Streets paved with Silica: An Assessment of Solar Roadways

I woke up this morning to find a link to this video sitting on my facebook newsfeed:

The video promotes solar (freaking) roadways: octagonal road tiles topped with frosted glass that not only generate power, but can also use it to light up in different patterns to direct traffic, heat themselves up to melt snow, and communicate with each other to detect the presence of obstructions on the road. The technology is also proposed as a way or revolutionising outdoor public spaces such as parks and squares by allowing them to instantly transform themselves into basketball courts, children’s play areas, or anything else.

Solar roadways are a very intuitive concept. Solar power installations require a lot of space, while roads take up a lot of space, so why not combined the two? But the couple developing the technology have apparently gone way beyond this simple intuition. Not only have they built a prototype solar parking lot near their house, but they also have a lengthy FAQ on their website that answers a lot of pretty important and detailed technical questions. They’ve considered everything from traction to earthquake damage to what happens if people start stealing the tiles. They also have a very viable plan for expansion of the technology: They will start with parking lots, driveways and sidewalks before moving on to harder stuff like highways. And something definitely has to be said for their recent promotional efforts. The video seems destined to go viral, while the various images they have on their website seem like some pretty effective and attractive future visions. And above all that, they apparently have the backing of both Google and the Department of Highways. So that’s nice for them.

That being said, there is one gigantic red flag in both the videos and the website. They haven’t made any effort to price the technology. Not even a ballpark estimate. I can understand why this is the case. The technology is still at a very early phase of development, and they haven’t really had a chance to figure out the realistic production costs of the panels. But the entire premise of solar roadways seems to be that they can allow roads to pay for themselves by producing solar power-a promise which depends pretty heavily on whether the power generated by the panels over their average lifetime will be sufficient to pay for their production and replacement. So the cost question needs an answer, and quickly.

Of course, there are ways that the panels could be made a good deal cheaper. Maybe they can eventually be 3D printed. And it maybe by self-driving automated road maintenance robots could replace them. And maybe broken ones can be repaired in some centralized facility to keep replacement costs down. All of these seem like plausible ways that this system could in fact be affordable. But they are mere possibilities at this stage, and so we shouldn’t rely on them.

One of the proposals for this technology that I don’t like is snow clearing. The idea is that in the winter, heating elements installed in the tiles would maintain a temperature just warm enough to stop snow from collecting on the road, and that would mean no need to shovel snow. It sounds great, but some problems emerge as soon as you start to run the numbers. The website, to its credit, acknowledges that solar roadways would have to take power from the grid to melt snow. After doing a bit of math and wikipedia research, I was able to figure out that for a 3.7 meter wide highway lane, a one centimeter snowfall would require at least 85 megawatt-hours to melt. In Ontario, that would cost between $6000 and $11000. If the power came from natural gas, it would release 37 tons of CO2 into the atmosphere. If it came from coal, it would release 85 tons. And remember that this is just for one kilometer of road, with a measly one centimeter of snow. The financial and environmental costs of keeping the road clean all winter would be immense. So I’m not sure how suitable this technology would really be for some places. The snow-melting proposal doesn’t seem viable to me, and I don’t expect that solar roadways would do much good in, say, Manchester, where it’s always raining. You need sun to make solar panels work, even if those solar panels are cleverly integrated into roads.

There’s one other concern I have about this technology that I haven’t seen mentioned yet: surveillance. If the panels have pressure sensors in them, ostensibly to detect obstructions in the road, then it would be trivial to determine the mass of somebody’s car and use that information to track their movements. This would be handy in catching criminals or tracking stolen vehicles, of course, but I can think of a lot more nefarious uses for that capability and I don’t trust organisations like the NSA to avoid putting them into practice.

To conclude, then, I’m calling this project distinctly plausible. It has some interesting potential uses, a working prototype, a pretty good public relations campaign, and the backing of some big players. If these are rolled out strategically, starting with private driveways and then moving to public sidewalks and basketball courts and finally on to roads, then solar roadways could become a thing. And while I think the case for solar roadways is somewhat overstated (which is itself a strategic move), and there are issues with the costs of snow melting and surveillance, they do seem like a good idea on balance. So keep an eye on this, and maybe even go donate to their indiegogo campaign.


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