Peugeot Citroen to introduce compressed air hybrid by 2016


January 24, 2013

PSA Peugeot Citroen's Hybrid Air technology that combines an ICE with compressed air energy storage technology

PSA Peugeot Citroen's Hybrid Air technology that combines an ICE with compressed air energy storage technology

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Various compressed air-powered vehicles – of both the two- and four-wheeled variety – have graced our pages over the years, but with a few exceptions, such as Volvo’s Air Motion Concept, major automotive manufacturers have generally shied away from such technology. PSA Peugeot Citroen is bucking this trend with its “Hybrid Air” powertrain that addresses the limited range of compressed air energy storage technology by combining it with a gasoline powered internal combustion engine (ICE). The company plans to have Hybrid Air powered vehicles on the road by 2016.

PSA’s Hybrid Air technology is similar to current battery electric hybrid vehicles, such as the Toyota Prius, but it uses compressed air for energy storage rather than batteries. A hydraulic pump/motor unit recovers energy generated by the ICE and from braking and deceleration, storing it in a compressed air energy storage unit.

Like many conventional hybrids, the Hybrid Air system uses an electronic management system that independently adjusts different modes based on the current driving needs. For highway driving, the system will rely only on the ICE, switching to air power only below speeds of 70 km/h (43 mph). When more power is required at lower speeds or when the compressed air energy storage needs topping up, the system will run in combined mode.

PSA says for city driving, its Hybrid Air system provides fuel savings of 45 percent and increases a vehicle’s range by 90 percent compared to conventional engines with the same power rating. In standard body styles, such as the Citroen C3 and Peugeot 208, the company says the system achieves certified fuel consumption (combined cycle) figures of 2.9 l/100 km (81 mpg) and CO2 emissions of around 69 g/km.

For drivers that spend most of their time in town, Hybrid Air-powered vehicles can run on air power alone for 60 to 80 percent of the time (depending on traffic density) which cuts CO2 emissions even further according to PSA. In line with this, the company sees its new Hybrid Air engine is a “key step toward fuel consumption of 2 l/100 km" (117.6 mpg).

While pricing information hasn’t been released, PSA is keen to point out the affordability of the system, which is no doubt helped by ditching the expensive battery packs found in conventional hybrid vehicles. The system is also claimed to be easier to install and service than battery electric systems and allows for modular passenger compartment design without sacrificing boot volume.

Estimating that hybrid vehicles could account for 15 percent of the European market by 2020, PSA intends its Hybrid Air technology for B segment (82 hp gasoline engine) and C segment (110 hp gasoline engine) vehicles, as well as light commercial vehicles. The plan is to initially fit the technology on B-segment models from 2016 and make it available in vehicles both inside and outside Europe.

The video below gives an overview of the Hybrid Air system.

Source: PSA Peugeot Citroen

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Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

Again a compressed air technology from France. I wonder whether Guy Nègre had any involvement with this project from PSA. Last time I heard he was talking to TATA.

Anycase this sounds like a very good concept, doing away with those expensive batteries. Sounds a lot more environmental friendly than those chemical concoctions.

Europe and Asia seems to be the only players capable of bringing fuel economy to the masses. The States are still too busy denying that energy is becoming a scarce resource.


Why not simply use the gasoline engine to drive the compressor which in turn powers the air motors which then drive the wheels without any other drive-train components? The compressed air storage would then simply be a 'capacitor' that kicks in to meet high demand while accelerating, or for emergency propulsion to get the vehicle to a place of safety in the event of an engine failure.

Having a motor driving each wheel could make wheelspin as near to impossible as makes no difference and 4 X4 models simple to produce.

Mel Tisdale

PLEASE don't be misled by their name for the system - this a hybrid HYDRAULIC system! That is air (or a more inert gas) is just used to maintain pressure in the accumulator, but the working fluid is hydraulic, that is why they have the hydraulic pump and motor. That makes good sense and is a self-lubricating low-maintenance system. Air as a working fluid is pretty stupid because you need huge reservoirs and lose energy as heat every time air is compressed and must regain it every time the air is used - hard to do in cold climates. And forget the fairy tale about filling it at the gas station tire hose! I have been advocating such hybrid hydraulic systems for years, but in my case I would use a pure hydraulic drive also with hydraulic wheel motors. However I am inclined toward electric to get away from petrodollars.

Jesse Blenn

I have always wondered why they just didn't use hydraulics? Motors generate incredible torque. Could be placed at each wheel. Very good at recapture of energy during braking. Small pressure reservoir. And by the same token, dump the heavy and expensive batteries. Most energy lost during re-accelaration so use the stored braking energy then. Cruising at highway speed requires about a dozen horsepower in today's smaller aerodynamic efficient cars. Use a highly efficient small motor for the extended range highway mode and to aid the acceleration process. You can't expect 0-60 in 6 seconds and 60 mpg.


Not a compressed air hybrid, this is a hydraulic hybrid using accumulators. For a true pneumatic hybrid look up the scuderi cycle engine.


Pity they reverted to the hydraulics and the associated component weight and cost. The comment by Jesse makes no sense as the energy storage in this hydraulic system is only provided by the air volume in the accumulator. However, by using an oil working fluid a second low-pressure tank of equal volume is needed. With pure air, there is no need for a low-pressure container.

The heat issues associated with the much simpler use of air alone can be neatly met in by tapping the intake or exhaust of the ICE.

About the only good use of compressed air would be that first turn or two of a wheel from a dead stop. Even then it is an very shaky idea. More parts, more friction, more lost energy, more weight, more expense all point to a bad idea. For city cars I could believe a one cylinder diesel powering a good alternator into a battery bank. Batteries are progressing. I suspect the only reason we are not seeing faster changes in battery technology are companies trying to recapture investments in technologies that were surpassed rather quickly. It is rather like personal computers. Once you invest in a design you need time to make a few bucks before you set lose the next monster computer. Jim Sadler

at 116 mpg, i'm impressed...


they had a very similar system fitted to buses in Adelaide 20 years ago they used the stored air from braking to accelerate the bus from stationary.

Gavin Roe

The great thing is that every day we (collectively not just Europe and Asia) are making great technological strides in many areas including Solar, GeoThermal, and Nuclear so I love to see these new innovations like this compressed air technology. I hope it works though I see some serious limitations in using compressed air.

Heck, we could all jump forward in mileage if we used nothing more than a system that would get the vehicles from dead stop against all that inertia to a moving speed where the ICE can run relatively efficiently.

Dr. Veritas

My 1966 America ST steam-hydraulic hybrid used nitrogen in the accumulators as this Citroen/Peugeot design undoubtedly does. I used a tiny battery for electrical startup and ran all hydraulic driven fans, pumps, alternator, etc, while the steam power system was devoted to vehicle drive and, when excess power was available, recharged the accumulators. My smaller piston accumulators were light for their energy storage and could be hidden anywhere in the chassis. See Nearly 50 years later, I well know the allure of the concept. But true efficiency lies not in energy leveling with extreme complexity and many loss paths, but in better thermodynamics and minimal losses. That is why I am at Cyclone Power developing systems with higher efficiencies than the gas and diesel engines used in hybrids through great thermodynamics and highly regenerative systems design.


I think it would be fantastic for the air quality in the cities if veheicles could use compressed air.

Why can not real big cars also use a fixed electric pickup system similar to tracked slot cars? It could then use this system to either recharge batteries or compressed air tanks via an in vehicle compressor when driving on the high way. To make it cheaper, this system would not need to be installed during the whole highway but in smaller charging sections.

Christian Nygaard

Finally a hybrid that might be cost effective. I would prefer a pure pneumatic system to support the ICE and us a Stirling cycle to recover some of the waste heat and cold generated by the pneumatic system. This is a system that I would consider buying.


If it only makes it to the USA. If not some innovative Google dropouts should Kickstart this project and offer a 2 place 100 mpg commuter. Put me in for $10k.

Just imagine if the need for energy drops by 50%, there would be so many less energy industry employees for terrorists to kidnap.

Mark A

Cool your jets, guys, this is NOT a "compressed air car" where you can tank up on compressed air. It is a hydraulic Hybrid where hydraulic oil is pumped into an accumulator and nitrogen is used as the spring. It has the IC engine to do the pumping to store energy when handy to improve good acceleration and allow short hops without having the engine run. The good mileage is obtained by narrow band engine tuning and running in that band. Mechanical storage hybrids could give similar results, and each system has its tradeoffs. Sadly, the thermodynamics and practicality of a compressed air vehicle limits it to mine vehicles and other costly non-consumer applications.


Why not use something like freon instead of compressed air in concert with a small diesel engine? Ultimate pressures could be much lower with a much larger gas volume stored in the liquid phase. Waste heat from the engine could be used to increase the phase change efficiency and range, sort of a heat pump on wheels. An environmentally safe freon and eliminating the danger of ultra high pressure compressed air would make for a much safer design. I could imagine efficiencies approaching 200mpg.


I love it. You cant go air alone because of the thermal loss in the compress/decompress cycle. Why dont they use diesel in lieu of gas?

James Barbour

Being the owner of a granted US Patent for an electric hydraulic hybrid drive system, I am somewhat qualified to opine.

This Air Hybrid is a hydraulic hybrid. Nitrogen gas is used as it has the best compression/expansive qualities needed to reduce thermal changes. carbon fiber tanks reduce weight. It is everything they say it is. Those who speak otherwise are not informed.

I would like to point out that the best use of hydraulic energy recovery and launch is on EV's, as it will do more for EV range/cost than all the billions of dollars being poured into better battery research. Using the hydraulics to provide the (recycled) power density required to launch an electric vehicle eliminates the need for power dense (read expensive) batteries, which lowers the cost dramatically, reduces the overall system complexity, and increases the range, performance, safety and marketability of an EV.

Further, an electric hydraulic hybrid has dual regenerative braking. This is of enormous value because it allows even more of the recoverable energy to be recycled and gives the vehicle two rechargeable "gas tanks" instead of just one. The accumulator is limited by volume, recovering about 70% of the recoverable energy during a deceleration cycle of roughly 40mph and lower. Compare to an electric hybrid, which is limited by chemical properties and limits the energy recovery to around 15-20%. This is the current electric vs hydraulic argument that is going on now.

Instead of choosing one or the other, the patented ERS Drive electric hydraulic hybrid system combines the two systems to provide an outstanding and ultra efficient zero emission drive system that solves most of the power/energy density problems that keep EV's from storming the market. 70%+20%=90% (yes, added, not multiplied).

I have been trying to get capital to build a prototype, but so far I have been unsuccessful. Partly due to being way ahead of the curve (I have documentation going back to 1991), and party because it is such a huge, capital intensive investment. Changing the car companies isn't easy.

Additionally, International Truck (Navistar) applied for a similar patent and were rejected due to my early IP. Also, the US EPA filed for a patent almost identical to mine, and 14 of the 15 claims were rejected. The EPA had funded development of a University of Michigan Ann Arbor College of Engineering built electric hydraulic hybrid. Using only hydraulic regen on their EV mule, they achieved 69% better efficiency and a 26% reduction in energy consumption. A peer reviewed white paper was produced which claimed it was a game changer. If dual regen was used, in a smart architecture such as the ERS Drive, you can probably go twice as far on half the batteries (which would be of less expensive chemistry).

This lowers up front capital needs for fleet implementation. School buses and the US Post Office LLV delivery vehicles would be the perfect customers to use electric hydraulic hybrids. Due to chassis standardization retrofitting is a simple, straightforward solution that would save these two fleets billions in fuel costs. Their short route, high stop/start frequency is perfect for EHH's. They are zero emission, charge at night as a matter of function and utility need, and electricity is less expensive and more stable when compared to fuel, enabling less energy costs and better energy dollar forecasting. I want to call them PEVHA's (Plug-in Electric Vehicles w/ Hydraulic Augmentation).

Hydraulic hybrids are not as heavy as most people think, they are more reliable than electric only energy storage systems and are less expensive. I have patents pending that will utilize this technology in many markets and applications. Think of ERS on a subway car. See ya later third rail (and all the electromagnetic damage you do to the surrounding infrastructure).

Kudos to PSA for bring this technology to market. There is plenty of room in the market for others. But for the best, most efficient system you can make using todays off the shelf and affordable technology, the ERS electric hydraulic system is the perfect balance between power and energy density. I am always willing to discuss licensing with capable parties.

Thanks for your time.

ERS Drive

Whether hydraulic or pneumatic, any auxiliary drive system that does away with batteries is okay with me. Even alkaline dry-cells pose a greater health and safety risk when they rupture, than air or hydraulic fluid lines.

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