How Solar Panel Highways Work

Could solar panels eventually replace asphalt and concrete?
Could solar panels eventually replace asphalt and concrete?
Courtesy of Dan Walden

As the world focuses on renewable energy, scientists are looking more and more to a source of power than has kept mankind warm and alive for as long as we've been around: our sun.

These days, we can find solar panels -- also known as photovoltaic cells -- just about everywhere. They're on the roofs of our homes, bringing down the cost of electricity. The all-new 2010 Toyota Prius hybrid even has them on its roof, powering an electric air conditioner to keep the interior cool so the gasoline-powered engine doesn't have to work so hard [source: Carney].

The applications for solar panels are growing exponentially. Photovoltaic cells work by using semiconductors to absorb light and create a flow of electrons, which can power any number of electrical devices. Just as one simple example, it's probably safe to assume that most everyone has used a solar-powered calculator at one point or another.

Some have even theorized that if we were to lay down a gigantic amount of solar panels over a wide area, we could absorb enough sunlight to power entire cities, effectively ending our energy crisis. The problem is, there's nowhere to put them -- we can't exactly stick panels across the entire countryside.

Or can we? We have a network of roads all over the country, and now we even have cars being manufactured with solar panels on them. Put the two together and you get a unique solution: solar panels on our highways.

This could mean that the panels could be placed along our roadways as sound barriers, or an even more extreme idea -- that the roads themselves will be made of solar panels.

In this article, we'll examine the pros, cons and feasibility of these ideas and see if solar cells could be the asphalt of the 21st century.


Advantages of Solar Panel Highways

Each Solar Roadway panel consists of three basic layers: the base plate layer, electronics layer and the high-strength, translucent road surface layer.
Each Solar Roadway panel consists of three basic layers: the base plate layer, electronics layer and the high-strength, translucent road surface layer.
Courtesy of Dan Walden

You've probably seen traffic warning signs on the side of the road with small solar panels attached to them. While they're one example of how solar power can aid our driving experience, they're only the tip of the iceberg. In August 2008, the Oregon Department of Transportation installed a row of solar panels five feet (1.5 meters) wide and two football fields long at an interchange near two interstate highways. The panels are designed to feed into Portland General Electric's grid, supplying nearly 30 percent of the power necessary to run the highway's lights at night [source: Rivera].

As you can see, solar panels already have applications on our roads. But some are taking that idea even further and proposing that we build the roads themselves out of solar panels. Solar Roadways, a U.S. company, has a plan to create structurally engineered rows of solar panels that cars and trucks can actually drive on. And while we're driving on them, they'll collect solar power that can supply power to our homes and businesses.

The "solar highways" consist of individual panels with three layers -- a top layer of high-strength, textured glass that provides traction for vehicles, an array of solar cells beneath that for gathering energy, and a base plate that distributes the collected power [source: Solar Roadways].

They're more than just solar energy collectors, too. The panels contain LED lights, powered by the sun, that can act as road and warning signs built into the road itself. In addition, they can use gathered heat to melt snow and ice on the roads.

The company also says that having a source of electricity beneath cars at all times would make it easy for electric vehicles to stay charged up at roadside stations -- clearing the major hurdle that EVs face, which is finding places to charge when they spend their batteries [source: Solar Roadways].

With each 12-foot by 12-foot (3.7-meter by 3.7-meter) panel capable of producing 7.6-kilowatt hours of power each day, each mile of solar roadways could produce power to run as many as 500 homes [source: Jacquot].

The U.S. Department of Transportation thinks it's a good enough idea to give the company a $100,000 grant. But can the solar panels really hold up? On the next page, we'll look at the disadvantages of solar panel highways and see if the idea is truly feasible.

Disadvantages of Solar Panel Highways

Is this a realistic plan or will it prove to be too difficult and costly to implement?
Is this a realistic plan or will it prove to be too difficult and costly to implement?
Courtesy of Dan Walden

Sure, roads made of solar panels sounds like a great idea and one that could possibly get this country truly running on solar power; however, just how feasible is this plan?

For one, it would be quite costly. Each panel costs about $7,000 to build, and the plan calls for billions of them to cover the roadways [source:]. Installation would take huge amounts of time and money, and so would training crews to maintain them properly. Most likely, it would take several years before the electricity generated by the panels would recoup their own cost. For this reason, the company suggests smaller-scale projects are the best place to start.

Then there's the question of durability. Our roads take lots of punishment from cars, trucks, motorcycles and tractor trailers, not to mention the fact that they could be damaged in traffic accidents. How would these glass panels hold up against that kind of punishment? And if we depend on the solar cells for traffic signals and power for electric cars, what happens if the sunlight collectors become damaged?

In addition, the cost of repairing these solar panels is likely more expensive than it would be for fixing ordinary, asphalt roads. The company says it could utilize a type of self-cleaning glass to keep the surface clear of dirt and grime, but this process is yet unproven.

Then there's the big problem with solar energy: cloudy days. Current solar power technology is very inefficient -- in fact, most solar panels only convert about 14 percent of available energy into electricity [source: Northwestern University]. And on days when sunlight isn't readily available, like during the long winters in many parts of the country, you have to wonder where the power would come from. This is why solar energy is considered to be only one type of renewable energy source rather than the sole source of power -- it's difficult to rely on.

Despite these drawbacks, there's no doubt that solar panel highways are a unique and groundbreaking idea. It's the kind of thinking we need to do in order to get ourselves off of our fossil fuel addiction and running on a more eco-friendly power source. So in a few years, you just may find yourself driving on glass solar panels instead of asphalt.

For more information about solar power and other related topics, follow the links on the next page.

Related HowStuffWorks Articles

More Great Links


  • Carney, Dan. "Prius goes for more energy-saving firsts." May 18, 2009. (Nov. 11, 2009)
  • Jacquot, Jeremy Elton. "Solar Roadways: Energy-Generating Roads Made Out of Glass and Solar Cells." Aug. 20, 2007. (Nov. 11, 2009)
  • Northwestern University. "How efficient are solar panels?" (Nov. 11, 2009)
  • Rivera, Dylan. "Oregon installs first highway solar project." The Oregonian. Aug. 7, 2008. (Nov. 11, 2009)
  • Solar Roadways. (Nov. 11, 2009)
  • "Solar panel roads could solve energy crisis." Sept. 8, 2009. (Nov. 11, 2009)