Why “Solar Freaking Roadways” is a really FREAKING bad idea.

By now, everyone's seen the ad for the now-fully funded (for a Million Dollars) Solar Roadways project. If you haven't.. here it is below:

          The problem with "solar freaking roadways", is that they just wouldn’t work very well at any of the things they’re supposed to. No matter how many animated cartoon people or people who-met-when-they-were-three might say otherwise. It's a cool idea, and it's great it was done, but it's been marketed as the actual solution to the world's problems instead of a very expensive tech demonstration. And that doesn't sit right with me, so let's look into why.

The Solar Panel Part

            Solar panels are great. We all love them and should have them instead of roofs pretty much everywhere! But having them under the road is simply not a smart idea.

            To make energy, solar panels need to be in the sun. Obviously. That’s why many operators put them on fancy elevated arrays that track the movement like a sunflower in the first place! A road is a terrible place to get sun.

            Firstly, it’s flat. This is a huge deal when the sun isn't directly overhead, as it is in most of North America. In Thunder Bay for example, a solar cell on the ground receives between 30 and 72% less energy than one which tracks the sun depending upon the season. 

            Secondly, it’s flat! Solar panels are tilted not only because of the sun, but also so things don’t build up on the surface like dirt, grime and bird droppings. Most estimates show that regular solar panels lose between 10-20% when not cleaned, and a dimpled road-based solar panel with a high-friction surface would hold a whole lot more dirt.

            Thirdly, it’s under a road. The thick textured glass used to protect the photovoltaic cells and electronics is designed for strength, not transparency, and thicker glass loses light as it gets absorbed on the way through. Their own numbers show an 11% loss, before the glass has been scratched and scuffed by a million passing cars. You also end up with losses due to poor air circulation/cooling of panels, but that’s a little unpredictable for something like this.

            Solar panels as roadways.. don’t really work as solar panels very well. When you multiply the losses, roadways would have at most 21-56% of the generating ability of a purpose-built solar array for a much higher cost.

The Heated Roadways Part

Although heated roadways are a fantastic technology in a “gee-whiz tech” sort of way, they’re a terrible idea for North American roads. In fact, there is only one country on earth which uses heated roadways in any capacity at all (Iceland). It only works there as the whole city blocks where exists are already heated with geothermal water for free(ish), due to the hot spring-like conditions under the city where it's used. The warm wastewater is just pumped out under the asphalt.

  To give an idea of how much energy would be needed to heat roadways like the Solar Roadways people claim, you can use Iceland’s statistics. There, it’s calculated that 430kWh in heat is used each year for every square meter.  Using an average energy price of 9.93¢ per kilowatt-hour, and assuming perfectly efficient heating gives an energy cost of about $43 per year per square meter. To give an idea of how much that would cost for a roadway to be heated, one kilometer of two-lane roadway would consume $301,000 in electricity per year. Granted, we don’t live in Iceland, so that number can be reduced a bit due to climate, but it’s still outrageous at half the price! What’s more, all that energy would be produced from non-solar high-carbon sources in the vast majority of places, as solar input drops up to 83% in the winter.  No solar panel can produce that much energy under even optimal conditions, let alone in the 16-hour darkness of a Canadian winter. If that energy was drawn from the grid as it currently works, that 1 km road mentioned earlier would produce 130 tons of carbon emissions per year. That’s a lot of carbon for 1km of roadway, and by itself makes the whole thing a very, VERY non-eco friendly technology.

The Road Part

           The idea of using high-strength glass as a road surface isn’t terribly bad itself. The problem comes when you look at cost. Not even the cost of the panels themselves mind you, as that won't be released until just after the funding drive is over. (Which is absolutely not suspicious at all...)  The cost of repairing those panels is.
           Regular asphalt roads develop potholes big enough to ruin your car every year because of winter frost working underneath, and rainwater trickling through gaps on top. Putting solar cells on top doesn’t fix that problem, it only makes it much more expensive when it does fail. An asphalt patch takes 30 seconds to shovel in, costs pennies and can even be done by me. Cracked solar-cells-containing-computers on the other hand are just a little more difficult to fix, particularly ones connected  to a powerful electrical system which has to be managed while still running. And then you need to patch the hole under them with asphalt anyway! Of course they could build  more durable roads underneath, but then again, you could just do that without stacking expensive solar panels on top.

            The use of LED’s to paint out road markings is a good idea, but not a good enough one to justify having every inch of highway covered with a reconfigurable computer-controlled light show. A programming glitch on a section of fully-lit highway would be hilarious at best, and dangerously distracting at worst.

As an Electrical Source

            Solar panels produce DC current, while it’s “shipped” as AC. This happens because AC transmits well, whereas DC fizzles out after a few hundred meters unless it gets converted and “stepped up” into AC by transformers (Not the robot kind). So you’re not just building a roadway, you’re building an entirely new electrical grid to support that roadway. Which is cool, but really, really expensive, and would work a lot better with regular solar fields. The solution suggested by the solar roadways people themselves, of just "convert all appliances to use DC" is a bad solution. Solar power needs to be part of a much larger grid, as availability changes with clouds and daylight, and while your road might produce energy one day, it'll need it the next. An efficient mid-size grid like that needs AC current for shipping. In fact, they even say this is the type of storage used.

So to sum up:

 It’s a super cool idea that combines a lot of useful things into one package that couldn’t really do any of those things very well. The only thing the combination saves on is space. The only problem is that with 99% of roofs currently sitting empty, lack of space for solar has never been a problem. Ever.

 It’s also more than a little fishy that the cost of the technology is only being released just after their funding campaign ends. But seeing as how they've already raised over a million dollars in literally free money….

 I don’t think they particularly mind.