Hydraulic powertrains for cars would uses compressed air for energy storage and basically comprises two hydraulic units and their pressure accumulators. The technology—called “Hybrid Air”—will be fitted on B-segment models starting in 2016. The power-split concept allows the vehicle to be driven in three ways: the conventional mechanical way, hydraulically, or by a combination of the two. At low loads, therefore, the internal-combustion engine can be run at a more economical operating status. When braking, moreover, the kinetic energy 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. In addition, driving off can be done purely hydraulically, and short distances driven without any emissions. The result is a potential average CO2 reduction of 30 percent in the new European driving cycle, and as much as 45 percent in a purely urban driving cycle. Cost-effective hybrid powertrain for compact cars 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. 
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