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Peugeot to show 2008 HYbrid Air at Geneva show; more detail on operation

Peugeot 2008 HYbrid Air. The energy tank can be seen in the central tunnel, and the low-pressure tank at the rear. Click to enlarge.

Like its group partner Citroën (earlier post), Peugeot will display an application of the new Hybrid Air technology (earlier post)—the 2008 HYbrid Air—at the upcoming Geneva show.

The new hybrid combines a 3-cylinder gasoline engine with a compressed air/hydraulic motor/pump system comprising an energy tank containing pressurized air installed under the body in the central tunnel; a low-pressure tank at the rear suspension cross member acting as an expansion bottle; and a hydraulic unit consisting of a motor and a pump installed under the hood on the transmission.

The compressed air/hydraulic system will assist, or even take the place of, the gasoline engine during the phases which consume the most energy, i.e. acceleration and moving off.

An EGC (Electronic Gearbox Control) manages the distribution between the two power sources; it replaces the mechanical gearbox and in addition offers automated gear changes.

The 3-cylinder gasoline engine in the 2008 HYbrid Air features optimization of weight compactness by means of maximum integration of components; a reduction of internal friction by means of the use of Diamond Carbon coating, thermo-management and split-cooling for faster warm-up. The HYbrid Air is compatible with existing platforms, benefitting occupant space, modularity and the volume of the gasoline tank, which remains unchanged.

Operating modes. The system offers three modes: Air (ZEV), Gasoline, and Combined. In the Air (ZEV) mode, only the energy contained in the compressed air tank will drive the vehicle. As it depressurizes, the air occupies an increasing amount of space in the energy tank and so displaces a corresponding volume of oil. This is an energy carrier which supplies the hydraulic motor coupled to the drivetrain. As the engine is switched off, the vehicle moves without consuming any fuel or emitting any CO2. This mode is especially suited for driving in urban areas.

In Gasoline mode, only the 1.2-liter VTi 3-cylinder gasoline engine powers the vehicle. This engine benefits from the latest technology to offer, compared to the previous generation, a reduction in weight of 21 kg, friction reduced by 30% and advanced thermo-management to reach the optimum operating temperature more quickly. This mode is particularly suited to steady speeds on main roads and motorways.

In the Combined mode, the gasoline engine and hydraulic motor operate simultaneously to move the vehicle in proportions adjusted according to the situation to achieve optimum fuel economy. Adaptable, the HYbrid Air can supply the hydraulic motor from two sources. While the quantity of energy contained in the pressurized air tank is sufficient to fulfill the driver’s request, the hydraulic motor operates using this source. Then, if necessary, it can be supplied by the hydraulic pump directly. This mode is intended in particular for the transitional phases in urban areas and on the open road (moving off, acceleration).

The energy tank is filled in two ways. On deceleration (on braking or releasing the accelerator), the speed is reduced not by application of the brake pads to the brake discs but by the resistance to the compression of the air in this accumulator. The alternative consists of filling by restarting the internal combustion engine; in this situation, some of the energy produced by the gasoline engine is used to compress the air. In both cases, the maximum energy capacity of the pressurized accumulator is reached in just ten seconds.

The adaptability of the HYbrid Air technology allows it to offer numerous advantages, Peugeot suggests. By using tried and tested components, its durability makes it suited to a wide range of road conditions encountered across the world.

According to Peugeot, customers of cars and light commercial vehicles in segments B and C equipped with the Hybrid Air technology will experience:

  • urban driving in Air (ZEV) mode up to 80% of the time, with no fuel consumption;

  • a resulting 45% reduction in fuel consumption when driving in urban areas;

  • smooth driving due to the automation of the transmission; and

  • unchanged occupant space and modularity and unchanged fuel tank capacity.

Following a homologation cycle test, the HYbrid Air achieved CO2 levels of just 69 g/km.

Peugeot says the HYbrid Air is a key step towards 2.0l/100 km (118 mpg US) in association with other technological advances. This level of fuel consumption will be achievable with the contribution of the innovations relating to the gasoline engine and the platform, the company said. Regarding the engine, the down-sizing strategy, the thermo-management and the combustion are important progress areas. The platform is the modular construction component at the heart of the design and manufacture of any new model. The use of lighter materials and innovative industrial processes permit significant reductions in weight.



This one came from left field and has got me completely baffled.
On the face of it it sounds as though it should be highly inefficient, but apparently not.


Will it be has efficient, quiet and as smooth as claimed?

If so, it may be a game changer?


"urban driving in Air (ZEV) mode up to 80% of the time, with no fuel consumption;" how?


Agreed, Kelly. No explanation for that. A tank that fills in 10 seconds or less, but provides 80% of the energy for urband driving. Wow.


"urban driving in Air (ZEV) mode up to 80% of the time, with no fuel consumption;" how?

Presumably that ignores the extra petrol you use the rest of the time to power the compressor.

As they say, the air is supplied in two ways, by the engine and by regenerative braking.
Overall they claim:
'a resulting 45% reduction in fuel consumption when driving in urban areas;'

Roger Pham

The term HYbrid Air is a little misleading, since the air is only used as the spring, while hydraulic fluid and hydraulic motor/pump is used to provide power, thus, this concept is conventionally known as hydraulic hybrid. This concept is well known, with disadvantages in comparison with electric hybrid in the higher weight of the hydraulic hybrid system, lower round-trip efficiency, and lower amount of stored energy possible for a given volume of energy accumulator. For all those reasons, Ford, who has worked on hydraulic hybrid for cars, have abandoned hydraulic hybrid while progressed brilliantly with electric hybrid like the current HEV and PHEV offerings. I think that if Peugeot would use an electric hybrid system in this highly efficient vehicle with very efficient ICE, the result would be even better. The Prius C has demonstrated that electric hybrid can be offered at low cost that can be competitive with conventional ICE. I don't think that a hydraulic hybrid that is comparable with the Prius C can be offered at any lower cost, yet will have lower efficiency due to the inherent laws of physics.

The most important advantage of HEV is that it can be converted to PHEV with very little modification, and PHEV is a game changer because it can operate without using petroleum.


Cute little engineering experiment wouldn't you say? It redefines the need for a "plug in" and the car is just crying to be one. The best benefit of all is the huge number of plug in stations available with compressed air...gas stations. Why you can get air at the same place you get fuel. Those smart Frenchmen, what will they think of next? EVs? Maybe!


What Roger Pham said.


I would also agree with Roger Pham. There is no data on how far it would travel in the air (or hydraulic) mode. This is probably because it not very impressive. Again, this might work OK for trash trucks which have a lot of hydraulic functions anyway and it might even work for mail delivery where the distance between stops is quite limited but I do not think it would work well for a passenger vehicle even in larger US cities.


Lets see if the release it and real users and testers use it.
It probably won't be 45% better in urban areas, but if it turns out to be 30-35% better, it will be worth the trouble.
Also, who says hybrids have to be gas-electric hybrids, why not use compressed air to absorb the braking energy ?
The better it is, the more it will spur the electric hybrid guys to improve their systems.


A concept, I believe, not likely to be faced with real world competition.

They (apparently) use the air only as the spring for the hydraulic system. How could this provide much more than PART OF ONE or TWO accelerations?


Roger Pham

From I have read Air Hydraulic Hybrid are much more efficient that electric hybrid at braking recovery. They can swallow more energy in very short period of time than a 1.5KWh battery like on the Prius V. I read that they can return 70% of the initial kinetic energy, when the electric hybrid can barely recover 30%.

When you say the round-trip energy is less than for electric battery, this is not true for adiabatic compression / expansion in short period of time where you can control the thermal losses and stay almost adiabatic. Like they say the system recover and re-spit the energy in maximum 10 Seconds. Just enough to re accelerate the car after a braking, no more than that. Note that you can use the heat of the ICE exhaust to keep the compressed air warm too.

now for the cost, I agree that it is probably not cheaper than a electric hybrid system and almost as complex.

in the same time I think that that this system could me more suited to light or heavy trucks than an electric one. Batteries are still not powerful enough for heavy cars or truck.


I think Roger is right.

IF they are actually planning to market this, I think they are late.

HEVs, PHEVs and eventually EVs are becoming more practical.

Air Hydraulic Hybrid may be better than electric hybrid at recovery for hard braking, but you should rarely brake hard.

Adiabatic operation costs money, size & weight, as does an ICE exhaust heat exchanger.

10 Seconds is unlikely to be long enough for many/most situations.

But I agree this system may be suited to delivery/garbage trucks that NEED high kW but low kWHrs.


The concept has potential for city buses, which brake hard at every stop, at least the way they drive buses around here (although the hybrid bus drivers seem to drive more nicely, because they have mpg feedback?)

No REAL data on efficiency (mpg), not that I am surprised.
But 69g/km is not bad, Toyota Yaris Hybrid is 79g/km, per

Compressed air storage is notoriously inefficient. 10 sec braking and 30sec-2min unloading/loading passengers. What would be the heat loss?

Also would like to know what the *noise* level might be. Compressed air being released is rarely quiet, how do they solve that problem?

Give is more data and more specifics, Peugeot !!

mustafa rez

The hydraulic hybrid turbo transmission reduces emission and energy consumption up to 50%. The energy recovery from the breaking system is up to 80%, compared to the Electric hybrid vehicle which only recovers 25%. The HHTT system includes low-pressure storage, high-pressure accumulator, pump, and multi-stage turbines. The hydraulic hybrid turbo transmission operates without a torque converter, breaking system on the wheels, a large battery, and an electric motor. The hydraulic hybrid turbo transmission operates the vehicle in a direct drive mode at high speeds and in hydraulic mode at low speeds.
The number of turbines represents the number of gears; for example in a three speed transmission will be three turbines:
• Third gear : one pump works against one turbine
• Second gear : one pump works against two turbines
• First gear : one pump works against three turbines

The transmission will act as breaking system, when the three turbines turn in a reverse direction; the turbines will act as three inline pumps. This breaking system is the most powerful breaking system ever built.
The hydraulic hybrid turbo transmission is a:
• Energy recovery unit
• Energy management unit
• Automatic transmission
• Torque converter
• Breaking system
• And provides high pressure fluid for other uses such as a second breaking system, steering system, suspension system, and construction tools.



Battery vs air.

Has anyone noticed a new 12V lead-acid(LA) car battery is $100, the customer gets $5 exchange, but the customer exchange battery is 99% of the replacement battery materials.

The difference between new/good($100) and old/"bad"($5) battery is a little sulfide, which dissipates when the battery is melted and cooled into a new $100 battery.

Why doesn't the customer get at least $50 for bringing in the new battery materials?

The easy way to see we are being cheated is to bring in a motorcycle/lawn mower battery - 1/10th the weight - and get the same $5 exchange credit.

EV Li-ion batteries are called "bad" at 80% rechargeable, but they still hold 4 times the charge of a NEW lead-acid battery and may still take charge 100's of times more than new LA batteries in stationary use(power backup, etc).

This should REDUCE actual life cycle EV/battery costs by several times.


Kelly the materials of a spent lead acid battery are not worth $5, its a price set by law.. otherwise recyclers would compete and offer more.

Lets see if Peugeot can back up the efficiency claims in real life, hopefully lighter and lower cost than an electric solution.. but I'm sure the software can be optimized to game the NEDC and EPA testing cycles :)


Sorry for my broken English.
I've read that the amount of energy that can be stored in the hydraulic tank is only 42 Wh ( ).
This reduces drastically the advantages of such a great innovation. And then I start asking myself why ... Why limiting the possibilities ? To suit security compliances by limiting the pressure ? Not to bother with the greedy governments that makes money from gas taxes ?
From the 500 KW breaking power, they can get 70 %, so they say. This is instant value, hence it's not really relevant.
I was struggling on this idea myself for long, but I never thought of using 2 tanks. This is a great idea that avoids the issue of gas/liquid phases.
That's why I'd like it to be really efficient.
And this 42 Wh is disapointing.

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