A Bright Idea
As part of its Clean Energy Project, Hempstead, NY, located on the western part of Long Island, recently invested $7.5M - about $10 per resident - to replace 50,000 high-pressure sodium (HPS) streetlights with energy efficient LED fixtures. After putting the project out for bids, Hempstead chose Cree, a US manufacturer of lighting products, because its fixtures are American-made and because Cree is the only company that offers a 10-year standard warranty.
Orange Was the New … Yuck
When I was a kid in the early 1970s, my hometown, like many others, changed to HPS streetlights because they were more energy efficient than their predecessors. The new fixtures only appeared in the commercial downtown district, and I remember the eerie orange glow that we could see looking in that direction from our neighborhood. The response was universal: those lights were ugly. And when I started driving, I realized that the lights weren't just unattractive, they were also ineffective. I didn't know anything about color rendering index or color temperatures, but I knew that it was difficult to see, in spite of how bright the lights were.
Here's a comparison photo showing the orange glow of an HPS light compared to the natural daylight provided by an LED fixture:
Orange HPS vs White LED (image courtesy of US Department of Energy)
Any Color You Like
LED bulbs come in a variety of color temperatures, typically in the 2700K (warm) to 5000K (cool/daylight) range, allowing consumers to select the most appropriate light for the job. Warm lighting tends to be more pleasing to the eye, while cool/daylight provides better workspace illumination.
Hempstead is an east coast town with a historic neighborhood feel, and the residents want to keep the welcoming atmosphere in their street lighting. At the same time, its main thoroughfares and commercial parking lots can take advantage of lighting that's closer to natural daylight, which may not be ideal for neighborhoods. Township lighting designers chose luminaires that strike a balance between aesthetics and performance. The three different light fixtures chosen for this project - one for neighborhoods, another for parking lots, and a third for major roadways - deliver more than 100 lumens per watt with a 90% power factor and a decent color rendering index (CRI) of at least 70.
Better Lighting for a Safer Neighborhood (Image courtesy of Cree, Inc.)
Parking Lots (Image courtesy of Cree, Inc.)
Main Roadways (Image courtesy of Cree, Inc.)
More to Come
"Saving taxpayer dollars through the use of environmentally-friendly technology is a win-win for the town and residents," says town Supervisor Anthony J. Santino. "The new LED luminaires generate significant energy savings that provide unprecedented environmental and fiscal benefits to our town and residents. Due to this success of our street lighting upgrade to LED technology, the Town of Hempstead will soon convert an additional 4,000 indoor luminaires, yielding further savings to taxpayers of $200,000 over ten years."
The lighting investment will pay for itself in less than three years by saving $3M per year in energy costs. Over the expected life of the luminaires, the township expects to save $57M in energy and maintenance costs. Besides the financial benefit, the new fixtures also provide better visibility, improved aesthetics, and superior color rendering.
Cities around the world are becoming enlightened about energy efficiency and cost savings. To see a variety of case studies, check out the Department of Energy's page of demonstration projects.