Optimized pre-cooling for priming energy demand reduction of air conditioners in residential buildings

Cooling energy contributes significantly to residential energy demand in tropical regions. Specifically, the priming energy required for extracting the accumulated heat from the indoor environment to reach the desirable setpoint temperature, contributes to the peak demand. The priming energy accounts for up to 40% of the daily cooling energy in overheated and poorly ventilated spaces. Pre-cooling of buildings is a strategy that accelerates convective heat loss from the indoor environment, thereby reducing priming energy. This study establishes the priming energy demand reduction of air conditioners by adopting pre-cooling in a hot semi-arid (Köppen BSh) climate. Experimental studies were performed in a full-scale testbed where pre-cooling was enabled using a set of four speed-controllable ventilator fans. Validated energy simulations were conducted to optimize the ventilation rate and duration of fan operation for different time periods of the year. This helped establish optimal operational settings of the ventilator fans. Full-scale experiments confirmed that fan-forced pre-cooling contributed to a 40–75% reduction in the priming energy demand of the air conditioner based on the outdoor boundary conditions. The findings of the study can help in the development of control algorithms for pre-cooling systems in such residential settings.