Office of the Vice President for Global Communications

Thursday, May 24, 2012

Lighting control system in parking structures saves energy and costs

Installation of energy-saving lighting technology has helped U-M reduce electrical costs in the Hill Street parking structure by 68 percent in its first year of operation.

The reduction in energy use through smart technology supports President Mary Sue Coleman’s stated goal to reduce greenhouse gas emissions by 25 percent by the year 2025.


Since 2011, the university has operated a computerized management system called Limelight in the parking structure adjacent to the Stephen M. Ross School of Business. The system allows individual lights to be turned off and on by program settings, motion sensors and photocells.

The energy savings is equivalent to what it would take to power 16 average U.S. households for one year, or a carbon reduction equal to removing 46 vehicles from U.S. roads. At current electricity rates, this results in an annual savings of $32,000.

“The Limelight project at Hill has confirmed and even exceeded our expectations about energy savings,” says Steve Dolen, executive director of Parking & Transportation Services.

The university also installed the new lighting system in the Thayer Street parking structure. Installation was completed in October 2011, and university officials already have seen a 31 percent reduction in energy consumption through March.

A new lighting management system at the Hill Street parking structure hascut electrical costs by 68 percent in its first year. (Photo courtesy of Parking & Transportation Services)  

The system works like it would for a homeowner, where a motion detector turns on an outside light as the homeowner’s car approaches the garage.

Lights also can be controlled through computer programming. Each lighting fixture is assigned to a lighting group and the schedule for those lights is set based on the facility's typical use patterns.

Photo cells sense ambient lighting levels and activate alternate programs that turn off individual lamps. This is known as light harvesting.

Motion sensors also control the lighting fixtures. When motion is detected, the sensors override the programming to activate groups of lights.

For example, once turned off for the night, the lights would turn on when someone starts walking toward their vehicle. Lights would continue to light up along the path of the vehicle as it exits the darkened parking structure. The lights then turn off after 15 minutes of inactivity.

The Hill Street location was selected as the first test site for this technology when the old lighting system was ready for replacement. The old lighting fixtures used 250 watts compared with the new technology, which uses a 102-watt fluorescent fixture.

“New systems and technologies for sustainable lighting, particularly in parking facilities, are emerging rapidly,” says Diane DeLaTorre, associate director for parking operations and maintenance. “Based on what we have learned over the past year, we are excited to expand use of these technologies to achieve energy and operational savings at existing and new facilities, as they are developed.”

The project is consistent with the university’s overall efforts to reduce energy. The university recently announced that its Planet Blue operations team program decreased overall energy use on campus by 8.3 percent with a $3.8 million annual cost avoidance in 71 buildings on the Ann Arbor campus during the last year.