Why would it be impossible for all that at once?
Because of physics. You can't heat up the solar panel's area sufficiently to melt the snow using just the solar panel. I'm ignoring the fact that it would be under the snow and clouds for the time being. The efficiency of solar panels is very optimistically quoted at 15%. Converting this back to heat is quite efficient, let's say 100% for convenience. So we get 15% of the sun's energy converted back into heat. Cool.
Now, how much heat does snow already absorb?
https://en.wikipedia.org/wiki/Albedo#Snow
Between 10% and 60% depending on exact conditions. And guess what, usually that doesn't melt the ice. 15% won't do it either. You physically need more energy than you can produce with those panels.
I see the confusion now. See, I was always under the impression that the panels would use energy from the grid to melt the snow, not it's own solar cells. It was more of a "no more plow trucks" type of thing then "look at how efficient our panels are". Where did they make the claim that it'll melt the snow without using any grid power?
LEDs aren't exactly high powered lights.
Yeah, EEVblog's somewhat generous approximations suggest they would only use 24% of the panels' power, but he assumed a single straight line in the middle, so let's say 20-30% and call it that. I'm happy to admit that 70-80% of the energy can still be used for other stuff (no, not melting the snow, fuck off.), but that's bugger all. Again, going with EEVblog's calculations, we're looking at several hundred Watt-hours per square metre - and you can only use that during the day! For some reason the Solar Roadways people assume that you can magically store energy in the grid - that's just not how it works. You use it or you lose it.
Again, I always thought this was a "use the grid when you need to" system and not a "we don't need any outside energy!"
But I'm not stupid so I'm converting everything to metric.
Thank you.
So the total area needing to be covered is 6.096*1609.34 = 9,810.53664 m2
Each panel has an area of 1.942383212 m2
So dividing
9,810.53664/1.942383212
Total Panels needed: 5,051
You cannot realistically assume you're covering the entire road with solar panels. You need something there to actually support the cars, and the space for the LEDs, and the electronics.
Peak sun averages about 4 hours. But let's assume 2 because we have panels flat on the ground instead of at an angle.
You also assume that nothing on that strech of road is currently in shade of any sort. Not objecting to it, just pointing it out.
5,051 at 280watts = 1,414,280 watts.
Nnnnnnope. You will never get STC out of a solar panel. Make that 250W and you're still being generous. But okay, I'm liking where you're going, so let's go on with that number. Let's just keep in mind that anything you say isn't just the minimum - it's less than that.
So the flat cost of $2,020,400/mile and a return of $226/day, it would take roughly 24.5 years to break even.
You assume that the only cost incurred is the solar panel. The return will be lower, and the cost will be higher, but 24.5 years is greater than their 20 years anyway.
But what if we use cheaper panels?[...]
ROI: 10.6 years.
Again, you assume your only cost is the solar panel. It's not. They are putting A LOT of stuff in there. Also, the power losses on this thing would be ridiculous. Watch EEVblog's video, he goes over them rather nicely. You about tripled the actual power you'd get in both scenarios, even though you tried to be realistic.
Heating the road is easy and they've shown it working.
Have they? Could I see it?
It takes more energy than the panels will produce in the winter, but it can be done.
Whoah, whoah, moving-the-goalposts alert. Yes, I'm not denying that it's possible to heat stuff with electricity. I'm doing it in my room right now. Hilariously enough, that's easier to do with asphalt roads since they're better heat conductors. The problem with that is that it'd be EXTREMELY EXPENSIVE - pushing it off to the side of the road is simply more practical.
My goal was a "Magic" number that couldn't possibly be reached. And it's well above financial practicality at the moment.
Also, we seem to have different concepts on how it ties into the grid. I've always thought it would use grid energy when it needs it (like at night and during snowy weather) but you seem to think they claim self-sufficiency. If they do claim that then they're idiots.
What about the shoulder? You can have the panels supported with the "utility tunnel" under it which provides the drainage and the underground utility area. It still has solar panels and you can run heating elements from one end of the road to the other with grid tie-in to warm the asphalt.