Cell and System Modeling for Pressurized SOFC Applications

Kurzfassung

Pressurized solid oxide fuel cells (SOFC) are in consideration for application in hybrid power plants. These plants combine a gas turbine with an SOFC subsystem. Highest efficiencies can be reached when the SOFC is operated under pressurized conditions. First, this is due to the fact that the SOFC delivers higher power densities with higher pressure and second, the waste heat of the SOFC can be directly utilized in the gas turbine without further need of combustion. This presentation will focus on the cell and system level modeling performed at DLR. Cell modeling gives an insight into the pressure dependence of the governing reactions in SOFC as well as possible degradation effects at pressurized operation. The modeling results presented are based on our in house simulation tool using an elementary kinetic approach. Current work focuses on the validation of the model under pressurized conditions. We use the simulations as a tool for understanding experimental results and gaining a deeper understanding of the ongoing processes. Furthermore the detailed cell model can be implemented into the system model. On the system level the presentation will show the influence of various operating strategies on the system efficiency during load following operation. It will be shown that it is possible to maintain the heat in the fuel cell system during low-load operation while keeping the system efficiency high. Furthermore, it will be shown that the system is able to perform minor load changes with only little penalty to the exhaust gas temperature, which is essential for the operation with a gas turbine.