-1 SOLAR CELL PANEL Technical Field 5 This invention is directed to a solar cell panel, and a method of installing the panel. The invention has particular but not exclusive application to a solar cell panel on a corrugated roof for residential steel roofing and as such in a further aspect the invention is directed to a roofing assembly. 10 Background There is a rapidly escalating interest in sources of renewable energy including solar energy. Solar cells use a free source of energy for conversion to electricity and the current most popular commercial systems, which are based on crystalline silicon encased in glass, are very durable and require little or no maintenance. 15 However, the disadvantages of these solar cells are that they are very expensive leading to uneconomical payback periods necessitating subsidies to make them commercially viable. They are also not particularly efficient solar energy converters and can be bulky and heavy as well as visually obtrusive. Thin film solar cells are rapidly emerging that 20 use much lower cost materials often produced by roll to roll processes as plastic based composites. Whilst these thin film solar cells use much lower material costs, there is a continuing need to be able to develop solar collector systems using such thin film solar cells that are inexpensive to manufacture, install, and maintain to provide a viable commercial product. 25 Summary of Invention According to a first aspect, there is provided a solar collector panel comprising a substrate formed from sheet material and a thin film solar cell layer affixed to said substrate. 30 In one form, the solar cell layer terminates inboard from one or more edges of the substrate so as to provide one or more exposed margins that extends between an edge of the solar cell layer and the one or more edges of the substrate. In one form, the panel is arranged to be fixed to an underlying structure at the one or more exposed margins and 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -2 in a particular form, the panel is arranged to be fixed to an underlying structure by mechanical fasteners that are fixed at one or more of the exposed margins. In one form, the panel includes a opposite ends and opposite sides and wherein the 5 exposed margins are disposed along at least the opposite sides of the panel. In a particular form the panel is quadrilateral. In one form, the panel also has an exposed margin disposed along one end of the panel and in a particular form electrical connectors arranged to connect the solar cell layer to an electrical circuit are disposed at or adjacent one end of the panel. 10 In one form the panel may be profiled to at least partially conform to a profiled underlying structure. Such a structure may be a roof profile as will be described in more detail below. In one form the portion of the panel containing the thin film solar cell layer is generally flat and extends in a nominal plane of the panel and at least one of 15 the exposed margins is turned out of a nominal plane of the panel. In a particular form, the substrate is formed from sheet metal such as sheet steel that incorporates a corrosion resistant metal coating and optionally a decorative paint finish. 20 The solar collector panel in a least in one embodiment described above is ideally suited to be used in a roof assembly where the panel is affixed to a conventional roof such as a corrugated metal roof In that application of the panel overlays the corrugations and the exposed margins may be turned in to locate within valleys of the corrugations. The panel is fixed to the roof by fasteners that locate through the exposed margins and the 25 electrical connections of the panel may be concealed under the ridge capping of the roof. To aid in the overall simplicity of the system, the fasteners used may be the existing fasteners used in the roof. Further, the electrical connections may be connected under existing ridge capping. This reduces the number of components required to install the panel in place. 30 According to a further aspect, there is provided a roof assembly comprising; roof cladding formed from metal sheet profiled to include linear stiffening formations; and at 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -3 least one solar collector panel disposed on the roof cladding and overlying one or more of the profiled stiffening formations, the solar collector panel comprising a substrate formed from sheet material and a thin film solar cell layer affixed to said substrate. 5 In yet a further aspect, there is provided a method of fitting a solar collector to a roof incorporating roof cladding formed from metal sheet profiled to include linear stiffening formations, the method comprising the steps of: providing a solar collector panel comprising a substrate formed from sheet material and a thin film solar cell layer disposed on said substrate; locating the panel on the roof cladding so that it is disposed 10 over one or more of the stiffening formations; and securing the solar collector panel to said roof cladding. The solar collector panel when installed in a roofing assembly as described has the following advantages: 15 Raw Material Costs- the panel uses a thin film as the solar cell component. Both the film and the steel substrate cost significantly less than a thick crystalline silicon cell encased in a glass and aluminium box. The panel has been designed to be easily attached (and detached) to a corrugated steel roof, a very popular and relatively 20 inexpensive roof profile as compared to other wide pan profiles. Manufacturing Cost- the panel has been designed to readily allow solar film to be laminated to the substrate, either on a coil coating line while it is still in flat strip, or in the factory or on the building site after forming. This thin film lamination process is 25 much simpler than the multistage assembly of a cell in a glass box. In addition, the ability to apply the film to the substrate either during initial manufacture or subsequently enables some flexibility in manufacturing e.g. it is possible to minimise the cost of laminating by high speed coil coating manufacturing or, alternatively, minimise inventory costs by holding a stock of film at the profiler separate to the panel 30 and making to order. 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -4 Ease of Installation and Maintenance- the panel can be very easily attached to the roof and detached from it by means of a few Tec screws or rivets and by plug-in electrical connections from the solar film to the central wiring. The design of the panel allows the use of the same fasteners that are used to hold the corrugated roofing, although one set 5 of valley fasteners is recommended to hold the centre of the roofing below the flashing. The solar collector panel also offers the following benefits in terms of aesthetics, durability and versatility. 10 Aesthetics- The solar panel may be an integrated part of the roofing as much as any other flashing components on the building. It is possible to colour co-ordinate the panel to the roof colour. Durability- By making the solar collector panel an integrated but separate component to 15 the roof itself, it makes it possible to safeguard the weatherproofness and integrity of both the roof and the cell. If the solar cell needs maintenance it can be readily detached without compromising the roof and similarly, if the roof beneath the cell needs maintenance this can be easily accessed. 20 Versatility- By making the panel akin to a flashing component rather than a roofing profile, the solar flashing can be used in various ways. It can be part of the initial installation but it can also be retrofitted both to steel roofs and possibly to other roofing materials as well. In slightly different form, it can also be used as roof capping or barge flashings for smaller installations such as garages. 25 Brief Description of the Drawings It is convenient to hereinafter describe an embodiment of the present invention with reference to the accompanying drawings. The particularity of the drawings and the related description is to understood as not superseding the generality of the preceding 30 broad description of the invention. 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -5 In the drawings: Fig. 1 is a perspective view of a solar collector panel according to an embodiment of the invention; Fig. 2 is schematic view of a roof assembly including a corrugated roof and solar 5 collector panel of Fig. 1; Fig. 3 is an end view the roof assembly of Fig. 2 showing the fixing details; and Fig. 4 is a sectional view showing the connection detail of the electrical connectors of solar connecting panel to central wiring of the dwelling. 10 Detailed Description of Embodiments Turning to Fig. 1, a solar collector panel 10 is disclosed that comprises a substrate 12, which in the illustrated form is made from sheet steel, and a thin film solar cell layer 14 affixed to a mid region of the metal substrate 12. In the illustrated form, the substrate is formed from sheet strip that has a corrosion resistant metal coating (such as an Al-Zn 15 alloy coating) and a decorative paint finish. A suitable metal coated steel strip is sold by the applicant under the trade mark COLORBOND*. A suitable thin film solar cell layer is supplied by United Solar Ovonic LLC which manufactures a thin-film amorphorous-silicon photovoltaics (PV) under the trade mark UNI-SOLAR*. Such thin filmed solar cells are able to be laminated, or adhesively bonded under ambient 20 temperatures to the metal substrate. The solar cell layer is applied to a mid region of the substrate 12 so as to provide opposite end exposed margins (16, 18) of the substrate 12 and opposite side exposed margins (20, 22). The edges of the solar cell layer 14 are typically sealed to the 25 substrate 12 using a sealant to resist delamination of the thin film layer and to further inhibit any water penetration between the panel layers. Electrical connectors 24 are also provided adjacent one end margin 16. Whilst not shown, these connectors extend from an underside of the thin film solar cell layer 30 through apertures formed in the substrate 12. These connectors are arranged to be connected to the wiring of the dwelling where the panel is installed as will be discussed in more detail below. 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -6 The mid region of the panel 10 is flat whilst the side exposed margins 20, 24 are turned out of the plane of the majority of the panel. This is designed to conform these side margins to extend into respective valleys in a corrugated roof as will be described 5 below. In the illustrated form, the included angle formed at these side margins is in the order of 1500. As illustrated in Figs. 2 to 4, the panel 10 is suited to be fixed to a corrugated steel roof 100 formed from lapping corrugated sheets 102. A feature of the installation is that the 10 top edge 16 of the panel is located under the existing ridge capping 104 of the roof so that the electrical connectors 24, and other ancillary connectors such earth cables 26 and isolation switch box 28 can be concealed from view (see Fig. 4). Also the panel 10 is fixed to the roof using standard Tec screws 50 that extend through the side margins 20, 22of the panel 10. Also as both the substrate and the roofing is made from a similar 15 material (being a Zn -Al alloy coated metal strip with a paint finish) the colours of the substrate and the roof can be matched. Furthermore, as the panel 10 extends across the corrugations, channels 54 are formed between the underside of the panel 10 and the valleys in the corrugated roof 100 which 20 allow for air flow between the roof and the panel. This aids in reducing temperature rise in the panel under operation which is beneficial as an increase in temperature of the solar cell film layer can reduce the efficiency of the solar cell to produce electricity. The installation of a series of eight solar collector panels 10 (six of which are shown in 25 Fig. 2) may be undertaken as follows: The first step undertaken was to measure and mark the location of all the panels on the steel roof with a non-carbon marker to minimise the chance of dissimilar material corrosion. 30 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -7 The second step was to remove all ridge screws within the flashing areas and simultaneously replace the middle ridge fasteners 52 into the adjacent valleys (as best shown in Fig. 3). 5 The third step was to remove the ridge capping by taking out the ridge screws then breaking the ridge/hip joints, which were riveted and siliconed together. The ridge capping was put aside to allow the location of the solar cell panels under the edge of the ridge capping. Note: Care must be taken not to position the solar cell panels where ridge capping fasteners are likely to penetrate the solar cells when the ridge capping is re 10 applied. The fourth step was to lift the solar cell panels onto the roof and fully fix all eight solar cell modules in place starting at one end and working through until the eighth panel was fixed in place. 15 Step 5 was to connect 16mm 2 earthing cables between the flashings, and a similar earth cable from the flashings to the switchboard for lightening protection. Step 6 was to fix the solar cell module cables firmly in place along the ridge to protect 20 them against wear due to movement. Use of flexible conduit was made to protect the solar cell panel cables against the sharp ridge edges of the corrugated steel. Step 7 was to connect cables from each end of the solar cell panel string and the string isolation switch box which was fixed and weather sealed to the roof to reduce the risk 25 of electric shock. At this stage there is no voltage or circuit present at the string isolator as the solar cell modules have not been connected together and can be worked on quite safely. Wiring from the string isolation box then needs to be dropped into the roof cavity for later running and connection to the inverter. 30 Step 8 was to connect each of the solar cell panels together. Note: The connection of the solar cell panels is left last to reduce the risk of electric shock. 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -8 Step 9 was to check the insulation resistance of the solar cell modules to earth. Note: This is to determine if any damage was incurred during installation so that the module can be replaced before the ridge capping is fitted. 5 Before the ridge capping was re-applied the opaque coverings over the solar cell layers 30 (Fig. 4) were removed and discarded. These coverings are used to reduce glare when installing the panels. Then the open circuit voltage of the cells was measured to ensure that the modules were effectively connected together, operational and below the maximum input voltage level of the inverter. 10 Step 11 -the ridge capping is re-applied preferably with at least one fastening through the exposed margin of each solar cell panel. The ridge joints are also sealed and re riveted. It is noted that the fixture of cell cables on the roof ridge in this instance was facilitated by the availability of a timber ridge board to which cables were fixed by 15 nailed on cable clips. Most residential constructions in recent years have been done with pre-fabricated trusses which will necessitate a different approach to cable restraint. Accordingly, a solar collector panel is provided which is inexpensive to manufacture and easy to install and maintain. The panel uses existing fixing techniques to secure the 20 panel to the roof and wiring is able to be concealed under existing ridge capping. By using a metal sheet substrate in the panel it can be easily colour matched to the roof and profiled along at least its margins to appear an integrated component of the roof similar to conventional flashing. 25 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 30 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15 -9 It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention. 5 6580566_1 (GHMatters) P77802.AU.2 JASMINS 11/06/15