This Little Light of Mine

Many cities have been switching to the efficiencies of as-needed lighting, thanks to their computer programmers.
by | August 1, 2008

Sam Palmer is not a choreographer, but he plays one at the public library in Fayetteville, Arkansas. From his basement office, Palmer has created a dance for the building's interior lights on his computer system, giving each a role for different times of day. Some dim on bright days. Others turn on as staff members arrive. In the late afternoon, half of the lights turn off.

Ann Arbor, Michigan, also relies on sophisticated computer programming to light its city buildings and conduct some intriguing experiments with outdoor lighting. The city started out by replacing more than a thousand 100-watt globe streetlights in the downtown area with 56-watt LED lights. Now, energy officials are taking control of 28 of them and using radios to dim them, make them flash, or turn off one or more of the four lighting panels in each streetlight.

The benefits of these programmable lighting systems range from energy savings to reduced greenhouse-gas emissions. Many cities are interested in, or have been changing to, more efficient and as-needed lighting -- facilitated by improved computerized programs.

The Fayetteville library, where Palmer works as facility manager, opened in 2004. The exterior of the LEED-certified green building sports flaps and awnings for capturing or blocking out sunlight. Large windows provide much natural light. Palmer had to take these factors into account, as well as work-shift schedules, when figuring out how to computerize the lighting patterns for daily efficiency.

The lighting changes if it's sunny versus cloudy, or there's a special event or a staff member is on vacation. The building's computer reading room benefits from "light harvesting." When sensors discern a lot of sunlight streaming through the windows, artificial lights start dimming. Often, they go off completely in the middle of sunny days, allowing patrons to read by natural light.

The system serves several purposes. For instance, within a half hour of closing time, lights start to go off. That not only saves money but signals to library patrons that closing time is near. Staff office lights are set based on schedules of individual workers. But Palmer has set the technology so that if they don't show up one day, the lack of motion in their offices, detected by both heat and motion sensors, will signal that the lights can go off. If a manager has to work late, the lights for her hallway and the path to the parking garage will stay on. Although Palmer set up the original program for the basics, he constantly is tinkering around the edges to accommodate changes, such as special events at night.

Ann Arbor is a test bed for LED lighting. LED lights, with their 40-year life expectancy, are expected to replace more wasteful lights in all downtown fixtures by the end of the year. "It's leading to some pretty amazing things," says David Konkle, the city's energy coordinator.

Officials are testing 28 prototypes for futuristic programming. Light poles and fixtures each have an "address" so management systems can communicate with them individually to tell them what to do. This kind of precision wasn't possible with the old lights, which could take anywhere from two to five minutes to turn on fully. The LED lights turn on instantly, making it possible to add advanced features.

In the downtown restaurant area, for instance, people sometimes hang until the wee hours. The streetlights can be programmed to shine brightly until, say, 3 a.m. Then they can be dimmed, keeping the streets safely lighted, but not bright enough to do crossword puzzles by. In residential neighborhoods, light dimming could start as early as 11 p.m. And if someone complains about streetlights shining in a window, a panel or two of one particular fixture can be turned off to accommodate a single home.

The test lights have the ability to flash on and off. If someone calls 911, the streetlights in front of the house can be made to flash, so if police or fire fighters are unable to read house numbers, they can find the right house quickly. Or the lights can flash sequentially, leading emergency personnel in a certain direction or to a certain area.

Because the radios are two-way, a person who has called 911 could press a button on one of the emergency call boxes attached to the light poles and sit under a flashing streetlight until help arrived. All it takes is a sense of choreography and solid computer skills to program the latest features.

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