By Ellen Perlman,
Governing.com
Ann Arbor, Michigan is investigating LED street lighting in hopes of cutting its $1.4 million street lighting bill in half. (City of Ann Arbor photos)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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