Comparative analysis of the performance and energy consumption of air-conditioning systems in a plant factory during a cooling season

With the growth of urban populations and increasing food security concerns, plant factories have emerged as viable solutions for sustainable food production. These systems ensure consistent quality and yield through precise environmental controls in a closed system. However, the high energy costs of plant factories pose significant challenges. Heating, ventilation, and air-conditioning systems account for 16-54% of the total energy consumption. Thus, highly efficient systems and optimal control strategies are essential to reduce the energy consumption. This study compared the performance of a conventional electric heat pump system (System 1) with that of a system combining an electric heat pump and a dehumidification unit (System 2) in a lettuce-growing container farm. A building energy simulation model was employed to evaluate system performance. The results indicated that although both systems maintained adequate temperature control, System 1 allowed the relative humidity to reach 95.7%, making it challenging to maintain a suitable environment for crop growth. In contrast, System 2 significantly improved the humidity management, creating a more suitable environment for crop growth and improving the cooling efficiency of the electric heat pump. Consequently, System 2 achieved a 13.7-24.5% reduction in the monthly energy consumption of the electric heat pump. The total annual energy saving of System 2 was 5.9%, accounting for the energy consumption of the dehumidification system. Future research should focus on optimizing the system capacity and control strategies to further maximize the energy savings based on the findings of this study.