Using roads for electricity

[Lowpro]

I thought I had a brilliant epiphany to use highways as conductors for heat then use that heat to make electricity (Not sure if they get hot enough) used my Google-Fu and discovered there are already steps in this direction (damn, thought I had my chance at millions...)

Anyways the big talk seems to be in harnessing vibrations from vehicles to be transduced through piezo conductors ( I assume like a piezo bridge on a guitar)

Anyone have any knowledge, perhaps numbers on what the yield could be?

My first thought is that all you're doing is making engines work "harder" to communicate their mechanical energy down to the road, but if they'll already doing it anyways...

[Ziggurat]

I thought I had a brilliant epiphany to use highways as conductors for heat then use that heat to make electricity (Not sure if they get hot enough) used my Google-Fu and discovered there are already steps in this direction (damn, thought I had my chance at millions...)

Bad idea. Efficiency of a heat engine scales with the heat differential. For a hot road, you're talking maybe a few tens of degrees. For an internal combustion engine, in contrast, you're talking a few hundred degrees. But that few tens of degrees (at best) is WITHOUT a heat engine operating, the heat engine itself would act to lower that difference, further reducing the efficiency. So you'd have to run it at very low power density to keep the efficiency from falling through the floor completely. But that means vast infrastructure, for low power output. Single-purpose solar power plants aren't money-makers right now - we can expect that solar power bolted onto existing infrastructure as an afterought are going to be far worse, economically speaking.

I just can't imagine how you could make this even remotely cost effective.

Anyways the big talk seems to be in harnessing vibrations from vehicles to be transduced through piezo conductors ( I assume like a piezo bridge on a guitar)

Anyone have any knowledge, perhaps numbers on what the yield could be?

Another bad idea.

Roads don't vibrate very much. And that's a good thing. So there's really not much energy there to recover. And the last thing you want to do is build roads so that they vibrate more, because that will drop the fuel efficiency of your vehicles. And because of energy conversion inefficiencies, you're guaranteed to lose more energy fro vehicle mileage decreases than you recover fro the vibrations.

My first thought is that all you're doing is making engines work "harder" to communicate their mechanical energy down to the road

Your first thought is a good thought. It's also correct.

but if they'll already doing it anyways...

But they aren't doing much of that. Very little of a car's energy gets wasted on the vibrations of the road. Even aside from engine inefficiencies, far more of it goes into air resistance and rolling resistance (basically, friction within the tire from flexing of the tire). And (as per above) you don't want to increase road vibrations, or you WILL make the cars work harder and drop their mileage.

[Bikewer]

Years ago now, I read a book that was an overview of the then-newly-emerging nanotechnology. The author had compiled a bunch of highly speculative articles and papers that were geared to what the potential of nanotech might be.
One of the things mentioned was, in fact, using nanotech to make roads into what would effectively be solar cells. The electricity produced could be used not only to feed the grid, but to heat/dry the roads in bad weather.
Essentially, you'd have millions of solar cells built into the structure of the road itself, all done very cheaply using nanotechnology "assemblers".
So far as I know, we are still inching our way towards using nanotech in a big way, some 20 years after I read this.

[benbradley]

I thought I had a brilliant epiphany to use highways as conductors for heat then use that heat to make electricity (Not sure if they get hot enough) used my Google-Fu and discovered there are already steps in this direction (damn, thought I had my chance at millions...)

Anyways the big talk seems to be in harnessing vibrations from vehicles to be transduced through piezo conductors ( I assume like a piezo bridge on a guitar)

Anyone have any knowledge, perhaps numbers on what the yield could be?

My first thought is that all you're doing is making engines work "harder" to communicate their mechanical energy down to the road, but if they'll already doing it anyways...
This sort of thing is called energy harvesting (you can google that). It's not really for generating significant electric power to add to the grid, because there's not that much power to be had that can easily be converted to electricity.

It's to power VERY LOW power devices that would otherwise be battery powered, but they're located in places where it's inconvenient to get to to replace the battery. Here's a quintessential example:
http://www.intelligent-systems.info/bridge.htm

Years ago now, I read a book that was an overview of the then-newly-emerging nanotechnology. The author had compiled a bunch of highly speculative articles and papers that were geared to what the potential of nanotech might be.
One of the things mentioned was, in fact, using nanotech to make roads into what would effectively be solar cells. The electricity produced could be used not only to feed the grid, but to heat/dry the roads in bad weather.
Essentially, you'd have millions of solar cells built into the structure of the road itself, all done very cheaply using nanotechnology "assemblers".
So far as I know, we are still inching our way towards using nanotech in a big way, some 20 years after I read this.
Nanotech is interesting, there IS progress being made in the field, but some of those applications are going to be like commercial fusion power which has been "only ten years away" for about 50 years now.

[Crazycowbob]

Another, minor point to using roads as an energy source; roads suffer an extraordinary amount of abuse. Even the best laid concrete roads need fairly constant repair and attention, and those are the expensive thoroughfares, asphalt based roads have to be completely resurfaced or replaced every two or three years. I can't imagine any system you could incorporate into them that wouldn't fail in a ridiculously short amount of time.

[patchbunny]

I would hate to install anything out there that would require more effort to maintain. It's hard enough getting our Maintenance crews to clear culverts and keep the traffic count stations operating.

That being said, ISTR a few years ago an article describing an agency in Britain that was experimenting with a pressure plate on a ramp that powered a ramp meter. I found that interesting.

[C_Felix]

I would hate to install anything out there that would require more effort to maintain. It's hard enough getting our Maintenance crews to clear culverts and keep the traffic count stations operating.

That being said, ISTR a few years ago an article describing an agency in Britain that was experimenting with a pressure plate on a ramp that powered a ramp meter. I found that interesting.

That maintenance would also kill the cost effectiveness.

[patchbunny]

That maintenance would also kill the cost effectiveness.

It just may. I wish I'd saved the link. :(

[HoverBoarder]

I thought I had a brilliant epiphany to use highways as conductors for heat then use that heat to make electricity (Not sure if they get hot enough) used my Google-Fu and discovered there are already steps in this direction (damn, thought I had my chance at millions...)

Anyways the big talk seems to be in harnessing vibrations from vehicles to be transduced through piezo conductors ( I assume like a piezo bridge on a guitar)

Anyone have any knowledge, perhaps numbers on what the yield could be?

My first thought is that all you're doing is making engines work "harder" to communicate their mechanical energy down to the road, but if they'll already doing it anyways...

You could also put wind generators in the highway medians (or just on the light posts) along with small solar arrays on the highway lights to make them self powered. Transporting in energy through long lines just to power the lights is very wasteful.

http://i1208.photobucket.com/albums/cc363/evann0/scan0002.jpg

[ApolloGnomon]

Similarly, I had an idea once while driving through Nebraska -- put a small wind turbine on every power pole. Really small - about the size of weather station anemometers. The trick is that there's one on every single pole, so they cover a large geographic area. They may not make much power, but I think they could be designed to at least offset the line resistance.

[HoverBoarder]

Similarly, I had an idea once while driving through Nebraska -- put a small wind turbine on every power pole. Really small - about the size of weather station anemometers. The trick is that there's one on every single pole, so they cover a large geographic area. They may not make much power, but I think they could be designed to at least offset the line resistance.

There has been a fair amount of different model ideas on this, and there are a lot of advantages to this type of wind energy utilization. One aspect is that you usually have to have large spaces for wind farms, and the energy created from them has to be sent long distances through power lines. Having highway wind power would mean that you could generate power right where it would be consumed, without requiring more land space to do so. I do see the advantages of using vertical wind generators on the light polls themselves though.

http://www.greencarreports.com/news/1042537_could-passing-cars-power-wind-turbine-highway-lights

http://i1208.photobucket.com/albums/cc363/evann0/wind-turbine-powered-highway-lights-concept-by-tak-studio_100306330_s.jpghttp://i1208.photobucket.com/albums/cc363/evann0/wind-turbine-powered-highway-lights-concept-by-tak-studio_100306332_s.jpg

And you don't really have to get that theoretical about it. There are over a thousand wind and solar street lights that are made in China. There are 1423 wind street lighting products sold at the Made-in-China.com store alone. (http://www.made-in-china.com/productdirectory.do?subaction=hunt&mode=and&style=b&isOpenCorrection=1&word=Wind+Light+street&comProvince=nolimit&code=0)

Here is just one of many:

http://i1208.photobucket.com/albums/cc363/evann0/Solar-Wind-Street-Light-with-Solar-Panels-and-Wind-Turbine-to-Power-The-LED-Lighting-Source-SW-BSL801-400W-600W-.jpg

[HoverBoarder]

Another, minor point to using roads as an energy source; roads suffer an extraordinary amount of abuse. Even the best laid concrete roads need fairly constant repair and attention, and those are the expensive thoroughfares, asphalt based roads have to be completely resurfaced or replaced every two or three years. I can't imagine any system you could incorporate into them that wouldn't fail in a ridiculously short amount of time.

I would hate to install anything out there that would require more effort to maintain. It's hard enough getting our Maintenance crews to clear culverts and keep the traffic count stations operating.

That being said, ISTR a few years ago an article describing an agency in Britain that was experimenting with a pressure plate on a ramp that powered a ramp meter. I found that interesting.

Both of these are good points, but if you are not using the roads themselves to generate electricity, the same power lines that are used now could be used for backup power for lighting. Wind/solar lightposts would just make it so that the main power source would rarely if ever have to be used.

If you are going to talk about capturing energy from roadways, than piezoelectric would not be the way to go.

Solar roadways on the other hand might be an option:
Ep4L18zOEYI

[falkowsi]

Having highway wind power would mean that you could generate power right where it would be consumed, without requiring more land space to do so. I do see the advantages of using vertical wind generators on the light polls themselves though.

On the other hand, the efficiency for small generators is a lot worse than for big (and tall) generators. Instead of putting one per pole, it's probably more efficient to construct a huge one every so many poles.

[Cuddles]

On the other hand, the efficiency for small generators is a lot worse than for big (and tall) generators. Instead of putting one per pole, it's probably more efficient to construct a huge one every so many poles.

Very much this. It's reasonably common to see small solar panels powering isolated signs and such, and even small turbines aren't unheard of around here. The problem is that it's horribly inefficient compared to centralised generation, and even worse for maintenance. It can make sense in certain niches, but it's just not a sensible option for general use.

[Debaser]

Very much this. It's reasonably common to see small solar panels powering isolated signs and such, and even small turbines aren't unheard of around here. The problem is that it's horribly inefficient compared to centralised generation, and even worse for maintenance. It can make sense in certain niches, but it's just not a sensible option for general use.

Along with getting rid of any unneccessary lighting (of motorways for example) we're already doing what we can to reduce power consumption of street furniture;

http://online.carmarthenshire.gov.uk/agendas/eng/SJSC20060126/REP05_01-1.gif

http://www.dft.gov.uk/itstoolkit/Pictures/Tools/T5c.jpg

http://www.traffic-products.co.uk/product-overview/bollards/solalite/

Trouble is, even with LEDs, you still need battery backup for all this kit, and as you say, at present it really only makes sense where there's no economic way to get a mains feed.

[Debaser]

As for the OPs 'epiphany', I'm afraid people (in this case the Dutch) are way ahead of you.

http://www.foxnews.com/story/0,2933,319434,00.html

http://www.foreveropenroad.eu/?m=5&page=2

http://www.brighthub.com/environment/renewable-energy/articles/8289.aspx

[HoverBoarder]

On the other hand, the efficiency for small generators is a lot worse than for big (and tall) generators. Instead of putting one per pole, it's probably more efficient to construct a huge one every so many poles.
Very much this. It's reasonably common to see small solar panels powering isolated signs and such, and even small turbines aren't unheard of around here. The problem is that it's horribly inefficient compared to centralised generation, and even worse for maintenance. It can make sense in certain niches, but it's just not a sensible option for general use.

In a general wind farm that would definitely make sense, but in this application, there would be major problems and disadvantages in using large wind turbines over small pole based or median based turbines.

One of the main reasons is space. In some areas there is room for a large wind turbine, but this is definitely not the case in all areas. Using large turbines along roadways to power the highway lighting would work in specific remote areas, but this would require extra land, new power lines (which would have to be run underneath the roadways), would require a whole slew of major environmental assessments/analyses of the structural affects of the roadways, and would take a long time to get up and running. The compromise for large turbines would most likely be to put them far away from the road requiring new power cabling and land purchases.

Another main reason is that large turbines make sense in wind corridors, and this only occurs in a portion of America. Pole based roadway turbines on the otherhand can constantly generate energy from low lying wind generated from passing vehicles. Large turbines require a lot of space, lose a lot of electricity in the transmission of energy, and face not-in-my-backyard opposition. By using large wind turbines, you would lose most of the main advantages of using turbines right along the roadway.

Small pole based turbines:

Generate constant energy from low lying wind generated from passing vehicles.
Do not require any extra land purchases.
Do not have long distance energy losses.
Do not require capacitors as they would just hook into the light pole and existing power lines.
Do not have to be repaired right away as they would be connected to the main power line, allowing crews to fix any broken ones at their leisure.
Are much easier to install and get working. Just clip them onto the pole and you're done.


I think we need more wind power generation in some areas, but in this case, it makes much more sense to have small pole based wind power generation.

[Ziggurat]

Small pole based turbines:

Generate constant energy from low lying wind generated from passing vehicles.
Do not require any extra land purchases.
Do not have long distance energy losses.
Do not require capacitors as they would just hook into the light pole and existing power lines.
Do not have to be repaired right away as they would be connected to the main power line, allowing crews to fix any broken ones at their leisure.
Are much easier to install and get working. Just clip them onto the pole and you're done.


That reason seems exactly backwards. The only significant advantage of small individual generators would be not needing to connect them the the grid at all. Otherwise, I just can't see them as being cost efficient. The fact that they might work better than large wind turbines in certain areas where large wind turbines are not cost effective doesn't mean that they will be. As far as I can tell, all the products in that China link do exactly that: store energy in a local battery so that you don't need to wire them up.

[ben m]

Some people have pointed out that road-based piezoelectric power is not free (it saps energy from the cars). I want to point out that passing-car "wind" is likewise not free, and the cars themselves are more efficient if the wind turbines are absent.

For a sort of reductive approach, picture a line of cars going down a narrow tunnel with open-mesh walls. We'll look at the difference between (a) leaving this mesh open and (b) filling it with some sort of generator that partially resists the flow of air.

The car displaces air ahead of around itself; some of that air rushes out through the mesh as the car passes, then closes in again behind the car. Indeed, the front end of the car (like a piston) slightly increases the air pressure in front of the car, and that increased pressure is what encourages the air to rush away. The same thing happens in reverse behind the car. A lot of the work that a car does at high speed is to move uphill against that pressure differential.

OK, now look at this effect in our tunnel. The car's job is easiest if the pressure difference is low---i.e. if air rushes easily away from the front of the car and towards the back. Power-generating turbines necessarily impede this flow; the car has to generate more pressure to get the air out of the way fast enough; and thus a car in a turbine-corridor has to do more aerodynamic work.

That's not all of the work the car does; there's also a lot of skin drag, turbulence, and whatnot. The car leaves a wake of swirling, blowing air behind it, which usually just dissipates by friction. If this turbulence gets drawn down by a turbine, rather than friction, that is indeed free for the car that generated it. But it's not free for other traffic on the road. My car's wake of moving air is a huge efficiency-boost to the car behind mine; the closer the better. The continuous "wind" blowing down a busy highway is an efficiency boost to every car on it. A set of turbines, by deliberately damping this wind, is forcing the traffic to drive in a column of still air rather than moving air, decreasing car efficiency.

This is all pretty marginal stuff. I doubt that the traffic-wind boost recaptures more than a few percent of the energy that the cars spend stirring it up, and I doubt that even the densest wind turbines could tap more than a few percent of it. Likewise, the "tunnel pressure" effect you'd get driving past a wind turbine is probably not much different than the one you'd get driving past (say) a concrete wall.

So---I'm all for self-powered lampposts and saving on wiring and transmission, which will have marginal to zero effect on cars. But if anyone starts talking about getting lots of grid power this way, I'd say it sounds absurd.

[ben m]

I also want to comment on microturbines.

Suppose you gave me, and 999 of my neighbors, neighbors $1500 each and said we're allowed to build wind turbines. One way to spend that would be to put a 500W turbine on everyone's roof (and I think that's on the generous side) for a total of 500 kW nameplate power. We might get a 10% capacity factor out of that, so we just spent $1.5M on 50kW.

Another way to spend it would be to pool the money and buy one $1.5M turbine on a mountaintop nearby. That'd get us a 1.5MW nameplate, we could choose a site with 30% capacity, and our $1.5M investment is now getting 500kW.

Wind has some really funny scaling laws. I think it's hard to make a good case for small-scale wind until (a) the turbines are really dirt cheap or (b) connecting to a grid is really, really expensive. We're a long way from dirt cheap; small turbines still cost 4-5x as much per rated watt as industrial ones, plus you're forced to install them on short towers in non-optimal locations.

Distributed generation is a nice goal, but it's not an end in itself. I'm all for distributed solar photovoltaics, urban biomass gasification. But first and foremost I'm for the fastest and deepest cuts in our carbon footprint, and in the wind sector that means pooling resources on the biggest possible units.

[falkowsi]

In a general wind farm that would definitely make sense, but in this application, there would be major problems and disadvantages in using large wind turbines over small pole based or median based turbines.

The distributed approach would also suffer from the fact that the wind isn't always blowing, so you'd have to accept that the lights may go out. Depending on the location, they could be out for extended periods of time.

If that's not a problem, you may consider an even simpler solution: retro-reflectors. Many roads already use them.