Solar power in office windows
Troy - Cityscapes of glass-clad buildings gleaming in the sun make Anna Dyson think about wasted energy.
Dyson heads the Centre for Architecture Science and Ecology, or Case, a research consortium that wants to turn office windows into multifaceted solar power generators.
Their "integrated concentrating dynamic solar facade" consists of grids of clear pyramids that help focus the sun's rays to generate energy. It would essentially make buildings look as if they were draped in giant jewelled curtains.
A prototype gets a real-world tryout after the opening this week of an eco-friendly research building in Syracuse. Researchers at Case - a collaborative research group involving Rensselaer Polytechnic Institute in Troy and the international architecture firm Skidmore, Owings & Merrill - call it a step toward exploiting the huge but largely untapped "green" resource of building exteriors.
"The reason we're interested in windows is because they have the largest surface areas, typically, in buildings - especially in tall, urban buildings," said Dyson, a professor of architecture at RPI. "We have a lot of vertical surface area to work with to really generate a lot of power."
In contrast to typical flat solar panels, Case's system is designed to do several things.
Each clear pyramid - with facets less than 10cm - has a lens to focus sunlight onto a tiny solar cell. The concentrated cells are designed to be more efficient in generating energy than traditional cells.
And the pyramid modules rotate to track the sun. Pumped water keeps the solar cells cool to maximise efficiency. The cooling water also "captures" that waste heat for other uses, such as hot water or radiant heat for the building.
The pattern of pyramids also would deflect and diffuse the sun's rays, meaning office workers with eastern exposures could work in natural light all morning instead of drawing the blinds against the glare. Windows will still provide a view, albeit one obstructed a bit where the patterns of pyramids are placed.
The technology behind concentrating the sun's energy through a lens is not new, nor is the concept of placing solar cells on the side of a building. But the integration of all these ideas to perform multiple tasks in this way is novel.
Dyson noted that a building's biggest energy suckers are usually cooling, heating and lighting. This system would tackle all three, whether it's extracting maximum solar power in New York City or deflecting and diffusing sunlight in Phoenix.
Jason Vollen, an RPI architecture professor at Case, said their integrated system squeezes every bit of usability out of the system.
The system has already been tested on an RPI rooftop. Now, a prototype has been built into the facade of the Syracuse headquarters of the Centre of Excellence in Environmental & Energy Systems, a public-private research partnership devoted to sustainability research.
The prototype, one of many green features of the state-of-the-art building, is a 2.4-by-2.4 metre panel and will become fully operational sometime after the building is dedicated on Friday. A second, portable prototype will be generating energy earlier.
Syracuse - where the winters can be long, snowy and gray - might not seem the best place to try out a new system to generate solar power, but Vollen said it will be a good test in "less than optimal solar climates".
Vollen believes the system can catch on in the fast-growing market for "green building" and energy efficiency systems.
He said the system would be especially suitable for older buildings undergoing retrofits, which is expected to be a growth market. McGraw-Hill Construction projected in 2009 that the market for major green retrofit projects could more than triple by 2014 to up to $15.1bn.
The solar system is included in construction documents for a high-profile construction project being planned for the Fashion Institute of Technology in New York City, according to Jonathan Maille, a director of HeliOptix, which is licensed to market the system. Maille said it's being considered for other projects as well.
Dyson did not provide a price, though the complex system will cost more than planting some photovoltaic cells on the roof. But she clams the payback time is sooner.
Still, one veteran solar energy consultant not involved in the project said that while he likes the concept, users should be ready for the potential for costs down the road.
Peter Talmage, now a professor of renewable energy at Greenfield Community College in Massachusetts, said whatever the limits of traditional solar panels, they require only minimal maintenance needs.
He noted that this system is far more complicated.
"You have to throw in a good chunk for operation and maintenance costs," Talmage said.