Here's an idea that could provide the United States with all the solar power it needs, while also helping to fix a large part of our crumbling infrastructure: pave our 25,000 square miles of roadways with intelligent solar panels. A road "that pays for itself," its designers propose.

Is this a feasible idea, or something akin to trying to build a bridge across the Atlantic?

There may be some economic justification. Liquid asphalt, a petroleum-based derivative, now costs close to $1,000 a ton, while asphalt itself is still under $100 a ton, says Scott Brusaw of Solar Roadways, an engineer proposing the idea. "We can't keep building asphalt roads, doing the same thing... its an antiquated system we've been doing too long," he says. "Let's move on and leave the fossil fuels behind us."

Solar panels, operating at just 15 percent efficiency, installed as roadway surfaces within the 25,000 square miles of existing roads in the lower 48 states, would be capable of producing "three times as much electricity that we produce on an annual basis -- almost enough to power the entire world," Brusaw says.

The prototypes for Solar Roadways were funded by a research award from the US Department of Transportation, which solicited ideas for an "intelligent pavement" that could generate power and pay for itself. Brusaw and his team built a 12' by 12' solar road panel prototype, along with a 3' by 3' LED-lit "crosswalk" panel. The smaller panel could be used to mark and illuminate the edges of roads and other hazards, Brusaw says.

"Roads are collecting heat anyway," Brusaw says, adding that "the technology behind it has already been done today."

Can a sheet of glass withstand pounding by two-ton cars, trucks, and buses? This is possible, Brusaw says, as "glass can have as high of strength as steel." There are other issues to be addressed, he adds, noting that driving on glass "has got to have the same traction as asphalt," as well as be shatterproof and glareproof.

However, the idea has its critics. When the DOT award was made for the idea, for example, a commentary at The Infrastructurist site poo-pooed the idea as impracticable:

"Solar Roadways is engineering PV panels to withstand 40-ton vehicles going 80 miles an hour over them day and night for decades. How much more does it cost to make solar panels–already a bit pricey–totally indestructible? We’re guessing a lot. And this all so we can avoid putting them someplace sensible, like on all those empty rooftops in America’s sunnier climes, where cars and trucks don’t drive and where there also happens to be an existing electrical grid for them to hook into."

It may be too expensive and impracticable to lay out 25,000 square miles of solar panels. But perhaps some hybrid or partial approaches can be put in place. Or are we better off using more -- as The Infrastructurist suggests -- "sensible" locales for solar panels?

This post was originally published on Smartplanet.com