Red LEDs in
Philadelphia and Minnesota
Red LEDs in Philadelphia and Minnesota
In Philadelphia, the municipal energy office is considering replacing all of the city's red signal heads - between 27000 and 28000 units -with LEDs. If funds come through, the city could begin the retrofit project by mid-1996.
Retrofitting Philadelphia's red signal heads would save an average of 1 MW load and some 5 million kWh of electricity annually. "The project would be very cost-effective " says Jack O'Connell at the city's energy office. "It would yield an internal rate-of-return of some 40 per cent, which translates into a payback time of only two years."
In an attempt to determine the rate of degradation, the city has commissioned accelerated testing of various LED makes. According to Jack O'Connell, although the variation between products is large, it is not considered to be a serious enough problem to keep the city from making large investments in LED technology. The short payback time also reduces the city's risk: Even if the LEDs have to be replaced earlier than expected, they should last at least two years.
Results from the accelerated testing will be available by February 1996. The electric utility serving Philadelphia also tried to predict the impact that a large-scale conversion over to LED technology would have on power quality. Their conclusion is that such a conversion would have no significant impact. In Minnesota, the highway authorities of Hennepin County are also very interested in LED technology. Since Minnesota's summers can be very hot and its winters very cold and dry, Minnesota offers the perfect place to carry out field tests under tough conditions. Starting in April 1996, the county will test red LEDs at the rural intersections with red flashing signals only.
(For an overview of LED traffic light technology, see Sixty Percent Less Energy with LED traffic Lights, IAEEL 3-4/95)
Contacts:
Jack O'Connell City of Philadelphia Municipal Energy Office 1600 Arch St., 7th Fl., Philapdelhia, PA, 19103, USA
Tel +1 215 686 3905
Larry Blackstad 1st Level South 300 South 6th St. Minneapolis, MN, 55487-0012, USA
Tel: + 1 612 348 5859
Fax: +1 612 348 3932
Email:Larry.Blackstad @co.hennepin.mn.us