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Old 07-27-2014, 01:48 PM   #41
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Maybe this could have something to do with the topic? Or are we going somewhere with this?
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Old 07-27-2014, 02:34 PM   #42
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Originally Posted by krotoole View Post

This seems like a potentially interesting, scalable and maintable idea.

..l.

I think your'e right. I like the fact that the concept is actually being used with pedestrian foot traffic.
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Old 07-27-2014, 02:41 PM   #43
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Sure is a long thread for what most seem to think is a really bad idea . . .
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Old 07-27-2014, 02:48 PM   #44
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. . . this thread did get me thinking about roads and energy which got me wondering about road compression from traffic and weather as a source of power. The energy of traffic and the freeze/thaw compression destroys roads. Could we somehow capture it?
The quick search I did indicated the existing pilot projects aren't producing much juice. One key fact to know would be whether producing the power reduces the fuel efficiency of the vehicles even a tiny bit. For example, we could imagine a simple treadle or pressure-plate arrangement what would produce power from passing vehicles, but the fact that the car then needs to regain the lost 1/4" of height it lost would swamp any gains from the electricity produced.
I've seen schemes for small wind-turbines along roads to capture the energy from the wake of passing vehicles. Same question: Is there a net gain? Is it worth it?
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Old 07-27-2014, 02:52 PM   #45
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At the risk of unleashing a hurricane of criticism, this thread did get me thinking about roads and energy which got me wondering about road compression from traffic and weather as a source of power. The energy of traffic and the freeze/thaw compression destroys roads. Could we somehow capture it?

Knowing that there is rarely such a thing as an original idea, I did some googling:

robinmeadows.tumblr.com/harvestinggreenenergyfromcars

This seems like a potentially interesting, scalable and maintable idea.

I feel certain someone will tell me why this idea sucks rotten eggs. Please do so without also suggesting I am somehow genetically or educationally deficient or a stooge for some lobby or other...it's just a link to something interesting on a Sunday afternoon, not a manifesto or a request for funding.

Time to take the kids to the pool.
I have a minute, so I'll take a stab at it.

It is interesting and it might have some niche applications that make sense. But the law of conservation of energy tells me this can't create any significant power in general.

OK, so the road is compressed when a car/truck goes over it. If we aren't capturing this energy now, it must be turning into heat, right? Are the roads generating significant heat from traffic weight? I doubt it.

But if we capture it, the element has to be moving a little. What allows it to move? The rest of the road would need to be made stiffer, so the element would absorb the movement. Otherwise, the relatively soft asphalt would still just absorb (most of) the energy.

Think of it like this - imagine a spring loaded bike pump. You push it down 6" and the spring returns 6" so you get some work done (pumping air) with each stroke. Now imagine you put a balloon between your fist and the bike pump. You push, but the balloon squishes out the sides, so the pump goes down far less. The asphalt is kind of like that balloon.

The energy is coming from the vehicle. To the degree that the road flexes, it means the vehicle is getting somewhat less mpg. If we capture wasted energy, fine (but I don't think that is practical), but if we actually try to make roads more flexible, to get more energy into these elements, we are just robbing Peter (the vehicles) to pay Paul (the elements). And there will be losses in the conversion, so it is just a lost cause.

That's what they did in the sidewalk example - they are not 'creating' energy - it comes from the people. Walking on soft sand is harder than walking on a firm surface. Maybe it doesn't matter here, but it just isn't a big source of energy, or those people would be working up a sweat. Conservation of energy.

Now, to capture some of this and use it locally so you don't need to run power - that might make sense. But those are niche applications, and just not practical at high power levels.

-ERD50
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Old 07-27-2014, 04:42 PM   #46
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+1 to what Samclem and ERD50 said.

While they were posting, I did my own little investigation and like to share what I have found.

Piezo transducers have been long used as microphones or phono cartridges to convert vibrations into electrical signals. And they have been used as spark generators in cigarette and BBQ igniters. But these are tiny signals. To use them for large-scale electric power generation from road vibrations? Sounds like a harebrained scheme to me, but some articles suggested that some took it very seriously. So, I decided to take a look on the Web to see what has been done.

A Google search revealed several articles describing how an Israeli company called Innowattech in 2008 demonstrated a prototype generator embedded in a road in Israel. Details were sketchy, as some articles said that the test section of the road was 10m, some said 100m. But many repeated the claim that an energy of 2000 Wh was accumulated.

While 2 KWh is a respectable amount of energy, the time to accumulate this amount was not noted. A 200W solar panel costing around $300 retail can accumulate that much energy in 10 hours. Is that section of piezo-road cheaper than that, and can collect the same amount in less time?

Nearly all articles repeat the claim of the company that a 1-km section of the road can generate 400 KW (note that some articles said 400KWh, which is meaningless if the accumulation time was not also noted). That seems awfully high to me.

OK, so 400kW/km is 640 kW/mi. To verify that this is absurdly high compared to my intuition, I did the following simple calculation. All that energy comes from the vehicles. And how much energy are the vehicles expending? A car with an ICE converts most of its energy to heat, so let's take the Tesla which uses about 350Wh per mile.

Energy expended = 350 Wh/mile = 1,260 KJ/mile
At 60 mph, power = 1260 KJ/60 = 21,000 W = 21 KW

Using the 3-sec rule spacing between cars, and ignoring car lengths, we have 20 cars in each lane in the 1-mile length.

Total power expended = 21 KW x 20 = 420 KW/lane.

So, let's assume a 4-lane busy highway, and we still have only 1,680 KW. Of that power, how much is used by the cars to push the air in front and around them, to overcome tire rolling friction, etc..., compared to the power used to "pound" the road? And then, how much of the road compression energy these piezo elements can capture? How are we going to get 640 KW out of the total 1,680 KW?

I am sure many people here also like to see the magic formula people at Innowattech used to come up with their "guesstimate". By the way, I would like to find a truly scientific article by an independent source about the above experiment in 2008. There is also no follow-up project that I could find.


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Sure is a long thread for what most seem to think is a really bad idea . . .
But, but, but there are so many bad ideas floating around, more than the engineers among us can shake a stick at.

We are f****** doomed!
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Old 07-27-2014, 05:42 PM   #47
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Sure is a long thread for what most seem to think is a really bad idea . . .
They're engineers. This is sport for them.
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Old 07-27-2014, 07:40 PM   #48
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Following is a bit more of how common sense will tell you that the 400 kW/mile of road claimed by that Israeli company is all hogwash. I will expound on the post by our friend ERD50 a bit more.

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Originally Posted by ERD50 View Post
It is interesting and it might have some niche applications that make sense. But the law of conservation of energy tells me this can't create any significant power in general.

OK, so the road is compressed when a car/truck goes over it. If we aren't capturing this energy now, it must be turning into heat, right? Are the roads generating significant heat from traffic weight? I doubt it.

But if we capture it, the element has to be moving a little...
The basic high school physics class taught us that "Energy = Force x Displacement". A rock of 100 tons provides us with no energy if it just sits there. If it drops 10 ft, it now releases the potential energy in that drop. Hydroelectric dams cannot get energy from water sitting in a stagnant lake; they need that water to flow from high to low. Displacement, my friends, we need displacement.

In the case of the cars pounding the road, I am not a civil engineer to know how much the typical asphalt road "sinks" as a car passes over a spot. But my own eyes tell me that the road flexes a lot less than the tires that the car is riding on. So the car tires dissipate a whole lot more energy than the road, because the former flex a whole lot more.

Now, tires do get hot when driven. But how much energy is wasted this way? Common sense tells us that a lot more heat is generated in the tires than in the road, but suppose that they are the same. Then, as the Israeli company claimed that 640 kW would be generated in each mile of the road, then assuming that the piezo generators are 100% efficient, that the highway is 4-lane, that it is busy with cars spaced 3 seconds apart, then there would be 80 cars occupying each mile of highway, and that they will be absorbing the total of 640 kW in their tires, which works out to 2 kW per tire.

2 kW of heating per tire? Darn! I would believe the number if you are driving 60 mph on a flat tire, but normally inflated tires would not be able to take this abuse!

And in my earlier post, these 80 cars were expending a total of 1680 kW to travel at 60 mph, and I do not believe that 640 kW or 38% of that is used to heat up the tires, let alone "heating" up the road by "pounding" it.

PS. Bad ideas are amusing, and really frivolous ones can be annoying. But the ones that truly upset are those that manage to waste public money. But perhaps we should focus the attention on the gullible officials who authorize such waste.
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Old 07-27-2014, 09:12 PM   #49
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I'm so glad I found this thread. For months I thought my wife and I were the only ones who thought the idea of solar freakin roadways was retarded.


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Old 07-27-2014, 09:35 PM   #50
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I LOVE this!
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Emotional versus Logical thinkers?
Old 07-28-2014, 02:49 PM   #51
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Emotional versus Logical thinkers?

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I'm really surprised at how much money they've been able to raise through kickstarter ($2M). I would have thought that the comments would have been filled with substantive criticisms that we see posted here and that this would have warned people off. However, the comments appear to be mostly positive.
Emotional versus Logical thinkers? : Yes, I find it surprising, and as I alluded earlier, dangerous and unsettling. If this many people were actually willing to put up their own money on this hair-brained scheme, just imagine how many more would be excited to see other people's money (tax incentives) applied to this.

Yes, dangerous and unsettling because that money and mental energy/effort should be going to ideas with merit rather than wasting it. It's a waste plus an opportunity cost. And then it becomes one more failed project that people can point to that might discourage support of real projects. Just sad all around.

I just read something about emotional versus logical thinkers, and though it didn't provide much in the way of solutions, I suppose it is helpful to at least acknowledge the difference and try to understand the emotional thinkers. So if I try to look at this on a purely emotional view, envisioning the concepts w/o any critical thought applied, sure, it sounds great:

Roads that generate enough clean energy to pay for themselves! Sounds wonderful!

Roads made out of glass tiles that are far more durable than current roads! Fewer construction delays, plus maintenance savings! Sounds wonderful!

Roads that have LED markers in them to make them safer and provide more information! Sounds wonderful!

Roads that are heated to melt snow and ice before it can build up! Saves plowing, makes the roads safer, no salt used! Sounds wonderful!



So is that how the proponents of these things think? They look at the suggested positives w/o any critical thought, and then think critics 'have no vision'? Looking through some comments, I see a common response goes along the lines of 'Sure, and people thought the car could never replace the horse, or that the Wright Brothers were crazy! Let's give this a chance people, it could turn out wonderful!'.

But there is a huge difference between early cars and planes with their sputtering engines, barely able to move their own weight, and the technologies used in this solar road idea. Solar panels, LEDs, heated roads, road surfaces - none of these are emerging technologies in their crude, first-step infancy. They are relatively mature products, we know how to use them, and most won't improve all that much in the next 10-20 years.

Solar PV runs ~ 15% efficiency now, and the theoretical limit of single cells is only about 33%. You can get to ~ 86% by stacking multiple cells to capture multiple wavelengths, but that gets $$$$ and hits diminishing returns quickly. Solar PV today is probably more like a 1970's car than an 1898 'horseless carriage'. No one would think a horse could outperform a 1970's vehicle.

LEDS about the same. As mentioned, we don't use tiles for roads for a reason. If they were better, even w/o the added restriction of needing to be translucent, we would. Asphalt is a mature technology. Same with heated roads, the idea has been around about forever, if it made sense on a large scale, we'd be doing it.

And there really is no synergy to this idea. The LEDs are powered at night - from the grid. The snow melters are powered from the grid. If solar will pay for itself, it can do it better if it isn't put in the road. No advantage whatsoever. Nothing adds up. So any advances are best applied separately, not joined together inefficiently in a 'solar road'.

Does that capture how the people who comment 'Cool' and 'fascinating' think? I'm curious, because I'm trying to understand how ideas like this get support.




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Originally Posted by krotoole View Post
At the risk of unleashing a hurricane of criticism, this thread did get me thinking about roads and energy which got me wondering about road compression from traffic and weather as a source of power. The energy of traffic and the freeze/thaw compression destroys roads. Could we somehow capture it?

Knowing that there is rarely such a thing as an original idea, I did some googling:

robinmeadows.tumblr.com/harvestinggreenenergyfromcars

This seems like a potentially interesting, scalable and maintable idea.

I feel certain someone will tell me why this idea sucks rotten eggs. Please do so without also suggesting I am somehow genetically or educationally deficient or a stooge for some lobby or other...it's just a link to something interesting on a Sunday afternoon, not a manifesto or a request for funding.

Time to take the kids to the pool.
You got some responses, I don't think any were denigrating at all. Did those responses answer your questions?



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I LOVE this!
Could you expound on that? Do you still LOVE the idea, or do you LOVE the discussion that has uncloaked this as a fraud?

-ERD50
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Old 07-28-2014, 03:08 PM   #52
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Could you expound on that? Do you still LOVE the idea, or do you LOVE the discussion that has uncloaked this as a fraud?
I think it's a fantastic idea. I wish I could come up with something that would let me sell that many bumper stickers, coffee mugs, tote bags, and t-shirts with such a nice markup!

The roads? Not so much...
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Old 07-28-2014, 03:18 PM   #53
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I think it's a fantastic idea. I wish I could come up with something that would let me sell that many bumper stickers, coffee mugs, tote bags, and t-shirts with such a nice markup!

...


But then I couldn't sleep at night. So I'll pass, even if I do come up with such a 'fantastic' idea!

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Old 07-28-2014, 05:33 PM   #54
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But then I couldn't sleep at night. So I'll pass, even if I do come up with such a 'fantastic' idea!

-ERD50
Well, I'll give him the benefit of the doubt right now. I've known a number of 'true believers' in various tech projects in Silicon Valley, who found lots of interesting ways to fund their visions, no matter how impractical. ("Black, cubical non-scientific workstations? And you missed your price point by a factor of 5 times? But... You talked Ross Perot into WHAT?!??")

Maybe he really intends to build that solar parking lot someday from the trinket sales profits.

Could be worse. Could be a IndieGoGo for a perpetual motion machine.
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Old 07-28-2014, 05:33 PM   #55
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Personally, I am wondering if we can use giant mirrors to focus the sunlight onto the asphalt in order to soften it so it can be applied and rolled out properly.
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Old 07-28-2014, 07:18 PM   #56
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Personally, I am wondering if we can use giant mirrors to focus the sunlight onto the asphalt in order to soften it so it can be applied and rolled out properly.
I'm not an engineer, but I enjoy threads like this. Whoever said engineers don't have a sense of humor was badly mistaken.
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Old 07-28-2014, 07:54 PM   #57
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Emotional versus Logical thinkers? : Yes, I find it surprising, and as I alluded earlier, dangerous and unsettling. If this many people were actually willing to put up their own money on this hair-brained scheme, just imagine how many more would be excited to see other people's money (tax incentives) applied to this.
I completely understand your line of thinking....but, at the same time, I wouldn't put too much concern with the general public with this for two reasons:

1. IMO, with the crowd-funded project, while I haven't looked at the actual numbers, my guess is that of the $2M raised, the average donation will probably be like $20-$40.

I think it's then the result of it more being that to the average consumer, that's "just" $20-$40. Just like they'll drop $5 on that latte, or $150 on a Saturday night out, because it's "just" money, and in the grand scheme of things, $40 is "just" $40 (unfortunately for them, they hit occasions of spending "just" $5/$40/$150 every week, so it siphons away all available cash). I don't necessarily think that they would have a huge follow-on run to simply dish out money left and right on scam "research" projects, and that it's more of the effect of it being "just" $20 rather than wanting to fund every hair-brained idea.

2. AFAIK, politicians that get money for these projects are really the ones in control. So you have more to fear from what the average politician is like, rather than the average rube that would donate to a scheme like this, because it's the politicians that control the purse.

Is the average politician more like the donee to the solar freakin' roadways than we realize? I'll leave that exercise up to the individual voter....
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Old 07-28-2014, 09:51 PM   #58
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Is the average politician more like the donee to the solar freakin' roadways than we realize? I'll leave that exercise up to the individual voter....
Exhibit A: Does anyone remember this section from a State of the Union speech by a recent President:

Quote:
Tonight I am proposing 1.2 billion dollars in research funding so that America can lead the world in developing clean, hydrogen-powered automobiles.

A simple chemical reaction between hydrogen and oxygen generates energy, which can be used to power a car - producing only water, not exhaust fumes.
$1.2 billion!! And the whole idea was unworkable and even undesirable for clearly identifiable and easily understood reasons. But the money got allocated and spent (in large part--the craziness was finally stopped).

I have no great heartburn if a person wants to "invest" their own money in such things, but when they take my money from me to waste on them--then I do take it personally.
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Old 07-31-2014, 06:26 PM   #59
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ok Fine. you don't like Solar roads.

I have another idea I found

As it turns out, Arizona Public Service was tasked with building a 20 MW power plant, without fueling it with fossil fuels or nuclear.

They considered one of those mega solar farms. It would be expensive, and you know, it kills animals.

Some smart laddie came up with an alternative.

They'd put solar systems on 3,000 homes. Free. And pay the homeowners $30 a month, in the form of a credit on their bill, for 20 years. And maintain the system.

Here's the smart part. The power wouldn't be used for the home the system was on, it would go directly into the APS power system and they'd sell the power back to homeowners.

Now lets think about this for a moment. APS gets it's 20 MW generation "plant" cheaper than a solar farm.
Homeowners get $30 a month for the use of their roofs, which they aren't using anyway, except to keep the weather out.
Who could get upset over the idea?
The solar retail industry, that's who. They are up in arms, cause you know, this effectively takes 3,000 customers away; an estimated value of $50-$75 Million in sales. And, you know, APS is subsidized and they aren't.

You just can't please everyone, ever.
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Old 07-31-2014, 06:53 PM   #60
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$30/month to rent out my roof to the utility company? I dunno. I am sure it's a good deal for the utility, else they would not do it.

If there's a leak on my roof, and it is not necessarily caused by the solar array, fixing the leak is going to cost more with the array in place. Who's going to pay for the extra cost?
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