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From the "wow, that's a good idea" department: Ramps/Roads that gen electricity
Thu, 04/19/2007 - 11:43 — charlie.collins
The exact implementation details are being a bit debated, but over at BoingBoing they have the dirt on a ramp that generates electricity from cars passing over it.
That is a really ingenious concept. (Update, the comments on BB, and here, are correct that we would need to look for instances where energy is being transferred to heat or otherwise "lost" in order to make this useful - such as in braking - my previous comments about "who cares the car is driving around anyway" were stupid.)
If we could take the energy of the weight and motion of kabillions of cars on every road and somehow convert a tiny fraction of each to energy, that would be monumental.
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Um, you're still losing energy. Those cars that are "driving around anyway" have to expend *extra* energy on the plate, so you're wasting energy by burning additional gas, and the laws of thermodynamics guarantee you'll lose some energy in the transaction. So there's no "whether or not" about it, you simply lose energy. The only advantage would be if the energy were destined for loss anyway, like in braking; hence the boing boing comments about putting it at the bottom of a hill (and only for the traffic heading down -- not up).
Yeah I get the hill part, or
Yeah I get the hill part, or the speed bumps, I just meant we don't have to really look very far for cars already doing what they do. If the cars have to expend more energy than they are already using anyway - extra - then of course it doesn't fly. In all instances though I do not *speculate* that that would have to be the case.
Oh yes... free energy here we come...
Ah dear... I love these sorts of ideas.
It's another way of spelling perpetual motion machine and has the same problems.
Here, we have:
Petrol (chemical potential energy) -> kinetic energy of car -> kinetic energy of ramp/roller thing -> electrical potential energy.
Each transformation is inefficient (e.g. the first of these is only about 30% efficient!) and you can't get energy out that you haven't put in. So yes, if you wanted to get electrical energy out of the ramp, then you'd have to burn more petrol to begin with. This is just a petrol-driven generator and not a very efficient one at that.
BUT if you put it somewhere like a freeway exit ramp, where cars are slowing anyway, then you could possibly do something better than turning the kinetic energy of the car into heat, which is what your brake pads currently do.
Now, the hybrid cars already do this (regenerative breaking) and gain a lot of extra efficiency out of this (modern trains normally do this too, actually). So if you were trying to (inefficiently) suck kinetic energy out of the fancy hybrid car instead of letting the car do it itself then you're actually not helping the hybrid car owner. On the other hand, since so few people are running around in hybrid cars, you can get a lot of energy from the rest of the motoring public.
Bah. It's all silly.
Sure each transformation is
Sure each transformation is inefficient, but what I was saying is if there was some way to capture some of the kinetic energy the cars have already generated, and are not using (heat), then we might be on to something. No, it would make no sense to "rob" the power from the cars to power some generator, but there may be instances where a net gain could be achieved. Not just hills. Hills, general deceleration areas, etc.
Very good points though. I did not mean to imply anyone has solved anything, I just though this might be an area where an actual scientist (not a clown like myself) might be able to focus and come up with something. (And yes, my 7 year old Honda Insight had regenerative braking, and if the road was sucking it away from the vehicle that would affect that process in the vehicle, but as you state very few people have hybrid cars - though yes making CARS more efficient in the first place would generally be a better idea.)
I don't think it's "all silly" though.