Lightweight, self-ballasting photovoltaic roofing assembly

Abstract

A photovoltaic roofing assembly comprises a roofing membrane (102), a plurality of photovoltaic modules (104, 106, 108) disposed as a layer on top of the roofing membrane (102), and a plurality of pre-formed spacers, pedestals or supports (112, 114, 116, 118, 120, 122) which are respectively disposed below the plurality of photovoltaic modules (104, 106, 108) and integral therewith, or fixed thereto. Spacers (112, 114, 116, 118, 120, 122) are disposed on top of roofing membrane (102). Membrane (102) is supported on conventional roof framing, and attached thereto by conventional methods. In an alternative embodiment, the roofing assembly may have insulation block (322) below the spacers (314, 314′, 315, 315′). The geometry of the pre-formed spacers (112, 114, 116, 118, 120, 122, 314, 314′, 315, 315′) is such that wind tunnel testing has shown its maximum effectiveness in reducing net forces of wind uplift on the overall assembly. Such construction results in a simple, lightweight, self-ballasting, readily assembled roofing assembly which resists the forces of wind uplift using no roofing penetrations.

Description

[0001]This invention was made with Government support under Agreement No. FG09-95EE15638 awarded by the Department of Energy. The Government has certain rights in this invention.CROSS REFERENCE TO RELATED APPLICATIONS[0002]This application is related to U.S. Pat. No. 5,316,592, issued May 31, 1994 to Dinwoodie, and U.S. Pat. No. 5,505,788, issued Apr. 9, 1996 to Dinwoodie, the disclosures of which are incorporated by reference.BACKGROUND OF THE INVENTION[0003]This invention generally relates to a photovoltaic roofing assembly, and in particular to a lightweight photovoltaic roofing assembly requiring no roofing penetrations and which resists wind up-lift due to specialized component geometry and by acting as an integral assembly.[0004]As the cost of solar cells declines, the non-solar cell components necessary for a functioning photovoltaic system begin to dominate the overall system costs. For this reason, there is a growing trend to develop photovoltaic assemblies which eliminate ...

AI Technical Summary

Benefits of technology

[0015]According to the present invention, a lightweight, self-ballasting solar cell roofing assembly is preferably formed with two portions. One portion consists of a plurality of photovoltaic modules, together with spacers which rest on a conventional building rooftop. The spacers are preferably pre-formed and are sized and configured to provide passageways beneath the photovoltaic modules extending from at least two sides of the modules to reduce uplift forces on the modules. The photovoltaic modules with spacers preferably have interlocking edges or corners. The second portion is a means of perimeter securement which avoid roof membrane penetrations, such as the use of roofing pavers.

Problems solved by technology

As the cost of solar cells declines, the non-solar cell components necessary for a functioning photovoltaic system begin to dominate the overall system costs.

a) by including a roofing paver, the assembly is more complicated than necessary and more costly to manufacture.

b) the assembly does not employ a method by which to limit the temperatures experienced by the solar cells and other components. Solar cells are known to decline in efficiency with increasing temperatures. Hence, by offering no mechanism for temperature abatement, the assembly will operate less efficiently, with unknown long-term effects due to high temperature exposure.

c) by placing both a concrete paver and photovoltaic module onto the insulation block, the insulation block is inhibited from ventilating and expiring moisture. As a result, upon exposure to moisture, the insulation block takes longer to dry out, thus reducing its insulating value and degrading the integrity of the insulation block over time.

d) the assembly has multiple modes of potential failure, which include the paver component and its means of bonding. These components will be subjected to 20-30 years of an exposed and harsh weather environment at elevated temperatures. Any form of delamination is unacceptable. Delamination would cause dislocation of solar cells due to wind loading, and potential exposure of the insulation and membrane layers below.

a) the assembly does not employ a method by which to limit the temperatures that will be experienced by the solar cells and roofing membrane, thus reducing the efficiency of the solar cells and reducing the life of the roofing membrane.

b) the assembly has multiple modes of potential failure, which include failure due to thermal stresses on the roofing membrane and its means of bonding.

c) the assembly requires roof fasteners which penetrate the protective roofing membrane, which make the installation much more complicated and more costly than is necessary. In addition, such penetrations increase the risk of water leakage, with consequent damage to the building and its contents.

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