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County of Hawaii - A Unique LED Street Light Conversion

In 2010 the County of Hawaii was paying $0.40/kW-Hr for electricity, $1.5 mil annual bill for 8,500 street lights. Over the past 20 years costs have increased on an average of 7% per year. Inventory maintenance frequency for the 8,500 lights was 35%, which meant 3,000 visits per year. The current LPS street lights were nearing 20 years of service and a complete replacement was imminent, a significant cost for the County of Hawaii and its 185,000 citizens.

The astronomy community impact was identified early on and discussions conducted for an acceptable conversion path. Key concerns centered on the blue light content of the LED and reflected light.

A demo project with Federal ARRA funds installed 1,000 LED full cut off fixtures achieving an energy savings of $200K annually. The results were extremely successful and were loudly applauded by both the general public and the Astronomy Institute. Hence, the Traffic Division recommended to the County administration changing the remaining lights, now numbering 9,000, to new LED lights. The County administration approved the change to the LED lights and an upgrade to the outdoor lighting ordinance.

The remainder of the conversion, amounting to $6 million for materials and labor, is expected to yield an energy savings of approximately $800K annually with a 5 year recovery of costs that includes both energy savings and maintenance reduction.

Additional benefits achieved from using full cutoff fixtures include reduction in glare for drivers, pedestrians, and elimination of trespass light onto neighboring residences.

Benefits achieved by using a filtered LED includes reducing blue light to <1 %, diffusing the harshness of the direct LED light and the ability to use the most energy efficient lumen producing fixture to achieve in excess of 63% reduction in energy costs.

Additional aspects of this conversion presentation will include steps to gather quantitative data showing reduction in light pollution, aerial and satellite surveys for gathering before and after ground level brightness plots along the roadways, and interpretive spectral analysis on skyward impacts.

Ronald Thiel

AUTHORS/INSTITUTIONS: R.L. Thiel, Public Works, County of Hawaii, Hilo, Hawaii, UNITED STATES PRESENTATION TYPE: Oral

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