Building-integrated photovoltaics (BIPV) are exactly what the name implies: a photovoltaic system that’s part of the building structure. It replaces traditional roof, shade, and façade products, and blends into the building, becoming unnoticeable (it makes solar-generated power much prettier). “BIPV system advantages include the potential to reduce installation costs, improve aesthetics, and address roofing-warranty issues,” says Tucson, AZ-based Global Solar Energy Business Development Manager Mark McIntyre.
Patrick Thibaudeau, vice president for sustainable design at Minneapolis-based HGA, explains that there are four parts to a BIPV system:
- The building element (roof, canopy, exterior wall finish, skylight, glass, or sunshade).
- The collector (the part that responds to the sun and allows sunlight to be converted to electricity).
- The conductor (the part that carries electricity generated by the collector surface through a conductive material).
- The combiner/converter (electricity can be used directly to a point of use, like a solar power calculator, or the power from many panels can be conducted to a combiner box and routed through wires to distribution if the equipment uses direct current – or passed through a converter system to change DC to AC).
There are several systems available for use in BIPV construction, say Thibaudeau and John Gardner, sales engineer with Standard Renewable Energy. They include:
- Thin-film systems for flat and standing-seam metal roofs, and spandrel glass (used in skylights or as a canopy over a building entrance, a parking lot, etc.). They produce less electricity per square foot than traditional panels. They produce financial paybacks if they replace other building materials, and they’re more aesthetically pleasing.
- Traditional framed panels that can be part of the façade, providing shade for windows or acting as an architectural aspect. They can be thin and long, square, or rectangular. These systems usually generate more electricity per square foot than other systems.
- Transparent systems, which are thin films that use an organic dye and metals other than silicon. They can be transparent or translucent, allowing approximately 50 percent of visible light through.
- Ultraviolet systems, which convert ultraviolet light into electricity, allowing larger surfaces for glass and for the combination of power generation, lighting, and temperature control.
Although BIPV will work for almost any building, there are some things to think about before you make the jump. “At the design level, the key questions are: ‘How does PV fit into the architecture aesthetically? How should you deploy the PV for optimal performance at the site and location of the building, and how can this be done most cost effectively?’ ” says McIntyre.
Other things to think about, according to Thibaudeau, include:
- Total building electricity load.
- The surface area available for BIPV.
- The amount of power that can be generated by BIPV.
- The efficiency of the system being considered.
- The solar orientation of the building. Does the location have enough sunlight to be worth the investment?
- Available credits, incentives, or financing options.
- Whether the power will be used direct to DC-compatible equipment or converted to AC and made part of the general building power.
Leah B. Garris ([email protected]) is managing editor at Buildings magazine.