Determining optimal thermal energy storage charging temperature for cooling using integrated building and coil modeling

초록

Thermal energy storage (TES) systems coupled with heat pumps offer significant potential for improving building energy efficiency by shifting electricity demand to off-peak hours. However, conventional operating strategies maintain conservatively low chilled water temperatures throughout the cooling season, a practice that results in suboptimal heat pump performance. This study proposes a physics-based integrated simulation method to determine the maximum feasible chilled water supply temperature while ensuring cooling stability. The framework integrates four sub models: relative humidity prediction, dynamic cooling load estimation, cooling coil performance prediction, and TES discharge temperature prediction. Validation against measured data from an office building demonstrates reliable accuracy across all sub models (e.g., a coefficient of variation of root mean square error (CVRMSE) of 9.3% for cooling load and R2 of 0.91 for peak-time discharge temperature). The integrated simulation reveals that, compared to conventional fixed-temperature operation, the proposed method can theoretically increase the chilled water supply temperature by an average of 4.52 degrees C when considering only the physical limits of the cooling coil. Furthermore, when comprehensively accounting for the physical discharge constraints of the TES, a practical average increase of 2.55 degrees C is feasible without compromising cooling stability, enabling the heat pump to operate at a higher coefficient of performance. This study contributes a practical methodology for optimizing TES charging temperatures in building heating, ventilation, and air conditioning (HVAC) systems while maintaining indoor setpoint temperatures.

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