Peugeot Citroen evaluates free-piston linear generator for range extender

Aquarius free-piston linear generator 3

PSA Group, the maker of the Peugeot, Citroen and DS brands, is preparing to test a free-piston linear generator from Israeli startup Aquarius Engines as a range extender for its EVs.

“We are evaluating the technology,” said PSA Research and Development Director Gilles Le Borgne. “Nothing has been decided yet.”

The free-piston linear generator has a single piston, and generates electricity directly rather than driving a drive shaft.

According to Aquarius, several prototype vehicles using its free-piston generator will be road-tested by the carmaker early in 2017. The company expects costs to undercut both conventional hybrids and pure EVs.

“Aquarius offers an alternative to a 100-percent electric vehicle,” Board Member Efraim Wasservogel said. The range extender reduces the required quantity of battery cells “that no one knows how to recycle,” he added.

“If the concept works in reality it’s going to have a lot of potential,” IHS Automotive powertrain analyst Pavan Potluri told Reuters. “But vehicle manufacturers are always very risk-averse, so the biggest challenge may be getting one to sign up to it.”

Toyota unveiled its own free-piston generator design in 2014 but has yet to announce any production plans.

Renault, a partner of Nissan and a rival of PSA, also reviewed Aquarius’s technology, but decided to pass, said Senior VP Arnaud Deboeuf. Instead, Renault-Nissan is putting its money on future improvements in battery performance and costs. “We’re going to extend [EVs’] range,” Deboeuf said. “But we’ll do it without range extenders.”

Aquarius, founded in 2014, has filed three patents and raised $8 million in a first funding round.

Aquarius free-piston linear generator 3 Aquarius free-piston linear generator 3


SEE ALSO: Toyota R&D team improves free piston linear generators


Sources: Aquarius Engines, Reuters, Green Car Congress

  • dogphlap dogphlap

    A quote from the article: Board Member Efraim Wasservogel said. The range extender reduces the required quantity of battery cells “that no one knows how to recycle,” he added.

    Well that is a bombshell of a quote, if it is true it makes Nissan and Tesla (and probably everyone else making or about to produce an electric vehicle) out as either dishonest or delusional. It comes down to which party to believe. Do the electric vehicle manufacturers or the companies they have partnered with know how to recycle battery cells or not. Up to this point I have assumed this was a problem with no particular set of unknowns at least for the Li-ion and NMh cells, the two technologies currently employed in pure battery electric vehicles and hybrid vehicles. Do we believe Elon Musk for example or Efraim Waservogel, and if one is incorrect that could have real consequences for the companies they are associated with. I’m inclined to think that Waservogel could be spreading FUD to further the prospects of Aquarius Engines but if not I’d sure like to know where this lack of knowledge when it comes to cell recycling lies.

    • Alexis Boom

      Since GM, BMW, and Peugeot have all already recycled cells into static applications and Nissan and Tesla have recycled cells into new battery packs AND Tesla Motors say they have a way to chemically disassemble their cells I’d believe them as this yields profits for them and their shareholders.

      Meanwhile, someone’s trying to keep crude flowing.

  • James Dierickx

    I am trying to understand what makes their range extender anymore efficient than say the standard gen-set on say a Chevy Volt. Also in no article that I have seen show or say just how much range can be increased using this system. I also wonder if it is so good of a technology why Renault-Nissan passed on this.

    • dogphlap dogphlap

      Good point. It does avoid the loses associated with little end, big end, crankshaft and generator rotor bearings but whether those gains produce a gen-set with overall efficiency greater than the conventional approach is not clear to me, or if it does what is the reason it has not been embraced as the current technology of choice for gen-sets in general especially since on the face of it just being able to avoid the weight of a flywheel, crankshaft, connecting rod(s) and crankcase appear very attractive (along with reduced volume for a given power output). The AC power out would be a long way from sinusoidal but with modern electronics that should not be problem, though it would increase cost a little. Perhaps it is just inertia from the status quo or is there some deal breaker we aren’t being told about. I suspect Honda would have put some development money into similar ideas but no product announcement yet so just what is the drawback of this approach ?

    • Gideon Goudsmit

      Weight, simplicity, size and efficiëncy are 3 reasons to go this route for the coming years until H2 or batteries can really replace filossil fuels , only one moving part instead of a few hundred is a huge advantage !

      • Knut Erik Ballestad

        I would guess an Ethanol-based piston engine range-extender is just as energy-efficient as an H2 Fuel Cell engine – and way cheaper to implement since today’s gasoline infrastructure can be utilised.

    • Knut Erik Ballestad

      The first iteration of the Toyota engine referenced in the article reached 42% thermal efficiency

      The main thing with piston engine generators are these
      – The piston engines are extremely small (2 feet by 8 inches round = 15 hp/10kW)!
      – The engines have higher thermal efficiency than any traditional ICE engine (42% vs 20-30%).
      – Pair up and sync two of these (30hp/20kW), and vibration is also eliminated!
      – 20kW should be enough to by itself power a normal car at highway speed, so empty batteries in a PHEV should not be a problem, you would get a driving experience similar to a BMW i3 on empty batteries.

      Therefore, this kind of engine is extremely well suited for plug-in hybrid vehicles.
      Even the BMW i3 Rex engine is big compared to these engines, and the fuel will give a lot more kWh’s with the piston engine.


  • John

    A crankshaft and the associated pumping losses of the 4-stroke cycle create great inefficiencies. That is why 80% of the energy in the fuel tank is wasted.

    1. Getting rid of the crankshaft improves efficiencies greatly to start.
    2. Have a 2-stroke cycle again improves efficiencies.
    3. Have a double-ended piston giving a power stroke at every stroke of the piston.
    4. Have HCCI ignition efficiencies and emissions are improved.

    I hear gasps at the words “2-stroke”. Things have moved on. The advantage of a range-extender is that it works at a constant speed. Matters are now much more predictable, with many parameters fixed, when designing a 2-stroke combustion chamber. A pre-mixed forced charge into the combustion chamber using HCCI ignition with an exhaust poppet valve will give excellent results.

    Then we will have a highly efficient generator. But! advances on the Wankel rotary engine (see Mazda and HCCI ign and David Garside’s advances) may preclude all other types for range-extenders.