Study on the Potential Benefits of Plug-in Hybrid Systems 2008-01-0456

There is ever increasing interest in the issues of fossil fuel depletion, global warming, due to increased atmospheric CO₂, and air pollution, all of which are due in some extent to transportation, including automobiles. Hybrid Vehicles (HVs), whose performance and usage are equivalent to existing conventional vehicles, attract lots of attention and have started to come into wider use. Meanwhile, EVs have been considered by many as the best solution for the issues mentioned above. But the technical difficulty of battery energy density is an obstruction to successful implementation. Currently the Plug-in HV (PHEV), which combines the advantages of HV and EV, is being considered as one promising solution.

PHEVs can be categorized into two types, according to operating modes. The first uses battery stored energy initially, only stating the internal combustion engine when the battery is depleted. This we call the All Electric Range (AER) system. The second is the Blended system, which “blends” power from both the battery and an Internal Combustion Engine (ICE) based on driver demand. For example, under modest demand the vehicle operates all electrically, but when high power is demanded the engine starts. The AER type utilizes only electric energy to propel the vehicle, requiring that the battery, power electronics and motor be large enough to supply 100% of the drive power. On the other hand, the Blended type enables the powertrain to be sized to take advantage of the variable output flexibility of an ICE, thus decreasing the maximum output required by the battery and motor. As a result, we believe the Blended system to have advantages over the AER system in terms of system size, cost and packaging.