PSA Peugeot Citroën and Bosch developing hydraulic hybrid powertrain for passenger cars; 30% reduction in fuel consumption in NEDC, up to 45% urban; B-segment application in 2016
|Elements of the “Hybrid Air” hydraulic hybrid powertrain under development for B, C, and D vehicles. Click to enlarge.
Following the introduction of the Bosch electric axle-split hybrid in PSA Peugeot Citroën diesel vehicles (earlier post), the two companies are now planning to develop a hydraulic hybrid powertrain for passenger cars. The hydraulic system, which uses compressed air for energy storage, basically comprises two hydraulic units and their pressure accumulators. PSA says the technology—called “Hybrid Air”—will be fitted on B-segment models starting in 2016.
The hydraulic components (motor and pump) recover and store the energy generated by the internal combustion engine and by braking and deceleration (kinetic energy); kinetic energy from braking that would otherwise be lost as heat is converted into hydraulic energy and stored in a pressure accumulator. This energy can then be used to drive the car.
A specific continuous transmission enables optimal use of the different energy sources depending on the type of driving in three operating modes:
Gasoline power, with the gasoline engine as the sole source of propulsion.
Air power, with the hydraulic motor alone transmitting energy to the wheels via the accumulators.
Combined power, with the internal combustion engine and hydraulic motor working together. At low loads, the internal-combustion engine can be run at a more economical operating point.
The result is a potential average CO2 reduction of 30% in the new European driving cycle, and as much as 45% in a purely urban driving cycle. Certified fuel consumption stands at 2.9 l/100km (81.1 mpg US) in combined-cycle driving, for CO2 emissions of around 69 g/km for standard body style models such as the Citroën C3 or Peugeot 208.
In comparison, PSA Peugeot Citroën’s 3-cylinder gasoline engines with manual gearshift produce 104 g of CO2 per km in combined-cycle driving. Vehicles equipped with Hybrid Air technology can also run on Air Power alone (with no CO2 emissions) 60 to 80% of the time in city driving, depending on traffic density, thanks to the optimal efficiency of energy recovery during braking.
PSA suggests that the technology—based on materials that are both plentiful and easily recyclable,—offers a CO2/price trade-off unmatched by any of the current hybrid technologies, representing a breakthrough. The company has filed 80 patents on the work.
|Price vs. emissions positioning of the Hybrid Air technology. Click to enlarge.
In principle, this technology can be combined with any conventional engine. In an initial phase, it is to be used in the compact car segment, but it is also suitable for other passenger-car segments and light delivery trucks in urban traffic. This hydraulic-mechanical powertrain system results in a hybrid powertrain that is more cost-effective, robust, and service-friendly. In addition, it does not require any special infrastructure, and can be deployed anywhere in the world, Bosch noted.
The technology works on the same hydraulic powertrain principles as those used worldwide on a wide scale by the Bosch Rexroth. Bosch and PSA see great potential for adapting this technology to passenger cars.
The close collaboration between PSA Peugeot Citroën and Bosch dates back to an engineering alliance set up in 2008. In the context of this strategic partnership, Peugeot launched the 3008 HYbrid4 in 2011, the first series-produced diesel hybrid passenger car with an axle-split powertrain.
In close collaboration with Bosch, PSA Peugeot Citroën developed the electrical components (electric motor, power electronics, and high-voltage generator) as well as the special technical design of the ESP electronic stability program required for hybrid vehicles. This powertrain concept now also features in PSA’s Peugeot 508 (both the RXH station wagon and the HYbrid4 sedan) and Citroen DS5 HYbrid4 models. For these models as well, Bosch supplies the components for the electrical powertrain.
Automotive technology is the largest Bosch Group business sector; its sales came to €30.4 billion, or 59% of total group sales, in fiscal 2011.