CARD report documents benefits of energy efficient street lighting
With almost 500,000 street lamps in use in Minnesota, replacing older less-efficient high-intensity discharge (HID) or metal halide technologies with more efficient options, such as light-emitting diode (LED) and induction lamps, represents a real opportunity for reducing costs and energy use. In order to encourage wider acceptance of these new technologies, a 2011 Conservation Applied Research and Development (CARD) grant was awarded to Energy Management Solutions (EMS) to examine the major design and specification concerns of roadway lighting and to quantify costs and benefits of upgrading to more efficient street lighting.
The final report on the project, “Cost-Benefit Analysis of Energy Efficient Technologies Available for Use in Roadway Lighting,” includes: a comprehensive discussion of induction and LED roadway technologies; a 10-step “how-to” manual for the appropriate selection of LED roadway luminaries; an economic analysis of replacing HID roadway lighting systems with comparable LED technologies; and a section on CIP considerations. In addition, the report documents the outcomes from a demonstration pilot implemented in conjunction with the City of Chanhassen Public Works Department.
Results from the economic analysis show simple paybacks ranging from 8 to 12 years and internal rate of returns of 8 to 10.5 percent over a 22-year practical lifetime and based on August 2012 pricing. The most sensitive factors affecting these results were the monthly leasing rates for HID luminaires, the costs for purchasing and installing new poles, expected lifetimes of the LED luminaires, and the purchase costs for new LED roadway luminaires.
The Chanhassen demonstration pilot compared energy consumption, light quality, light distribution, and luminaire performance between incumbent 250W high-pressure sodium (HPS) roadway luminaires and 10 different LED roadway luminaires from seven different manufacturers (see figures 1 and 2).
Figure 1. Daytime street view of Coulter Blvd in Chanhassen, Minn., with existing 250W HPS luminaires (photo courtesy of EMS).
Figure 2. Nighttime street view of Coulter Blvd in Chanhassen, Minn., with replacement LED luminaires (photo courtesy of EMS).
The LED luminaires resulted in energy savings ranging from 50 to 80 percent. In addition, the LED luminaires provided significantly improved color identification and contrast compared to the light quality produced by the HPS luminaires, resulting in increased safety for motorists and pedestrians. The measured light distribution of all LED luminaires was more uniform. The LED luminaires also exhibited low backlight, uplight and glare ratings and directed very few lumens toward the sky, helpful for eliminating light pollution.
Aside from product performance, success of a given installation largely depends on parameters of the location and the specific information provided to manufacturers when ordering replacement luminaires. The 10-step how-to manual included in the final report is designed to help maximize this success rate by providing cities and municipalities with a simplified step-by-step process for properly requesting and selecting roadway lighting luminaires.