A method of manufacturing a solar module and solar module

Abstract

A roof tile solar module 102 has a base layer 104, with a fastening feature (e.g. screw hole or slot [118, 120 figure 1] with water sealing membrane) for securing to a roof. A photovoltaic solar cell

Description

Technical Field The present invention relates to a method of manufacturing a solar module and a solar module, such as a roof tile solar module. The present invention particularly, although not exclusively to a method of manufacturing a solar module comprising at least one solar cell and a polycarbonate layer, wherein the polycarbonate layer is bonded to the solar cell. Background In order to incorporate solar power generation into a roof of a building, solar modules (typically referred to as solar panels) are often installed over an existing roof covering, such as ceramic tiles or slates. This tends to be the simplest and most cost-effective way of installing solar power generation on existing roofs. However, for new buildings for which solar power generation is to be installed, providing a conventional roof covering, such as tiles or slates, and then installing solar modules is inefficient. Rooftile solar modules configured in the same shape and size as a conventional roof tile are therefore increasingly being used as an alternative. The roof tile solar modules provide the dual function of a conventional roof covering (i.e. protecting a building from inclement weather) and power generation. Existing roof tile solar modules are, however, based on conventional solar modules comprising multiple solar cells located between a back layer made from glass or plastic and a front layer made of glass. Existing roof tile solar modules are therefore relatively heavy and easily damaged. In addition, existing roof tile solar modules are time consuming to install. Therefore, there exists a need for an improved rooftile solar module. Summary of the Invention According to a first aspect of the invention there is provided a roof tile solar module comprising a base layer; at least one solar cell having a light-receiving surface, the at least one solar cell is disposed overlying the base layer and arranged such that the light-receiving surface faces away from the base layer, and a protective layer having a transparent portion, the protective layer being disposed overlying the at least one solar cell and the base layer such that the at least one solar cell is disposed between the transparent portion of the protective layer and the base layer. Optionally, the base layer may comprise at least one fastening feature for securing the roof tile solar module to a roof structure. Optionally, the base layer has a peripheral portion that extends around a periphery of the at least one solar cell and the protective layer is joined to the peripheral portion such that the at least one solar cell is encapsulated between the transparent portion of the protective layer and the base layer. Optionally, the at least one fastening feature is provided on the peripheral portion of the base layer. Optionally, the peripheral portion comprises an upper peripheral portion which defines an upper edge of the roof tile solar module and a lower peripheral portion which defines a lower edge of the roof tile solar module, the upper peripheral portion has a first fastening feature in the form of a first aperture through the upper peripheral portion and the lower peripheral portion has a second fastening feature in the form of a second aperture through the lower peripheral portion. Optionally, the roof tile solar module has a central installation axis which extends parallel to the base layer and perpendicular to a horizontal direction when the rooftile solar module is secured to a roof structure which extends horizontally. Optionally, the second fastening feature is spaced from the central installation axis by a first predetermined offset distance and the first fastening feature is spaced from the central installation axis by a second predetermined offset distance which is different from the first predetermined offset difference such that the first fastening feature and the second fastening feature are spaced from each other and the central installation axis. Optionally, the second predetermined distance is equal to the half of a width of the roof tile solar module less the first predetermined distance. Optionally, the first fastening feature is spaced from the central installation axis by a first predetermined offset distance and the second fastening feature is spaced from the central installation axis by the first predetermined offset distance such that the first fastening feature and the second fastening feature are aligned in a direction which is parallel to the central installation axis. Optionally, the first fastening feature comprises an elongate slot arranged to extend in a direction which is parallel with the central installation axis. Optionally, the elongate slot is provided with a membrane which occludes the slot. Optionally, the integrated rooftile solar module has a first lateral edge and a second lateral edge. Optionally, the first lateral edge comprises a first interlocking feature and the second lateral edge comprises a second interlocking feature configured to interlock with a first interlocking feature of an adjacent roof tile solar module having corresponding first and second interlocking features. Optionally, the rooftile solar module is substantially rectangular. Optionally, the roof tile solar module has a central alignment feature. Optionally, a locating element is provided at an underside of the base layer, the locating element is configured to engage with the roof structure such that the roof tile module is suspended by the locating element. Optionally, the locating element is a batten lug. Optionally, the at least one solar cell comprises a photovoltaic solar cell. Optionally, the solar module comprises a plurality of solar cells. Optionally, the base layer has a recess configured to receive the at least one solar cell. Optionally, the base layer is formed from a unsaturated polyester resin containing mineral fillers and reinforced with glass fibre. Optionally, the protective layer is bonded to at least a portion of the peripheral portion by an adhesive. Optionally, the protective layer comprises a polycarbonate layer or glass. Optionally, the protective layer is bonded to the least one solar cell by an adhesive. According to a second aspect of the invention there is provided a method of manufacturing a solar module comprising the steps: providing at least one solar cell having a light-receiving surface; disposing a dry polycarbonate layer over at least a portion of the light-receiving surface of the at least one solar cell, and bonding the polycarbonate layer to said portion of the light-receiving surface of the at least one solar cell. In the context of the invention, the term 'dry polycarbonate layer' means a polycarbonate layer having a predetermined water content which is not greater than an amount at which at which out-gassing does not occur during normal ambient operating conditions of the solar module, and particularly to the extent that bubbles of fluid form between the polycarbonate layer and the solar cell. A polycarbonate layer may be considered to be a 'dry polycarbonate layer' if the polycarbonate layer has a water content which is not greater than 0.05%wt. Optionally, the method further comprises the step of disposing an adhesive between said portion of the light-receiving surface the at least one solar cell and at least a portion of the polycarbonate layer prior to bonding the polycarbonate layer to said portion of the lightreceiving surface of the at least one solar cell. Optionally, the adhesive is a heat-activated adhesive. Optionally, the step of bonding the polycarbonate layer to the at least one solar cell comprises the step of heating the at least one solar cell, the heat-activated adhesive and the polycarbonate layer to not less than a minimum bonding temperature which is not less than 50 degrees centigrade, and optionally not less than 100 degrees centigrade, and optionally not less than 130 degrees centigrade. Optionally, the step of bonding the polycarbonate layer to the at least one solar cell comprises the step of maintaining the temperature of the at least one solar cell, the heat-activated adhesive and the polycarbonate layer at a temperature which is not less than the minimum bonding temperature for a predetermined bonding period. Optionally, the step of bonding the polycarbonate layer to the at least one solar cell comprises the step of heating the at least one solar cell, the heat-activated adhesive and the polycarbonate layer to not greater than a maximum bonding temperature which is not greater than 250 degrees centigrade, and optionally not greater than 200 degrees centigrade, and optionally not greater than 150 degrees centigrade. Optionally, the step of bonding the polycarbonate layer to the at least one solar cell comprises the step of maintaining the temperature of the at least one solar cell, the heat-activated adhesive and the polycarbonate layer at a temperature which is not greater than the maximum bonding temperature for a predetermined bonding period. Optionally, the predetermined bonding period is not less than 1 minute, and optionally not less than 10 minutes. Optionally, the predetermined bonding period is not greater than 60 minutes, and optionally not greater than 30 minutes. Optionally, the dry polycarbonate layer has a predetermined water content which is not greater than an amount at which at which out-gassing does not occur during normal ambient operating conditions of the solar module to the extent that bubbles of fluid form between the polycarbonate layer and the solar cell. Optionally, the dry polycarbonate layer has a predetermined water content which is not greater than 0.05%wt. Optionally, the step of providing a polycarbonate layer having a water content which is not greater that a predetermined water content comprises a step of drying the polycarbonate layer. Optionally, the step of drying the polycarbonate layer comprises the step of increasing the temperature of the polycarbonate layer to a temperature which is not less than a predetermined drying temperature. Optionally, the predetermined drying temperature is not less than 100 degrees centigrade. Optionally, the step of drying the polycarbonate layer comprises the step of maintaining the polycarbonate layer at not less than the predetermined drying temperature for a predetermined drying period. Optionally, the predetermined drying period is not less than 0.5 hours, and optionally not less than 1 hour, and optionally not less than 2 hours, such as not less than 4 hours. Optionally, the step of bonding the polycarbonate layer to the at least one solar cell comprises the step of applying a predetermined bonding pressure to the at least one solar cell, the heat-activated adhesive and the polycarbonate layer which is not greater than 300kPa, and optionally not greater than 150kPa, and optionally not greater than lOOkPa. Optionally, the predetermined bonding pressure is not less than 5kPa, and optionally not less than 20kPa, and optionally not less than 60kPa. Optionally, the method further comprises the steps of: providing a base layer; disposing the at least one solar cell on the base layer, wherein the step of disposing the polycarbonate layer over at least a portion of the light-receiving surface of the at least one solar cell includes disposing at least a portion of the polycarbonate layer not disposed over at least one solar cell over at least a portion of the base layer. Optionally, the method further comprises the step of disposing an adhesive between at least a portion of the solar cell and at least a portion the base layer. Optionally, the base layer has a recess and the step of disposing an adhesive between at least a portion of the solar cell and at least a portion the base layer includes the step of disposing the adhesive within the recess. Optionally, the method further comprises the step of disposing an adhesive between at least the portion of the polycarbonate layer not disposed over at least one solar cell and the base layer. Optionally, the at least one solar cell comprises a photovoltaic solar cell. Optionally, the solar module comprises a plurality of solar cells. According to a third aspect of the invention there is provided a solar module comprising: at least one solar cell having a light-receiving surface; a polycarbonate layer disposed over at least a portion of the light-receiving surface of the at least one solar cell, wherein the polycarbonate layer is bonded to the light-receiving surface of the at least one solar cell. Optionally, the polycarbonate layer is bonded to the light-receiving surface of the at least one solar cell by an adhesive. Optionally, the solar module further comprising: a base layer, wherein at least a portion of the polycarbonate layer not disposed over at least a portion of the light-receiving surface of the at least one solar cell is disposed over at least a portion of the base layer. Optionally, said at least a portion of the polycarbonate layer disposed over at least a portion of the base layer is bonded to at least a portion of the base layer. Optionally, the base layer has a recess configured to receive the at least one solar cell. Optionally, the base layer is formed from a unsaturated polyester resin containing mineral fillers and reinforced with glass fibre. Optionally, the polycarbonate layer is configured to provide at least 80% transmission of electromagnetic radiation within a wavelength range which is not less than 300nm and not greater than 2400nm. Optionally, the polycarbonate layer is configured to provide at least 80% transmission of light within a wavelength range which is not less than 400nm and not greater than 780nm. Certain aspects of the invention provide an integrated solar roof tile module. Certain aspects of the invention provide a solar rooftile module which can be secured directly to a roof structure. The need to use a supporting frame or intermediate structure in order to secure the solar roof tile module to a roof structure is therefore avoided. Certain aspects of the invention provide a solar rooftile module in which at least one solar cell is encapsulated between a protective layer and a base layer such that the solar cell is hermetically sealed between the protective layer and a base layer. This prevents fluid ingress, such as ingress of air, vapour or water into the region between the protective layer and a base layer within which the solar cell is sealed. The rooftile solar module is therefore very durable. Certain aspects of the present invention provide a solar rooftile module which can be secured to a roof structure using fasting features which are formed integrally with the solar roof tile module. Certain aspects of the present invention provide a solar rooftile module having fastening features which allow for multiple solar roof tile modules to be secured to a roof structure in various configurations such as a grid arrangement or a 'brick bond' arrangement in accordance with a preference of an installer. Certain aspects of the present invention provide a solar rooftile module having fastening features are configured to allow for different amounts of overlap of solar roof tile modules in the direction of a slope of a roof structure thereby allowing for the solar roof tile modules to be installed on a roof structures having different pitch angles. Certain aspects of the invention provide a solar module which is lightweight, and particularly lightweight compared against traditional solar modules having protective layer made of glass. Certain aspects of the invention provide a solar module which comprises a polycarbonate layer which forms a protective layer over a solar cell and for which significant out-gassing from the polycarbonate does not occurduring normal operation of the solar module. Normal operation may be expected to be operation in ambient temperature which does not exceed 50 degrees centigrade. Certain aspects of the invention provide a solar module, such as a roof tile solar module, which has a high strength-to-weight ratio compared with conventional solar modules. Various further features and aspects of the invention are defined in the claims. Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which this invention belongs. Brief Description of the Drawings Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings where like parts are provided with corresponding reference numerals and in which: Figure 1 is a top view of a solar module; Figure 2 is a bottom view of the solar module shown in Figure 1; Figure 3 is a side view of the solar module shown in Figure 1; Figure 4 is a flow chart illustrating a method of manufacturing the solar module shown in Figures 1 to 3; Figure 5 is a schematic representation of a layup used to manufacture the solar module shown in Figures 1 to 4; Figure 6 shows a first example arrangement of solar modules, and Figure 7 shows a second example arrangement of solar modules. Detailed Description Figures 1 to 3 show a roof tile solar module 102 comprising a base layer 104, a plurality of photovoltaic solar cells 106 and a polycarbonate layer 108. The roof tile solar module 102 is substantially rectangular and has a central installation axis X which extends in the longitudinal direction of the roof tile solar module 102, parallel to the base layer and perpendicular to a horizontal direction when the roof tile solar module 102 is secured to a roof structure. The base layer 104 is substantially planer and has a recess 110 surrounded by a peripheral portion 112. The recess 110 is configured to receive the photovoltaic solar cells 106 and the polycarbonate layer 108. In the embodiment shown, the base layer 104 is substantially rectangular (as viewed from above) having a first lateral edge 113a, a second lateral edge 113b, a top edge 113c and a bottom edge 113d. The base layer 104, and hence the rooftile solar module 102, has a width of 1028.27mm and a length of 1364.58mm. The recess 110 has a depth of 3.2 mm. The recess depth must be sufficient to accommodate the photovoltaic solar cells 106, the polycarbonate layer 108, and any adhesive between the layers. The base layer 104 is made of a sheet moulding compound comprising an unsaturated polyester resin containing mineral fillers and reinforced with glass fibre. The sheet moulding compound has a density of 1.85 g / cmA3 and so is light weight compared with materials traditionally used for base layers of solar modules. The sheet moulding compound has a Young's Modulus of 11 GPa (in accordance with EN ISO 527-4) and a Flex Modulus of 11.5 GPa (in accordance with EN ISO 14125) and so is sufficiently rigid to be handled and provide structural support for the roof tile solar module 102, but is also able to flex to accommodate expected movement or expansion of the roof tile solar module 102 when in situ. The sheet moulding compound has an impact strength of 70KJ / mA2 and so has sufficient impact strength to withstand impacts that can be expected during installation and subsequent operation of the roof tile solar module 102. Furthermore, the sheet moulding compound has a fire retardancy of 3mm HB and a limited oxygen index of 24% (in accordance with EN ISO 4589-2), and so is effective at inhibiting the spread of fire. The sheet moulding compound is therefore particularly beneficial for use as a base layer for the roof tile solar module 102 since it is lightweight, rigid and has good fire retardant properties. Use of a sheet moulding compound helps provide a roof tile solar module which has a high strength-to-weight ratio compared with conventional solar modules. In addition, the sheet moulding compound provides good thermal insulation. The base layer 104 is substantially planar and comprises a first male interlocking feature 114 extending along one of the edges extending in the lengthwise direction and a second female interlocking feature 116 extending along the other edge extending in the lengthwise direction. The male interlocking feature 114 and the female interlocking feature 116 are configured to interlock such that adjacent rooftile solar modules 102 can be connected by their respective male interlocking feature 114 and female interlocking feature 116. The base layer 104 is also provided with multiple fastening features in the form of apertures 118a, 118b, 118c, 118d, 120a, 120b, 120c, 120d for securing the roof file solar module to a roof structure. The fastening features 118a, 118b, 118c, 118d, 120a, 120b, 120c, 120d comprise screw holes 118a, 118b, 118c, 118d and screw slots 120a, 120b, 120c, 120d through which screws can be inserted to secure the rooftile solar module 102 to a roof. A first screw hole 118a and a second screw hole 118b are provided in a lower peripheral portion of the peripheral portion 112. A first screw slot 120a and a second screw slot 120b are provided in an upper peripheral portion of the peripheral portion 112. Each of the first and second screw holes 118a, 118b is aligned with the first screw slot 120a and the second screw slot 120b respectively, in a direction which is parallel with the central installation axis X. The first screw hole 118a and the first screw slot 120a are each spaced by a first predetermined distance from the central installation axis X in a direction which is perpendicular to the central installation axis X towards the first lateral edge 113a. The second screw hole 118b and the second screw slot 120b are each spaced by the first predetermined distance from the central installation axis X in a direction which is perpendicular to the central installation axis X towards the second lateral edge 113b. A third screw slot 120c and a fourth screw slot 120d are further provided in the upper peripheral portion of the peripheral portion 112. The third screw slot 120c is spaced from the central installation axis X by a second predetermined distance in a direction which is perpendicular to the central installation axis X towards the second lateral edge 113b. The fourth screw slot 120d is spaced from the central installation axis X by the second predetermined distance in a direction which is perpendicular to the central installation axis X towards the first lateral edge 113a. In the embodiment show, the second predetermined distance is equal to the half of the width of the roof tile solar module 102 less the first predetermined distance. The third screw slot 120c is therefore spaced half of the width of the roof tile solar module 102 from the first screw slot 120a in the direction of the second lateral edge 113b and the fourth screw slot 120d is spaced half of the width of the roof tile solar module 102 from the second screw slot 120b in the direction of the first lateral edge 113a. The first screw slot 120a, second screw slot 120b, third screw slot 120c and fourth screw slot 120d are provided with a respective thin membrane which occludes each slot 120a, 120b, 12c, 120d. Each membrane may be formed from the sheet moulding compound during moulding of the base layer 104. The membranes provide a fluid-tight seal which prevents fluid from passing through each slot 120a, 120b, 12c, 120d. Each membrane is configured to be pierced by a screw during installation of the roof tile solar module 102, as explained below. A third screw hole 118c and a fourth screw hole 118d are further provided in the upper peripheral portion of the peripheral portion 112. The third screw hole 118c is disposed between the first screw slot 120a and the fourth screw slot 120d. The fourth screw hole 118d is disposed between the third screw slot 120a and the third screw slot 120d. A locating element in the form of a batten lug 122 is provided on the underside of the base layer 104 along the top edge of the base layer 104 extending in the width-wise direction. The base layer 104 is provided with an alignment feature 124 positioned centrally proximate the top edge of the base layer 104 on the upper surface, and orientation features 126 (see Figure 2) positioned at either side of the base layer 104 proximate the top edge of the base layer 104 on the lower surface. The orientation features indicate the correct orientation of the rooftile solar module 102 for installation. A junction box 128 is also provided on the underside of the base layer 104 (see Figure 2). There are forty-two photovoltaic cells 106 arranged in a six-by-seven grid and electrically connected to the junction box 128. The photovoltaic solar cells 106 are disposed within the recess 110 and bonded to the base layer 104 by an adhesive 130. Each photovoltaic solar cell 106 is a conventional monocrystalline cell having an upper lightreceiving surface 106a through which light is received by the photovoltaic solar cell 106 for conversion into electrical energy. In the embodiment shown, each photovoltaic solar cell 106 is a mono crystalline cell made by YIXINGJS solar having the product reference JS156M5. Each photovoltaic solar cell 106 measures 156.75mm by 156.75mm and has a thickness of 200pm. Each photovoltaic solar cell 106 has a relative spectral response of at least 0.3 for wavelengths between 400nm and llOOnm. Each photovoltaic solar cell 106 provides a power output of at least 5W. The combined power output of the forty-eight photovoltaic solar cells 106 is not less than 240W. The adhesive 130 is a copolymer adhesive, such as ethylene vinyl acetate "EVA". Preferably, an adhesive is selected which has desirable properties, such as high light-transmissibility, temperature stability and resistance to UV degradation during operation, for use in a solar module. The polycarbonate layer 108 is made of a 2mm thick sheet of polycarbonate. The polycarbonate is configured to provide at least 80% transmission of electromagnetic radiation within the wavelength range 300nm to 2400nm, and specifically at least 80% transmission of light within the wavelength range 400nm to 780nm (typically classed as visible light radiation). The polycarbonate has a density of 1.2 g / cmA2 and so is lightweight compared with other materials having similar light transmissibility, such as glass. A 2mm thick sheet of polycarbonate has a weight off 2.4 kg / mA2. The polycarbonate has a Young's Modulus of 2.3 GPa (in accordance with ASTM D-638) and a Flex Modulus of 2.35 GPa (in accordance with ASTM D-790) and so is sufficiently rigid to be handled and provide structural support for the roof tile solar module 102, but is also able to flex to accommodate movement or expansion of the roof tile solar module 102 when in situ. The polycarbonate has an impact strength of 0.8KJ / m and so has sufficient impact strength to withstand impacts that can be expected during installation and subsequent operation of the roof tile solar module 102. Furthermore, the polycarbonate complies with international fire resistance standards B, si, dO in accordance with EN13501 and CC1 in accordance with ASTM D-635. The polycarbonate is resistant to UV degradation, for example, the polycarbonate may have less than 5% reduction in transmissibility following 100 hours of accelerated weathering equivalent to 1 year of actual outdoor exposure in warm climates. The polycarbonate is also resistant to chemicals and provides good thermal insulation and is easy to clean. The polycarbonate is thermally stable over a long period of time, for example 10 years, at temperatures between minus 50 degrees centigrade and 100 degrees centigrade. The polycarbonate can also withstand temperatures between minus 50 degrees centigrade and 120 degrees centigrade for relatively short periods of time, for example over periods less than 1 hour, such as periods less than 30 minutes, without significantly affecting its mechanical properties. The polycarbonate has a heat deflection temperature of 135 degrees centigrade (in accordance with ATSM D-648 with Load: 1.82 MPa) and a Vicat Softening Softening Temperature of 150 degrees centigrade (in accordance with D-1525 with Load: 1 kg). By way of example, a preferred polycarbonate is a flat solid polycarbonate sheet having a thickness of 2mm. The thickness of the polycarbonate sheet is selected to provide sufficient strength when combined with the base layer 104 and to provide adequate impact protection during normal use, without being unduly heavy. Use of polycarbonate helps provide a roof tile solar module which has a high strength-to-weight ratio compared with conventional solar modules. The polycarbonate layer 108 is disposed on the photovoltaic solar cell 106 such that it overlies the photovoltaic solar cell 106 within the recess 110. The polycarbonate layer 108 is bonded to the upper light-receiving surfaces 106a of the photovoltaic solar cells 106 by an adhesive 130 which is the same adhesive used to bond the photovoltaic solar cell 106 to the base layer 104. The polycarbonate layer 108 is also bonded at its peripheral edge directly to the base layer 104 by the adhesive 130 such that the photovoltaic solar cells 106 are encapsulated between the polycarbonate layer 108 and the base layer 104. Bonding the polycarbonate layer 108 directly to the base layer 104 about the periphery of each or all photovoltaic solar cells 106 hermetically seals the photovoltaic solar cells 106 between the polycarbonate layer 108 and the base layer 104. This prevents fluid ingress, such as ingress of air, vapour or water. The roof tile solar module 102 is therefore very durable. This is particularly beneficial where the polycarbonate layer 108 is dried to reduce water content during manufacture of the roof tile solar module 102, as described below, since it prevents the polycarbonate layer 108 from reabsorbing moisture through the surface of the polycarbonate layer 108 facing the solar cells 106 after manufacture. The water content of the polycarbonate layer 108 is therefore maintained below that which would result in out-gassing from the polycarbonate layer 108 at the interface between the polycarbonate layer 108 and the solar cells 106 during normal operation. Bubbles that would therefore otherwise be expected to form between the polycarbonate layer 108 and the solar cells 106 are therefore significantly reduces and preferably eliminated altogether. Figure 4, with reference to Figure 5, illustrates a method of manufacturing the roof tile solar module 102 shown in Figures 1 to 3. At Step 1002, a base layer 104 is arranged with recess 110 facing upwardly. At Step 1004, a first layer of adhesive 130a is laid within the recess 110. At Step 1006, photovoltaic solar cells 106 are then arranged on top of the first layer of adhesive 130a in a desired layout, for example a six-by-seven grid as shown in Figure 1, and electrically connected together (known as tabbing and stringing). The photovoltaic solar cells 106 are arranged such that is a small gap between the periphery of the arrangement of the photovoltaic solar cells 106 and peripheral rim 112 of the recess 110. At Step 1008, a second layer of adhesive 130b is laid over the photovoltaic solar cells 106 within the recess 110. The first layer of adhesive 130a and the second layer of adhesive 130b are formed from sheets of adhesive cut to substantially the same size as the recess 110. Each sheet has a thickness of 0.45mm. The first layer of adhesive 130a and the second layer of adhesive 130b may be continuous layers of adhesive or may be configured to bond only portions of each upper lightreceiving surface 106a of each photovoltaic solar cells 106. At Step 1010, a dry polycarbonate layer 108 having a water content which is not greater than a predetermined water content, for example a water content which is not greater than 0.05% is provided. At Step 2002, the polycarbonate layer 108 having a water content which is not greater than a predetermined water content is provided by drying the polycarbonate layer 108 in order to reduce the water content of the polycarbonate layer to an amount at which out-gassing (i.e. the escape of water as vapour from the polycarbonate) does not occur during normal ambient operating conditions of the roof tile solar module 102 to the extent that bubbles of gas form between the polycarbonate layer and the underlying photovoltaic solar cells 106, particularly to the degree that they would appreciably affect the integrity or operation of the roof tile solar module 102. For example, the polycarbonate layer 108 may be dried by heating a sheet of polycarbonate to a temperature which is not less than a predetermined drying temperature for a period which is not less than a predetermined drying period. This causes moisture within the polycarbonate sheet to be expelled from the polycarbonate sheet. In the embodiment shown, the predetermined drying temperature is not less than 100 degrees centigrade and not greater than 120 degrees. The predetermined drying period is not less than 0.5 hours, for example not less than 1 hour and preferably not less than 2 hours. Furthermore, the predetermined drying period is not greater than 48 hours, for example not greater than 8 hours, and preferably not greater than 4 hours. The amount of drying time required will depend on several parameters, such as the drying temperature and the surface area of the polycarbonate sheet, or sheets if multiple sheets are dried simultaneous, being dried. The drying process must, however, be sufficient to ensure that out-gassing does not occur during normal ambient operating conditions of the roof tile solar module 102 to the extent that bubbles of gas form between the polycarbonate layer and the underlying photovoltaic solar cells 106. Once dried, the polycarbonate sheet is allowed to cool, or actively cooled, in a low-humidity environment, such as a hermetically sealed chamber having a humidity which is suitable for maintaining the water content of the polycarbonate layer 108 at not greater than the predetermined amount. At Step 1012, the dried polycarbonate layer 108 is laid on top of the photovoltaic solar cells 106 within the recess 110. The polycarbonate layer 108 has a length and width which are slightly less, approximately 5mm less, than the length and width of the recess 110, respectively, such that a small gap is formed between the edge of the polycarbonate layer 108 and the peripheral rim 112 of the recess 110. The assembled layup is shown in Figure 5. At Step 1014, the assembled layup of the base layer 104, the first layer of adhesive 130a, photovoltaic solar cells 106, the second layer of adhesive 130b and the polycarbonate layer 108 is then heated to a temperature which is not less than a predetermined bonding temperature. In the embodiment shown, the predetermined bonding temperature is 135 degrees centigrade. The temperature is then maintained at 135 degrees centigrade for a predetermined bonding period of 15 minutes. This causes the first layer of adhesive 130a and the second layer of adhesive 130b to melt and pool within the recess 110. The recess 110 therefore retains the melted adhesive 130 and prevents escape. The layup is then allowed to cool, or is actively cooled, which sets (i.e. cures) the adhesive 130. This process is known as laminating. During the bonding process, the layup is held at a predetermined bonding pressure of 60kPa forthe predetermined bonding period in orderto ensure effective adhesion of the layers and the photovoltaic solar cells to each other. The pressure is applied using conventional techniques such as by covering the layup with a suitable membrane and then evacuating the space covered by the membrane in order to draw the membrane into contact with the layup and apply the pressure. In alternative embodiments, the predetermined bonding pressure may be not less than 5kPa, and preferably not less than 20kPa. It should be appreciated that the bonding process must heat the adhesive to a predetermined boding temperature at which cross-linking can occur and that the layup must then be held at or above the predetermined bonding temperature for a sufficient amount of time in order to allow a suitable amount of cross-linking to take place. A suitable amount of cross-linking is at least 70% cross-linking in order to ensure adequate bonding and optical properties. This may be done as a single step, as described, or separate steps, such as by heating the layup to the predetermined boding temperature and maintaining the layup at not less than the predetermined boding temperature for separate periods of time which together are not less than the predetermined bonding period, for example two steps which are 7.5 minutes in duration. The total time at which the layup is held at or above the predetermined boding temperature must not be less than the predetermined bonding period in order for effective cross-linking to occur. Once cooled, the adhesive 130 bonds the photovoltaic solar cells 106, or at least portions thereof, and the periphery of the polycarbonate layer 108 to the base layer 104. The adhesive 130 also bonds the polycarbonate layer 108 directly to the light-receiving surfaces 106a of the photovoltaic solar cells 106. The photovoltaic solar cells 106 are therefore secured directly to the base layer 104 and the polycarbonate layer 108 is secured directly to the photovoltaic solar cells 106 and the base layer 104. It will be appreciated that in alternative embodiments, only a portion the light-receiving surface 106a of each solar cell 106 may be bonded to the polycarbonate layer 108, although it is anticipated that preferred embodiments will bond the entire light-receiving surface 106a of each solar cell 106 surface to the polycarbonate layer 108. The adhesive 130 is sufficiently compliant to accommodate expansion of the polycarbonate layer 108 with respect to the base layer 104. Furthermore, the elasticity of the adhesive 130 increases with temperature and so, during use of the rooftile solar module 102, as the temperature of the roof tile solar module 102, and the amount of expansion of the polycarbonate layer 108 relative to the base layer 104 increases, the better the adhesive 130 is able to accommodate the expansion. Once cooled, the junction box 128 is secured to the base layer 104. The rooftile solar module 102 is then ready for installation. By providing a roof tile solar module 102 in which the polycarbonate layer 108 is dried to reduce water content during manufacture of the roof tile solar module 102, and then preventing moisture or vapour ingress to the region between the polycarbonate layer 108, prevents moisture from being reabsorbed through the surface of the polycarbonate layer 108 facing the solar cells 106 after manufacture and during subsequent operation. Bubbles that would therefore otherwise be expected to form between the polycarbonate layer 108 and the solar cells 106 as a consequence of out-gassing from the polycarbonate layer 108 are therefore significantly reduced and potentially eliminated altogether. In particular, outgassing post manufacture is avoided during normal operation for example in ambient temperature which does not exceed 50 degrees centigrade. This improves the integrity and / or operational performance of the roof tile solar module 102. In order to install the roof tile solar module 102, the roof tile solar module 102 is carried to a roof. The size and weight of the roof tile solar module 102 make the roof tile solar module 102 particularly suitable for manual installation since each can be readily lifted and carried by a single person. The batten lug 122 is hooked over a roof batten such that the rooftile solar module 102 hangs downwardly from the batten along the pitch of the roof and the light-receiving surfaces 106a of the photovoltaic solar cells 106 face upwardly. The male interlocking feature 114 and / or the female interlocking feature 116 is brought into engagement with a respective female interlocking feature 116 and / or male interlocking feature 114 of an adjacent roof tile module already in situ to join the adjacent roof tile solar modules 102 together. The roof tile solar module 102 is then secured to the batten using respective screws passing through the third screw hole 118c and a fourth screw hole 118d into the batten. With reference to Figure 6, an upper roof tile solar module 102 may be placed over two adjacent lower rooftile solar modules 102 such that the alignment feature 124 is aligned with the join between the adjacent lower rooftile solar modules 102. The upper rooftile solar module 102 is arranged such that the lower peripheral portion of the upper roof tile solar module 102 overlays the upper peripheral portions of the lower roof tile module, as shown in Figure 6. The first screw hole 118a is aligned with the third screw slot 120c of a lower roof tile solar module 102 on the left of the lower adjacent roof tile solar modules 102 and the second screw hole 118b is aligned with the fourth screw slot 120d of a lower roof tile solar module 102 on the right of the lower adjacent roof tile solar modules 102. The slots 120a, 120b, 120c, 120d allow for upper and lower rooftile solar modules 102 to be overlapped by varying amounts depending on the pitch of a roof on which they are installed. For example, if the roof tile solar modules 102 are installed on a roof with a relatively small pitch angle, the roof tile solar modules 102 would be secured by screws passing though the lower ends of the slots 120a, 120b, 120c, 120d in order to provide maximum amount of overlap. Conversely, if the rooftile solar modules 102 are installed on a roof with a relatively large pitch angle (or even vertically as a facade), the roof tile solar modules 102 would be secured by screws passing though the upper ends of the slots 120a, 120b, 120c, 120d in order to provide minimum amount of overlap. The upper roof tile solar module 102 is then secured to an underlying batten using a screw passing through the first screw hole 118a of the upper roof tile solar module 102 and the third screw slot 120c of the lower roof tile solar module 102 on the left, and also using a screw passing through the second screw hole 118b of the upper roof tile solar module 102 and the fourth screw slot 120d of the lower rooftile solar module 102 on the right. The screws each pierce the respective membranes occluding each of the slots 120c, 120d. The remaining unpunctured portion of each membrane provides a seal that prevents water from passing through the slots 120c, 120d and so prevents water ingress between the overlapping rooftile solar modules 102. The upper roof tile module 102 is further secured to a further batten using screws passing through the third screw hole 118c and the further screw hole 118d, respectively. In this manner, the roof tile solar modules 102 can be fixed in a traditional 'brick-bond' arrangement. It will, however, be appreciated that this is just one example of how the roof tile solar modules 102 may be arranged. The roof tile solar modules 102 may, for example, be arranged in a grid pattern as shown in Figure 7 in which the respective the first and second screw slots 120a, 120b of an lower roof tile solar module 102 are aligned with the first and second screw holes 118a, 118b of an upper roof tile solar module 102. The roof tile modules may be used as an alternative to traditional roof coverings (e.g. tile and slate) for roofs having not less than 15 degree pitch and also as a vertical covering, such as a facade. During installation, each junction box 128 is electrically connected to either an adjacent roof tile module or a central connector. In an alternative embodiment, the polycarbonate layer may be replaced by a glass layer. With such an embodiment, the method of manufacturing the solar module remains substantially the same, however, the predetermined bonding temperature is 147 degrees centigrade. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for sake of clarity. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims are generally intended as "open" terms (e.g., the term "including" or "comprising"should be interpreted as "including but not limited to," the term "having"should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and / or "an"should be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). It will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope being indicated by the following claims. 03 07 25

Claims

1. A roof tile solar module comprising:a base layer having at least two fastening features for securing the roof tile solar 5 module to a roof structure;at least one solar cell having a light-receiving surface, the at least one solar cell is disposed overlying the base layer and arranged such that the light-receiving surface faces away from the base layer, anda protective layer having a transparent portion, the protective layer being disposed 10 overlying the at least one solar cell and the base layer such that the at least one solar cellis disposed between the transparent portion of the protective layer and the base layer, wherein the base layer has a peripheral portion that extends around a periphery ofthe at least one solar cell and the protective layer is joined to the peripheral portion such that the at least one solar cell is encapsulated between the transparent portion of the15 protective layer and the base layer,wherein the at least two fastening features are provided on the peripheral portion of the base layer,wherein the peripheral portion comprises an upper peripheral portion which defines an upper edge of the roof tile solar module and a lower peripheral portion which defines20 a lower edge of the roof tile solar module, the upper peripheral portion has a first fastening feature in the form of a first aperture through the upper peripheral portion and the lower peripheral portion has a second fastening feature in the form of a second aperture through the lower peripheral portion,wherein the rooftile solar module has a central installation axis which extends parallel25 to the base layer and perpendicular to a horizontal direction when the roof tile solar module is secured to a roof structure which extends horizontally,wherein the first fastening feature comprises an elongate slot arranged to extend in a direction which is parallel with the central installation axis.03 07 252. The rooftile solar module of claim 1, wherein the second fastening feature is spaced from the central installation axis by a first offset distance and the first fastening feature is spaced from the central installation axis by a second offset distance which is different5 from the first offset difference such that the first fastening feature and the second fastening feature are spaced from each other and the central installation axis.

3. The rooftile solar module of claim 2, wherein the second distance is equal to the half of a width of the roof tile solar module less the first distance.

104. The roof tile solar module of claim 1, wherein the first fastening feature is spaced from the central installation axis by a first offset distance and the second fastening feature is spaced from the central installation axis by the first offset distance such that the first fastening feature and the second fastening feature are aligned in a direction which is15 parallel to the central installation axis.

5. The roof tile solar module of any one of the preceding claims, wherein the elongate slot is provided with a membrane which occludes the slot.

206. The rooftile solar module of any one of the preceding claims, wherein the integrated roof tile solar module has a first lateral edge and a second lateral edge.

7. The roof tile solar module of claim 6 wherein the first lateral edge comprises a first25 interlocking feature and the second lateral edge comprises a second interlocking feature configured to interlock with a first interlocking feature of an adjacent roof tile solar module having corresponding first and second interlocking features.

8. The roof tile solar module of any one of the preceding claims, wherein the roof tile solar 30 module is substantially rectangular.

9. The roof tile solar module of any one of the preceding claims, wherein the roof tile solar module has a central alignment feature.03 07 2510. The rooftile solar module of any one of the preceding claims, wherein a locating element is provided at an underside of the base layer, the locating element is configured to engage with the roof structure such that the roof tile module is suspended by the locating 5 element.

11. The rooftile solar module of claim 10, wherein the locating element is a batten lug.10 12. The roof tile solar module of any one of the preceding claims, wherein the solar modulecomprises a plurality of solar cells.

13. The roof tile solar module of any one of the preceding claims, wherein the base layer has a recess configured to receive the at least one solar cell.1514. The roof tile solar module of any one of the preceding claims, wherein the base layer is formed from a unsaturated polyester resin containing mineral fillers and reinforced with glass fibre.20 15. The rooftile solar module of any one of the preceding claims, wherein the protective layeris bonded to at least a portion of the peripheral portion by an adhesive.

16. The rooftile solar module of any one of the preceding claims, wherein the protective layer comprises a polycarbonate layer or glass.2517. The rooftile solar module of any one of the preceding claims, wherein the protective layer is bonded to the least one solar cell by an adhesive.

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