Thin-filmsolarcompany HelioVolt Corp. said Tuesday it has partnered with the Architectural Glass & Aluminum Co. to develop building-integrated solar products.

The company is targeting curtain wall products, which are the exterior glass facades common in skyscrapers and other modern buildings.

It’s the second such announcement in a week. The Dow Chemical Co. (NYSE: DOW) last week announced it was partnering with thin-film firm Global Solar Energy to also develop building-integrated photovoltaics, known as BIPV, in the form of flexible roof shingles instead of rigid glass. Dow Chemical picked Global Solar for the U.S. Department of Energy project after its previous partner, Miasolé, dropped out (see Miasolé Drops Out of DOE Program).

The idea of combining construction materials with solar panels isn’t a new one, and it’s appealing because it could potentially make it far easier and cheaper to install solar power on new buildings. Thin-film advocates have long called the possibility one of the major advantages of thin films, which also use little or no silicon, the costliest part of most solar cells.

How attractive is it?

The US Department of Energy estimates that development of “practical, efficient and economical” BIPV products, deployed on roofs and façades of commercial buildings and homes, can generate 50 percent of the electrical needs of developed countries such as the United States, according to the HelioVolt announcement. The press release also cited NanoMarkets, an industry analyst firm that forecasts that BIPV products will be the largest opportunity within the thin-film market, making up about $800 million in 2011.

But companies say solar construction materials are still years away.

When Global Solar opened a thin-film plant in March, Tim Teich, vice president for sales and marketing, said building-integrated PV could be three to five years away (see Q&A: Global Solar VPs Dish Thin-Film Details).

And Miasolé CEO Joseph Laia last week said his company had backed out of deals with the DOE because it didn’t want to focus on building-integrated PV. It decided against going down that path because the technology requires a special membrane that isn’t available today and isn’t likely to be economical for another two years, he said then.

John Langdon, vice president of marketing at HelioVolt, also acknowledged the longer timeline, saying he doesn’t know when the partnership will result in products.

“We know it will take longer than the standard module products, which are 90-some-odd [percent] of the market right now,” he said. “We don’t want to rush it. The obvious interest is the reduction in the construction cost, but we need to make the components as easy to install as existing materials.”

One of the challenges is that many building components have longer warranties than solar panels’ 20- to 25-year warranties, he said.

“That turns into cost because the longer you want something to last, the more [robust] packaging you need,” he said. “So we need to do some work to match the normal cost of PV to the normal cost of curtain wall products.”

Another challenge is weather sealing, because copper-indium-gallium-diselenide films – which HelioVolt is developing – corrode in water. CIGS films are more sensitive to water than amorphous-silicon films, for example, but have about twice the efficiency, Langdon said.

“You have to come up with a compromise between power output and long lifetime, and do both with the cost that fits into the application,” he said. “There are some tradeoffs.”

Finally, there’s work to be done to match up the connectors and other components to make the installation of the BIPV is similar to regular construction as possible, he said.

HelioVolt hopes its partnership with the Architectural Glass & Aluminum Co. will help it solve these problems.

In spite of the challenges, Langdon said BIPV is worth pursuing.

He claimed BIPV isn’t a distraction for HelioVolt, which is working to build its first thin-film plant after closing a $101 million round last year, because its thin-film technology has been designed as a “platform” that can be used in many different applications without being completely redesigned.

“The first [application will be] a standard solar module, but we designed all along with the intention to put it in integrated products,” Langdon said.