OcAPO: Occupancy-Aware, PDC Control for Open-Plan, Shared Workspaces

Passive Displacement Cooling (PDC) has gained popularity as a means of significantly reducing building energy consumption overheads, especially in tropical climates. PDC eliminates the use of mechanical fans, instead using chilled-water heat exchangers to perform convective cooling. In this paper, we evaluate the impact of different parameters affecting occupant comfort in a
$1000m^{2}$
open-floor area (consisting of multiple zones) of a ZEB (Zero Energy Building) deployed with PDC units and tackle the problem of setting the temperature setpoint of the PDC units to assure occupant thermal comfort. We tackle two key practical challenges: (a) the zone-level (i.e., occupant-experienced) temperature differs significantly, depending on occupancy levels, from that measured by the ceiling-mounted thermal sensors that drive the PDC control loop, and (b) sparsely deployed sensors are unable to distinguish between ambient temperature variations across neighboring zones. Using extensive real-world measurement data (collected over 60 days), we devise a trace-based model that helps identify the optimum combination of PDC setpoints, collectively across multiple zones, while accommodating variations in the occupancy levels and weather conditions. We deploy OcAPO on our real-world testbed to demonstrate its efficacy: while OcAPO reliably assures occupancy comfort within a tolerance of 0.2°C, the current practice of occupancy-agnostic rule-based setpoint control violates this tolerance value 75.2% of the time.