Woodruff School of Mechanical Engineering
Mechanical Engineering Seminar
High-Temperature Solar Thermochemical Processes for Sustainable Fuel Production
Dr. Alon Lidor
Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
Thursday, November 18, 2021 at 11:00:00 AM Add to Calendar
MRDC Building, Room MRDC 4211
The production of drop-in solar fuels can eliminate greenhouse gas emissions and provide the path to sustainable aviation. One such promising pathway to solar fuels is via a thermochemical redox cycle for splitting H2O and CO2, driven by concentrated sunlight. The product is a specific mixture of H2 and CO which can be further processed downstream by established Fischer-Tropsch synthesis to liquid hydrocarbons. The entire solar fuel process chain has been successfully demonstrated in a solar tower and a solar dish configurations, but with a limited solar-to-fuel energy efficiency of 5-6%. This value can be significantly increased by mainly recovering the heat lost during the temperature-swing redox cycle, accounting for up to 62.8% of the total solar energy input. We have developed a novel method for heat recovery, utilizing the thermocline concept. The solar reactor is coupled with a thermal energy storage (TES) unit, and a heat transfer fluid (HTF) is used to extract high-temperature heat from the redox material and charge the TES unit. The high-temperature heat can then be delivered back to the solar reactor prior to reduction, or utilized in another process. An experimental setup was designed and constructed, consisting of a lab-scale solar reactor and several thermocline-based TES units, made of a packed-bed of alumina spheres or ceramic honeycombs. A numerical analysis of the TES units have been performed, studying the effects of various parameters on its operation for high-temperature service. The TES units have been experimentally studied using air heaters, before integration with the complete setup. Testing in the ETH high-flux solar simulator demonstrated the concept feasibility. The measured heat recovery effectiveness was over 80%, with extracted HTF temperatures over 1250C. The experimental campaign included the study of several key parameters on the performance: the HTF flow rate, oxidation start and end temperatures, HTF inlet temperature during the heat recovery step, and stability during consecutive redox cycles. These results show the potential of high-temperature heat recovery in solar reactors, outline the challenges, and provide important insights for high-temperature heat transfer processes.
Dr. Lidor is a Postdoctoral Associate at the Professorship of Renewable Energy Carriers at ETH Zurich since 2019. He received his B.Sc. (2011) from the Department of Mechanical Engineering at Ben-Gurion University, and his M.Sc. (2013) and Ph.D. (2017) from the Faculty of Aerospace Engineering at the Technion Israel Institute of Technology. He was a DLR-DAAD Postdoctoral Fellow at the German Aerospace Center (DLR) in 2018-2019, before winning a Marie-Curie Individual Fellowship and starting his current position at ETH. His research interests include solar thermochemical processes, high-temperature heat recovery, thermal energy storage, small-scale propulsion units, and fundamental topics in thermodynamics, and his work combines theoretical, numerical and experimental approaches.
The seminar link is at: https://bluejeans.com/711454501