Session: 03-01 Thermochemical Energy Storage

Paper Number: 114587

114587 - Predicting Energy and Power Trade-Offs in Salt Hydrate Composites for Building Heating and Thermal Storage 

Salt hydrates offer the potential to store building thermal loads with energy densities 2–10 times higher than phase change materials at low cost. During hydration the salts uptake water vapor from the air producing heat and induce cooling during dehydration when they release the stored water vapor. Since energy is kept in chemical bonds, heat can be stored loss free. While promising, deployment of pure salt hydrates has been limited due to the tendency of salts to swell and agglomerate during hydration, which limits their reaction rates and cyclability. This agglomeration blocks water vapor transport through the porous salt bed slowing reaction rates. To mitigate this problem, it is common to mix the salts in a support structure, such as the mineral vermiculite, to increase internal porosity and prevent particle agglomeration. However, since vermiculite is an inert host structure, it lowers the effective energy density of the salt. We conduct experiments comparing the hydration/dehydration rates of pure and composite salt hydrates. Preliminary results show that a 50% loading of vermiculite can make strontium bromide hydrate three times faster as compared to the pure salt. Applying a Ragone framework, we explore the trade-off between power and energy density and explore implications to meet the demands of home air heating. Additionally, in-situ imaging is used to provide additional insights on dynamic changes to the internal porous structure of composite salts and how this impacts water vapor uptake/release. Overall, results from this study will enable future development of thermochemical batteries for heat-transfer and heat-storage applications.

Presenting Author: Bryan Kinzer University of Michigan

Presenting Author Biography: Bryan Kinzer is a 5th year PhD student in mechanical engineering at the University of Michigan. Prior to coming to Michigan, Bryan conducted a Fulbright on rural village electrification in Lesotho, Africa. His current research focuses on salt hydrate thermochemical batteries for building heating and cooling. Using a combination of modelling and experiments his results help optimize reactor performance and explore the fundamental mechanisms of how salts uptake and release water vapor during cycling.