Emissions Reduction via 48V Active Engine-Off Coasting
Global CO2 reduction by 2021, according to some projections, will be comprised of multiple vehicle technologies with 7% represented by hybrid and electric vehicles (2% in 2014) . Other low cost hybrid methods are necessary in order to achieve widespread CO2 reduction. One such method is engine-off coasting and regenerative braking (or recuperation) using a conventional internal combustion engine (ICE).
This paper will show that a 48V power system, compared to a 12V system with energy storage module for vehicle segments B, D and E during WLTP and NEDC, is much more efficient at reducing CO2. Passive engine-off coasting using 12V energy storage shows a CO2 benefit for practical real world driving, but, during NEDC, multiple sources of friction slow the vehicle down to the extent that the maximum benefit is not achieved. By adding active engine-off coasting at the 48V level the CO2 emissions for NEDC are improved by decreasing the rate of deceleration with a 48V electric motor for propulsion. Also important, which will be explored in more detail, are the necessary power dimensions for the major components for different electrical load profiles.