Regenerative suspension... What happened to that?

Regenerative suspension... What happened to that?
A look at how Audi's eROT system works
A look at how Audi's eROT system works
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A look at how Audi's eROT system works
A look at how Audi's eROT system works

Where there's relative movement, there's a chance to generate electricity, and vehicle wheels move up and down on their suspension the entire time they're in motion. We first encountered regenerative suspension 15 years ago – so how's it going?

The idea is simple enough; traditional shock absorbers simply dissipate this energy of relative movement as heat, typically by squeezing oil through valves. Why not try to harness it using electric generators instead, which could feed energy back into a car's battery, potentially extending range in the EV era?

So... Where's it at? Well, here are a few milestones and attempts we can pinpoint.

Tufts University professor Ronald Goldner and colleague Peter Zerigan patented an "electromagnetic linear generator and shock absorber" back somewhere around the turn of the millennium, as it turns out.

In 2004, audio company Bose announced a back-room skunk works-type product it had been working on called Bose Ride, which attempted to predict car suspension movements in advance and force the wheels down to meet potholes, for example. Somewhat like a noise-cancelling system for wheel motions, it was also able to recapture energy on the back-strokes from these motions.

Bose active suspension

Around 2005, one David Oxenreider won second prize in a "Create the Future" design contest with an "almost identical concept" to Goldner and Zerigan's Tufts design.

In 2009, Goldner and Zerigan's design was sold to Electric Truck, LLC, with a view to commercializing the technology. This company's website is now vacant.

Also around 2009, MIT graduates Shakeel Avadhany and Zack Anderson founded Levant Power, and set about commercializing the "GenShock" – which they called the "world's first hydraulic regenerative active suspension." Capable of actively forcing the wheels up and down – thus acting like a built-in jack for tire changes – as well as drawing power from their movements, the company said it was in talks with automotive OEMs to bring it to market.

Genshock system

By 2013, Levant Power had teamed up with multi-billion dollar automotive supplier ZF Friedrichstafen AG to take the GenShock into production at scale – but we can find no mention of it any more on ZF's website.

In 2015, Audi announced its "eROT," or electromechanical rotary suspension system, a prototype designed to enhance ride comfort while also harvesting electricity. And here we actually got to see some figures: on a smooth road, it generated around 3 watts. Driven on a bumpy road, it returned up to 613 W – and on average, the system recuperated somewhere between 100-150 W. Not exactly Earth-shattering figures.

By 2018, Levant had been renamed ClearMotion. The group had bought up the Bose Ride technology, and had raised around US$130 million to get it to market.

By 2020, Audi had developed an electromechanical roll stabilization system it called eAWS, and had rolled it out on four top-of-the-line Q range cars. Like the eROT system, it's capable of capturing energy and sending it back to the car's battery – but that's really not the focus. The focus here is on eliminating body roll for sporty performance in corners.

In 2022, a company called GIG Performance popped up at SEMA, with a prototype of a retrofit design called the Roadkil 5000. The company hasn't said much since, and while its website says a lot about how it "captures 2X the power," it never specifies 2X what, exactly. A SEMA interview by YouTuber MixFlip clarifies: GIG's design counter-rotates the stator and rotor to double the spin compared to other rotary units on which one would stay still.

Capture Lost Vibrational Energy and Convert It Into Power With Gig Performance

In December 2022, CarBuzz dug up patents that BMW has applied for on a novel flywheel-based regenerative suspension technology. Mind you, automotive company patents frequently outline technology ideas that never make it to production.

In December 2023, ClearMotion announced a production order for three million ClearMotion1 active suspension units, for Chinese EV company NIO's ET9 flagship. But it's fairly clear that this is much more of a ride comfort and handling system that being about energy generation.

NIO ET9 SkyRide Fully Active Suspension system test

So it seems there have been a few abortive attempts to recover energy from suspension motion, and some others that have morphed more toward active ride comfort and handling systems. And if Audi's figures are any indication, it's probably because... Well, they just don't recover enough energy to materially impact your EV range.

Interestingly, these devices may yet find their place – in the combustion world. In a paper released in March in the journal Applied Energy, a group of Italian, Mexican and US researchers suggest regenerative suspension as a plausible way to reduce per-mile carbon emissions by around 5 g /km, more than 5% of the total allowable CO2 emissions specified by 2020 EU regulations.

Wow Loz! This was a great update on this tech. We are often left wondering whatever happened to a promising technology and why it had not been commercialized yet. Now we at least know what happened with this one. More of these please.
with SoCal roads, and my average watts per mile at 175-225, with an average speed of 1 mile in 5 minutes in SoCal, that’s 12 miles x 200watts= 2400 watts - a regain of even 50 watts in an hour would drop me to 196 watt hrs per mile. Over 57.4kw (90% batt to 30%), I’d go 292.58 miles vs 287 miles.
I don’t know how much this system would weigh, but if it wouldn’t be more than 10-20lbs I think I could get on board.
I'm afraid the reason why we have not seen this idea develop is because, like, for example, hydrogen fuel cell transport, it simply does not make any practical sense. People who advocate this sort of thing simply do not understand the physics. In a suspension system it may sound like a feasible way of damping unwanted motion but in practice, harnessing the energy involved would cost hugely more than it would be worth.

As for doing the same with vibration, just spend the research money on getting rid of the source of vibration in the first place!

I am minded of the rather daft idea of generating electricity from paths due to people walking on them. Harnessing a force means imparting and equal and opposite one to 'the force'. All that would happen is that people would find walking on the path harder work than if it were just a plain (rigid) surface and thus, the whole idea would fail.
Thanks Loz! After my one experience with Honda Engineering propensity to minimize the time an alternator is charging the tiny battery and purchasing automotive batteries every 2 years, I thankfully unloaded that "over-engineered & under-equipped" automobile for one that doesn't leave me stranded. But you know, once burned, twice shy! I still own ICE vehicles and appreciate any functional necessity that could help reduce the risk of battery drain. So many of my trips require two starts and don't run the engine long enough to fully recharge the battery for the engine starts. It would be nice to have something else charging my system! I know the roads I drive, I have to buy new tires before the mileage estimates and always pay through the nose for shocks - why not utilize those systems for some return!
Gregg Eshelman
Remember the Shake Light flashlight? I have one of the real ones (there were tons of fakes) with a rechargeable battery. The cool thing about it is the way the coil and circuit are designed, when the light is held upright the high strength magnet *levitates inside the coil*. As gravity attempts to pull the magnet down it generates a counter-EMF in the coil that opposes the force of gravity.

Where this could be employed is in lights for bicycles. Package the design as a low power generator. Mounted vertically, everyday riding would cause the magnet to bounce up and down, charging a small battery to power a headlight or taillight. The the efficiency advances in LEDs since these shake lights were introduced, the brightness would be enough for night riding.

They could also work for people who go hiking, to provide a little power to keep a phone or small battery bank topped up.
@ Greg Eshelman - I love your idea.

As for suspension systems driving generators, I have yet to see a suspension system that can take the abuse of daily use long-term, let alone convert that violent boggidge into power without breaking something quickly.