During the first project period, work focused on the development of the single plant components and the design, manufacturing and assembly of a first testing plant. The operating conditions for the single units and their interfaces have been defined and a detailed plant concept has been worked out. With this system design, the SOFC is operated with a side stream of the product gas from the gasifier while the remaining product gas is combusted in a burner directly coupled with a boiler. This provides the advantage that the SOFC can be operated at nominal load while the amount of the product gas directly utilised for heat production is variable and can be adapted to the heat demand of the consumer. Therefore, high load flexibility in a heat controlled system is provided while maintaining a maximum of full load operating hours of the SOFC unit.
Regarding the gasifier, a product gas heating and extraction system which also provides a thermal tar reforming stage was developed. Moreover, the gasifier was further developed towards the utilisation of biomass fuels with comparably low ash melting temperatures (such as agro-pellets) thus achieving a significantly enhanced fuel flexibility. Therefore, experimental studies and comprehensive CFD (computational fluid dynamics) simulations have been performed. With respect to the gas cleaning unit (GCU), experimental work, process modelling and chemical equilibrium calculations were employed in order to develop the different reactors needed and to select appropriate sorbents for Cl and S-removal as well as catalysts for tar reforming. Based on this, a first generation GCU has been designed and constructed. Furthermore, a SOFC system tailored to the gas composition of the product gas downstream the GCU has been developed. The stack module has been modified with respect to the product gas properties and the balance of plant components have been newly developed for integration into the whole plant concept.
At the end of the first project period, the assembly of the first generation FlexiFuel-SOFC testing plant took place. The second project period started with cold and warm start-up tests. Then, test runs for the evaluation of the GCU have been performed and several adaptations have been made in order to gain continuous operation and to meet the gas quality requirements of the SOFC. Subsequently, testing campaigns with the whole CHP system followed. At the end of the second project period the new technology has for the first time been operated in CHP mode at the targeted electricity production of 6 kW.
Subsequently, during the third project period, the gasifier, the GCU and the SOFC system as well as the whole CHP system have been further developed based on the evaluation of the test run results and the experiences made during plant operation. A second generation testing plant has been assembled and comprehensive test runs have been performed. The purification targets set for the GCU could be reached and again, an electrical load above 6 kW and flexible thermal output could be achieved. Moreover, the fuel flexibility of the gasifier could be proven during test runs with wood chips, willow, poplar and Miscanthus pellets. In total more than 250 hours of CHP operation have been reached and TRL 5 could be achieved. Based on these promising results, a final system design has been worked out, which shall form the first step for later industrialisation.
Economic and environmental assessments as well as market analyses accompanied the technical development work throughout the whole project resulting in a comprehensive market study regarding the market potentials and future trends for micro-scale biomass CHP systems in Europe, a long-term roadmap for the successful deployment of the FlexiFuel-SOFC technology on the market, techno-economic analyses and environmental and overall impact assessment reports. These studies show considerable market opportunities for the FlexiFuel-SOFC technology as well as high positive EU-wide impacts on the environment and on energy security.
