7. Hydraulic parallel hybrids

This type of hybrid does not fall into the – category of thermal electric hybrids, as it has no electric motor, but it is interesting to look at this technology, which PSA has presented via its Hybrid Air program.

This technology uses an energy reservoir containing pressurized air compressed by oil. The hydraulic circuit comprises a high-pressure (HP) reservoir, a low-pressure reservoir acting as an expansion tank, and a hydraulic unit consisting of a motor and a pump to supply and recover mechanical power (figure 36 ).