# Switched Moving Boundary Modeling of Phase Change Thermal Energy Storage Systems

**Authors:** Trent J. Sakakini, Justin P. Koeln  
**arXiv:** [2303.15687](https://arxiv.org/abs/2303.15687)  
**Date:** 2023-03-28  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2303.15687v2/

## Key points

- Thermal Energy Storage (TES) devices with Phase Change Materials (PCMs) are important in thermal management systems
- TES devices use constant-temperature thermal capacity of PCMs to decouple absorption and rejection of thermal energy
- Control-oriented models of TES are necessary for predicting behavior and making informed control decisions
- A switched Moving Boundary (MB) model captures key dynamics of TES with fewer dynamic states
- MB model uses graph-based modeling approach to represent heat flow through TES and a MB approach to model time-varying liquid and solid regions of PCM
- Finite State Machine (FSM) is used to switch between four different modes of operation based on State-of-Charge (SOC) of TES
- Numerical simulations show that the proposed MB approach accurately models behavior while using far fewer states, leading to five times faster simulations
- MB models can be effective tools for predicting TES behavior and making informed control decisions in various thermal management systems.

## Summary

Thermal Energy Storage (TES) devices that use Phase Change Materials (PCMs) are becoming increasingly important in thermal management systems. TES devices leverage the constant-temperature thermal capacity of PCMs to decouple the absorption and rejection of thermal energy, similar to how batteries function in electrical systems. To maximize its efficiency and capabilities, control-oriented models of TES are necessary to predict its behavior and make informed control decisions. This paper proposes a switched Moving Boundary (MB) model that captures the key dynamics of the TES with significantly fewer dynamic states. The MB model uses a graph-based modeling approach to represent heat flow through the TES and a MB approach to model the time-varying liquid and solid regions of the PCM. Additionally, a Finite State Machine (FSM) is used to switch between four different modes of operation based on the State-of-Charge (SOC) of the TES. Numerical simulations comparing the proposed MB approach with traditional Fixed Grid (FG) approaches show that it accurately models the behavior of FG models while using far fewer states, leading to five times faster simulations. This makes it an attractive option for real-time control applications where speed is critical. Their research highlights how MB models can be used as effective tools for predicting TES behavior and making informed control decisions in various thermal management systems.