An explorative study on transient cooling pattern and energy efficiency while using micro-zonal occupant-centric control

Virtually dividing thermal zones into micro-zones and conditioning them using occupant-centric control (OCC) has emerged as a significant method in reducing cooling energy. Hence, the need arises to study time-sensitive thermal behaviour within micro-zones under OCC as thermal coupling from adjacent micro-zones significantly influences cooling patterns. This will explain possible variations in cooling time and energy consumption under different occupancies and aid in analysing the feasibility of micro-zoning as an efficient strategy. This study aims at exploring the key parameters that influence cooling patterns under micro-zonal OCC. Effects of four factors, namely indoor ambient temperature, supply air velocity, thermostat location and occupancy are explored using validated transient state CFD simulations for a hypothetical open-plan office. Results indicate that compared to zone conditioning, micro-zonal OCC can reduce about 20%–70% overall cooling energy while maintaining setpoint conditions and show the following three patterns: rate of cooling in occupied micro-zones decreases as they start to cool unoccupied zones through thermal coupling; supply air velocity and ambient temperature impact thermal coupling and the size of a chosen micro-zone influences energy load. This study is the first attempt at transient exploration of thermal developments within micro-zones under the influence of relevant parameters and is a necessary precursor to experimental studies on micro-zonal OCC. HIGHLIGHTS • Dividing thermal zones into micro-zones under the OCC saves 20%–70% energy. • First attempt at transient exploration of thermal developments within micro-zones. • The supplied air velocity, ambient temperature and micro-zone size influence HVAC energy.