Title of Invention

AN IMPROVED LOW-EMBODIED ENERGY BUILDING INTEGRATED PHOTOVOLTAIC ROOF SYSTEM

Abstract

The invention relates to a low-embodied energy building integrated photovoltaic (BIPV) roof system comprising a plurality of crystalline silicon solar cells connected in series to form a string, the string has a high transmissivity glass superstrate and a Tedlar back sheet. This is encapsulated under vacuum to form a laminate; a plurality of laminates each being fixedly disposed on a modular frame such that each modular frame gets interlocked with the succeeding and the preceding modular frame and aligned into the succeeding laminate"s frame; at least one clamping means provided at each of the interlaminate joint; a roof rafter comprising a beam section capable of holding the plurality of laminates according to the span and load, the roof rafter being provided with inbuilt draining means and an anchoring means; and an inter-overlapping mechanism provided at the joints of the frame laminates with each laminate butting onto the rubber gasket lining of the succeeding laminate.

Full Text

2 FIELD OF INVENTION The present invention relates to a low-embodied energy building integrated photovoltaic roof system. The invention also relates to a method for manufacturing a low-embodied energy building integrated photovoltaic (BIPV) roof system. BACKGROUND OF INVENTION BIPV roofs employ double laminated PV modules affixed onto roof structural grids typically made from aluminium/special alloys. In these roof structures, the roof and often the facade/walls, also are designed to incorporate a structural grid pattern to match the shape and aesthetics of the building. Accordingly, the PV modules are sized, segregated and disposed such as to co-ordinate with the roof grid pattern. The BIPV roofs and facades are also constructed as a double-layer structure having enclosed air gaps which act as an insulation for the building inner space from the atmosphere outside with a view to maintaining necessary temperature and humidity for occupant comfort. The appropriate selection and integration of the PV modules, as the roof is further important to ensure that the roof is water proof. Metal profiles provide seating for the BIPV laminates, and in addition specially chosen adhesives, synthetic rubber gaskets including room temperature vulcanizing (RTV) sealants are employed to obtain water - tight roof joints to avoid rain water ingress. 3 For the conventional roof BIPV systems adaptable in tropical environments, it is essential that the structure be designed to provide thermal comfort in addition to providing a rain-resistant envelope for the building. Typically the Indian sub- continent climate experiences high diurnal temperature variation - from nearly sub-zero temperatures in winter to around 45°C in summer; with variation in humidity ranging from 30% to 100% RH. Moreover, the effect of monsoon rains, on an average, lasting 4 to 5 months annually needs to be addressed in the design. The effectiveness of the internationally available gaskets and sealants for the BIPV applications over a longer period of time in tropical climate such as India is yet to be evaluated. A disadvantage of the prior art is the imminent climate change due to the extensive usage of high energy intensive anodized aluminium (alloy) extrusions. Another disadvantage is the high cost of input metal and glass content (embodied energy involved in the manufacturing, extrusion, and anodizing) which is also indirectly responsible for contribution to global warming. Thus, a low-energy intensive structure with minimum metal and glass would be extremely desirable from the environmental and embodied energy point of view. This is expected to open an entirely new approach to BIPV design and implementation. The hitherto perceived technical compulsion to employ double-laminated BIPV modules, aluminium intensive mounting frames and known weather sealants in tropical regions, hinders the popularizing of BIPV power systems in tropical regions. Accordingly, a configuration in which standard single-laminate PV (as compared to double-laminate PV) modules are integrated as a leak-resistant roof 4 in conjunction with a conventional tropical roof support structure would help to eliminate the disadvantages of the prior art. US Application no. 10/240,875 discloses a method of framing system of solar panels by employing PV solar roof tile. This paper titled "Framing system for Solar panel" describes extruded elongated elements wherein the frame elements are adapted to be interconnected at respective corners of the frame system at roof-lateral panel joints along the slope of the roof. US Application no. 20040187909 titled "Solar cell unit and method for mounting the solar cell unit on roof" discloses a solar cell unit comprising a solar cell module, a module frame provided around the solar cell module as supporting the solar cell module for mounting the solar cell unit on an oblique roof; and a drain channel provided along an edge of the module frame outside the module frame. The rainwater intruding into the gaps between adjacent solar cell units is prevented from reaching the base surface of roof, so that corrosion of the base surface of the roof can be prevented. Conventional BIPV structures and architecture employ double-laminate solar PV panels which are inserted into a ready-made roof grid mostly composed of anodized extruded aluminium (alloy) profiles. Each panel is locked and sealed into position using metal anchors and rubber-based gaskets and sealants to prevent rain water ingress. Available frames do not facilitate a water-resistant joint between adjacent PV modules for the purpose of constructing a weather-proof ceiling/roof, and the frames do not provide interlocking features for mechanical rigidity. 5 All such prior art are not suitable for applications in tropical countries, and they entail high cost, lower operational life, and are non-friendly to environment. OBJECT OF INVENTION It is therefore an object of the invention to propose a low-embodied energy building integrated photovoltaic roof system which enables direct usage of conventional single-glass PV laminates in BIPV roof. Another object of the invention is to propose a low-embodied energy building integrated photovoltaic roof system which decreases dependence on energy- intensive building components such as, extruded and anodized aluminium profiles and glass laminate. A further object of the invention is to propose a low-embodied energy building integrated photovoltaic roof system which provides an easy mechanism, with option of internal and/or external clamping which eases the tropical weather concerns with respect to rain water ingress and serviceability. A still further object of the invention is to propose a method for manufacturing a low-embodied energy building integrated photovoltaic (BIPV) roof system. SUMMARY OF INVENTION In the present invention, a technical solution is devised to obtain a ready-to-use conventional single-glass laminate PV module by employing available aluminium profiles. A clamping mechanism is also developed to obtain rain water resistant 6 joints between the adjacent modules of the BIPV roof. The invention also features a method to address water-ingress which may arise from intense monsoon conditions. The mountability and rain water resistance test of the BIPV modules has been carried out including the testing of their outdoor reliability on a Veal' roof grid. By modifying the conventional single-laminate PV module [Figure 1(a)] a newly designed frame profile and a low - embodied energy mounting system has been evolved to establish a BIPV roof system for tropical weather conditions. By subjecting the installed BIPV roof to simulated rain water (heavy downpour) test, it was determined that the optimal design for BIPV modules combines the features of an interlocking cum-overlapping (henceforth referred to as inter- overlapping) mechanism of single-laminated PV frames and a water draining method to obtain a leak-resistant joint. The invention enables the BIPV roof to withstand severe tropical weather conditions with reduced dependence on adhesive/sealant-based jointing. The emphasis here is on the design of interlocking water-tight (weather proof) mechanism of laminate frames. In contrast to the standard internationally adopted procedure of sealing and clamping the discussed inter-overlapping configuration enhances easy drainage of rain water by normal gradient flow. Further, while minimizing the dependency on the excessive use of gasket and sealants, the design integrates single-glass laminates which are conventionally employed for roof top/ground mounted systems. 7 The invention further provides a method for fabricating a low-embodied energy building integrated photovoltaic (BIPV) roof system. The invention also encompasses a low-embodied energy approach by using minimum metal and glass. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 (a) and Figure 1 (b) respectively show conventional single laminate PV module with aluminium extruded frame and Single laminated BIPV module according to the invention Figure 2 is a pictorial view of a BIPV module inter-overlapping arrangement according to the invention Figure 3 is a pictorial representation of a clamping mechanism to achieve rain water - resistant mounting on roof rafter incorporating drain mechanism according to the invention Figure 4 shows a BIPV roofing system according to the invention Figure 5 shows the GI rafter and gutter cross section of the BIPV roofing system of the invention. 8 DETAILED DESCRIPTION OF INVENTION According to the invention a plurality of single laminate PV modules are provided with anodized aluminium extruded frames which enable their rigid assembly and mountability as a variety of building roof structure. The scope of fabrication comprises of: - fabrication of BIPV laminates, from single-glass laminated solar cells with electrical power rating typically, 150 Wp (1594mm x 800mm) confirming to international standards; - treatment of vulnerabilities with respect to rainwater penetrating the roof either through joints perpendicular to the slope of the roof and/or at the joints along the slope of the roof; - providing a plurality of major rain water channels along the slope of the roof and a several minor water-ingress channels at the joints perpendicular to the roof slope, the minor water-ingress channel acting as a pressure release channel to drain out any incidental water seeping into inter-overlapping frame joints perpendicular to the roof slope; - providing inter - overlapping mechanism with aluminium extruded frames; - selecting and providing gaskets for major and minor gutter, and - providing a clamping mechanism. 9 Formation of rafters for roof grid To facilitate single-glass PV laminate to act as the roof, the support rafters are placed longitudinally (defining the roof slope). The hollow rafters are made of 2 mm GI sheets internally braced with mild steel angle sections and steel ribs placed at appropriate locations within the cross-section. The rafters are anchored at either ends to the load bearing walls of the building with mild steel inverted 'IT rods, grouted using proprietary adhesives. The slope provided is close to the latitude of the location. The configuration of the rafter is based on minimum- defection criteria for the roof-span to withstand dead loads of PV laminates and live loads of servicing and wind. Extreme wind gush loads are also factored in while designing the rafter. The rafter beams are given treatment with rust- resistant coatings. Formation of a leak-resistant, inter-overlapping arrangement Inter-overlapping mechanism as invented is depicted in Figure 2 and Figure 3. The interfacing joint of two laminate frames may have a hair-line gap which might result in water ingress. To ensure a water resistant joint, the laminate is designed to butt onto the rubber gasket lining the subsequent laminate's frame. Also, the inter-overlapping joint thus formed comprises of a water-ingress channel/drain to eliminate incidental water ingress. The mechanical attachment has a gasket mechanism to 10 prevent water splash and pressure ingress below the panel leading to leakage under severe flow conditions. EXAMPLES/PREFERRED EMBODIMENT A single-glass PV laminate as per the present invention consists of: a. Crystalline silicon solar cells connected in series called the string. b. The string has a high transmissivity glass superstrate. The laminate is formed with encapsulating material and Tedlar back sheet (substrate) by vacuum lamination. c. He electrical output of the laminate is terminated in a weather proof junction box. d. The inventive laminate may have rectangular shape [ref Figure 1(b)]. The module frame of the laminate interlocks with the succeeding and the preceding laminates. The top glass of the preceding laminate comfortably fits and align itself into the succeeding laminate's frame. e. At any inter-laminate joint, the frames are provided with a clamping mechanism which help in alignment and holding to the main support member viz. the roof rafter. 11 f. The inventive roof rafter consist of beam section which is designed for the span and loads considered. The rafter itself incorporates draining mechanism, (ref Figure 3). g. The inventive roof rafter has an anchoring mechanism to interlock with the laminate frame clamps. h. At the same time, during rains, if water settles and seeps through the joint the same is collected in water-ingress/pressure release channel leading to the major rainwater channel, (ref Figure 2) i. The inventive laminate frame section, at its joint, is provided with a inter- overlapping mechanism (ref Figure 2). 12 WE CLAIM 1. A low-embodied energy building integrated photovoltaic roof system comprising: - a plurality of crystalline silicon solar cells connected in series to form a string, the string has a high transmissivity glass superstate and a Tedlar back sheet. This is encapsulated under vacuum to form a laminate; - a plurality of laminates each being fixedly disposed on a modular frame such that each modular frame gets interlocked with the succeeding and the preceding modular frame and aligned into the succeeding laminate's frame; - at least one clamping means provided at each of the interlaminate joint; - a roof rafter comprising a beam section capable of holding the plurality of laminates according to the span and load, the roof rafter being provided with in - built draining means and an anchoring means; and - an inter-overlapping mechanism provided at the joints of the framed laminates with each laminate butting onto the rubber gasket lining of the succeeding laminate; and 13 - a mechanical attachment having a gasket to prevent water splash and pressure ingress below the joints leading to leakage under severe flow conditions. 2. The system as claimed in claim 1, wherein the draining means comprises a plurality of major rain-water channels and a plurality of minor water- ingress channels. 3. The system as claimed in claim 1, wherein the interlocking means comprises aluminium extruded frames. 4. A method for manufacturing a low-embodied energy building integrated photovoltaic (BIPV) roof system comprising the steps of: - fabricating a plurality of BIPV-laminates from a plurality of single- glass laminated solar cells connected in series - fixing each of the BIPV-laminated on a modular frame, and joining the modules over a roof rafter; - providing a plurality of major rain water channels and minor-water ingress channels respectively along the slope of roof rafter and at the joints perpendicular to the roof slope; - providing interlocking means comprising aluminium extruded frames between the modular joints; 14 - configuring gasket profiles for major and minor gutters of the roof rafter; and - providing at least one clamping means disposable at each of the plurality of joints. 5. A low-embodied energy building integrated photovoltaic roof system (BIPV) comprising as substantially described and illustrated herein with reference to the accompanying drawings. 6. A method for manufacturing a low-embodied energy building integrated photovoltaic (BIPV) roof system comprising as substantially described and illustrated herein with reference to the accompanying drawings. Dated this 4th Day of JANUARY, 2008 The invention relates to a low-embodied energy building integrated photovoltaic (BIPV) roof system comprising a plurality of crystalline silicon solar cells connected in series to form a string, the string has a high transmissivity glass superstrate and a Tedlar back sheet. This is encapsulated under vacuum to form a laminate; a plurality of laminates each being fixedly disposed on a modular frame such that each modular frame gets interlocked with the succeeding and the preceding modular frame and aligned into the succeeding laminate's frame; at least one clamping means provided at each of the interlaminate joint; a roof rafter comprising a beam section capable of holding the plurality of laminates according to the span and load, the roof rafter being provided with inbuilt draining means and an anchoring means; and an inter-overlapping mechanism provided at the joints of the frame laminates with each laminate butting onto the rubber gasket lining of the succeeding laminate.

Documents:

00032-kol-2008-abstract.pdf

00032-kol-2008-claims.pdf

00032-kol-2008-correspondence others.pdf

00032-kol-2008-description complete.pdf

00032-kol-2008-drawings.pdf

00032-kol-2008-form 1.pdf

00032-kol-2008-form 2.pdf

00032-kol-2008-form 3.pdf

00032-kol-2008-gpa.pdf

32-KOL-2008-(14-08-2014)-FORM-13.pdf

32-KOL-2008-(16-01-2012)-CORRESPONDENCE.pdf

32-KOL-2008-(16-01-2012)-FORM 13.pdf

32-KOL-2008-(16-01-2012)-FORM 2.pdf

32-KOL-2008-(16-01-2012)-FORM 3.pdf

32-KOL-2008-(16-01-2012)-OTHERS.pdf

32-KOL-2008-(18-10-2012)-ABSTRACT-1.pdf

32-KOL-2008-(18-10-2012)-ABSTRACT.pdf

32-KOL-2008-(18-10-2012)-ANNEXURE TO FORM 3-1.pdf

32-KOL-2008-(18-10-2012)-ANNEXURE TO FORM 3.pdf

32-KOL-2008-(18-10-2012)-CLAIMS-1.pdf

32-KOL-2008-(18-10-2012)-CLAIMS.pdf

32-KOL-2008-(18-10-2012)-CORRESPONDENCE-1.pdf

32-KOL-2008-(18-10-2012)-CORRESPONDENCE.pdf

32-KOL-2008-(18-10-2012)-DESCRIPTION (COMPLETE).pdf

32-KOL-2008-(18-10-2012)-DRAWINGS-1.pdf

32-KOL-2008-(18-10-2012)-DRAWINGS.pdf

32-KOL-2008-(18-10-2012)-FORM-1-1.pdf

32-KOL-2008-(18-10-2012)-FORM-1.pdf

32-KOL-2008-(18-10-2012)-FORM-2-1.pdf

32-KOL-2008-(18-10-2012)-FORM-2.pdf

32-KOL-2008-(18-10-2012)-OTHERS-1.pdf

32-KOL-2008-(18-10-2012)-OTHERS.pdf

32-KOL-2008-(31-10-2012-RI)-CORRESPONDENCE-1.1.pdf

32-KOL-2008-(31-10-2012-RI)-CORRESPONDENCE.pdf

32-KOL-2008-(31-10-2012-RI)-PA-1.1.pdf

32-KOL-2008-(31-10-2012-RI)-PA.pdf

32-kol-2008-form 18.pdf

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