Energy Management for a Fuel Cell/Battery Hybrid System

摘要

Direct methanol fuel cells (DMFCs) directly convert liquid methanol into electric energy. Due to the high energy density of methanol, they permit a longer operating time. Therefore, DMFC systems are attractive for various applications as replacements for batteries. A market analysis showed that the best potential lies in the material-handling sector. A DMFC system was designed for a horizontal order picker, which belongs to this application class. To fulfill the requirements of a highly fluctuating load profile, the DMFC has to be hybridized. The hybridization concept for the DMFC energy system as well as the dimensioning of the DMFC stack and the battery are described. The main focus will be set on the energy management for this fuel cell/battery hybrid system. The energy management strategy is used to control the power flow between the DMFC stack and the battery according to their actual states. Additionally, this strategy has three different aims. The first is to maintain the state of charge of the battery on a constant level. The others regard the aging of the DMFC stack: avoiding and identification. Several control strategies will be analyzed with simulations and experiments.