Energy Conservation Utilizing Wireless Dimmable Lighting Control in a Shared-Space Office

Overhead light fixtures in shared-space offices are typically grouped into banks, each of which is controlled by a single switch. Even in offices with daylight responsive systems, the luminaires are divided into zones controlled by one photosensor per zone. Too often, the geographically-defined “zone” does not correspond to occupied areas, and energy is wasted illuminating the unoccupied areas. Research has also shown that people have diverse preferences for lighting and that optimal personal lighting is highly correlated to productivity. Systems that deliver identical lighting can compromise personal preferences. Various researchers have pointed out that individual light control can increase both user satisfaction and energy efficiency. The main obstacles are the exorbitant initial cost of long-distance rewiring and the lack of efficient control. Leveraging the emergence of wireless sensor/actuator network technologies, we developed a module interfaced with a dimming ballast to enable individual, dimmable light control. As a pilot implementation, the modules were installed in a shared-space office with 19 luminaires without out-of-fixture rewiring. Occupants were allowed to set their preferences and given the ability to override current light settings through a dedicated webpage. A kiosk was set up by the entryway so occupants could easily select their preferred lighting when entering the space. A short term energy monitoring revealed a 46% energy savings even though there was no window in the office to facilitate daylight harvesting. The occupants were also satisfied with working under their preferred lighting.