Solar Roadway

[Professor Science]

I'm thinking that if you want solar panels along a road, the best place might be on canopies above the traffic. Just like they build solar collectors above some parking lots.

That defeats the purpose of having them near the road. If you use them as a canopy then you still have to pay for the road, the idea is to get multiple uses out of the same infrastructure to potentially reduce costs.

[Art Carlson]

I'm thinking that if you want solar panels along a road, the best place might be on canopies above the traffic. Just like they build solar collectors above some parking lots.

That defeats the purpose of having them near the road. If you use them as a canopy then you still have to pay for the road, the idea is to get multiple uses out of the same infrastructure to potentially reduce costs.

Still there are a number of reasons, in addition to the obvious difficulty of making solar cells you can drive on for decades, that a canopy system might be more cost effective at the end of the day. They would help keep the roads dry and free of snow and ice. You could tilt the modules to collect sunlight more efficiently. Some of them could double as noise reduction walls. Compared to cells mounted on roofs, you may have to worry less about shadowing and being shadowed upon. Compared to cells mounted in fields, you have less expense and trouble getting the rights.

[Professor Science]

how high are you willing to build this solar canopy? semi's are big, but there are even taller 'chines I've seen driving sometimes.

[MirariNefas]

If, while you were at it, you added walls between opposing lanes, you'd channel airflow in a way which reduces resistance for cars. I've been thinking for awhile that a cheap, transparent plastic canopy might make sense on some highways for fuel efficiency and weather mitigation. Of course, if you actually entubed everything like I'd envision, you'd need semitransparent solar cells. I don't think such a thing exists. And if the snow builds up and blots out the light, you might just replace the snowplowing expense with a lighting expense. But given a reduction in accidents by keeping out crosswinds, wind, rain, and ice that might not be so bad.

[Skipjack]

how high are you willing to build this solar canopy? semi's are big, but there are even taller 'chines I've seen driving sometimes.

I would assume that it does not have to be any higher than the overhead signs, tunnels and bridges that go over the highway.

Here in Austria, we already have sound protection walls along long stretches of our highways. They can get many meters high. I am wondering whether it would pay off to simply cover make these out of panels covered with solar cells for a starter. But then solar cells would have to get cost efficient first.

Thinking about it, they are actually starting to line the railroads with these walls now also.

Having them go overhead like canopees would probably result in some difficulties, at least in our parts of the world. We can get meters of snow. That is a considerable amount of weight. Since the structure would have to be free carrying and span the entire width of a highway, you might end up facing some interesting static challenges. At least to a layman like me, who is not familiar with the static requirements for building something like that. The more lanes that highway has the worse the problem gets (4 lanes per direction is quite a few meters that have to be spanned without support collumns. I guess you could make it like suspension (correct word?) bridges, but I am not to sure about how well that would work, especially given the need for this to be rather cheap.

[MSimon]

The collapse of the world economy is driving down solar cell prices. They are expected to cost $1 per watt (peak) in 2010 and as low as $.50 per watt in 2011.

Current prices are in the $2 per watt range.

[pfrit]

how high are you willing to build this solar canopy? semi's are big, but there are even taller 'chines I've seen driving sometimes.

I would assume that it does not have to be any higher than the overhead signs, tunnels and bridges that go over the highway.

Here in Austria, we already have sound protection walls along long stretches of our highways. They can get many meters high. I am wondering whether it would pay off to simply cover make these out of panels covered with solar cells for a starter. But then solar cells would have to get cost efficient first.

Thinking about it, they are actually starting to line the railroads with these walls now also.

Having them go overhead like canopees would probably result in some difficulties, at least in our parts of the world. We can get meters of snow. That is a considerable amount of weight. Since the structure would have to be free carrying and span the entire width of a highway, you might end up facing some interesting static challenges. At least to a layman like me, who is not familiar with the static requirements for building something like that. The more lanes that highway has the worse the problem gets (4 lanes per direction is quite a few meters that have to be spanned without support collumns. I guess you could make it like suspension (correct word?) bridges, but I am not to sure about how well that would work, especially given the need for this to be rather cheap.

Think about Australia's dingo fence being entirely made of PV panels. HUGE amounts of power with no one to use it.

[Art Carlson]

how high are you willing to build this solar canopy? semi's are big, but there are even taller 'chines I've seen driving sometimes.

One inch higher than the lowest overpass or tunnel on that stretch, I suppose.

[Stoney3K]

how high are you willing to build this solar canopy? semi's are big, but there are even taller 'chines I've seen driving sometimes.

One inch higher than the lowest overpass or tunnel on that stretch, I suppose.

Would work for railway lines as well, those might even be easier to install as most railways already have a catenary system with support gantries, cables and everything in place.

Powering the trains underneath with the solar collectors overhead, and supplying the excess power to the grid would really make the train go zero-emission.

[MSimon]

how high are you willing to build this solar canopy? semi's are big, but there are even taller 'chines I've seen driving sometimes.

One inch higher than the lowest overpass or tunnel on that stretch, I suppose.

Would work for railway lines as well, those might even be easier to install as most railways already have a catenary system with support gantries, cables and everything in place.

Powering the trains underneath with the solar collectors overhead, and supplying the excess power to the grid would really make the train go zero-emission.

Not enough energy for that.

[Stoney3K]

Not enough energy for that.

Well, that DOES pretty much depend on the amount of traffic running over a line, right? Suppose a train passes over a specific section of track every 15 minutes, and takes about 45 seconds to pass (counting passenger trains here), that would mean the remaining 57 minutes *nothing* happens.

During the daytime, that means a section would be under zero-load conditions most of the time, and have time to charge batteries or supercapacitors which feed the existing catenary through the substations. The energy stored in the substations could be augmented subsequently if trains use regenerative braking.

I'm also suggesting covering the entire length of the track with panels, not just the spots where the gantries are (like, every 300 feet or so). That would amount to a considerable surface area which is lit during the daytime.

[Jboily]

One inch higher than the lowest overpass or tunnel on that stretch, I suppose.

Would work for railway lines as well, those might even be easier to install as most railways already have a catenary system with support gantries, cables and everything in place.

Powering the trains underneath with the solar collectors overhead, and supplying the excess power to the grid would really make the train go zero-emission.

Not enough energy for that.

I am not quite sure about that. A 100Km length of tract, with a 10 meter wide array (1Km^2) would produce about 300 Mw during a sunny day.

On the other hand, a 1Km^2 solar array on an unused piece of land makes the array much easier to maintain, and would have a much lower installation cost.