Solar Roadways: Crackpot Idea or Ingenious Concept?

Scott Brusaw wants you to drive on a solar panel super highway.

Scott and Julie Brusaw have a way of solving the energy crisis, it just involves you driving on glass. The Brusaws are the founders of Solar Roadways, an Idaho based startup looking to reinvent the US highway system by replacing asphalt roads with solar cells. Using photo-voltaic technology available today, Scott Brusaw calculates that a single mile of highway, if converted to solar cells, would provide enough power to run 428 homes in the US. And that’s on just four hours of sunlight a day. Solar Roadways has garnered the attention of think tanks, documentary film makers, and politicians. They even took home a grant from the Department of Transportation and created a prototype panel (12′ x 12′) that also functions as an intelligent roadway with sensors and dynamic lighting. The Solar Roadways project is remarkable for its vision, but there are many questions about costs, administration, and driving on glass surfaces that have yet to be answered. Check out videos of the prototype panel below and judge for yourself about whether solar panel roads are the ticket to living on easy street, or a just another highway to hell.

A desire for energy independence, worries about ‘peak oil‘, and environmental concerns have pushed the US towards exploring alternative energy concepts. We’ve seen all sorts of different ‘solutions’ to the energy crisis from flying saucer dirigibles to algae-fueled cars. The Solar Roadways project is interesting because Brusaw sees it as solving so many different problems all in the same structure. It will be an intelligent roadway (digital lights, dynamic displays, etc), it will collect solar energy, it will serve as the distribution of energy (power cables are embedded in the sides of the road), it will ease the way we recharge electric cars, it will generate energy without releasing carbon dioxide (ignoring carbon created during production and maintenance), and it will use processed garbage as its base layer to ease the stress on landfills. That’s a lot to pin on a single idea. Brusaw showcases the intelligent highway aspect of the Solar Roadway, and discusses other ideas, in the following clip from the documentary film Your Environmental Road Trip (YERT).

So are the Brusaw’s crazy, or is this a feasible idea? When it comes to projects like this, it’s all about the numbers. Sure, we could pave the streets with solar panels, but we could also pave them with gold. The question is, is the Solar Roadways concept worth it? Well, Scott Brusaw has a whole section on their website dealing with those numbers. If you’re interested in this project I greatly urge you to read that webpage (along with the FAQ) because it covers the idea in a detail I don’t have time for here. Instead, I have to summarize:

Commercial solar panels are available at 18.5% efficiency, if we replaced all the highways in the lower 48 states with solar panels of the same surface area then we’d get about 14 billion kilowatt hours of electricity. That’s roughly three times what the US uses each year, and about equal to what the world consumes each year. The cost? Brusaw is aiming for each road 12′ by 12′ panel to cost around $10,000 and for the average lifespan of the panel to be about 20 years. There is roughly 29,000 square miles (~800 billion square feet) of road surface to cover. We need roughly 5.6 billion panels to cover that area. That’s a price tag of $56 trillion! Brusaw points out, however, that at current retail electricity prices the road would pay for itself in about 22 years. Quicker if we used panels with greater efficiency.

He also says that asphalt roads aren’t that much cheaper. He supposes that an asphalt road costs about $16 per square foot and lasts for 7 years. If the solar panel road lasts for 20 years, it would be about the same cost per year.

He’s not quite right about that. First, $16 per square foot is about right for highway strength asphalt roads. Your average residential roadway is much closer to $2-3 per square foot, however. Also, many roads (highways or otherwise) aren’t replaced every 7 years, but rather every 10 to 20. In any case, even if we accept Brusaw’s numbers ($16 per square foot, 7 years versus $10,000 for 144 square feet every 20 years) the solar cell road is still about 50% more expensive ($3.47 per square foot -year versus $2.29 per square foot-year). Now, if petroleum prices continue to rise then maybe asphalt roads will be as expensive as $10k solar panels…but right now that’s simply not the case.

Still, a little hand waving in the cost of asphalt hasn’t lessened the exposure the Solar Roadways concept has received. Consulting firm Booz-Allen has brought the concept to Washington. Online media has covered the story extensively. Solar Roadways was a finalist in the Annual Creativity in Electronics Award (ACE). It’s a prominent feature in the YERT documentary, and Scott recently spoke at the TEDxSacramento conference. Here’s another video from YERT (much the same as the one above but with different editing) and two that cover the TEDx presentation. In these clips Brusaw reveals more of his philosophical and emotional stakes in the concept.

Unfortunately, nothing in the videos above, or the Solar Roadways website leads me to believe that they’ve generated significant amounts of electricity with the panel yet. That’s a major concern, I think. Along with a prototype that generates electricity in large quantities, I would also like to hear Brusaw, or anyone, explain how the roadway would store electrical energy. Solar power is not steady, even during the day, and there would have to be some major infrastructure to translate a solar road into a continuous source of electricity.

I’m also concerned with how much this project depends on the undeveloped technology of the glass surface. We haven’t seen a single panel of this magic substance which will be able to handle all the requirements that Brusaw has laid out for it. Nor have we really seen any numbers on what that substance will actually cost. And how will it stay clean? The Solar Roadways FAQ proposes that the roadway could use self-cleaning glass, or that we could simply clean it with a street sweeper. I sense some more hand-waving here.

But maybe we’ll have clearer answers to these concerns in the years ahead. Solar Roadways seems bent on raising funds and developing future prototypes. You can vote for their concept in the GE Ecomagination competition where $200 million in funding (in total) is at stake, and you can personally donate to the cause through their website. Hopefully additional funds would allow Solar Roadways to build a prototype that actually generates usable amounts of electricity and stores it for later use.

Until they do produce such a prototype, I’m not sure I’ll believe in the Solar Roadways concept. It’s definitely a cool idea, and the Brusaws have put some very interesting thought into it, but there’s just too many important questions that have yet to be fully answered. I don’t think it’s a crackpot idea, I just doubt it’s feasibility. But who knows. Maybe the glass technology will appear soon, the storage technology will be developed, and the costs will prove to be reasonable. If that does happen, believe me, I’ll be one of the first to endorse and drive on a solar panel road.

[screen capture: YERT/Solar Roadways]

[source: Solar Roadways]

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