Regenerative suspension… What happened to it?

Relative motion has the ability to generate electricity and the vehicle wheels move up and down on their suspension throughout the journey. We first came across regenerative suspension 15 years ago – so how’s it going?

The idea is simple enough; Conventional shock absorbers simply dissipate this energy of relative motion as heat, typically by forcing oil through valves. Instead, why not try harnessing it using electrical generators that could feed energy back into a car’s battery, potentially increasing range in the electric vehicle era?

So… Where is it? Well, here are a few milestones and trials that we can point out.

As it turns out, Professor Ronald Goldner of Tufts University and his colleague Peter Zerigan patented an “electromagnetic linear generator and shock absorber” around the turn of the millennium.

In 2004, the audio company Bose announced a product it had been working on in the backroom called “Bose Ride” that attempted to predict the movements of the vehicle’s suspension in advance and push the wheels down in the event of potholes, for example. In a way like a noise cancellation system for wheel movements, it was also able to recover energy from the rebounds of these movements.

Around 2005, David Oxenreider won second prize in a “Create the Future” design competition 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 to commercialize the technology. This company’s website is currently empty.

Also in 2009, MIT graduates Shakeel Avadhany and Zack Anderson founded Levant Power and began commercializing the “GenShock,” which they described as “the world’s first hydraulic regenerative active suspension.” The company is able to actively move the wheels up and down – acting like a built-in jack for changing tires – and draws power from their movements. The company said it is in talks with automakers to bring it to market.

By 2013, Levant Power had teamed up with billion-dollar automotive supplier ZF Friedrichstafen AG to bring the GenShock into large-scale production – but we no longer see any mention of it on the ZF website.

In 2015, Audi announced its “eROT” (electromechanical rotational suspension system), a prototype designed to increase driving comfort while generating electricity. And here we could actually see some numbers: around 3 watts were generated on a slippery road. When driving on a bumpy road, up to 613 W was returned – and on average the system recuperated between 100 and 150 W. Not exactly earth-shattering numbers.

By 2018, Levant was renamed ClearMotion. The company had bought the Bose Ride technology and raised around $130 million to bring it to market.

By 2020, Audi had developed an electromechanical roll stabilization system called eAWS and introduced it in four top-of-the-line Q-series vehicles. Like the eROT system, it is able to capture energy and send it back to the car battery – but that’s not actually the focus. The focus here is on eliminating body roll for sporty cornering behavior.

In 2022, a company called GIG Performance showed up at SEMA with a prototype of an aftermarket design called the Roadkil 5000. The company hasn’t said much since, and while its website says a lot about how it “captures twice the power,” “It never states 2X exactly what. A SEMA interview from YouTuber MixFlip clarifies: GIG’s design rotates the stator and rotor in opposite directions to double the rotation compared to other rotating units where one would stand still.

In December 2022, CarBuzz has unearthed patents that BMW has filed for a novel flywheel-based regenerative suspension technology. However, automobile company patents often describe technology ideas that never make it into production.

In December 2023, ClearMotion announced a production order for three million ClearMotion1 active suspension units for Chinese electric vehicle manufacturer NIO’s flagship ET9. But it’s pretty clear that this is more about ride comfort and handling than power production.

So it seems there have been a few failed attempts to recapture energy from suspension movement, and a few others that have moved more towards active ride comfort and handling systems. And if Audi’s numbers are any indication, it’s probably because… well, they just don’t recover enough energy to significantly impact your electric vehicle’s range.

Interestingly, these devices could still find a place – in the world of combustion. In an article published in the magazine in March Applied EnergyA group of Italian, Mexican and US researchers propose regenerative suspension as a plausible way to reduce CO2 emissions per mile by about 5g/km, more than 5% of the total allowable CO2 emissions in the EU -Regulations for 2020 are set.