System performance and economic assessment of a thermal energy storage based air-conditioning unit for transport applications

Traditional air conditioning (AC) faces low energy efficiency and thermal comfort challenges. This study explores the integration of thermal energy storage (TES) containing a phase change material (PCM) with a conventional AC unit (PCM-AC) to meet the challenge. A PCM based TES device was designed and fabricated and an experimental system was established. Comparisons are made between AC and PCM-AC scenarios in terms of spatial temperature changes at the initial transient stage, spatial temperature fluctuations at the steady-state operations, relative humidity, coefficient of performance (COP), energy savings, and emergency ventilation/cooling. A developed model was used to simulate the room temperature fluctuations with and without PCM under the Matlab Simulink environment. The experimental results showed that, compared with the AC, the testing space temperature fluctuation of the PCM-AC was reduced significantly to ∼2.56 °C (compared with 4.31 °C for the AC case); the ON-OFF frequency of the compressor of the PCM-AC was reduced by 27%; the overall COP was increased by 19.05%; and the emergency ventilation/cooling time was prolonged by almost 9 times. The results also showed the potential of the use of PCM-AC to significantly narrow down the relative humidity fluctuations and hence the potential for enhancing the thermal comfort. The simulation results agree well with the experimental data. The economic analysis showed that the electrical cost of the PCM-AC could be reduced by ∼17.82%, leading to a payback period between 1.83 and 3.3 depending on the grade the PCM used and the scale of operations.