Solar Roadways - Working prototype and pictures!

[dsm363]

Up here in the frigid north, the snow-clearing ability of this proposal is intriguing. Solar sidewalks, anyone?

That is where I think it could be of use. Is it powered from the grid if there isn't enough sun?

 

[ToddRLockwood]

The concept assumes a very stable roadbed. What about frost heaves? It's unlikely that the modules would be able to conform to seasonal bumps in the road. This seems like a warm-climate-only solution.

 

[bsd]

The concept assumes a very stable roadbed. What about frost heaves? It's unlikely that the modules would be able to conform to seasonal bumps in the road. This seems like a warm-climate-only solution.

Since they're generating heat to melt snow so that it doesn't build up on the surface, the ground below will not freeze and so no heaves will occur? (Speculation on my part.)

 

[wart]

Since they're generating heat to melt snow so that it doesn't build up on the surface, the ground below will not freeze and so no heaves will occur? (Speculation on my part.)

I think that part was pretty well covered by the video posted by HVM on the previous page. It takes a LOT of power to melt snow. Probably far more than the panels would be able to generate. So if the panel can't keep up on its own, then it will get covered in snow, in which case it's not generating power, so the power has to come from somewhere else. So if you need another source of power anyway, what's the point having solar panels in the road?

They have their crowdfunding money, so maybe we'll see a larger scale demo in the next few months. Then we'll find out if they have answers to some of the basic engineering issues that many people have raised.

 

[djplong]

A mall here in New Hampshire would be better off with a solar roadway parking lot versus solar canopies. You put solar canopies up and, all of a sudden, the front-end loaders that do the bulk snow removal can't operate. *IF* the solar roadway melts it in the first place. you can consider the cost of that electricity versus the cost of plowing.

 

[RichardC]

A mall here in New Hampshire would be better off with a solar roadway parking lot versus solar canopies. You put solar canopies up and, all of a sudden, the front-end loaders that do the bulk snow removal can't operate. *IF* the solar roadway melts it in the first place. you can consider the cost of that electricity versus the cost of plowing.

Agreed, but the "IF" is a very big one. There a many communities in Canada where it is too cold to use salt to melt ice and the frost goes to a depth of six feet or more. I cannot believe that it would be feasible to use resistance electric heating to melt snow and to keep the resulting water liquid when the ambient temperature is minus 50 or 60 degrees. It would be helpful for the proponents to provide some technical information concerning the temperature bands in which this technology is proposed to be viable, and the energy required to melt snow and dispose of the resulting water.

 

[TheTalkingMule]

If you have a solar parking lot, isn't it going to be slightly inefficient with hundreds of cars parked on top of it.

 

[Mookuh]

Melting the snow on top of the roads with the energy generated is impossible.
Most important, when the road is covered in snow, the panels will not generate electricity. So all the energy required would have to be "brought in" anyway, and as was pointed out before, the energy required would be ludicrous. It's unlikely to be available from other parts of the solar-panel roadwork as the energy harvested in winter, especially of unaligned panels, is low.
On a more theoretical basis, if the energy the sun delivers to the area was enough to melt the snow, well... the sun would melt the snow. Solar panels operating "at 15% efficency" would simply be unable to generate the energy required.

 

[bsd]

Melting the snow on top of the roads with the energy generated is impossible.

They acknowledged that: it would have to draw on the grid somehow. (It's one of my concerns about putting up solar panels on my roof).

The question would then be: is it better to suck up energy to melt vs the energy used to plough and salt/sand the roads (with associated wear and tear)?

 

[Robert.Boston]

Here on the East Coast, we often have the heaviest snows when temperatures are not very far below freezing. If the solar roadway/parking lot was "pretreated" by warming it modestly to, say, 40°F then the snow would not accumulate at all. If ambient temperatures were -40°, then you've got a problem.

Someone with the necessary physics knowledge, some time and a calculator could probably figure out the energy requirements to keep a road surface above freezing at various temperatures and various rates of snowfall.

 

[derekt75]

Let's say your road is 20 m wide, snow is falling at 1"/hr, and the ambient temperature is 0°C.
In one km of road, you have 20,000 m². We're getting about 2 mm of water per hour, so that's 40 metric tons of water per hour, or 10 kg per second.
We need 334 kJ to melt 1 kg, so we need about 3 MW of power per km of road.

There are over 50,000 km of road in MA, so that would be about 170 GW to melt all the snow falling. Massachusetts can currently handle about 14 GW on its grid, so melting snow on all the roads would require something like 10 times the current generation capacity of the state.

or you could toss some salt down. Aluminum cars don't rust.

 

[ToddRLockwood]

Since they're generating heat to melt snow so that it doesn't build up on the surface, the ground below will not freeze and so no heaves will occur? (Speculation on my part.)

Frost can go down into the ground several feet, and the heat from the solar road would rise rather than going into the ground.

The other problem is this: What if a snowstorm starts at sunset and lasts through the night? Even if you had a clear morning, you'd have to plow before the panels would begin generating heat.

I still can't believe that the road surface would maintain its texture after a year of heavy traffic. When you wear down asphalt, you just get more asphalt, but when you wear down textured glass, you get polished glass.

 

[Mookuh]

Massachusetts can currently handle about 14 GW on its grid, so melting snow on all the roads would require something like 10 times the current generation capacity of the state.

Well, they are proposing to set up an entire new grid under the earth. Which is possible, but I think they underestimate just how difficult high voltages and currents become to handle. You can't really transfer AC through cables for long distances, so it would have to be DC. Which needs very high voltages to be efficient, which needs a lot of isolation, etc. etc.

 

[artsci]

Well, they are proposing to set up an entire new grid under the earth. Which is possible, but I think they underestimate just how difficult high voltages and currents become to handle. You can't really transfer AC through cables for long distances, so it would have to be DC. Which needs very high voltages to be efficient, which needs a lot of isolation, etc. etc.

Where is Nikola Tesla now that we need him? Imagine if his inventive imagination were set loose on these problems. Sadly such genius is conspicuously absent today.

 

[derekt75]

Well, they are proposing to set up an entire new grid under the earth. Which is possible, but I think they underestimate just how difficult high voltages and currents become to handle. You can't really transfer AC through cables for long distances, so it would have to be DC. Which needs very high voltages to be efficient, which needs a lot of isolation, etc. etc.

The problem with melting snow isn't how much power can be transmitted from here to there; the problem is that melting snow takes too much energy. Why would you use an order of magnitude more power than the state currently uses just to melt snow. If you can easily create that much power, put it on the grid and sell it as electricity, not melted snow. Large scale melting of snow is simply a waste of electricity. Even on a small scale, melting snow on the edge of your roof is more costly than a snow rake, but an individual can justify the convenience. It's hard to see how spending terawatt-hours of electricity to melt snow (hundreds of billions of dollars) can justify fewer snowplows (hundreds of millions of dollars).

 

[tdelta1000]

The Solar Roadway can be used to help grow the Supercharger Network with added costs to TM. Just a thought.

 

[Jaff]

True, but remember... the salt / sand / brine used to treat our roadways for safer winter use is a major cause of both land and water pollution and a very costly maintenance expense ...does the expense of hundreds of billions of dollars of electricity to melt the snow on our roads really matter if the solar roadway (in some way, shape or form) generates enough surplus electricity to justify the cost?

The problem with melting snow isn't how much power can be transmitted from here to there; the problem is that melting snow takes too much energy. Why would you use an order of magnitude more power than the state currently uses just to melt snow. If you can easily create that much power, put it on the grid and sell it as electricity, not melted snow. Large scale melting of snow is simply a waste of electricity. Even on a small scale, melting snow on the edge of your roof is more costly than a snow rake, but an individual can justify the convenience. It's hard to see how spending terawatt-hours of electricity to melt snow (hundreds of billions of dollars) can justify fewer snowplows (hundreds of millions of dollars).

 

[santana338]

Well, they are proposing to set up an entire new grid under the earth. Which is possible, but I think they underestimate just how difficult high voltages and currents become to handle. You can't really transfer AC through cables for long distances, so it would have to be DC. Which needs very high voltages to be efficient, which needs a lot of isolation, etc. etc.

Um, I thought it was the other way around. AC is needed in transmission lines because DC loses too much through line resistance. In fact, Nicola Tesla was an AC proponent and Thomas Edison was a DC proponent. What am I missing here?

In any case, there are other issue with putting high voltages underground. The cost of making sure runoff does not allow water to come anywhere near the high voltage lines will definitely make the road bed design much more expensive than it currently is. On the flip side though, a properly built road bed will make the road last longer whether the surface is asphalt, concrete, or solar tiles.

 

[Skotty]

Well, they are proposing to set up an entire new grid under the earth. Which is possible, but I think they underestimate just how difficult high voltages and currents become to handle. You can't really transfer AC through cables for long distances, so it would have to be DC. Which needs very high voltages to be efficient, which needs a lot of isolation, etc. etc.

EDIT: This confused me, because I know I had read before something about how AC can be used to transfer energy over long distances. But what I was recalling ended up having more to do with the ease of converting to higher voltage for transmission than the use of AC.

I did a little greenhorn web research on AC vs DC, and this site is pretty good (though still a longer read than I was looking for to explain the differences): AC vs. DC Powerlines and the Electrical Grid | The Energy Collective

For anyone who wants a quick summary of why AC rather than DC (currently and in the past), just read the last paragraph. The first line of that paragraph gives the really short answer:

"Nearly all of the above factors would seem to favor DC over AC transmission, so why are most transmission lines, and virtually all power distribution lines AC? Simply put: transformers (which change voltage of electrical power) and circuit breakers are dramatically less expensive for AC than for DC power."

 

[santana338]

I'll have to research this more. I've heard it both ways regarding what is better for distance.

Good wikipedia article here. AC for short distances, HVDC for very long distances. I guess Edison got even in the end...

Wikipedia Electric Power Transmission