The Terrible Idea That Won't Die: Solar Roads

From Engadget:

Solar Roadways' dreams of sunlight-gathering paths are one step closer to taking shape. Missouri's Department of Transportation is aiming to install a test version of the startup's solar road tiles in a sidewalk at the Historic Route 66 Welcome Center in Conway. Okay, it won't be on Route 66 just yet, but that's not the point -- the goal is to see whether or not the technology is viable enough that it could safely be used on regular streets. You should see it in action toward the end of the year.

The tiles will be familiar if you've followed Solar Roadways before. Each one combines a solar cell with LED lighting, a heating element and tempered glass that's strong enough to support the weight of a semi-trailer truck. If successful, the panels will feed the electrical grid (ideally paying for themselves) and make the roads safer by both lighting the way as well as keeping the roads free of rain and snow. They should be easier to repair than asphalt, too, since you don't need to take out whole patches of road to fix small cracks....

As the Transportation Department's Tom Blair observes, it would be odd to push self-driving cars in the state's Road to Tomorrow initiative when the streets aren't as smart as the vehicles using them.

This has so much stupid in it, I don't even know where to start.  First, solar roads are a terrible idea.  Even if they can be made to sort of work, the cost per KwH has to be higher than for solar panels in a more traditional installations -- the panels are more expensive because they have to be hardened for traffic, and their production will be lower due to dirt and shade and the fact that they can't be angled to the optimal pitch to catch the most sun.  Plus, because the whole road has to be blocked (creating traffic snafus) just to fix one panel, it is far more likely that dead panels will just be left in place rather than replaced.

And who in their right mind would ever accept the statement that the solar panel roads would be cheaper to fix than a roadway?  What agency anywhere takes out whole patches of road to fix small cracks?  Square foot for square foot a solar road would be orders of magnitude harder to fix than just patching a pothole somewhere.

I love the line about "ideally" paying for themselves.  I am sure this is their ideal, but what is the reality?  I will bet anyone a million dollars that if all installation and maintenance costs are included, these will not come close to paying for themselves.  The first rule of alternate energy in any news article is to give the installation cost or the energy output, but never both, so actual return on investment can't be calculated.  If they give neither, as in this case, it really sucks.

And finally, what is not to love about the last paragraph, which says effectively that roads should be as smart as the cars that drive on them.  I have toyed with the idea of creating a whole new blog category on things people say that get millennials excited but make absolutely no sense.  This would be a good example.  Embedding solar panels in a road when just about any other flat surface anywhere would be a better place to put them is not "smart", it is painfully stupid.  A smart road might embed guide wires or some other technology to aid self-driving cars, but nothing like this.


  1. DaveK:

    I always liked the idea of putting in "piezoelectric speed bumps" that harvested energy from the cars running over them. Moar Free Energy!


  2. Richard Harrington:

    About that whole, "paying for itself" sort of concept - what do you think the more traditional boondoggles like public transit systems? The problem I see is that because of their cost structure there is no economy of scale. Just looking at top line numbers from the King County Metro (Puget Sound area) it costs about $12 per trip (budget = $1.4B / 120.9M trips). I've seen other analysis as high as $20/trip (I think they purposely make it hard to analyze their budgets, and leave critical information out). That's an incredible cost considering the quality of service! If there are no, or perhaps negative, economies of scale, and as these transit systems force customers to switch, that $1.4B for 3% of daily trips becomes actual money really quickly.

    In other words, can we even afford to drastically increase the size of transit systems considering how inefficient they are on simple things like buses???

  3. kajota:

    EEVBlog has went through the math more than once on these ridiculous things.

  4. Don:

    The smart part is the guy who designed a new scam to get politicians to give him our money.

  5. Arne:

    "Streets aren't as smart as the vehicles using them" is the equivalent of "dirt isn't as smart as the implements harvesting crops on it" or "coal isn't as smart as the equipment mining it" or "trash isn't as smart as the dumpsters hauling it"

  6. Ike Pigott:

    What does Warren think about the more traditional boondoggles like public transit? Just do a search on this site for "light rail."

    And don't wear anything flammable.

  7. jdgalt:

    Public transit, and especially rail transit, is indeed a major waste of money if you assume it's intended to replace driving. But if it is understood as a form of welfare for people who either can't afford a car, or can't qualify for a driver's license, then at least bus service makes a lot more sense.

  8. KAF:

    So, can anyone do the math on how much energy it would require to keep the snow melted during a Missouri winter? I'm guessing that would be a requirement if you're going to have a glass roadway.

  9. ToddF:

    "And who in their right mind would ever accept the statement that the solar panel roads would be cheaper to fix than a roadway?"

    Any graduate of a school of government. But you did state "right mind," didn't you.

  10. marque2:

    Except at any chance they get rid of bus service for the poor and replace it withight rail for the middle class.

  11. ano333:

    The only positive thing to say about these solar roads is at least you would not have to cut down a forest to install the solar panels....

    Edit: Unless you cut down trees next to the roads in order to let early/late day sun hit it at an angle, I guess...

  12. Ward Chartier:

    The ones who write this drivel are the ones who wail, "Math is hard! Science is hard!"

  13. Corky Boyd:

    If you read the original article you will see an artist's rendering of glass topped road in segments with the PV cells beneath each one. I doubt anyone has checked the skid resistance of such a surface, especially under damp conditions with a misting of oil on it. But we will find out how bad it is when it gets built.

  14. Jaedo Drax:

    It's simple, the roads are paid for with OPM (other peoples money) so they don't care that it will be wasted, as long as they get their cut. Incentives matter.

  15. Ann_In_Illinois:

    We have to build it to see what's in it? These proposals keep coming from the Party that claims to be about science and the evidence.

  16. markm:

    Quite aside from the economic insanity of solar panels placed at a low angle to the sun, and where they'll accumulate dirt to block the light, it would make a very poor road surface in many ways. What is the coefficient of friction for rubber on glass? How much is that reduced by oil, water, and both? I suspect that even with an etched surface, solar cells will be much slicker than asphalt roads.

    Sand blows on roads, even in a wet climate like Michigan or Oregon, and quartz granules are as hard or harder than glass. Tires will grind that into the glass, scratching it extensively. How will that affect light transmission? Furthermore, I expect that the glass will wear down much faster than asphalt/aggregate roads; the aggregate (pebbles and sand) is tougher than glass, and the asphalt "tar" itself will usually give under a sand grain and then gradually recover it's shape, where bits of glass will be gouged out and become more grit on the road.

    And that's assuming that the glass is tempered and thick enough that a pebble stuck in a tire tread won't shatter it. Each slab of glass would be very expensive. I suspect that if we really needed to use the road surface area for solar panels, it would be cheaper to roof over the road (or build the framework for a roof but don't cover it) and put normal panels up there, slanted to the optimal angle.

    The road might become undrivable even before the panels break down. Instead of a continuous ribbon of slightly compliant asphalt/aggregate, it's a series of rigid slabs. With weather and heavy vehicles, things shift under the roadbed all the time. Asphalt can bend to cover minor shifts, but gives potholes and cracks if it goes too far; these can be repaired by pouring in more asphalt, although the repairs are always bumpy. With glass slabs, any shift and the edges no longer match up. Instead of irregular little bumps, you get bumps spaced regularly, at the length of the slabs; better hope that doesn't match a natural frequency harmonic of your suspension. It also allows rainwater to flow through the cracks and erode the bed, so I guess a road crew would have to go around pouring tar around the edges of the solar panels, blocking more light.

  17. Max Lybbert:

    What effect will this have on apprapriating the mineral rights for the land under double yellow lines on the roads? ( )

  18. karl_lembke:

    Someone else who's done the math: