Smart Outdoor Lighting Alliance

Gloucester, UK LED Streetlight Project

The genesis of the Gloucester project occurred when the highway division prepared a plan to help the UK meet ambitious carbon reduction goals by 2020.

The actual planning for the conversion of 60,000 streetlights started in 2010 by installing pilot tests of a variety of LED fixtures. Approximately 5,500 LED fixtures were installed over a period of 5 ½ years. They tested color temperatures ranging from 5,700K CCT to 4,000K CCT and settled on 4,000K CCT. Adaptive controls and dimming were also tested during this time. The pilot tests were primary done as a proof of concept with no public outreach or surveys to solicit preferences. The fixture selected for residential street is the Schreder Ampera Mini 26 watt that is a B1-U1-G1 and produces about 3350 lumens. Larger wattage versions of the Ampera will be used on main roadways.

Gloucester is replacing HPS fixtures, some of which had already been modified with dual ballasts in order to dim them to 50%. So dimming the LED fixtures was part of the plans for the beginning. The plan to retrofit the remaining 55,000 streetlights will include approximately 40,000 residential and 10,000 on main roadways. 6,000 fixtures will be replaced in 2015, 25,000 in 2016 and the balance in 2017.

Gloucester chose Talensa smart controls and will dim residential lights by 50% after peak traffic periods. The project is projected to reduce energy and CO² by approximately 70% and save about £1.7 million annually. The total cost of the project is £13.7 million of which Gloucester received a £5 million grant from the UK Department of Transport. 40% of the remaining £8.7 million is being financed with a 0% interest loan from Salix. Gloucester estimates a payback period of about 5 years for the fixtures and controls.

Gloucester Street Lighting Manager, Ken Pitt, said in a phone call that the county has made an effort to keep the public informed throughout the process and will be sending a letter to all residents detailing the plans for the conversion. He also said the the previous dimming of the HPS fixtures had been well received by the residents and that they had received no complaints regarding the lower lighting levels. We believe that this may be the largest LED conversion to date to use smart controls and dimming for all streetlights.

While the color temperature of the LED fixtures are higher than SOLA recommends, the choice of a low-glare fixture is commendable and should help improve community acceptance. However as with many pilot tests for LED projects, public surveys were not conducted and fixtures with warm white (<3,100K CCT) LEDs were not tested. Not asking for resident feedback on color temperature during pilot tests misses an important opportunity to gauge potential public reaction before full-scale rollout. (See Davis, CA LED Retrofit) Considering the decision to adopt aggressive dimming to maximize energy savings, using <3,100K CCT fixtures would have cost very little to implement (<10%) and would help preserve the neighborhood ambiance and visual comfort for the residents.