Practical Systems for Personal Thermal Comfort

Abstract

Conventional centralized HVAC systems cannot provide office workers with personalized thermal comfort because workers in a single zone share a common air handling unit and thus a single air temperature. Moreover, they heat or cool an entire zone even if a single worker is present, which can waste energy. Both drawbacks are addressed by Personal Environmental Control (PEC) systems that modify the thermal envelope around a worker’s body to provide personalized comfort. However, most PEC systems are both expensive and difficult to deploy, making them unsuitable for large-scale deployment. In contrast, we present two novel PEC systems: SPOTlight and its successor OpenTherm. These systems are carefully designed for practical, rapid, and scalable deployment. Intuitive web-based interfaces for user controls allow OpenTherm to be installed in only about 15 minutes, including user training. It is also low-cost (as low as US$80, in volume) because it uses the fewest possible sensors and a lightweight compute engine that can optionally be located in the cloud. In this thesis, we present the detailed design of SPOTlight and OpenTherm systems, and results from a cumulative 81 months of OpenTherm’s operation in 15 offices. In our objective evaluation, we find that OpenTherm improved user comfort by ∼67%. This is in comparison to when only the central HVAC system with no knowledge of occupancy and inability to control offices individually is used.