Plastics put solar on the verge, again

March 21, 2012

Recent gains in the efficiency, lifespan and manufacturing of thin-film plastic solar panels have advocates convinced that, this time, solar really is on the verge of a revolution – even as the market crashes around them.

By Doug Struck

for the Daily Climate 

In what was once a Polaroid factory 50 miles south of Boston, a high-tech company is printing sheets of solar cells made of plastic, trying to create tomorrow's energy source amid the tumult of today's energy market.

The solar collectors made by the Konarka company in New Bedford, Ma., are thin and transparent. They curl into lightweight rolls and can be unfurled and put on a wall or a tent or an impoverished hut to begin producing electricity – though feeble electricity at this point – from sunlight.

Scientists in university and private labs worldwide have raced to make these plastic solar cells practical for 30 years. A recent succession of efficiency gains has researchers, investors and companies convinced the effort is finally close to success.

"This will be 'energy to go,'" said Steffanie Rohr, head of marketing for Heliatek, a German company that also has plans to begin commercial production of 1-foot by 4-foot plastic solar strips this year. 

Heliatek, Konarka, and spin-offs from labs at Princeton University and the University of California, Los Angeles, have been leapfrogging one another to announce new gains in efficiency, starting from barely 3 percent five years ago. Heliatek announced in December it had achieved a sunlight-to-electricity efficiency of 9.8 percent in their lab. "Ten percent is a psychological barrier to be on the market," Rohr said. "We are scratching that."

But their advances are coming just as the commercial market for solar cell manufacturing is in a tailspin. Prospects for the market success of the plastic photovoltaics are dimmed by plunging prices of silicon solar modules, which have fallen from $4 per watt in 2008 to just over $1 a watt now. 

Oversold technology

"This technology has been oversold," said Jonathan Melnick, an analyst for Boston-based Lux Research who follows the plastic solar industry. Researchers, he added, "talk about promise and potential and show very intriguing graphs. But year after year the graphs always look the same – the potential is always three or four years out."

But researchers – and companies putting their bet on the product – plunge ahead with the stubborn faith of all new inventors who have faced skeptics. 

Vishal Shrotriya, a vice president of Solarmer Energy, created by researchers at UCLA to develop the plastic solar cells, argues that lightweight, portable solar will create markets where bulky, rigid silicon panels cannot compete.

"Asia and India are going to be a huge market for low-cost solar energy," he said. "There are plenty of places off the grid there that could use this." He envisions the material providing portable power for military uses, rescue missions, sailors. It can be mounted on the wings of drones or on backpacks to power portable electronics, among other possibilities.

Non-toxicity as advantage

John Warner, founder of the Warner Babcock Institute for Green Chemistry near Boston, welcomes alternative energy but said caution is needed before embracing the new molecular materials of organic, or carbon-based, photovoltaics.

"We need solar panels now. I don't want in any way to detract from the great work going on now in organic photovoltaics," he said. "However, we have not invented the ... things necessary to do it in an environmentally benign way."

But Howard Berke, co-founder and CEO of Konarka, the company manufacturing the new material in Massachusetts, said the non-toxicity of a carbon-based solar cell is one of its advantages.  

"We have the lightest footprint of any photovoltaic material," Berke said. "Our material is cadmium-free, lead-free, arsenic-free, and uses no harmful gases. It's got the lowest carbon footprint relative to other solar technology, and we have the shortest energy payback."

Tools of nanotechnology

Scientists have long known that the energy of sunlight stirs faint movement of electrons in many materials. These include organic materials – ones that contain carbon molecules – and the complex organics called polymers, which include plastics.

Working at a molecular level with the tools of nanotechnology, researchers have been trying to find – or construct – the right substance to most efficiently stimulate those electrons and convert sunlight to electricity.

But their competition – traditional silicon solar panels – has an in-lab efficiency of about 20 percent. And once erected, the rigid, glass-encased silicon solar cells can stand for 25 years or more, whereas photovoltaics printed on plastic tend to deteriorate within five years – though Berke said Konarka will soon announce a breakthrough that gives flexible solar cells a 10-year outdoor life.

With lower efficiency and shorter lifespan, organic photovoltaics "just don't make sense," said Lux's Melnick. 

All solar manufacturers are further threatened by a flood of cheap silicon solar panels from China that have undermined American manufacturers even as solar installers and homeowners have rejoiced. Skeptics say that flood leaves little room for a less-efficient challenger. 

But plastic photovoltaics can be made with reconfigured paper printing presses, and Solarmer Energy's Shrotiya is confident that, even with lower silicon prices, plastic can undercut them by two or three times.

Proponents foresee room for both technologies.

"I don't think we are going to have our roofs covered with organic solar" instead of silicon panels, said Alan Aspuru-Guzik, an associate professor at Harvard University, working with IBM to stretch plastic solar's efficiency further. "But the big, big thing is for the one-and-a-half billion people who do not have electricity.... Organic is going to be the best application for them."

© Doug Struck 2012. All rights reserved

Photo of woman holding transparent solar film, man in bus shelter, and roll of plastic solar strip courtesy Konarka Power Plastic. Detail of bus shelter roof courtesy Jumanji Solar/flickr.

Doug Struck covered climate change issues for The Washington Post and is a freelance writer and associate chair of journalism at Emerson College in Boston. DailyClimate.org is a nonprofit news service that covers climate change.

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