Batteries Not Included – PSA’s Hybrid Air System

PSA Peugeot-Citroën has unveiled new tech that could turn the world of hybrids on its head.

Talk about starting the New Year on the front foot. After enduring a 2012 that could be described as ’challenging’ if you were feeling charitable, PSA Peugeot-Citroën hasn’t waited log before unveiling a raft of fresh, highly relevant technology that looks set to put it back into the headlines for all the right reasons.

The French group has looked at to the tough CO₂ emissions targets that manufacturers will have to meet by 2020 – a fleet average of 95g/km in Europe and 117g/km in Chine and plotted ways to meet that challenge.

“Full hybrid vehicles will be a necessary part of the equation to meet the targets, even though the vast majority of automobiles will still be powered by internal combustion engines,” explains Guillaume Faury, PSA’s research and development boss. “Hybrid technology needs to evolve very quickly. We need to improve emissions and we need to think of new breakthroughs.”

“Full hybrid vehicles will be a necessary part of the equation to meet the targets, even though the vast majority of automobiles will still be powered by internal combustion engines,”

Of the half-dozen items of new technology that PSA unveiled at its Velizy technical center just outside Paris last week, the potential game-changer is its new hybrid system, called Hybrid Air. It follows on from the French automotive group’s existing Hybird4 technology – the banner under which the first diesel hybrid passenger car was introduced to the market in 2011 but couldn’t be more different.

For a start, batteries aren’t needed to store and discharge the energy. In addition to the petrol combustion engine, Hybrid Air incorporates a compressed air energy storage unit mounted longitudinally under the car, a hydraulic pump/motor unit and a bespoke automatic transmission.

Energy gathered from deceleration, including braking, is used to compress the air in the storage unit. Then, in low-speed city driving situations where a traditional hybrid would switch to full battery power, the air is deployed to drive a hydraulic motor mounted alongside the internal combustion engine.

After driving the motor, the hydraulic fluid is pushed to a low-pressure storage tank housed at the rear of the car, where the spare wheel would normally be located.

The benefits are manifold. “Hybrid Air is attractive because it is based on robust, well proven and simple technology,” says project manager Karim Mokaddem. “The system is also highly efficient in the way it stores energy and releases it. There is no cold-weather drop-off in the performance of the hybrid system. We are still working on the technology but the tank will last for the duration of the car’s life.”

The system adds about 100kg to the weight of a conventionally powered small car, which is about half the weight of battery hybrid equipment. That in itself makes the system more flexible and particularly well suited to smaller cars.

Costs kept low

The project has passed through four prototype stages, and German engineering giant Bosch has been brought in to provide some of the hydraulic componentry. PSA chiefs say that the amount of investment in the project so far has been relatively modest – it has been developed using off-the-sheft parts except for the automatic gearbox, which is specific to Hybrid Air.

Low-pressure storage unit sits just aft of the rear axle

PSA has attained homologation for the system at 72g/km of CO₂. By comparison, PSA’s three-cylinder petrol engines with manual gearshift produce 104g/km on the combined cycle. Company chiefs believe further efficiencies can be found, and talk of 69g/km by the time Hybrid Air is production ready in three years. PSA president Philippe Varin says that the company has targeted 117mpg across its range by 2020, and Hybrid Air will play a crucial role in achieving that.

“When we started to work on the technology, there were two objectives,” says Mokaddem. “The first one was to ensure it was never a niche application. The second was to ensure it isn’t ‘one-shot technology’ that can’t be improved further. We know there are steps we can take on the technology and also on the car that will lead us to 117mpg.”

PSA chiefs concede that a good deal of work is necessary before Hybrid Air will be ready for market. It predicts that full-scale production could start in 2016, although both Peugeot and Citroën intend to show off cars equipped with the system at the Geneva motor show this March.

Setting aside the ecological benefits, Hybrid Air’s biggest asset could be the low cost of the relatively straightforward hydraulic technology compared with batteries and electric motors, which are still making today’s hybrids a less than attractive option for many motorists.

Although there is still work to be done to assess the cost of adapting the new system for large-scale production, PSA estimates that a city car equipped with Hybrid Air could come in at between $19,500 and $25,500 before any government financial incentives are taken into account. If that turns out to be the case in 2016, it could transform hybrids into a cost-viable alternative to petrol and diesels.

“You don’t need any precious metals like you do with batteries, which are very costly and the customer ends up paying for,” says Mokaddem. “The second advantage is that you have worldwide technology. It isn’t affected by different climates, and any market could build and use the technology, which can be made using recyclable materials.”

A hydraulic motor sits next to the three-cylinder petrol

According to Faury, the Hybrid Air prototypes deliver an “exceptionally fluid” driving sensation. “We have modified many things during the course of this project, so it is still changing, but the driving experience right now is amazing,” he says. “It brings something new. It has direct drive so that car is very reactive, and it’s simple, easy and fun.”

Mokaddem believes Hybrid Air could exist alongside existing battery hybrid technology, rather than render it obsolete: “I don’t really consider this the end of battery. In the future, we will need lots of technologies. It doesn’t mean we need to focus on just one technology. The aim with Hybrid Air is to say, ‘Look, if you use mechanical components in a special way, you can do something really outstanding’. Batteries will still have a future, but could be much more dedicated to upper car segments.”

So although the lighter, very efficient Hybrid Air technology could be well suited to B-segment and C-segment cars and small vans, the existing Hybrid4 system could be more beneficial in larger, more luxurious vehicles where the extra weight of batteries has less impact.

Hybrid Air’s revolution comes not so much in the technology, which is relatively simple and inspired in part by hydraulic systems found on heavy-duty machinery and aero planes, but in the fact that PSA is bringing it to the car market for the first time.

The company has spent just over two years developing the system at a special technical ‘skunk works’ that brought together sharp thinkers from every division of the company and put them in an environment where their radical ideas could flourish.

Now that the idea has been made public, it is an encouraging sign that although Europe’s car makers have been experiencing a torrid time in recent years, ingenuity and creativity haven’t been stifled.