Marc Nalbach

Key Items for Future Hybrid Applications: Energy Storage and Power Electronics for Micro Hybrids up to Full Hybrids and EVs

Research/Engineering Question: Micro-Hybrid applications like start/stop system and intelligent alternator control are well known and widely implemented to achieve first improvements regarding the reduction of CO2 emission. Key items for their realization are the 12 V lead acid battery monitoring and power system stabilization approaches as well as optimizations of aerodynamics, enhanced warm cranking procedures and energy efficient electrification of power loads like electrical power steering systems. To achieve the upcoming CO2 reduction targets in 2020 further optimization potentials have to be elaborated and have to be introduced. Results/Conclusion: Additional improvements can be achieved by extrapolated techniques like enhanced start/stop application, which means stop–start at vehicle speed of 30 km/h, and idle cruising/sailing. But these functionalities have a significant impact onto the stability and reliability of the power system based on the previous experiences with the common stop–start function. They can only be realized within a low voltage power system by the introduction of new enhanced energy storage solutions like additional batteries, double-layer capacitors or lithium-ion cells in combination with power electronics. By the prevention of high voltage implementations these solutions show a promising benefit to cost ratio in comparison to Full-Hybrid solutions. If further efficient functionalities like high power regenerative braking and electrical creeping are intended to implement, additional electrical measures have to be introduced. For instance a dual low voltage power system architecture with a system voltages lower than 60 V can be used to fulfill the requested energy and power capability of the power system for these corresponding vehicle functions. Double layer capacitors are suitable for high power regenerative braking due to their high charge acceptance and high current discharge capability. If functions with high energy demand like electrical creeping should be applied, then solutions using lithium ion cells are much more sufficient. Full-Hybrid and pure electric driven vehicles offer the maximum of CO2 reduction potential. Here, nickel-metal-hydride or lithium ion batteries are used to reach the balance between power and high energy demand. Methodology/Limitation: Within this chapter the impact of these new vehicle applications onto the energy storage and their integration into the power system using power electronics is discussed from a supplier perspective based on actual pre- and series development projects.