The coupled effects of personalized occupancy profile based HVAC schedules and room reassignment on building energy use

Buildings account for nearly 38% of the total energy use in the U.S., and 46% of this use is associated with commercial buildings. More than 40% of the energy in commercial buildings is consumed by HVAC systems, which provide heating, cooling and ventilation to individual zones to maintain comfortable and healthy indoor environments. A more refined control strategy based on actual occupancy might improve HVAC system related energy efficiency. Accurate occupancy profiles are important to determine actual energy demands and corresponding control schedules. This paper focuses on energy efficiency in office buildings with centrally controlled VAV systems by setting zone-level HVAC start/stop schedules using personalized occupancy profiles, which represent occupants' long-term presence patterns. Evaluation of the method was performed using a simulation model, calibrated by the actual energy use data of an office test bed building. Up to 9% of the energy was saved when personalized occupancy profile based HVAC schedules were used. However, if occupants of a zone have different occupancy patterns, the aggregated patterns may hinder any potential efficiency that might be realized from zone-level HVAC start/stop schedules. This paper also presents an approach for reassigning rooms to unify the start/stop times at the zone level by placing occupants with similar profiles in the same mechanical zones. When room reassignment was implemented and coupled with profile based control schedule, HVAC energy use was reduced by another 8%. The proposed methods could provide reliable personalized HVAC control for small-size office buildings without advanced building automation systems, nevertheless, they could also be extended to buildings with packaged HVAC systems and individual air-conditioning systems.