Session: 03-01 Low Temperature Thermal Storage

Paper Number: 137605

137605 - Low-Cost, High-Density Thermal Storage for Space Conditioning Using Phase Change Materials 

Abstract: 

In the United States, water heating, space heating, and space cooling account for 49% of energy consumption in buildings (residential and commercial). To meet peak demand, additional fossil‐fuel peaker plants need to be brought online, resulting in lower system energy efficiency, reduced grid reliability, higher transmission dissipation, and increased carbon emissions. Thermal ice storage, intrinsically a battery for building air conditioning, is an economical, efficient, and environmentally friendly strategy to balance power supply and demand and can reduce building energy cost and improve system energy efficiency via shifting peak demand. Thermal ice storage exploits standard air-conditioning equipment to build and store ice during off‐peak energy‐demanding hours while releasing the cooling during peak hours. Current commercial thermal ice storage techniques rely on the self-limiting process of forming and melting ice on heat exchanger coils, where, in both the charging and discharging phases, the freezing/melting front moves radially outward, and the latent heat released/absorbed must be transferred through the bulk ice/water respectively, adding to the thermal resistance between the heat source and heat sink.

An innovative, modular and scalable, “dynamic” ice storage system—which we term “dynIce”—that addresses the challenges of conventional static icing/melting to enhance thermal storage performance and reduce cost and can be retrofit into existing HVAC installations is presented here. The system consists of a piston that couples the freezing/melting characteristics to the piston movement and leverages the close-contact melting phenomenon. The key innovation is the dynamic control of the thermal resistance across the water or ice by separating the newly formed ice layer from the cold surface to allow for rapid charging using low ice adhesion surfaces and draining melted ice during discharge to ensure a close ice-surface contact. In contrast to State-of-the-art storage systems, this system enables lower cost and efficient control of thermal resistance, resulting in enhanced performance and energy density. In this work, we demonstrate the fundamental limits of dynIce thermal storage systems, such as the peak heat fluxes, energy and power density, and power required to drive the actuation system, demonstrating theoretical peak heat fluxes, energy densities, and power densities ~10x higher than conventional methods, at low (< 10%) heat flux-to-piston power ratios. Analytically and experimentally, we characterize thermal resistances present in both a component-level dynamic ice thermal storage apparatus, and a complete HVAC-integrated system. We explore and experimentally validate a variety of designs to manage the transport and storage of the water and ice to enable cyclical performance within compact systems.

Presenting Author: Vivek Garimella University of Illinois Urbana-Champaign

Presenting Author Biography: Vivek received his B.S. in Mechanical Engineering with Highest Honors from the Georgia Institute of Technology in 2021. His topics of interest include waste heat recovery, energy storage, refrigeration, and two-phase heat transfer. In the ETRL, he studies electrostatic separation and energy storage using dynamic phase change materials. Vivek has served as the President of the Illinois Graduate MechSE Society since 2022.

Authors:

Vivek Garimella University of Illinois Urbana-Champaign
Wuchen Fu University of Illinois Urbana-Champaign
Adrika Vats University of Illinois Urbana-Champaign
Zachary Yashar University of Illinois Urbana-Champaign
Shravan Gokul Birla Institute of Technology and Science Pilani
Nenad Miljkovic University of Illinois Urbana-Champaign