SOFC4City - SOFC-waste heat utilization for buildings and industry
Due to the high operating temperature of the SOFC fuel cell, various fuels (natural gas, biogas, hydrogen, methanol and others) could be used and fossil fuels could be substituted by renewable energy sources (second generation biofuels, e.g. SNG, BtL).
However, the lifecycle of fuel cells essentially depends on their respective heating rate in the start-up and shut-down cycle. High heating rates cause high thermal stress in the stacks, which leads to high degradation rates. Therefore, SOFC-systems react slowly and cannot meet fast changes in power demand. An efficient, decentral integration of SOFC-systems requires an optimized system configuration which can fulfil thermic and electric load demands at the same time.
Contents and Objectives
In the beginning of this project, the needs of end users in residential buildings and the needs of the most important industry branches were analyzed. Apart from developing high-resolution thermic and electric load profiles of individual flats, opportunities to avoid fast load changes were evaluated. Among others, short time storages were analyzed in terms of their influence on the ratio between heat and electricity consumption. Moreover, the effect of electric integration of residential buildings was investigated. Using the resulting flexibility potential possible SOFC-systems configurations were proposed, depending on the possible electricity/heat ratio, the potential of using waste heat and the use of the building (residential, industry branch, etc.). Moreover, a detailed analysis of the legal and economic issues related to SOFC-systems was performed, taking into account possible waste heat potentials.
The thermal and electrical load profiles for multi-family houses for various living quarters were developed with a simulation tool called synPRO. A specially developed post-processing tool within Matlab® was used for data analysis. For the SOFC-systems simulation a numerically efficient stack and reformer module were developed. Therefore, CFD-parameter studies were performed to qualify the temperature distribution in the stack. Due to long processing times a one-dimensional stack model was developed and validated with the CFD-simulation results and own measurements.
Based on that, the one-dimensional stack model was used to identify the influence of the kinetics of the chemical reactions and the electrochemical losses on the temperature distribution in the stack. The results were used to build a numerically very efficient white-box-model and control strategies. Based on this white-box-model, different SOFC-system concepts were characterized and the feasibility of heat extraction on different temperature levels was analyzed. Moreover, a detailed analysis of the legal and economic issues regarding SOFC systems was carried out.
The results show that SOFC-systems with short time storages can adapt to the electricity and heat demands very well because of their flexibility regarding configuration. The use of the electricity grid on district basis allows realizing load balance potentials and decentralized waste heat potentials. Hence, heat distribution losses can be minimized which leads to an efficient energy supply system.
Prospects / Suggestions for future research
In a consecutive project, the results are used to develop a SOFC-system. Furthermore, the developed simulation models became part of the University of Applied Sciences' Master's Program „Building Technology and Building Management". By way of this program, the understanding of an optimized SOFC-system can be enhanced in the industry and the potential of concrete SOFC-projects is increased.
Forschung Burgenland GmbH
Project or cooperation partners
Austrian Energy Agency (AEA)
Vaillant Group Austria GmbH