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Anchorage Sets the Course for LED Roadway Lighting

Justin Sternberg | Tuesday February 10th, 2009 | 3 Comments

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In June of 2007, the former Mayor of Anchorage and newly elected US Senator from Alaska, (D) Mark Begich, created an Energy Efficiency Coordinator position at the municipality to examine the potential cost savings unrealized within Anchorage’s lighting systems. In addition, the city hired lighting design firm Clanton & Associates to aid and guide in the city-wide examination. After two years of light testing and due diligence, the city assembly approved the Mayor’s request to purchase 4,300 LED light fixtures, the largest municipal purchase in the United States at that time, as the first phase toward retrofitting the city’s entire municipal lighting portfolio.

The project revealed a 7-year payback period which included a 4% interest rate to offset cost of capital. The mayor and the Anchorage Assembly agreed that a reasonable payback period on a project that reduced long-term operational cost was a wise of use of tax dollars and the fixture purchase was approved in August of 2008. In implementing the first large-scale municipal LED retrofit in the United States, the City of Anchorage has emerged as a leader of large-scale LED retrofitting.

In the US, approximately 120 million roadway lamps turn on each night, with utilities, municipalities, and state governments consuming electricity to light roadways. Roadway lighting consumes 1.3% of all end-use electricity in the EU25 1, or 35 TWh per year, and 1% of all end-use electricity in the USA 2, while occupying 10% to 38% of a municipalities’ electricity consumption and greenhouse gas emissions 3.

The predominant outdoor lighting technologies in the U.S. today, include High Pressure Sodium (HPS), Low Pressure Sodium (LPS) and Metal Halide (MH). HPS, the most common lighting source on public roadways came to the market in the 1980′s, replacing Mercury Vapor fixtures used across the United States at the time. Some municipalities (e.g. San Diego) are planning to deploy Induction lighting (“electrodeless” or QL), and a small but growing number of Light Emitting Diode (LED) systems are being tested and deployed by cities from New York City to Anchorage. Over the next decade, new outdoor lighting technologies, particularly LED and control systems, will be phased in and brought to scale as production costs decrease and efficiencies improve.

Current LED technology provides 50% cost savings through simple retrofits of existing HPS fixtures. When combined with centralized control systems used to dim streetlights depending on the weather and time of day, early studies in Anchorage show energy savings approaching 80% over their HPS system in some instances (150watt HPS retrofits). The first phase of the project will retrofit 4,300 municipal lights and is due to be completed in April, 2009. It is estimated to cut the city’s lighting expenses by $360,000 annually. In planning the retrofit, Anchorage has also seized a number of opportunities that go beyond saving money but also positively impact the health and wellness of its citizens.

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Residential streets in Anchorage, AK. A thirty LED fixture with a color temperature between 4100-4300 Kelvin, the same as a full moon. A street such as this would utilize dimming solutions. Copyright of the MOA.

Light pollution is a growing problem throughout the world. One form of light pollution is sky glow, which is largely the result of poorly designed fixtures that release light into the night sky, blocking stars, turning night clouds purple, and in Anchorage’s case, dimming the Aurora Borealis. In the long and arduous Alaskan winters, where the beauty of the Aurora Borealis has inspired poets, challenged photographers, and offered a treasured spectacle for those who brave the season in these northern latitudes, this represents an unquantifiable loss to city residents.

Light trespass is another form of light pollution, with outdoor HPS “drop lens” fixtures directing light beyond the public right of way into bedrooms, yards, and private property. Anchorage’s new lighting fixtures have been certified by the International Dark Sky Association for reducing sky glow, meaning that all Anchorage street lights will be full-cutoff and no lumens will escape the 80′ angle from the fixture head, reducing the amount of light that shines into the windows of living spaces and preventing light from shining into the sky.

Blue wavelengths in the color spectrum of artificial lighting that mimic daylight, have been shown to interfere with circadian rhythms and suppress melatonin during sleep cycles. This has been linked to an increased likelihood of cancer and a number of other health disorders, representing yet another form of light pollution. Human’s evolved without any artificial illumination over millions of years–after sunset, only fire and the bright full moon were used for illumination–and the affect of artificial lighting on our health has only recently been a topic of academic research. Anchorage city managers insisted that LED’s approximate the color temperature (CCT) of the moon (4,125 Kelvin), rather than typical blue colored LEDs (5100 – 6500K). While these LEDs luminaires still contain a bio-active light spectrum, their modern optical design and color afford a precautionary stop gap until LED technology advances, as well as our understanding of photo-biology.

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Typical drop lenses (left) direct light onto the road, but allow light to escape up and around the fixture, creating light pollution. Full-cutoff lenses (right) contain light beneath the luminaire, preventing light trespass.

Beyond responsible fixtures that reduce all forms of light pollution, outdoor lighting is shifting from it’s historical strategies of the last 25 years. HPS lighting provides a massive lumen package (lumen to watt ratio), and this HPS efficiency was such a compelling story, that the poor quality of its light was seen as a small sacrifice when achieving needed cost savings. With lighting technology shifting toward broad spectrum technologies, lighting shifts from using large amounts of poor quality orange light, toward utilizing the superior color rendering and visibility improvements of white light.

The LEDs in Anchorage increase color rendering by 300%, stimulate both the rods and the cones of the eye ball (rather than just the cones), improve peripheral vision, and feel extremely comfortable to walk or drive beneath–it feels like your walking under a full moon. These visibility improvements allow lighting designers to increase color rendering and contrast of small targets (e.g. children), while decreasing the overall light levels. In many scenarios, the lighting strategy on roadways will change from blasting roadways with large low quality lumen packages toward lower overall light levels (another efficiency) that are more effective at achieving visibility of small targets.

Another change in lighting strategy will come from the emergence of “smart” municipal lighting systems. Centralized controls that send and receive data from each fixture head or roadway circuit will allow municipalities to “curfew” dim residential lighting when volumes of traffic reduce between the hours of 8pm and 5am. Other dimming strategies Anchorage is testing will be dusk and dawn dimming in the summer, snow fall dimming to account for the dramatic reflective light of new snow on the ground, or action point dimming, where intersection lights or other points of interest maintain 100% output, while in between lights receive dimming. Among these strategies, California utilities and cities are investigating peak load dimming options as well.

The most advanced “smart” municipal lighting systems being developed come out of the California Lighting Technology Center (CLTC) at UCDavis. The CLTC was established through a joint effort of the California Energy Commission (CEC) and the University of California, Davis to stimulate the research and development of energy-efficient lighting. Through CEC’s Public Interest Energy Research (PIER) Program funding at CLTC, manufacturers can come to the CLTC for research and design support, creating innovative and cutting edge products. Perhaps the most notable of these products, especially for municipalities, are their LED and Induction garage fixtures with dimming smarts integrated. Garage lighting is 24/7 for safety, so to achieve radical energy savings, the CLTC developed an integrated system of efficient white light fixtures that dim to 50% when the garage is closed and no activity is taking place. If for some reason there is activity in the garage, the lights in that area step back up to 100% immediately.

Ultimately, it is only a matter of time before high-efficiency lighting retrofits expand throughout the rest of the country. However, municipal managers would be wise to learn from Anchorage’s example and look beyond the obvious cost savings opportunities toward the significant health and wellness benefits that should be accomplished in tandem.

Michael Barber — Lighting Program Manager and Energy Efficiency Coordinator for the City of Anchorage, 2007-2010

Justin Sternberg — Sustainable Management, San Francisco

In 2010, the authors co-founded Continuum Industries, to develop turnkey lighting efficiency projects for the municipal, military, commercial, and utility sectors.

Citations:
1: P. Van Tichelen, “Final Report Lot 9: Public Street Lighting,” 2007.
2: Navigant Consulting, “National Lighting Inventory and Energy Consumption Estimate,” 2002.
3a: City of Boston Climate Action Plan, “2005 Boston Greenhouse Gas Inventories,” January 2008.
3b: Australian Greenhouse Office in the Department of the Environment and Heritage. “Public Lighting in Australia,” 2005.
3c: Grow, Robert T. “Energy-Efficient Streetlights – Potential for Reducing Greater Washington’s Carbon Footprint,” 2008.


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  • http://sustyapps.blogspot.com Amelie Lie

    Incredible that this project also ensure that lighting color is comfortable to salmon, and does not contribute to seasonal affective disorder (SAD). Truly a triple-bottom line story.

  • http://sustyapps.blogspot.com Lee

    Incredible that this project also ensure that lighting color is comfortable to salmon, and does not contribute to seasonal affective disorder (SAD). Truly a triple-bottom line story.

  • http://www.slideshare.com/iamthedarkranger Kevin Poe

    Congratulations Citizens of Anchorage!
    I hope you realize how progressive and ecologically minded the decision to switch outdoor lights to LEDs really is. I look forwarding to touting your success in my efforts to heighten global awareness to the evils of light pollution and the benefits of energy conservation. I give you two thumbs up! Congratulate yourselves and your city government!
    BRAVO!