The transition wouldn't be cheap. Scott estimates the cost would run anywhere from 50 percent to 300 percent more than the cost of using asphalt to pave a roadway. How the material would stand up to weather, road salt in colder climates, snowplows, crashes and other challenges also remains to be seen.
While there are plenty of skeptics, the Brusaws also have been gaining backers. They've secured several grants from the Federal Highway Administration, including one for $750,000 in 2011.
They've since turned to the Indiegogo crowdsourcing site for more support, and the reception has substantially exceeded their $1 million goal . As of Friday, Solar Roadways had already pulled in more than $1.6 million from more than 38,000 supporters, a record for the most individual contributions to a single campaign.
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While the Brusaws want to use roads to generate electricity, others see a way to provide electric power through the roads to power battery vehicles. That could be a major breakthrough for proponents of alternative energy, offering a way to overcome the limitations of battery-based vehicles.
Volvo is pairing up with the Swedish Transport Association to create short stretches of electrified roadway in Gothenberg, the Scandinavian country's second-largest city. Using a concept called inductive charging—essentially, what's used to wirelessly charge many electric razors and toothbrushes—specially designed city buses would simply have to drive along dedicated portions of pavement to partially replenish their batteries.
Because there are no exposed wires, the system would be safe for humans and animals, who might inadvertently walk across the chargers.
"Vehicles capable of being charged directly from the road during operation could become the next pioneering step in the development towards reduced environmental impact," said Niklas Gustavsson, executive vice president of corporate sustainability for the Volvo Group.
Other induction charging systems have been put to use in several locations, including Utah; Torin, Italy; and Gumi, South Korea, with more under study. Longer-term, proponents believe the technology could be incorporated into highways for use by electric passenger cars such as the Nissan Leaf and the Tesla Model S—perhaps built into existing high-occupancy vehicle (HOV) lanes or dedicated lanes for use by battery cars only.
Right now, such induction charging systems have to be linked to the conventional electric power grid. But the Brusaws have suggested that they could combine in-road chargers with their solar roadways, eventually allowing highways to both generate power and use that energy to operate a fleet of zero-emissions cars, trucks and buses.
—By CNBC Contributor Paul A. Eisenstein. Follow him on Twitter @DetroitBureau or at thedetroitbureau.com.