Effect of an off-peak ground pre-cool control strategy on hybrid ground-source heat pump systems

Hybrid Ground-Source Heat Pump (HGSHP) systems have been introduced as an alternate system configuration to remedy the current financial hurdles associated to the installation of geo-exchange technology. However, there still remains potential for increased economic feasibility with the addition of improved system control. This study introduces an operational strategy referred to as an 'Off-Peak Ground Pre-Cool', employing time-of-use conscious operating logic to facilitate artificial bore-field pre-conditioning. Artificially pre-cooling a system's bore-field during an off-peak operating bracket allows for improved thermal characteristics for the following peak period. With improved bore-field thermal characteristics during peak periods, cooling mode operation can be exploited more efficiently, resulting in a reduction in peak power consumption and operating costs. This study presents a preliminary evaluation of the impact the proposed off-peak ground pre-cool strategy has on the operation of a HGSHP system, simulated for a mid-rise multi-residential facility located in Toronto, Canada. Two analyses are presented simulating the strategy's impact as a function of pre-cool duration and hybrid system proportions. This study explores the potential benefit that a proactive bore-field pre-condition poses for the operation of a HGSHP system, intending to concurrently address improving system economics and aid in the balancing of the electrical grid