PV array designs for flat-roof buildings

In the mid-1980s Ascension Technology´s principals, then working at the Massachusetts Institute of Technology, developed the Roof-Jack mounting system for attaching PV arrays to pitched, shingled residential roofs. The driving motivation of that effort was to simplify and reduce the cost of residential PV array balance-of-systems. Since that time the Roof-Jack mounting system has been used successfully in more than 40 pitched-roof PV array installations across the country. In anticipation of the installation of grid-connected PV system for the Environmental Protection Agency´s Photovoltaic Demand Side Management demonstration (EPA PV-DSM), Ascension Technology undertook a similar engineering effort targeting cost reduction of balance-of-systems for flat-roof PV array installations. As a result, they have completed the design and fabrication of a mounting system which greatly simplifies the installation of PV arrays on typical flat-roof commercial buildings. This paper describes this mounting system, including loading analysis and experience with installations in Massachusetts and elsewhere in the country as part of the EPA PV-DSM demonstration