Hierarchical Hybrid MPC for Management of Distributed Phase Change Thermal Energy Storage

Switched Moving Boundary Modeling of Phase Change Thermal Energy Storage Systems

“…The need for higher performance and more efficient thermal management systems has driven the design of systems with integrated Thermal Energy Storage (TES) devices that leverage the latent heat of a Phase Change Material (PCM). The design and performance of PCM-based TES has been well-studied [1]- [3], resulting in a wide range of applications including building [4], [5] and aircraft [6], [7] thermal management, power electronics cooling [8], and combined heating and cooling [9].…”

“…The utility of a TES is heavily dependent on the dynamics associated with charging (where the PCM solidifies from liquid to solid), discharging (where the PCM melts from solid to liquid), and strategic switching between these two modes of operation. Therefore, accurate control-oriented models of PCM-based TES are needed that capture their hybrid, nonlinear dynamics to be used in predictive controllers like Model Predictive Control (MPC), which have been developed for single-phase [4], [5] and phase change TES [8].…”

“…This paper aims to develop accurate control-oriented models of PCM-based TES devices using a graph-based switched Moving Boundary (MB) approach. Graph-based modeling [6]- [8], [10], [14] is used to develop both FG and MB models, where a graph is used to clearly identify the underlying structure of thermal energy storage and transfer throughout the TES device. While the FG model divides the PCM into n sections, each with its own dynamic enthalpy state, the proposed MB approach only requires three states corresponding to the enthalpies of the solid and liquid regions of the PCM and the overall State-of-Charge (SOC), defined as the mass of the solid portion compared to the total mass of the PCM.…”

“…Several MB approaches to TES modeling have recently been proposed [7], [8], [12] but each has limitations. Specifically, the TES devices modeled in both [7] and [12] are limited to operation where heat flows in only one direction through the PCM, i.e., heat always enters on one side and exits on the other.…”

“…However, many TES devices operate by exchanging heat with a single working fluid flowing through the center of the TES. The TES model developed in [8] captures how a heat transfer effectiveness coefficient for the PCM is a function of SOC and the mode of operation (charging or discharging) but modeling the completely melted or solidified modes of operation is left for future work.…”