Solar Roads...Why Not?

If you stop to think about it, highways take up a heck of a lot of space. The US Interstate Highway System is almost 48,000 miles long. Even if every interstate were only the bare minimum two lanes wide, the system would take up almost 13 billion square feet. Obviously, this space is absolutely necessary for efficient transportation, but imagine if this space could be multipurposed to, maybe, generate energy as well as accommodate vehicles?

Last month, Missouri’s Department of Transportation (MDOT) announced that a small section of the Route 66 Welcome Center in Conway will be fitted with walkable solar panels. While the project is apparently not yet funded, its announcement marks the first experiment with solar roads in the US. The solar pavers will be provided by Idaho-based Solar Roadways, an eccentric husband-and-wife startup bent on building energy-generating panels into the entire US highway system. MDOT will first test them on a stretch of sidewalk leading up to the welcome center; if successful (whatever that means) a portion of the parking lot would come next. MDOT and Solar Roadways hope to eventually generate electricity for the welcome center itself.

Solar Roadways’ product consists of strips and fitted with a thin film of polycrystalline silicon. The company claims the strips, which are glued to the road surface, are durable enough to withstand the weight of a 6 axle truck. They believe their panels may also be used to filter stormwater, replace conventional power cables, melt snow, or alert drivers via LED or similar lamps.

Solar road tests are becoming relatively common in Europe. In the Netherlands, a country well-known for heavy infrastructure investment, a 70 meter “SolaRoad” bike path outside Amsterdam made its debut in late 2014. SolaRoad generated 3,000 kWh during its first six months of operation—enough to power a typical single-person home for a year—and suffered only one design flaw thus far: a degraded section of topside laminate. In February France announced plans to cover 1,000 km of their roads with solar panels in order to generate enough power to supply a small town. The French plan would use a panel design very similar to Solar Roadways’.

Despite appearing cool and revolutionary at first glance, solar roadway implementation faces a host of potential and actual problems. Cost is one of the bigger obstacles. The bill for covering large sections of US roadways would quickly run to trillions of dollars. Since the introduction of solar roads, many have decried them as completely impractical. This electrical engineer’s (30+ minute) video provides a convincing case against the concept by pitting power loss and other technical calculations against Solar Roadways’ claimed statements. Plus, consider the beating the average roadway takes on a daily basis. Bicycle tires caused SolaRoad’s degradation—imagine how much more damage a car tire might cause. And in cold climates, water could damage panels through infiltration or by freezing between them.

The solar roadway is in its infancy and will probably remain a “that would be cool” idea for some time. It might gain more traction in countries like Japan, where investment in alternative energy is increasing but space is severely limited. In more spacious areas like the US, it seems they’ll only become practical if used to generate heat for snow removal or for some other secondary benefit. Until then, potholes will be more common than panels on our highways.

Image credit: By Dan Walden [CC BY-SA 1.0], via Wikimedia Commons