The US Department of Energy (DOE) has published the final report from a roadway lighting demonstration conducted in Palo Alto, California, to evaluate the feasibility of replacing high-pressure sodium (HPS) streetlights with LED and induction streetlights. The report is the tenth in a series, all of which can be downloaded from the Gateway website.
In this project, three groups of HPS streetlights were replaced — four with one type of LED luminaire, three with another type of LED luminaire, and three with induction luminaires — allowing comparisons between the three groups as well as to the existing technology.
In addition, two LED and two induction luminaires were installed on a commercial street in the center of Palo Alto to test a remote streetlight monitoring system. These luminaires were equipped with Echelon communication hardware that can be remotely controlled through a desktop or laptop personal computer. These luminaires were programmed to turn on and off on a schedule similar to that of the streetlight luminaires controlled by a photocell but then were dimmed by 25% of full power for 5 hours each evening.
This report provides an overview of project results including lighting performance, economic performance, and potential energy savings.
Key findings include:
- Of the three roadway lighting systems (induction, HPS, and LED), LED used the least energy (44% reduction compared to the baseline HPS) and provided comparable average illuminance on the street.
- LED luminaires produced more uniform light output than HPS or induction luminaires, and had better cutoff on the curbside, resulting in significantly reduced light trespass onto residential properties.
- Simple payback for retrofitting a 70-watt (nominal) HPS with an LED luminaire was estimated to be around 12 years, improving to about 10 years in a new construction scenario.
Community feedback was obtained during this study, and overall results from respondents show a marked preference for LED lights over induction lights. Nevertheless, two common concerns related to LED lights were excessive glare and the perceived blue/cold color of the LED light output. These issues will have to be resolved prior to a mass rollout of LED streetlights for Palo Alto. The LED luminaires tested in the demonstration have a correlated color temperature (CCT) of 6000K; by comparison, the CCT for the induction and HPS streetlights were 5000K and 2100K, respectively.
