Public buildings in the U.S. waste approximately one-third of the energy they use. This kind of energy waste is not a way to ensure a sustainable future. The city of Pleasanton, Calif., recognized this and decided to do something about it. One of the ways they met this challenge was to install wireless lighting controls at one of the city’s most prominent public buildings.

In July 2011 the Pleasanton Public Library underwent a lighting retrofit project coupled with the installation of a wireless lighting controls system that enabled the city to significantly reduce energy use while increasing comfort and occupants’ sense of security. A wireless lighting control system best met the library’s needs and here’s why.

Traditionally, libraries have often been unable to utilize occupancy sensors in their book stack areas to save energy. Because most sensors must be directly wired to the fixtures they control, the height of the stacks creates challenging obstructions to the range of detection for the sensor. This can create challenges if the library wants to move stacks around and also can cause lights to turn off abruptly even when the space is still occupied. The ability to program dynamic software created zones of multiple fixtures wirelessly listening to one or more occupancy sensors overcame this challenge and enabled Pleasanton’s library to realize energy savings not previously possible.

The library also had a lot of potential for daylight harvesting with several large skylights and many windows, but due to circuiting limitations, the city could not leverage this or any other advanced lighting control strategy. To complicate matters even more, the hard-lid ceiling type made running conduit and wires for new circuiting or occupancy sensors nearly impossible. A wireless lighting control system became the only logical choice.

The City of Pleasanton needed a solution that could be configured to meet the unique challenges of the space. After evaluating environment and occupant needs, the system put in place utilized the following control strategies:

Daylight Harvesting: The existing fixtures around the skylights and along window lines were upgraded with dimming or bi-level ballasts and long life lamps. These fixtures respond to inputs from nearby photocells to dim or switch to a lower light level when daylight is prevalent.

Occupancy Sensing: Occupancy sensors signal lights to dim or turn off when a space is not in use. The sensor density of the library was designed to ensure occupant detection knowing library patrons are near motionless for extended periods of time. The addition of a “transition scene” of gradual dimming ensures occupant comfort instead of lights turning off suddenly. By configuring dynamic zones of lights controlled by each sensor as well as each light responding to input from multiple sensors, the stack height ceased to be an obstacle to occupancy-based controls.

Smart Scheduling: The occupancy sensor time out period is shorter during staff-only hours than during public hours, resulting in the lights in the main area turning off even though the staff area continues to be lit until they leave.

Task Tuning: The new lamps were set to an initial maximum output of 80 percent, resulting in an immediate energy savings of 20 percent. This setting can be adjusted upward as light output depreciates from fixture aging.

Because of the new controls and the strategies they allow, the library’s lighting energy use has been reduced by 46 percent, representing a reduction of more than 18 percent of the library’s total energy use. The Pleasanton Public Library is an example of a public facility leading the way in sustainable energy reduction tactics.

For more information on the retrofit, a case study is available at www.aduratech.com/pdf/ETAP-Pleasanton-Wireless-Lighting-Case-Study_FINAL.pdf.