Will Windows be Used for Solar Power?
October 15, 2005
FEATURE ARTICLE | Products, Energy Efficiency, Materials & Components
When it comes to today’s fenestration products, homeowners expect windows and doors to keep their homes warm in the winter and cool in the summer. There may come a day in the future, however, when homeowners can actually put their fenestration products to work. Window systems incorporating solar panels, for example, can support a home’s energy needs by producing power rather than being a source of energy loss.
“The nice thing about solar voltaic technology is that it’s very adaptable,” says Mark Burger of Spire Solar Chicago. “Those who think about solar electricity can only think about utilitarian panels you have to put on a roof or a pole. Because of the development of the architectural photovoltaic market, the possibilities are much more varied and exciting.”
Although solar windows have not yet made their way into the residential market on a widespread scale, certain specialty projects are paving the way toward greater architect and homeowner awareness of photovoltaic possibilities. Spire Solar Chicago, a subsidiary of Bedford, MA-based Spire Corp., recently produced custom Building Integrated Photovoltaic panels for windows, to be installed at a new visitors’ center in Alaska’s Denali National Park. The goal for the project is to have the solar windows produce 50 percent of the building’s electricity. “The Parks Service wanted people to understand that solar power can work anywhere. This technology works in Alaska, not just California or Hawaii,” Burger says.
Finding the right balance
Spire’s BIVP panels are laminates designed to fit into Pozzi window systems manufactured by Jeld-Wen Inc. based in Klamath Falls, OR. Although Spire had done solar projects for curtain walls, awnings and canopies, the visitors’ center was its first attempt at a vertically integrated window project. “With the windows, we were able to fit the basic look of the visitors’ center’s lodge appearance,” Burger says. “The whole design team wanted people to see that the building was getting a lot of its electricity from solar power, but it needed to be the right balance of looks and function.”
The building is open to park visitors during the summer months, when Alaska has peak sunlight. To maximize kilowatt hours, the solar panels are aimed due south at an angle that is roughly less than latitude. Yet, photovoltaic windows can also adapt to individual building designs. “If [the BIVP panel] is vertical in a window, you’ll collect less energy, but you’ll [still] have a photovoltaic surface that’s part of the building design. That’s very important for design and aesthetic purposes,” Burger says.
Neil Petrie of Davis Constructors and Engineers Inc., Anchorage, AK, was the project manager for the Denali Park lodge and says solar panels were a good option for this particular project as the design team worked toward Leadership in Energy and Environmental Design certification. Still, cost considerations and obstructed views through the windows were challenges that had to be weighed. “I don’t see the combination [of windows and solar panels] being a LEED[-driven] product due to cost and architectural considerations. I would prefer a window with a view to look at if I’m going to install one. Solar [technology] can be integrated into a building much more economically and efficiently if it is built from a standard panel that is positioned for maximum benefit from the sun.”
Expanding the products’ reach
Spire’s BIVP panels are not a first-generation technology. In fact, solar technologies have been used in the space program since the 1950s, on land since the 1960s and in commercial buildings since the 1970s, Burger reports. The next steps for solar panels have less to do with research and development and more to do with collaboration building and marketing. “This is pretty much a mature technology. It’s something that architects can present to clients that’s not risky. It’s a safe and reliable thing to do.”
Educating architects about the potential of solar technology in residential settings may expand the products’ reach, especially as national energy initiatives move closer to requiring zero-energy homes, Burger notes. “It used to be if someone wanted solar on their house, they had to overcome a lot of barriers, the least of which was finding an architect or builder willing to do something like that. When you have an architect on board, you remove a huge barrier.”
Burger points out that as people get more comfortable with the technology, the economic scale of photovoltaics will increase, causing the price to go down. Currently, depending on what type of solar technology is used and how much coverage it has on the window system, he estimates an additional cost of $30-60 per square foot. “With proper design and careful budgeting, you can do a zero-energy home that costs just a few percent higher than a comparable home. Especially with higher-end homes, photovoltaics will be a key factor in that.”
Mass-produced solar windows?
The jury seems to be out as to whether or not this technology will gain widespread consumer acceptance. Burger asserts that the window industry may latch onto solar technology because it’s one more thing that can differentiate their windows from the competition. “This is just one more architectural feature. In terms of being electronically connected, you already have window systems that are connected for electronic shading or tinting. This is just another variation. It’s not such a leap.”
Plus, the residential tax credit for energy-saving measures that goes into effect January 1 may encourage homeowners to look at the long-term savings solar power offers, he points out. “It’s minor, but a $2,000 credit is still a $2,000 credit.”
Still, others believe solar technology will remain in commercial buildings due to their much larger glass surface areas. “At this particular point, there’s not a lot of glazing on the residential side to make it worthwhile,” says Tom Djokovich, CEO of XsunX, the Aliso Viejo, CA-based developer of photovoltaic Power Glass. “On the average home, the roof is really the most ideal location for solar. In commercial applications, it’s the reverse. The roof is smaller compared to the glazing surfaces.”
XsunX’s involvement in photovoltaic technology has been primarily limited to the commercial arena. The company has developed semi-transparent solar cells for use on transparent substrates such as glass.
Djokovich says there may be an evolving market for solar-powered glass in the residential arena, especially as consumer awareness of energy supply issues grows, but he doesn’t think the $2,000 tax credit will go far in terms of being an incentive. “I think LEED helps, but I think the biggest amount of attention is coming from the fact that there’s an electrical infrastructure shortage,” he says. “It’s really a collaborative awareness that’s starting to develop—at the government level, the energy supply level and then trickling down to the consumer level. People are realizing that the cost of expanding the infrastructure is enormous.”
Incorporating solar panels into skylights makes sense, Djokovich notes, but he thinks that most consumers will simply find it too costly to use in some or all of their windows and doors. “On the residential side, it’s a real tough nut to crack. It has to be backed by government or utility incentives. That’s the bottom line.”