Innovative thermodynamic cycles for renewable energy supply

With the COP 21 declaration, almost all countries worldwide have dedicated themselves to a clear path towards CO2 neutrality, or even decarbonization. Consequently, in the long term CO2 neutral power generation systems will be obligatory and maybe even CO2 negative systems will be necessary. This requires major installation of wind and solar power. However, these only provide intermittent electricity. Thus, additional balancing power has to be provided. Biomass can partly fill this gap, for example via biogenous fuel gases from anaerobic digestion or thermochemical gasification. For this purpose, the available biomass has to be used at the highest possible efficiency, in order to maximize its potential. Electrochemical conversion offers very high efficiency, especially in Solid Oxide Cells (SOC). In this work, novel system configurations for optimized utilization of biomass resources for electricity generation and storage are investigated. A focus is put on exergetic optimization with utilization of SOC waste heat in gasification and biogas generation. Thereby, the work contributes to a better understanding of the interaction between gas generation from biomass and SOC. The primary goal is to achieve optimal integration of material and heat streams in combined biomass SOC systems. The scope of the optimization is high exergy efficiency as well as to provide a system design, which allows maximum operation flexibility. It is shown that the exergy efficiency can be increased significantly in comparison to state-of-the-art technologies and also latest scientific literature results. Furthermore, high flexibility can be obtained. Following the thermodynamic analysis and optimization, an economic evaluation of biogas-based Reversible Solid Oxide Cell (RSOC) systems is performed in comparison with state-of-the-art technology for biogas utilization. Under the conditions of the analysis the RSOC systems perform better than the state of the art and a potential for economic operation is found. Finally, it is estimated to which extend optimized bio-RSOC systems could contribute to a more stable electricity supply.