DOE releases Gateway report on Palo Alto roadway lighting

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.