2023ICERD8-C18 -- A Case Study Exploring Micro-Zonal Occupant Centric Control (MZOCC) for HVAC Energy Efficiency

Air-conditioning systems consume the maximum energy in the buildings. This can be reduced by air-conditioning only the occupied regions. Though occupancy-based smart controllers are available, they are mostly employed for physically separated HVAC zones. With surge in open-plan offices with flexible seat allocation and work hours, there is a need to improve zone level control of HVAC systems to allow diffuser level control. Micro-zonal occupant centric control (MZOCC), that conditions only the occupied virtual zones can save energy, improve thermal comfort and requires only 5%-6% additional investment. Nonetheless, unplanned MZOCC can increase energy consumption and discomfort. Previous studies discuss the need for framing protocols for micro-zoning. In continuation, the aim of this study is to frame protocols ensuring bilevel optimization of MZOCC were the first level focusses on micro-zonal planning and second on airflow control. In this regard, Indian open-plan offices are surveyed to explore the characteristics of open-plan offices. Occupant behavior and duration of absence from assigned work spaces are also surveyed. First level of the bi-level framework gives guidelines on planning micro-zones by considering the contextual, spatial and temporal usage of the space. The second level gives guidelines for airflow control in each micro-zone considering the predicted occupancy. MZOCC following the first level of protocols are evaluated in this study by considering occupancy as observed from field studies. A case study is performed to compare energy consumed under MZOCC to typical zone level air-conditioning system. Results indicate that MZOCC can reduce 50%-70% energy compared to zone level conditioning. Thus, the study establishes the effectiveness of protocols for MZOCC and gives a systematic method by which they can be applied to real buildings.