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.
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.
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.
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.
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.
