The challenge of plug-in hybrids: CO2 efficiency and low cold engine start emissions
Hybrid vehicles utilize their potential for CO2 savings by shutting off the combustion engine as often as possible and using electric power instead. This results in longer operating pauses in the combustion engine during which the vehicle does not emit CO2. During these phases, the engine cools down. If it is required and restarted, the exhaust flow is also cold at first – possibly too cold to convert pollutant gases in the catalyst. “In other words, the cold start is actually the rule, especially with efficiently-driven hybrids,” says Rolf Brück, head of Catalysts and Filters at Vitesco Technologies. “From the perspective of emission reduction, this is a challenge, as the greatest share of the emissions in a cycle can be generated during cold start situations.” If you want to make the best possible use of electrification in a vehicle to save CO2, a solution is required for all cold start events.
This form of exhaust gas aftertreatment has so far not been available for high-voltage hybrids – such as the increasingly popular plug-in hybrid – because the heating disc cannot be supplied directly from the high-voltage system at 200-450 V. The newly-developed DC/DC converter now generates the low voltage and power for the heating disc from the high voltage of the drive system. The compact unit is based on state-of-the-art printed circuit board technology and the latest components with small dimensions, and enables a high degree of efficiency of 95%.
The system solution, consisting of heating disc and DC/DC converter, upgrades exhaust-gas aftertreatment systems for even stricter emission standards worldwide in the future.