February 26, 2010

FEATURE | Roadbuilding

University labs look at pulling solar heat from asphalt roads

KORKY KOROLUK

correspondent

KINGSTON, R.I.

Could our highways capture the sun’s energy? A team of scientists from three universities — University of Rhode Island, Brown University in Providence Rhode Island and the University of Massachusetts at Dartmouth — have a short list of four ideas ranging from simple to complex to harvest solar power from asphalt.

“We have mile after mile of asphalt pavement and in the summer it absorbs a great deal of heat, warming the roads up to 140°F or more, says Kang-Won Wayne Lee, who heads the Transportation Research Center at the University of Rhode Island.

“If we can harvest that heat, we can use it, save on fossil fuels and reduce global warming.”

The simplest idea is to wrap flexible photovoltaic cells around meridian barriers.

“This technology already exists,” says Lee. “The new generation of solar cells are so flexible, they can be installed so that no matter what the angle of the sun, they generate electricity.”

Another idea builds on research from England, Holland and America and involves embedding pipe containing glycol, or other liquid, in the asphalt which collects heat as the road warms under the sun.

The liquid could be piped through bridge decks to melt snow and ice, reducing the use of salt. It could also be piped to nearby buildings to provide heat or hot water.

Andrew Correia, a recent graduate in civil/environmental engineering, has built a prototype and testing different ferent asphalt mixes and piping systems, hoping to show that the technology can work in the field as well as in the laboratory.

He’s keen on the idea of using the technology in de-icing applications.

“Say you have an overpass over a roadway,” he said. “You could have pipes in the lower level collecting heat during the day and going into some sort of storage facility. As the deck of the overpass cools to near freezing, the stored heat could be piped through the network of pipes embedded in the bridge deck, extending its service life.”

A third system earmarked by the researchers involves a thermoelectric effect to generate a small, but usable, amount of electricity. When two types of semiconductors are connected to form a circuit linking a hot and a cold spot, a small amount of electricity is generated.

Chemistry professor Sze Yang says such materials could be embedded in the roadway at different depths and the temperature differential would generate a weak current. With many such systems wired in parallel, enough power could be produced to defrost roadways.

“It’s a somewhat futuristic idea,” says Yang, noting there’s nothing on the market like it. “But it has been demonstrated to work in the laboratory.”

Even more futuristic is the solar road, which would use drop-in solar panels as the roadway.

The idea is to develop a solar cell system embedded in a composite material that can be used as a road surface even under severe load conditions.

Each panel might consist of three sub-layers: a surface layer, an electronics layer and a base-plate layer.

The panels would be able to generate electricity, illuminate roadway lanes in a variety of configurations, and provide early warning of any need for maintenance.

Lee says the technology underlying this concept already exists, but is extremely expensive.

Correi said an Illinois researcher created a short section, but it’s prohibitively expensive at $100,000 for a 12-by-12-foot section, meaning it’s more likely for corporate parking lots before it is practical for roadway use.

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