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# Generating electricity from road traffic

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Source

Thought this was worth posting. Check out some of the websites that the article cites, they're really interesting.

Edited by brian0918
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a cockamamie idea!

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The energy—80 kilowattt-hours per kilometer of road for car traffic

A kWh is a measurement of energy (It's 3.600.000 joules). Saying something produces 80 kWh's without mentioning in how long tells me exactly nothing.

Does he mean it produces 80 kilowatts? That would be kinda impressive (enough to power 80 households, by my calculations), depending on the cost of installing and maintaining the thing. But I doubt he's saying that.

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A kWh is a measurement of energy (It's 3.600.000 joules). Saying something produces 80 kWh's without mentioning in how long tells me exactly nothing.

Does he mean it produces 80 kilowatts? That would be kinda impressive (enough to power 80 households, by my calculations), depending on the cost of installing and maintaining the thing. But I doubt he's saying that.

A kWh is a kilowatt hour - so perhaps they mean 80 kW in an hour?

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A kWh is a kilowatt hour - so perhaps they mean 80 kW in an hour?

No, that would be 80 kW/hr. The average house uses about 1.2 kWh per hour. So a power source would have to continuously provide roughly 1.2 kW to power that home (assuming the home draws the same power throughout the day).

As Jake said, whether or not the technology is impressive depends on what time frame it takes to produce that energy. Does it take a month for that 1 km of road to generate 80 kWh? Then it is only producing 0.11 W, and couldn't even power a lightbulb.

Edited by brian0918
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I've thought of things like this many times (generally, using fast moving traffic and capturing energy in different ways) - However, I just have to believe that there isn't enough energy there - If there were, someone would be exploiting it. We could all put solar panels on our roofs too, but oil and coal is still cheaper.

There are plenty of great ideas out there, just not great enough to compete with what we have... yet.

Reminds me a bit of:

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From the company website:

According to Innowattech's mathematical model, IPEGs™ have a potential to generate an average of 200 kWh per hour for the highway with traffic of 600 heavy trucks/buses per hour on average. This energy constitutes a percentage of the total energy expended by the heavy truck.

On the surface, the idea seems... fucking brilliant...

But I'm not an engineer. Tell me why that's wrong?

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And that quote leaves out a different, but equally vital measurement - the length of highway necessary to generate that amount of power. So again we know nothing.

Are these 600 trucks driving for an hour on a 60-mile long power-generating road, just to produce 200 kWh of energy? Or does it only take 600 heavy trucks driving over a single spot in the road in one hour to generate that energy? Those are two possible interpretations.

Edited by brian0918
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Turnaround on investment expected to be:

6-12 years, depending on the volume of traffic on the site.

That's the kind of return only Government would go for...

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No, that would be 80 kW/hr.

Right, which would still not make sense. I guess we could also speculate that by kW he meant kWh (since I guess some people might mistakenly say kilowatt when they mean kilowatt-hour, in conversations about their electric bills), and then we would presume he meant to write 80 kWh/hour.

80 kWh/hour = 80 * 3.600.000 joules/ 3600 s = 80.000 joules/s = 80 kW. That would power about 70-80 homes, so if the technology can be developed to be durable and cheap enough, I guess it could be feasible in some places. Maybe a journalist who paid attention in Science class enough to get the units right can talk to the guys behind this company and enlighten us some time.

Ok, that question is answered then. (Brian, the graphic at the bottom of the page Greebo linked to does say it's per kilometer of road. )

They also say it would cost 500.000 Euros to build a kilometer of road. If all those figures were based in reality, then the technology would obviously be worth huge amounts of money. But that's not the case at all, it is only a potential, based on mathematical models. You cannot estimate the cost of building and maintaining sophisticated equipment buried under asphalt for trucks to roll over it, based on mathematical models. You'd need to actually build it and start adrivin' trucks over it until it breaks. And you need to do that over and over again, under various temperatures, until you have statistically significant results.

Edited by Jake_Ellison
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They say they're reclaiming only 1% of 1 trucks worth of power from a road with 600 trucks on it... so what is that - .0016~% of the total energy being reclaimed?

I believe it's possible - but it needs to reclaim more.

I wonder if magnetic induction would work better...

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80 kWh/hour = 80 * 3.600.000 joules/ 3600 s = 80.000 joules/s = 80 kW.

You could have just canceled the "hour" components: 80 kW hr / hr = 80 kW.

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Think of all the intersections in a typical city, now think of the number of vehicles. A regenerative braking system are capable of more efficiently capture the energy of braking.

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Think of all the intersections in a typical city, now think of the number of vehicles. A regenerative braking system are capable of more efficiently capture the energy of braking.

Of course - and that system is used in electric and hybrid electric vehicles now.

But regenerative braking is something that has to be done in the car itself.

I think looking at the roads to see if any energy can be reclaimed from them is worthwhile, even if only to eliminate the idea from viable application. Energy reclaimed from the roads would add to overall energy efficiency in a different way.

I still think the idea is ingenious.

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I wonder if magnetic induction would work better...

Inductive charging is also another field that is currently in development. I was reading an article a while ago how in Italy, they have a few buses trialing it, where they've installed the coils underneath the asphalt/bus station and the bus 'sits' above it to have its batteries recharged. Actually here's the article: source. It covers New Zealand, China, Germany and Italy. And also related to the topic of this thread, an article concerning Wireless Power from the same website of IEEE. It's quite a long read but worth it. It also mentions how Nikola Tesla was already spearheading the idea of wireless power transmission some hundred years ago. But to answer your question, I don't know if it would work better. The thing with inductive charging is that you need an electric current to generate your magnetic field, with this idea of converting the vertical force of the automobile to electricity, you obviously don't.

Edited by Altan
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Hmm. I was getting my electro-magnetics reversed. I was forgetting that the cars and trucks themselves would need to be magnetic and be passing through a huge coil of wire to generate an electric pulse.

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This seems very interesting however as everyone else has said, I have no clue what amount of energy it has the potential to produce(article is vague on measurements). I have heard about a similar idea that generates power from cars rolling over speed bumps.

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