URI researchers see nation’s next energy source in paved roads

The endless miles of paved roads crisscrossing America could become the country’s next energy source, if University of Rhode Island researchers have their way.
As luck would have it America’s roadways – particularly the larger ones – tend to be paved with black asphalt that attracts sun-generated heat. URI researchers see potential to trap that heat and use it for everything from melting icy roadways to generating electricity.
“If I can reuse the heat from the asphalt pavement, maybe we can generate more electricity and we would have less dependency on fossil fuel,” explained URI professor of civil and environmental engineering K. Wayne Lee.
Working with other professors and a graduate student, Lee is actively pursuing two concepts to tap into the heat that now does little more than burn the feet of barefoot walkers.
His first idea is relatively straightforward: build a network of conductive pipes under roadway surfaces, which in Rhode Island are known to reach 140 degrees or more. The heat would pass to water flowing through the pipes.
With money from the Korea Institute for Construction Technology, URI graduate student Andrew Correia built a prototype system, which delivered positive results.
“One property of asphalt is that it retains heat really well so even after the sun goes down the asphalt and the water in the pipes stays warm,” Correia said.
With hot water, the possibilities are endless. Hot water pumped under bridges could melt surface ice that poses a danger to speeding vehicles. Nearby factories may need hot water for a manufacturing process. And Lee said a nearby homeowner could draw on the water for a hot shower. The water could also drive a turbine, which could produce electricity.
Then there is concept No. 2, which skips the whole collection of pipes in favor of flexible photovoltaic systems. The technology – just now gaining traction – allows workers to fit solar panels around curved shapes. For Lee that means fitting them around Jersey barriers that are a staple of so many highways. The electricity could then flow to streetlights and electronic highway signs. Lee said such a system – while pricey to install – could save transportation departments carloads of money over time. He noted that the R.I. Department of Transportation has taken to turning off highway lights on some highways during the early morning hours in an effort to save on utility bills.
And many transportation departments – including the one in Rhode Island – already use traditional rigid solar panels to power electronic signs or flashing warning lights.
But to demonstrate that the flexible cousins work as well as their rigid peers, Lee and his team are heading to the roof of the university’s engineering building in South Kingstown. There they plan to install both types of systems. One will power a streetlight out front and the other an identical streetlight. Lee and his team will monitor them for any differences in quality.
If the test finds no distinction, Lee thinks transportation departments could roll out flexible material using present technology. The pipe network too could quickly be implemented.
Longer-term – think five to 10 years from now, Lee said – departments could embed thermo-electric materials directly in roadways at different depths. The difference in temperature between the two materials would generate an electric current.
Ultimately, the goal is to eliminate any special equipment, Lee said. His team wants to develop a paving material that will contain solar-collection technology already embedded. That, however, could take some time, as engineers need to ensure the material holds up under the pounding of cars and trucks and remains affordable.
“That’s the beauty of the engineer,” Lee said. “We have the freedom to think about all [the possibilities].” •