Efficient Streetlights will increase Light Pollution, not Savings

New efficient LED lights are the scariest nemesis to the night sky, yet they could be a solution to light pollution. Bob King recently wrote, why. Now there is another reason why next generation luminaires should be used in a light pollution minimizing way: Without such measures, they do not save energy and money - they might even lead to higher cost and greenhouse gas emissions.

In only a few human generations, the nighttime environment has radically changed over large fractions of the Earth’s surface.
Photograph of the United States at night from the International Space Station is courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center (ISS030-E-55521).
In a recently published article (pdf) in the journal “Energy & Environmental Science”, scientists from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin (IGB) and the Museum am Schölerberg in Osnabrück, Germany, explain why: When light becomes cheaper, many users will increase illumination, and some previously unlit areas may become lit.

This is an example of a “rebound effect”, a case where higher efficiency due to technological innovation actually leads to greater consumption rather than reduced energy use. The scientists point to the case of the UK (pdf) between the years 1950 and 2000 as an example: even though lamps became twice as efficient at producing light, per capita electricity consumption for lighting in the UK increased fourfold.

Three steps to sustainable illumination

The study authors made three recommendations to make nighttime outdoor area lighting more sustainable. Their first recommendation is a transition to need-based lighting, where lighting is only provided where and when it is needed. Franz Hölker of the IGB explains, “the idea is that by directing light more carefully, visibility could actually be improved while saving energy and money. In suburban and rural locations with very little activity after midnight, modern lamps could also be dimmed to 10% of their normal power until morning traffic begins.” In the future, motion sensors could be used to run lamps at full power only during periods with activity.

The second recommendation is for policymakers that specify minimum requirements for street lighting. The scientists say they should also stipulate conservative maximum illuminances, because in many cases in the US and Europe, the amount of light far exceeds current standards. “If you use twice as much light as is needed for a task, then half the energy is wasted”, says Hölker.

An example of poor lighting from the USA. A large portion of the parking lot is unlit, and waste light shines uselessly on the house façade, the tree, and into the sky. Photograph by Christopher Kyba.
Finally the scientists recommend adopting a new definition for efficiency in urban area lighting. “We need a more appropriate measure for reporting energy efficiency, that would allow apple-to-apple comparisons of radically different lighting delivery systems”, explains physicist Christopher Kyba, also of the IGB. “For example, suburban streets with lights that are dimmed after midnight could potentially use less energy in a year than a more efficient lamp that burns at full power all night.”

Saving energy without without leaving cities in the dark

According to the experts, if cities acted on these recommendations, real reductions in energy use would be possible without compromising the public experience and use of outdoor lighting. They say the goal of lighting policy should be to provide exactly the right amount of light needed, while minimizing electricity consumption and unintentional influence on people’s sleep, or on nearby natural areas.

Source: C.C.M. Kyba, A. Hänel and F. Hölker (2014) Redefining efficiency for outdoor lighting. Energy & Environmental Science, DOI: 10.1039/C4EE00566J

In the interdisciplinary Loss of the Night research project, Hölker, Kyba and colleagues investigate the reasons for the increasing illumination of the night, its ecological, cultural and socioeconomic effects, and the effects on human health. The results of this research will help to develop improved lighting concepts and sustainable technologies. Loss of the Night was funded by the German Ministry of Education and Research and the Berlin Senator for Economics, Technology and Research.

Photographs of good and poor lighting installations from around the world can be found in the project's blog.

The United Nations declared 2015 the "International Year of Light and Light Based Technologies". You're invited to join - and make the year also about energy efficiency and light pollution!

Chris Kyba also recently wrote a good article on the AWB Dark Sky Awareness Blog: You Can Change the World’s Skies

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