Experimental Validation of a Transient Model for a SOFC / Li-Ion Battery Hybrid

Abstract

The EU project Nautilus aims to implement SOFC/Li-ion battery hybrids into cruise ships for high fuel efficiency and low emissions. Two individual models of a SOFC and a Li-ion battery shall be validated using experimental data. For this, a SOFC / battery hybrid proof of concept at the DLR test-site is prepared and tested in real and digital operations. In this thesis, pre-simulations for the experimental operation of the SOFC are done, examining the effects of changing inputs on the SOFC. Hereby, an objective criterion for the steady-state determination is defined. Due to component failure, no experimental data from the SOFC could be generated in this thesis, and thus the model cannot be finally validated. To validate the equivalent circuit model provided by the RWTH Aachen, a test bench for 38.9 kWh battery was built and commissioned. For operation, a LabVIEW control is implemented. The battery characteristics were determined with various test runs. The correspondence between experiment and simulation with the tested current rates is hereby rated as sufficiently accurate. At the time of submitting the master thesis, both the battery test stand and the SOFC test stand are ready to be connected into a hybrid. A control strategy based on an existing algorithm is developed to operate the hybrid. This algorithm is modified to ensure reliable power sharing of the load profile for SOFC and battery operation.