UC Berkeley

Refrigeration, heat pumping, and thermal energy storage will play a critical role in decarbonizing the residential and industrial sectors. Refrigeration and heat pumping are abundant but employ refrigerants with high global warming potential. Thermal energy storage can provide low cost solutions for load-shifting and demand side flexibility to enable a more renewable grid, but implementation in the real world has been slowed by economic barriers. Thus, shifting to new heating and cooling technologies with zero global warming potential and connecting those technologies to affordable thermal storage solutions is an important step toward carbon neutrality. This thesis takes a critical look at the fundamental principles governing thermal energy storage from the material level up to the system level, specifically focusing on the solid to liquid phase transition. Both equilibrium material properties and non-equilibrium material behavior are treated in relation to their applications in thermal energy storage systems. In addition, we analyze up and coming thermal storage technologies, such as thermochemical reaction-based storage, wherein we demonstrate design rules, equilibrium, and non-equilibrium stability criteria for hydration/dehydration based storage, along with a novel liquid-solubilized reactant storage. Finally, we show how fundamental understanding of the solid to liquid transition leads to insight on phase stabilization, from which we develop the ionocaloric effect. We then show how we can embed the ionocaloric effect in various thermodynamic cycles, and demonstrate how a novel, condensed-phase and zero global warming potential heat pumping cycle emerges.