Comment by gorkonsine | Hacker News Reader

Comment by gorkonsine | Hacker News Reader

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There's another way: put solar panels above the road. Especially for big, wide highways, there's a lot of area that's basically not used for anything except cars and trucks to drive over. Cover these with solar panels and now that land isn't just used for transportation, but also a lot of energy generation. On top of that, the cars underneath will be shaded from the Sun, which can be really useful in sunny climates, and would help people use less A/C in their cars, thus saving energy.

The two problems I see with this idea are people complaining about the "view" (which is why it shouldn't be done on some really nice scenic part of a road, but in the middle of an ugly part of the city it should), and the possible problems with wind-loading, especially during storms, though surely this has been dealt with before, as there's a lot of places where they cover parking lots with elevated solar panels like this. For the view problem, they don't even have to cover the whole road with panels, they could just cover some lanes, put them in the median and extending over the inner lanes some, etc.

>though surely this has been dealt with before, as there's a lot of places where they cover parking lots with elevated solar panels like this.

As a side note, you have to consider how in parking lots it is rare to have cars and trucks passing under the panels at 70 Mph, and more generally accidents are usually very low speed. Besides the "normal" resistance to wind, if you want to build a sort of half-pipe covering a highway you need to consider the pressure induced from the inside by high-speed moving objects and the possibility to resist accidents (preventing an 18 wheeler from completely crash a - say - 100 m section of the half-pipe in case of an accident needs a rather sturdy structure).

So, more or less it would be needed to build an artificial tunnel (concrete, rather thick) similar to a "snow shed":

https://en.wikipedia.org/wiki/Snow_shed

http://wsdotblog.blogspot.it/2014/03/the-i-90-snowshed-retir...

The "lighter" metal/lattice ones are only used usually for railways.

That's true, I didn't fully elaborate on all that but yeah, there's concerns there that wouldn't exist for a parking lot.

However, you bring up a great point with the "snow shed": covering all or part of a road with solar panels like this would also have the side effect of keeping bad weather off the road. How much money would that save in show-shoveling costs, and the costs to society of having roads blocked by snow (and snowplows), and having weather-induced accidents (both rain and snow)? Now, it's probably not feasible to cover every little road in a city with these things, but at least covering major arteries, while probably somewhat expensive due to the engineering challenges you raise, would have some major benefits: keeping the main roads clear even during horrible weather, and also providing a lot of energy from the solar panels.

You have an excellent point there, but the costs are unfortunately way too high to be feasible, not even remotely.

And you have to consider how - in places where there is snow - you have to choose to either forfeit the (possibly little) energy the panels can produce in winter or anyway clean them from the snow anyway.

The good ol' rule of the thumb is that (of course it depends on the country) the cost is 10,000,000 Euro's per km of highway (plain, mainly earthworks), 20,000,000 per km on bridges/viaducts, 30,000,000 per km in tunnels. (the "base" price may of course vary, but the relative proportions remain roughly valid)

An artifical tunnel or sbow shed, besides the solar panels, would be probably 1.5 to 1.7 times the cost of the "simple" highway.

> Besides the "normal" resistance to wind, if you want to build a sort of half-pipe covering a highway you need to consider the pressure induced from the inside by high-speed moving objects and the possibility to resist accidents (preventing an 18 wheeler from completely crash a - say - 100 m section of the half-pipe in case of an accident needs a rather sturdy structure).

I mean, aren't these issues already basically solved? I frequently drive through miles-long tunnels under Boston at 70mph.

A tunnel is already massively over specced for that because it's preventing the tons of soil/rock/building overhead from collapsing down. The forces for cars passing underneath is minuscule compared to that. For a hypothetical covered roadway you want something much cheaper and lighter so it's not mind numbingly expensive to build.

Ignoring the massive infrastructural costs and practicalities, but given the efficiency losses of the wireless-charging freeway idea, what would be the benefit of putting solar panels above the freeway and chargers underneath, over just having solar panels on the car instead?

There's not enough surface area on a car to power it in motion though. With a covered roadway you at least get the extra square footage from the empty space between cars. Still probably not feasible but it gets mildly closer.

On the whole idea powering cars wirelessly while they drive just doesn't work on mass scales. It's going to be massively expensive to build it out.

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