Renewable energy recently got an unprecedented boost. On May 9, the California Energy Commission (CEC) voted unanimously to require all new homes to be solar-powered. Effective Jan. 1, 2020, the mandate will necessitate the provision of photovoltaic systems that provide 2 to 3 kilowatts of energy, depending on house size. This requirement's modest size, about one-third to half that of a typical solar array, is presumably intended to control costs. Considering that roughly 80,000 new houses are built annually in the state, however, the subsequent demand for renewable technologies will increase dramatically. According to The New York Times, approximately 15,000 houses in California typically include solar, thus resulting in a fivefold increase in installations in less than two years.
Although the new mandate is anticipated to save home buyers money in the form of lower energy bills, the $8,000 to $10,000 additional cost for photovoltaic (PV) systems remains a concern. The CEC’s focus on new construction suggests that the use of building integrated photovoltaics (BIPVs) could be preferential to typical standalone PV arrays. Put simply, specifying cladding products with photovoltaic capabilities could be more economical than purchasing the products separately. Although BIPVs have thus far been an atypical strategy, California’s solar decree could substantially increase the demand for integrated energy-harvesting in architecture. The following examples highlight a few BIPV technologies that represent a transforming aesthetic for buildings.
Alternative Roofing Materials
Given that most building solar installations occur on rooftops, it is obvious that PV-integrated roofing materials are gaining traction. Tesla’s Solar Roof collection of tempered glass solar tiles mimic the dimensions and application methods of traditional roof shingle and tile materials.
Netherlands-based Zep BV likewise offers a line of solar roof modules that emulate ceramic tiles. The company claims that the output efficiency of each module is more than 20 percent—higher than the 14 percent to 17 percent efficiency expected of the typical PV panel. Zep BV has tested its tiles in extreme environmental conditions and provides a 30-year warranty against leakage.
Scientists at Soochow University in Suzhou, China, have taken the solar roof tile a step further—enabling it to harness energy from the rain as well as the sun. Although not yet commercially available, the novel technology includes a triboelectric nanogenerator device that derives mechanical energy from the pressure exerted by a heavy rainfall.
Many companies have been developing solar technologies for windows that enable power-generation without blocking visible light or views. For example, Columbia, Md.–based Solar Window Technologies applies ultra-thin layers of fluid coatings to transparent glass and polymers. The coatings function as aggregations of micro-scaled, interconnected solar cells—collectively called an organic photovoltaic (OPV) solar array. According to the manufacturer, the product can outperform rooftop power harvesting in buildings that are window-dominant—such as skyscrapers—and can return the initial investment within a single year.
Vilnius, Lithuania–based SmartFlex offers a comprehensive, customizable solution for solar-powered curtain walls. According to the company, it aims to bridge “the gap between photovoltaic manufacturers and architects” by anticipating the technical complexities of both BIPV technologies and modern building envelopes.
Yet another glass-oriented manufacturer is Build Solar, which makes solar-powered glass block. The product of research developed by University of Exeter scientists, the modules consist of an array of small PV cells and exhibit a higher insulating value than standard glass blocks.
Embracing the Façade
A growing number of PV-generation options exists in other aspects of the building enclosure. Given the importance of light absorption, many of these products are faced with glass. For example, Eindhoven, Netherland–based Studio Solarix—a partnership between product designer Reinier Bosch and architect Marloes van Heteren—makes a solar façade system composed of customizable glazed modules. The individual panels can vary in dimension, depth, angle, color, and pattern. LED strips may also be embedded within the tiles’ frames to communicate power generation through light.
The Copenhagen International School in Nordhavn, designed by Danish architect C.F. Møller, utilizes a similarly modular system of colored PV panels on its façade. Based on technology developed at the École Polytechnique Fédérale de Lausanne (EPFL), the 12,000 modules deliver an estimated 300 MWh of electricity and collectively comprise the “largest solar façade in the world,” according to an EPFL press release.
) technology. With no frame, glass face, mounting hardware, or silicon-purification process required, Sunflare is “the cleanest mass-produced solar power on the planet,” according to the company.
Other emerging technologies represent the fringe of solar-powered surfacing. DysCrete is an energy-harvesting concrete coated with dye-sensitized solar cells, light-reactive dyes held in suspension that deliver power to oxide electrodes. Another case is a spray-based application of nanoparticle solar cells developed by researchers at the University of Alberta. Scientist abd professor of chemistry Jillian Buriak and her team devised the application method as a cost-saving measure with intriguing possibilities. “Nanoparticle-based 'inks' could be used to literally paint or print solar cells or precise compositions,” Buriak told ScienceDaily.
Challenges to Overcome
Despite BIPV’s compelling characteristics, the approach has challenges. According to a 2011 National Renewable Energy Laboratory Technical Report on BIPVs in the residential sector, BIPV “faces more complex product-development issues and market-adoption dynamics than rack-mounted PV.” These problems include the need for specialized labor for installation as well as the relative novelty (and lack of field-testing) of BIPV systems. Many advances have occurred in recent years, however, and the CEC’s solar power directive may finally motivate the widespread utilization of BIPVs. In addition to offering cost savings, customization, and resource efficiency, BIPVs also provide the rare design opportunity of an enhanced performance-based aesthetic.