Let's Conserve Together - A Lighting Study

Communications Director

Kristin Farley
(865) 215-2589

400 Main St., Room 691
Knoxville, TN 37902

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Let's Conserve Together - A Lighting Study

Posted: 12/17/2009
The City of Knoxville and three partnering organizations have turned Wall Avenue into a testing ground for new streetlights designed to improve the nighttime environment while reducing energy costs.

The city, Knoxville Utilities Board, Tennessee Valley Authority and the Electric Power Research Institute (EPRI) are collaborating on the project which began in late November after installation of 12 new LED lights was completed mostly along the north side of Wall. The avenue marks the northern boundary of Market Square and separates it from the TVA Towers.

The project is designed as a multiyear real world test of the LED (for Light Emitting Diodes) equipment. 
"The different groups worked together to develop a test to help KUB and other power distributors across the valley learn more about how the new LED street lighting equipment performs in a real world setting," said Gabriel Bolas, KUB's manager of engineering systems. "We want to see if it really does perform better, for less money, than existing street lighting systems." 
Bass said the LED equipment is being subjected to the same weather and electrical conditions as existing street lighting systems to test its efficiency, longevity and light output. Over the next two-and-a-half years the LED lights will be evaluated quarterly on light output levels and efficiency criteria.

The findings will allow Knoxville, TVA, KUB and EPRI to compare the LED performance with conventional systems and help determine if it can be cost effective for street lights over the long term.

A beneficial change could have a significant financial impact on the city. Knoxville operates 29,630 street lights with annual electricity and maintenance costs of about $2.8 million.

The groups looked at several sites with city representatives before selecting Wall Avenue as the best option for a street lighting test. Its advantages included being conveniently located to a significant amount of pedestrian traffic insuring the demonstration will be a visible one.

Designs were submitted by several manufacturers who had received technical evaluation prior to being considered. KUB, the city and TVA subsequently evaluated the options and selected lighting equipment together.

TVA provided technical research assistance through EPRI and funds for the equipment, KUB installed it and EPRI is responsible for monitoring it.

The LED street lights use 94 average measured watts per light, compared to the 310 input watts used by the existing high pressure sodium (HPS) light systems. During the course of a year that should generate savings of about 946 kWh per year, per light.

Two of the lights are decorative, 60-watt LED post top lights that have been installed on either side of the Market Square Stage replacing the decorative 100-watt high pressure sodium lights that had been there. That should save about 381 kWh per year.

The total annual kWh savings expected from the 12 lights translates into approximately the amount of electricity an average household would use during the year.

High pressure sodium, the typical orange light used in streetlights, is currently used for most exterior lighting in Knoxville. It's popular because it has a long life that reduced maintenance costs. The manufacturers of the LED lights contend they last longer than the HPS lights and use less energy.

However white sources such as white LED's render colors more true to life than orange light and studies indicate that reaction time to objects seen in peripheral vision is faster under white than orange light.

Additional research has shows that scenes lighted with white light appear brighter than those lit in color, potentially leading to use of lower wattages and less energy consumption for equal perceived brightness.

For more information call Susanna Bass, Sustainability Program Manager City of Knoxville at 865-215-4430.