Design and Modeling of Hydrogel-Based Adsorbent Bed for Energy Storage

Waste heat generation is ubiquitous in power systems operating in residential and industrial settings. While reuse of waste heat is common practice in industrial systems, an increase in the energy density of a waste heat collector is crucial for the improvement of system efficiency and feasibility. The hydrophilic nature of hydrogels creates a compelling prospect for thermal energy storage (TES), in the form of a chemical potential. In this work, we take advantage of the sorption capabilities of hydrogels, combined with waste heat collection from existing power systems such as HVAC, to design and engineer a hydrogel/salt composite. This composite is to be integrated into a compact TES device, to deliver an energy density greater than 200 kWh/m³/day.<br/>The hydrogel/salt synthesis requires paramount characterization and testing of polymer/salt combinations, to yield an effective, durable, and mechanically robust, high water uptake material, that will enable the required high-energy capacity. The composite’s kinetics and low-temperature desorption capabilities play a critical role in surpassing the device design requirements. A novel technique is used to adhere the hydrogel onto the device, while maintaining good mechanical and thermal stability. This novel technique allows for an effective thermal conductivity greater than 1 W/m K. We developed a numerical model to simulate and predict the heat and mass transfer of the hydrogel within the device. The critical component where the hydrogel is mounted is a tube-fin heat exchange. The thickness and kinetics of the hydrogel composite layer is optimized to maximize the energy density of the TES. We characterize the hydrogel experimentally to validate the developed numerical models.