Join The Community

Electricity from the suspension

Have you thought to use electric generator suspension? Compare to solar panel it's a big upgrade for autonomy, about hundreds of mile. That's an interesting website about this

Very cool even if it's 1/2 as a efficient as claimed.

Interesting approach. And I knew something like this could be done, but an average of 25 mm (~1 inch) vertical motion for each meter traveled? Is it really that much on highways? Certainly, hitting potholes and speed bumps causes a lot of energy loss, but that doesn't happen a lot over large distances. I'd be interested in seeing some actual data.

That is energy from losses that cause rolling resistance. Tiny part of that. It only works well in large machines that drive bad terrain, not in paved highways. Energy gain for passenger car would be rather small. Bigger than solar probably, but still not necessarily worth the added complexity or cost.

It is not the car body that moves up and down most of the time, it is the wheel. Car body is basically going ballistic over potholes, and suspension is doing its best to keep the wheel touching the ground. Creating energy from that movement means that you are resisting that movement. You just can't create much energy without rendering suspension undrivable.

In any case it is nowhere close to what the article says.

1st time I've heard of recovering the wasted energy created by suspension travel, but now that the subject is in play, it seem so obvious. I'm no scientist, but it seems to me that any passive method of recovering wasted energy is a good idea. If it even works half as well as those German inventors claim, it would be welcome electricity, as long as the technology isn't too expensive. The more ways the car can recharge itself without creating losses, the farther it will go. Any engineering types out there who can figure if this suspension will really extend the range significantly? I'm intrigued.

Not significantly. Range is ratio of energy available - losses over time at given speed. Without losses you have infinite range. Major losses include ancillary, aerodynamic, drivetrain and rolling. This suspension energy gain is small part of the rolling resistance. Entire rolling resistance is about 1/5 of the losses car has at 60mph, so that alone already tells that that article is using imaginary numbers to make big news from nowhere.

If car uses 60kWh at 300km it can't gain 45kWh from suspension back, because there is not that much energy lost in the suspension in the first place. If you eliminate entire rolling resistance it equals about 12kWh. This thing doesn't do that. Energy gain is way less than entire rolling resistance. Maybe one tenth of the entire rolling resistance. At best, I imagine. Otherwise you would need to capture entire suspension kinetic energy, which would make suspension rock hard.

also the energy gained from the suspension is related to speed,
if you only go 1 mile/h any bump or holes will not affect the suspension,
as the energy we try to harness is from the damper not the spring

I don't get the connection between rolling resistance and the electric suspension. Rolling resistance is the sum of outside forces acting against the horizontal propulsion of the car, like gravity, friction and aero drag. The proposed electric suspension captures inevitable vertical movement of wheels, shocks, springs and such, all of which move up and down as the car travels over discontinuities in the road surface like bumps, holes, road seams, gravel, etc, as well as pushing back to prevent the car from nosediving during braking and lifting during acceleration. Good paved roads seem smooth to us, if our car is well sprung, but even on what seem like smooth roads, suspension components are almost constantly moving in the vertical plane when the car is in motion. At 1 mph there is a lot of suspension travel, if you go over a speed bump (I'm not advocating that we build bumpy roads to generate electricity, but...nah!) Traditional suspensions dissipate that energy as heat so the occupants don't feel it. It is absolutely possible to convert some of it to electricity, instead of throwing it off as heat. Whether it's significant enough to bother with is the question being fervently debated in some quarters. Other researchers already created this kind of hardware a few years ago. Their quantitative estimates are far more conservative than those of Intertronic Gresser. IG's claim that it's possible to recover enough energy to extend your range by 50km during a 100km trip does sound like magical thinking, even to my admittedly mathematically deficient brain. But, if those guys are even in the ballpark, then driving on railroad ties would really crank out some major wattage! I'm not buying their hype yet, but I try to keep an open mind. Remember, the Wright Brothers were right!

If you're interested in what people at MIT and State University of New York have done, follow the links below.

Well, it has connection to some loss, and it isn't aerodynamic, ancillary or drivetrain loss. Otherwise you have invented an perpetual motion machine. Energy from nothing.

Rolling resistance most definitely doesn't include aero drag (aerodynamically created downforce is a different thing).

The inventors take pains to point out that this is in no way a perpetual motion machine. They aren't putting any energy into the system. The energy comes from variations of the road surface making the wheels move up and down. That occurs constantly in every moving car but shocks and springs turn it into heat, not electrons. Perpetual motion requires that you get more energy out of a device than you put in and they aren't doing that. It's supposed to capture energy made from suspension travel by fitting the modified "shocks", for lack of a better word, with some kine of transducer system which would presumably, in the simplest form, contain magnets and coils of wire. When the suspension moves, the magnets move within the coils, creating electricity, just like a microphone does when sound hits it. A microphone in a noisy environment constantly produces electricity, albeit only millivolts. Still, it converts motion into electricity without any input from a power source. The air vibrations provide the energy it captures. The electric suspension scheme is far more complex than my simple explanation, but the concept is simple and similar and would not cause loss. Them motion is already there and is conventionally dissipated as heat. Fitting it with electromagnetic transducers would take advantage of this unavoidable motion, without increasing resistance. If they are heavier than traditional suspension components, that would amount to loss, but who knows, they could be lighter. I wonder if anyone has considered including piezoelectric devices which would emit electricity when squeezed during the compression cycle of the shock travel? I can't imagine that would give much electricity either, but it too would not contribute to loss. It would just take advantage of motion inevitably produced by any sprung component on a vehicle vehicle. It all seems sound, but I'm dubious about the amount of energy they could capture this way. The German IG company makes some pretty grandiose claims about the output of their devices. They need to demonstrate that they can use passive components to convert the otherwise wasted mechanical energy to electricity in meaningful amounts to have a viable product. The idea sounds good, maybe too good to be true. Kind of like solar cells. They do make free electricity, but not enough to significantly increase the range of the car. These all might be areas for future technological growth that will someday pay off in the form of free electricity.


No. They don't claim any kind of perpetual motion. But keep in mind that up and down motion from road bumps takes energy from the forward motion of the car. If you're forced to go over bumpy roads, then some of the lost energy would be recovered by such a system. However, you'd be still better off to just drive on smooth roads.

@Lush1, this is where you are wrong:

"Still, it converts motion into electricity without any input from a power source."

There is an input from power source, the forward motion of the car. That causes the tires going up and down when road is not smooth. This suspension movement is not free energy, it still is subject to same initial energy source, though indirectly.

As I said in my first message, without losses your car has infinite range because then it doesn't need to use any energy to keep moving. Think satellites on orbit. They have forward motion that isn't slowed down by anything, so they keep that momentum they have infinitely. What you are suggesting is that if we eliminate losses and put car in bumpy road it somehow generates energy from nothing. It doesn't work that way.

Sorry, that was my second message, not first (we need that edit-function).

Timo, Perhaps the sentence you quoted was not clear, at least not out of context. When I say "without any input from a power source" I mean that the system is passive. It doesn't require electricity to operate and it shouldn't require and ADDITIONAL input to move the car. No matter what kind of suspension you have, you use energy to move the car. That's a given. I'm not suggesting that we can eliminate resistance and have perpetual motion and I'm not in favor of an uncomfortable car and bumpy roads. I made some comments about driving on railroad ties, but I was clear that I was kidding. The whole concept of the electric generating suspension is to make electricity from the vertical motion we presently convert to heat. Springs and shocks go up and down with variations in the road surface. Presently we use springs and shocks to keep that energy from reaching the passengers. Nobody has said that you could make enough electricity this way to run the car forever. These inventors are suggesting a way to extend the range by modifying conventional suspension components so that suspension travel makes electricity through induction (as I understand them), instead of making useless heat. The ride quality should be identical. The weight should be about the same, maybe less. The new suspension dampens the bumps, as do conventional suspensions, they just convert the energy differently. No additional resistance is introduced. What is wrong with the basic theory? I really would like to know. Much like solar cell technology, someday this technology may be efficient enough to recover sufficient energy to make a worthwhile contribution to the battery. The guys at IG claim their technology can already do that, but nobody is going to take their word for it or is suggesting perpetual motion, a point they were very clear about. But they need to demonstrate just how much energy their inventions can recover before anybody places an order.

Nothing is wrong in the theory, just the claim how much energy can be captured.

I'm guessing that complexity and cost of the system is not worth the cost, but OTOH, I have read that this system also makes excellent adaptive suspension possible (computerized electric systems can react in microseconds tweaking settings in real time, when traditional hydraulic systems just make a good guess for average suspension), so even if it isn't for energy gain it might be well worth for better suspension, in which case it would be really stupid not to use it for energy gain as well.

Yes Timo! You hit upon another feature that hadn't occurred to me, but now that you mention it, seems like an obvious choice for inclusion in the Model S; an active suspension! I try to stay informed about the car, but I haven't seen it mentioned, until now. Could be an oversight by me. If it's in play already, a link would be much appreciated.

I've never had a car with that feature so it's not something that springs to my mind. Anybody here own a car with active suspension? How do you like the feature and would you like the Model S to have it, either as an option or standard equipment?

I first learned of active suspension technology when Nigel Mansell was dominating F1 in his astonishing Williams FW14B in...1992 was it? Yikes, nearly 20 years ago. I'm aging too fast! Active suspensions are being fitted to street cars in increasing numbers of late. Guess it's long overdue. Acura had a big TV campaign about their magnetic/hydraulic suspension fluid fairly recently.

If somebody could make an active suspension that would also convert the energy it absorbs into electrons and put them into the Tesla's battery, it would be yet another great, unique innovation to set the Model S above other cars. Probably too late in the design cycle to make it into the 2012's, assuming it isn't vaporware or unaffordable.

I find the concept of a passive, range extending, electricity generating suspension system exciting. The basic theory is pretty simple, though I'm sure design and implementation aren't easy. I truly hope the extraordinary regenerative capability IG touts isn't just hype. I believe it technically will work, but I remain skeptical of the quantitative claims. I lack the math and physics needed to realistically evaluate the potential. Time will tell (or maybe an engineer or physicist on the board can break it down).

In the meantime, I hope this thread gets some good activity and news of this new technology keeps flowing.


I hope I didn't give you the wrong idea when I made some joking comments about driving on bumpy roads to make electricity. I'm not seriously suggesting it.

I agree that bumps do take energy from the forward motion of the car. That is true regardless of the type of suspension you have. Those losses are an unavoidable consequence of driving. If there is a system that can capture some of the wasted energy as electricity, the car goes farther. Don't know if it's possible to capture enough to matter or not.

I think the suspensions on our cars move a lot more than we realize. Smooth is a relative term. Roads that seem smooth to us are probably far from it from the suspension's vantage point. If it does a good job, we don't feel the almost constant movement happening in the wheel wells. I don't think it requires long excursions of the "electro-shocks" to make electricity. You might get more on bumpy roads, but that doesn't mean you won't get any on roads we perceive as smooth. I'm not claiming to be stating facts. This is my understanding from the reading I have done and my opinions, based on my experience and reasoning, but I'm not a scientist. It will surely work on some level. Will it be enough to bother with is the lingering question. If it doesn't yet, maybe someday it will.

As Timo has been saying. The question is how much energy can be recovered, and is it worth the expense. In any case there's no way this would appear on the Model S. There just isn't time (IMHO)

@David70 and Timo

Agreed. I realize I'm indulging in wishful thinking, but the car isn't 100% done so Tesla might yet have a few surprises for us. Hope that normal active suspension is among them, but it very well might not be and that's OK too. Can't have every feature ever invented in one $50-80K car.
If it turns out the electricity generating suspension is a viable technology, either now or some years down the road, perhaps it will find it's way into future Tesla products. Might even be possible to retrofit a Model S with it, if or when it really works, and yes, that's a BIG "if" right now.
I believe we are on the cusp of a major game change in the automobile world, led by Tesla. It's natural for us devotees to keep thinking and dreaming of growth and innovation yet to come. Also, I'm not complaining about what the car is lacking. I'm already quite thrilled with the Model S just the way it has been presented so far.
When I first read about IG's suspension concept, the idea seemed so obvious that I was surprised it hadn't come up before or that it never occurred to me, so I have been pondering it a lot this week. The basic concept is dead simple. Getting it to work in the real world is not.
As most humans foul the planet by consuming a rapidly diminishing resource, some seek alternative energy sources and ways to improve efficiency and capture wasted energy wherever possible. For example, if somebody told me 5 years ago that F1 cars would be hybrids by 2010, I would have thought they were crazy. But it happened. The KERS (Kinetic Energy Recovery System) uses regenerative braking technology to make electricity instead of heat to power an electric push-to-pass function. You can't really say it's helping save the planet, but the spirit of it is movement in a good direction. Racing has long been the birthplace and proving ground for cutting-edge technologies that eventually wind up in street cars (like Williams' active suspension in the 90's).
This is an exciting time and Tesla is way ahead of the curve. I'll be proud to drive one, not just because of it's small carbon footprint and low operating cost compared to ICE vehicles. I'll be proud to drive a beautiful, fast, roomy, quiet, efficient, safe, well designed car. Both the 230 and 300 mile batteries offer far greater range than I will ever need, so it is the perfect car for me, with no downside for my lifestyle. Sorry, I'm gushing again. Can't help it. I'm sure most of you know the feeling.

Great thread.. Who knows, Sig edition might have adaptive suspension. Not this of course since it would've already been in the news.

Also, BMW 550 LOADED has nearly every feature available in a car. Everything from rear active steering, adaptive suspension/cruise control to night vision, heads up display, auto park, Internet, etc.

I mentioned it because I had one on order for a week before canceling it for the Tesla Model S. I'm definitely expecting a host of luxury features considering the price and direct comparison of a 5 series. Sure it's electric but that only replaces the drivetrain, should'nt affect the features of the car. Heated seats is a must option considering almost every entry level car offers them.

Actually the driving on rails comment is pretty relevant. Using extremely stiff wheels on a rigid surface greatly reduces the rolling friction, which is part of the design benefit of a train over a car. If you had an ideal suspension system that truly could keep the body smooth and stiff like it is on rails, eliminating all the losses to flex of the body and the thermal losses of the suspension itself (this includes spring losses as well), you should have improved the range (probably not 50% by any means). I think Tesla selected wheels and tires with extending the range in mind, stiffer tires as the flex of the rubber is another energy loss. The main reason Buicks of old have those damned spongy tires is to "improve" the ride by absorbing all the smaller bumps, but this creates heat losses. I think Timo nailed it on the head when he brought up the rolling losses as this is the total energy available to the suspension system, and these losses are divided between the tires, the springs, the shocks, and the flex of the body. Ideally the shocks would absorb all of that energy, and the tires would not flex (from the perspective of getting that energy back to the car). I suspect that the 1/5 is at 60 mph on a smooth road, and that as the road gets bumpier these losses become greater.

If I recall there is also a company out there generating electricity from the flex in the road itself as vehicles drive over, so that means some of the rolling losses are to be found in the flex of the pavement itself also and this can't be recaptured by the suspension.

Naturally if the cost/benefit/comfort/performance of this type of suspension system makes sense, it will be integrated as an option. The fact that people are working on this type of thing is what gets us out of the catch 22. If there are no electric (or hybrid) vehicles there isn't a market for energy recapture, as there is nowhere to put the energy. Regenerative braking is a huge no brainer, but on an ICE vehicle it is pointless. Now that there is a large electric/hybrid market we should start seeing more innovations like this as every bit of energy is worth getting if the cost is not prohibitive.

Sadly at high speeds the major loss is wind resistance, and I think this will be hard to overcome.

"wind resistance"... yea, let's put a windmill on a pole mounted to the back bumper, and convert the wind into electricity.... or, better yet, the windmill above the roof spins due to wind, and that rotational energy is sent to the bottom of that pole, where a propeller spins (blades angled in the opposite direction) to provide additional thrust, thereby completely overcoming the wind resistance problem.

Sheesh, it's easy. Any other questions? ;-)

@dashrb: You forgot to add the optimization where the propeller on the roof is smaller so it spins faster and creates less drag but the propeller on the tail is bigger and moves slower so it needs less energy. Then you have extra energy left over that lets you use wind resistance to charge! I can drive forever! :)

Math is hard. Let's go shopping.