Performance of an LED lighting system in a parking application
The Energy Center completed a study of the performance of the LED lighting system at The Brewery parking structure in Milwaukee, Wisconsin including energy use monitoring over a two-year period. The study, funded by Focus on Energy and We Energies, included illuminance measurements within the structure, short-term power and power factor measurement, and monitoring of lighting energy consumption.
The Brewery parking structure, built in 2009 as part of the redevelopment of the historic Pabst brewery site, includes eight levels of parking over about 256,800 square feet. Area lighting includes 222 pendant fixtures and four pole-mount fixtures on the exposed rooftop. The installed LED lighting system was designed to be efficient, and had connected power density far below the maximum levels permitted by code. Measured light levels met or exceeded industry standards in most cases.
The Energy Center's research engineers explored energy savings possible through the use of LED lighting, and identified additional energy savings through the use of daylighting controls and motion sensors.
Key discoveries include:
- Lighting power density achieved by the LED system installed is excellent, at about 20 percent or less of the most aggressive current code requirements.
- Motion detectors, working together with daylighting controls, reduced power consumption 45 percent from the base value.
- Commissioning makes a difference—for example, the simple act of adjusting motion sensor timers from the 8 minute default to just 30 seconds reduced energy use by an additional 13 percent.
- Daylighting controls, used on about 40 percent of the fixtures, reduced power consumption by about 20 percent compared to a base "always-on" system.
- Parking garages, with the need for lighting during daytime as well as nighttime periods, offer perhaps an ideal application for LED technology.