2.0 wt.- %.21 . The photovoltaic module (1 ) according to one of claims 1 to 20, wherein the protective layer (7) comprises a filler, in particular a nano-material, especially selected from the group consisting of nano-SiO2, nano-TiO2 and nano- Mn02.

22. The photovoltaic module (1 ) according to claim 21 , wherein the filler is present in the protective layer (7) in a weight ratio of 1 to 10 wt.-%.

23. The photovoltaic module (1 ) according to one of claims 1 to 22, wherein the first and / or second encapsulant layer (5) comprises a material selected from the group consisting of polyolefins, ethyl vinyl acetates, ionomers, silicones, polyvinylbutyral, epoxies, polyurethanes and combinations thereof.

24. The photovoltaic module (1 ) according to one of claims 1 to 23, wherein the thickness of the protective layer (7) is 0.02 to 20 mm, preferably 0.1 to 10 mm, more preferably 1 to 5 mm.

25. The photovoltaic module (1 ) according to one of claims 1 to 24, wherein the thickness of the front sheet (2) is 1 to 20 mm, preferably 2 to 15 mm, more preferably 3 to 12 mm.

26. The photovoltaic module (1 ) according to one of claims 1 to 25, wherein the thickness of the first and / or second encapsulant layer (5) is 0.1 to 5 mm, preferably 0.2 to 4 mm, more preferably 0.4 to 2 mm.

27. The photovoltaic module (1 ) according to one of claims 1 to 26, wherein the thickness of the least one solar cell (4) is 0.01 to 3.0 mm, preferably 0.05 to 2.0 mm, more preferably 0.1 to 1 .0 mm.

28. The photovoltaic module (1 ) according to one of claims 1 to 27, wherein the thickness of the back sheet (6) is 0.1 to 20 mm, preferably 0.5 to 15 mm, more preferably 1 to 12 mm.

29. The photovoltaic module (1 ) according to one of claims 1 to 28, comprising a plurality of solar cells (4).

30. A photovoltaic module (1 ), in particular a photovoltaic module (1 ) according to one of claims 1 to 29, wherein an edge, preferably two edges, even more preferably all four edges, of the photovoltaic module (1 ) is / are sealed by a sealant (8).

31. The photovoltaic module (1 ) according to claim 30, wherein the sealant (8) comprises an intumescent material, preferably as defined in one of claims 9 to 12 and / or selected from the group consisting of ammonium polyphosphate intumescents, acrylic intumescents and graphite-based intumes- cents.

32. The photovoltaic module (1 ) according to claim 30, wherein the sealant (8) is a silicone-based sealant.

33. The photovoltaic module (1 ) according to claim 32, wherein the silicone- based sealant comprises a silicone copolymer.

34. The photovoltaic module (1 ) according to one of claims 32 or 33, wherein the silicone-based sealant comprises a filler, in particular selected form the group consisting of ceramic fillers, such as alumina, silica, titanium dioxide or silicate fillers, such as zirconium silicate or calcium silicate, boron nitride or silicon carbide, and expandable graphite.

35. The photovoltaic module (1 ) according to claim 30, wherein the sealant (8) is a water-releasing sealant, in particular aluminum trihydroxide.

36. The photovoltaic module (1 ) according to one of claims 32 or 35, wherein an edge, preferably two edges, even more preferably all four edges, of the photovoltaic module (1 ) is / are sealed by a first sealant (8) and optionally additionally a second sealant (9).

37. A method for manufacturing a photovoltaic module (1 ), in particular a photovoltaic module (1 ) according to one of claims 1 to 36, the method comprising the steps of: a. Providing a front sheet (2) having a front face and a back face; b. Applying to the front face of the front sheet (2) a protective layer (7), which protective layer (7) comprises an intumescent material; c. Providing a back sheet (6) having a front face and a back face, at least one solar cell (4) and an encapsulant;d. Encapsulating the at least one solar cell (4) in the encapsulant between the front sheet (2) and the back sheet (6).

38. The method according to claim 37, wherein the front sheet (2) and / or the back sheet (6) is a glass sheet.

39. The method according to claim 38, wherein after step a. and before step b. the front sheet (2) is subjected to a thermal treatment to obtain a tempered glass sheet.

40. The method according to one of claims 37 to 39, wherein in step b. application of the protective layer (7) is effected by spray coating. 41 . The method according to one of claims 37 to 40, wherein step c. additionally comprises:Applying to the back face of the back sheet (6) a protective layer (7), which protective layer (7) comprises an intumescent material.

42. The method according to one of claims 38 to 41 , wherein step c. additionally comprises:Subjecting the back sheet (6) to a thermal treatment to obtain a tempered glass sheet.

43. The method according to one of claims 37 to 42, further comprising a step e. after step d.:Sealing at least one edge, preferably two edges, even more preferably all four edges, of the photovoltaic module (1 ) with a sealant (8).

44. Use of a photovoltaic module (1 ) according to one of claims 1 to 36 in a building-integrated solar system, in particular in a facade or a roof.

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