OCCUPIED: Long-term field experiment results from an occupant-centric control in an office building

With the rapid development of sensing technology, occupancy-based control (OBC) demonstrated great energy saving potentials while maintaining a comfortable indoor environment. By leveraging advanced sensing technologies, OBC can adjust temperature and ventilation settings based on real-time occupancy information, thereby addressing the energy wastage issue caused by discrepancies between actual occupancy and pre-defined schedules. This study adopted a first two-year long-term field testing to evaluate the OBC performance in a medium-sized office building, which included one open space with up to 30 people and four cubicles with 4 individuals. Three state-of-art OBC algorithms were integrated with the real-time Heating, Ventilation, and Air-Conditioning (HVAC) system. And the results were compared with a data-driven baseline model. A 4% to 11.2% heating load reduction and a 3.6% to 6.5% cooling load reduction were observed for the open space. 8% to 16.3% of HVAC energy decreased during the heat wave and winter storm. As for the cubicles, OBC achieved a 4% to 64% cooling load reduction, along with an 18.3% reduction in fan power. However, the heating energy reduction was negligible (1%). Different OBCs failure cases caused by sensing errors or BACnet issues were discussed, which could make HVAC systems operate incorrectly and raise thermal comfort concerns. In summary, this long-term field study demonstrated the considerable energy-saving potential of OBC while identifying its five key drawbacks: thermal comfort issues, damper cycling, privacy concerns, peak load demand challenges, and limitations in free cooling. This research provided valuable insights for the practical implementation of OBC in HVAC control systems while guiding its real-world application.