UC Irvine

Sustainable energy conversion requires zero emissions of greenhouse gases and criteria pollutants using primary energy sources that the earth naturally replenishes quickly, like renewable resources. Solar and wind power conversion technologies have become cost effective recently, but challenges remain to manage electrical grid dynamics and to meet end-use requirements for energy dense fuels and chemicals. Renewable hydrogen can be made at very high efficiency using electrolysis systems that are dynamically operated to complement renewable wind and solar power dynamics and to provide feedstocks for chemicals and energy-dense fuels.A solid oxide electrolysis system is a highly efficient high temperature system that is suitable for large-scale hydrogen production. It has shown inherently high energetic and exergetic efficiencies for production of both hydrogen and other synthetic gases (e.g., methane synthesized from renewable hydrogen and captured CO2) via electrolysis and co-electrolysis processes. The high operating temperature of these systems eliminates the need for expensive catalysts and increases conversion efficiency and system integration opportunities. In this dissertation, first, a quasi-3D spatially and temporally resolved solid oxide electrolysis cell model is developed. A solid oxide electrolysis system including stack and balance of plant components, and its required control strategies is designed, modeled, and developed. A comparative analysis of an SOEC system for a stepwise dynamic operation under two different thermal control strategies is performed, by analyzing the overall system performance at different stack power loads. Moreover, the dynamic behavior of a SOE system which uses transient PV generated power as an input to produce compressed renewable hydrogen to be stored or injected directly into the natural gas network is analyzed under sunny and cloudy days scenarios. Next, a dynamic model is developed to evaluate the dynamic dispatch of solid oxide electrolysis system into the UCI microgrid to support high renewable use in the UCI microgrid. Also, an optimization model is developed to minimize imported electricity and natural gas consumption for different PV installed capacity scenarios in the UCI microgrid. Finally, a solid oxide short stack is experimentally evaluated in electrolysis mode in steady state and dynamic perspectives. Effects of different operating parameters i.e., operating temperature and fuel composition on the performance of the short stack are investigated. The capability of the short stack to operate dynamically under different input profiles is explored. Electrochemical impedance spectroscopy technique is employed to characterize the short stack in both cell and stack levels.