Last week I wrote a post about the Solar Roadways Indiegogo campaign that had been sweeping the media. In it I did a lot of back of the envelope math to come up with some figures that made them seem reasonable based on my assumptions which lead me to the conclusion that they looked feasible with the caveat that I was working with very little information. Still I did a decent amount of research into some of the various components to make sure I was in the same order of magnitude. You’d then think that the venerable Thunderf00t’s takedown video on this project would put me at odds with him but, for the most part, I agree with him although there were a couple of glaring oversights which I feel require some attention.
FIrst off let me start off with the stuff that I agree with. He’s completely correct in the assertion that the tile construction isn’t optimal for road usage and the issues that arise from it are non-trivial. The idea of using LEDs sounds great in principle but as he points out they’re nigh on invisible in broad daylight which would make the road appear unmarked, a worrying prospect.Transporting the energy generated by these panels will also be quite challenging as the current produced by your typical solar panel isn’t conducive to being put directly on the grid. The properties of the road also require further validation as whilst the demonstrations shown by Solar Roadways say they’re up to standard there’s little proof to back up these claims so far. Finally the idea of melting snow seemed plausible to me on first look but I had not run any numbers against that claim so I’d defer to Thunderf00t’s analysis on this one.
However his claims about the glass are off the mark in many cases. Firstly it’s completely possible to make clear glass from recycled colour glass, usually through the use of additives like erbium oxide or manganese oxide. I agree on his point that it’s unlikely that they have the facilities available to them to do this right now however it’s not out of the realm of possibility. Thunderf00t also makes the mistake of taking a single item price of a piece of tempered glass off eBay and then uses that to extrapolate to the astronomical cost for covering all of the roads in the USA with it. In fact tempered glass produced at volume is actually rather cheap, about $7.50 per square meter, when you check out some large scale manufacturers. This makes the cost look far more reasonable than the $20 trillion that was originally quoted.
The same thing can be said for the solar panels, PCBs, LEDs and microcontrollers that are underneath them. Solar panels can be had for the low low price of $0.53 per watt (a grand total of about $30 per panel) and RGB LEDs for about $0.08/each (could have 1000 in each panel for $80). Indeed the cost of the construction of the panels themselves are likely to not be that expensive, especially at volume, however the preparation for the surface and the conduit channel are likely to be more expensive than your traditional road. This is because you’d likely have to do the same amount of site prep work for both of them (you can’t just lay these tiles into dirt) and then the panels themselves would be an incidental cost on top.
Tempered glass is also a lot harder than your regular type of glass, something which Thunderf00t missed in his analysis. It’s true that regular glass has a Mohs hardness of around 5 but tempered glass can be up to 7 or higher, depending on the additives used. Traditional road surfaces have a very similar hardness to that of tempered glass meaning they’d stuffer no more wear than a traditional road surface would. Whether this would mean a degradation in optical quality, and therefore solar efficiency, over time is something I can’t really comment on but the argument of sand and other things wearing away the surface doesn’t really hold up.
All this being said though Thunderf00t hits on the big issues that Solar Roadways has to face in order for their idea to become a reality. Whilst I’m still erring on the side of it being possible I do admit that there are numerous gaps in our knowledge of the product, many of which could quickly lead to it being completely infeasible. Still there’s potential for this idea to work in many areas, like the vast highways throughout Australia, even if some of the more outlandish ideas like melting the snow on them might not work out. It will be interesting to see how Solar Roadways reacts to this as there are numerous questions which can’t go unanswered.