Lighting the Way to Energy Efficiency
- By Michael Fickes
- July 1st, 2008
The Eau Claire Area School District in Eau Claire, WI, recently adopted energy efficiency measures that will save the district about $224,000 per year, according to estimates developed by Focus On Energy, a non-profit public-private partnership formed by Wisconsin to encourage, manage, and help fund energy efficiency projects.
Lighting changes account for one-third of the district’s total estimated savings or about $74,000 per year.
The lion’s share of the savings will come from improved management of the heating, ventilating, and air-conditioning (HVAC) and boilers.
Lighting renovations are usually part of an overhaul of a school district’s overall energy profile. While the savings available from lighting retrofits is generally small, the payback is fast, usually six to 10 years. By comparison, new energy-efficient HVAC and boiler systems, while saving more, take 15 to 20 years to pay for themselves.
“The reason to combine lighting and HVAC projects is to reduce the payback period,” says Marc Aronson, manager of business development for Constellation Energy’s Projects and Services Group, which is based in Lowell, MA. The performance contracting side of a utility company, the group has designed and carried out numerous energy efficiency retrofits for school districts and other facilities.
Discussions with district facility, maintenance, finance, and business managers begin the process of retrofitting a district’s HVAC and lighting systems, continues Aronson. “We study mechanical drawings, layouts of the school, energy bills going back years, and determine their rate structures and demand,” he says.
Next, the work splits into an HVAC side and a lighting side. “The lighting piece is relatively simple,” Aronson says. “We send an audit team to each building and audit every light fixture, recording the type of lamp, ballast, and wiring system.”
Next the team specifies a retrofit for each lamp, calculating the savings fixture by fixture. For example, a conventional two-ft. by four-ft. fixture with four lamps and a ballast may draw 170 watts. The retrofit fixture may draw 60 watts for two lamps. Exact specifications depend on what lamp replaces what lamp. Super T8 fluorescent lamps may replace existing fluorescents; compact fluorescent lamps may replace incandescent bulbs.
The Eau Claire Lighting Retrofit
According to a case history of the Eau Claire Area School District project published by Focus On Energy, the district’s lighting retrofit began with an audit, which identified six lighting inefficiencies and suggested improvements.
More Light-Saving Ideas
- Over-lighting: A light survey conducted during the audit found that schools throughout the district were wasting energy by lighting certain areas more than necessary. The survey identified the areas, and maintenance staff removed bulbs to cut down the light. Across the district 3,700 bulbs came out, reducing electricity demand by 118kW and saving $13,000 per year.
- Replace HIDs in the gym: Wildly inefficient high intensity discharge (HID) lamps take 15 to 20 minutes to warm up. As a result, the maintenance staff often leaves the lights on in the gym throughout the day. Eau Claire replaced the HID fixtures with high efficiency fluorescent fixtures, which permit adjustments based on need. Eau Claire also installed sensors that turn the lights off automatically when no one was using the gym. Estimated savings: $20,000 per year.
- Four additional efficiency measures: Staff removed bulbs lighting the displays on vending machines. They replaced lighting around swimming pools with energy efficient fixtures with dimming switches and on/off sensors. Third, they removed lamps from certain fixtures during the summer. Finally, the replaced incandescent- and fluorescent-lighted exit signs with new exit signs lighted with LED lamps. The four measures together save about $41,000 per year.
While Eau Claire found several innovative ideas for cutting down on lighting costs, the district did not find all of the possible savings. When handling performance contracting assignments Constellation’s Aronson often explores and may recommend a number of additional measures.
One idea is to connect all of the outside lights to a control system that turns the lights on and off on a set schedule.
Constellation also recommends dimmable ballasts that enable a facility to participate in utility demand response programs. During peak loads, utilities pay users participating in such programs to cut back on electricity use by a preset amount.
Another angle related to the electricity provider is to select components for which utilities offer rebates. Some utilities, for instance, will rebate $20 for each LED exit sign purchased.
Another purchasing idea: design the lighting system consistently around a few lamps, ballasts, and fixtures. A uniform inventory can often save by making volume-purchasing agreements possible.
In classrooms and other rooms with many windows, sensor systems can be installed to dim artificial lighting so that it only supplements the natural night flowing into the room. Generally that will cut lighting costs.
Something else to consider when managing natural light: solar panels. “Lately, we’ve seen an increased interest in solar,” Aronson says. “We offer solar power through a program under which we sell electricity to a user for 12.5 cents per kW hour.”
As a performance contractor, Constellation buys and installs a solar array. A federal tax credit covers 30 percent of the system. State incentives, which vary, may cover another 30 percent of the system. Renewable energy tax credits may further reduce the cost of the system. Then Constellation generates electricity and sells it to the user for 10 percent to 15 percent less than the market price.
Public schools must use a performance contractor to get the tax credit benefits because schools as government entities pay no taxes from which to deduct credits.
“Of course, the most important reason to install this kind of system is to save money on electricity,” Aronson says. “It is also done as a hedge against future electricity price hikes. With a solar array, they know what their electricity costs will be for the next 15 years. A third benefit is educational — the solar array can be used in science, economic environmental curricula.”
Which is equally true of any other energy efficient lighting systems installed during a retrofit.