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Efficient simulation strategy for PCM-based cold-energy storage systems

G. Bejarano, M. Vargas, M. G. Ortega, F. Castaño, J. E. Normey-Rico

TL;DR

This work addresses the need for fast, integrated simulation of PCM-based cold-energy storage (TES) systems that complement existing refrigeration plants. It builds on a discrete PCM model by introducing an adaptive, time-efficient scheme that clusters sensible-zone layers and assumes constant-rate energy transfer over adaptive intervals, dramatically reducing computation time. The approach preserves key TES dynamics, achieving PCM charge-ratio errors below roughly 3% across full charging/discharging and sequences of partial operations, while delivering speedups up to about 127x. The resulting model enables feasible long-term energy-management studies where TES dynamics must couple with plant-level optimization, facilitating efficient scheduling and operation of cold energy production and storage.

Abstract

This paper proposes a computationally efficient simulation strategy for cold thermal energy storage (TES) systems based on phase change material (PCM). Taking as a starting point the recent design of a TES system based on PCM, designed to complement a vapour-compression refrigeration plant, the new highly efficient modelling strategy is described and its performance is compared against the pre-existing one. The need for a new computationally efficient approach comes from the fact that, in the near future, such a TES model is intended to be used in combination with the model of the own mother refrigeration plant, in order to address efficient, long-term energy management strategies, where computation time will become a major issue. Comparative simulations show that the proposed computationally efficient strategy reduces the simulation time to a small fraction of the original figure (from around 1/30th till around 1/120th, depending on the particular choice of the main sampling interval), at the expense of affordable inaccuracy in terms of the PCM charge ratio.

Efficient simulation strategy for PCM-based cold-energy storage systems

TL;DR

This work addresses the need for fast, integrated simulation of PCM-based cold-energy storage (TES) systems that complement existing refrigeration plants. It builds on a discrete PCM model by introducing an adaptive, time-efficient scheme that clusters sensible-zone layers and assumes constant-rate energy transfer over adaptive intervals, dramatically reducing computation time. The approach preserves key TES dynamics, achieving PCM charge-ratio errors below roughly 3% across full charging/discharging and sequences of partial operations, while delivering speedups up to about 127x. The resulting model enables feasible long-term energy-management studies where TES dynamics must couple with plant-level optimization, facilitating efficient scheduling and operation of cold energy production and storage.

Abstract

This paper proposes a computationally efficient simulation strategy for cold thermal energy storage (TES) systems based on phase change material (PCM). Taking as a starting point the recent design of a TES system based on PCM, designed to complement a vapour-compression refrigeration plant, the new highly efficient modelling strategy is described and its performance is compared against the pre-existing one. The need for a new computationally efficient approach comes from the fact that, in the near future, such a TES model is intended to be used in combination with the model of the own mother refrigeration plant, in order to address efficient, long-term energy management strategies, where computation time will become a major issue. Comparative simulations show that the proposed computationally efficient strategy reduces the simulation time to a small fraction of the original figure (from around 1/30th till around 1/120th, depending on the particular choice of the main sampling interval), at the expense of affordable inaccuracy in terms of the PCM charge ratio.
Paper Structure (15 sections, 13 equations, 14 figures, 7 tables)

This paper contains 15 sections, 13 equations, 14 figures, 7 tables.

Table of Contents

  1. Introduction
  2. System description
  3. Notation
  4. Design specifications of the TES system
  5. Discrete model of the TES system
  6. PCM-intermediate fluid dynamics
  7. Refrigerant - intermediate fluid dynamics
  8. Secondary fluid - intermediate fluid dynamics
  9. Time-efficient discrete model of the TES system
  10. Accuracy assessment of the time-efficient discrete model
  11. Evaluation under full charging operation
  12. Evaluation under full discharging operation
  13. Evaluation under series of partial charging/discharging operations
  14. Comparative computational cost evaluation
  15. Conclusions

Figures (14)

  • Figure 1: Schematic picture of the proposed configuration of the TES tank and input-output conceptualization of the TES system.
  • Figure 2: Temperature-enthalpy diagram of the PCM.
  • Figure 3: Scheme of the discretised PCM capsule for $n_{ \! l\!a\!y} = 5$, with a detail of the involved thermal resistances.
  • Figure 4: Comparison of the transferred cooling power between each PCM nodule and the intermediate fluid (upper plot) and its temperature (lower plot), in a typical charging operation.
  • Figure 5: Comparison of the PCM charge ratio during the simulated typical charging operation.
  • ...and 9 more figures