Thomas L. Dinwoodie

Optimizing roof-integrated photovoltaics: a case study of the PowerGuard roofing tile

This paper describes the development and implementation of a building-integrated photovoltaic (PV) roofing tile system that provides grid-connected electric power to buildings. The PV roofing tile system, together with waterproof membrane, insulation, and electrical interconnection, is called PowerGuard. PowerGuard is one of the first PV roofing systems for flat and moderately-sloped commercial buildings that replaces conventional roof materials without requiring membrane penetrations and mechanical fastening to building structures. When evaluated as a PV system, the building integration reduces the cost of a PowerGuard system by 14% to 26% rather than incurring a structural mounting cost of 18% to 22% to conventionally fasten the system. Data are reported from a 3.0 kW PowerGuard prototype operating in Folsom, California, USA. The PowerLight Corporation supplied the system using large-area amorphous silicon modules manufactured by Advanced Photovoltaic Systems, Inc. Performance data indicates the system is exceeding contractual requirements. Sensitivity analysis, based upon performance, installed costs, and supplier data, indicates: (1) a marginal economic advantage to tilting the PV array; (2) a marginal economic impact of increased PV efficiency; and (3) economies-of-scale which make PowerGuard systems economical today for commercial customers in sunny areas who pay high electricity rates.

PowerGuard® manufacturing innovation and expansion

PowerLight Corporation, with support from the DOE’s PVMaT program, has undertaken a comprehensive agenda to automate the manufacture of its PowerGuard PV roof tile system. The advanced manufacturing will lead to substantially reduced costs, quality improvements, and increased production capacity. Over the three years of the PVMaT contract, system costs are expected to fall

Lightweight, self-ballasting photovoltaic roofing assembly

2.65/Wp, with annual production capability increasing from 5 to 16 MW. PowerLight is on schedule with meeting its objectives under this program.