Lighting for Darker Skies: Strategies to Reduce Light Pollution
The source of light pollution and its solutions have changed as outdoor lighting technology advances. While the effort to preserve the night’s dark skies and prevent light spillage into neighboring property has been underway for decades, the conversation around how to do it is evolving.
The amount of artificial light aimed skyward has increased in radiance by 2% every year for the past four years, according to a 2019 global study led by members of the GFZ German Research Centre for Geosciences. The blue light emitted by LEDs is largely the culprit.
Recently, lighting designers and technology providers have focused on the impact of LED lighting color. One way the industry gauges how much glow is in the sky or how much spills over into other properties and neighborhoods is using correlated color temperature (CCT). For some communities, lower-impact yellow or warmer-colored lights provide the antidote to the more common blue lights of the recent past.
“LEDs have gone from emerging technology to becoming the dominant source for new outdoor lighting products,” said Eric Gibson, director, commercial outdoor for Acuity Brands Lighting, Atlanta.
The growth is due to the relatively greater efficacy, longer life, improved optical control, better light quality and greater dimming capabilities of LEDs. However, LEDs are colder or bluer in light, which causes some issues with light pollution.
Some cities, communities and parks have been designated as International Dark Sky Places (IDSPs), where the lights must be lowered at night. There are some 150 designated IDSPs today and counting. This has led to astrotourism, where travelers can have space-related experiences.
“It’s been a way to spread the good design principles of a dark-sky community,” he said. Tucson is a case in point, which shifted to LED lighting in its 20,000 streetlights to save $180,000 in monthly energy consumption as well as reduce its lumen output.
Recognizing the Problem
Identifying light pollution is an evolving problem, Strasser said, adding that people have gotten used to it as a result of years of spillover lighting into the sky.
Lighting designers are well acquainted with outdoor lighting strategies, focusing on what they are trying to illuminate instead of flooding an area in light. That results in properly placed, focused lights that enhance textures and architectural details.
Electrical contractors should consider the spillover of excess light. Strasser said that the 30% of light that goes skyward is wasted resources.
Such warmer lights feature a short wavelength emission that causes a warm glow. The lower the blue levels, the better.
LEDs deployed in previous years are grossly overlighting their streets; they were chosen for their relative efficiency, not considering other factors.
LED Industry Solutions
LED efficiency has been a boon to cities, building owners and others who pay the lighting bills. In fact, LED fixtures provide typical energy reductions of 70% over the products that they replace, making them attractive both financially and environmentally, Gibson said.
“[LEDs’] small size makes them more controllable, allowing the use of advanced optical designs to provide superior illumination where it is needed while minimizing light trespass outside the target area,” he said.
LEDs have provided a solution to some very particular problems. Blue light can obscure the view of the sky and can affect human health and wildlife. For instance, blue light in sea turtle nesting areas can confuse hatchlings and prevent them from heading into the ocean after hatching.
In general, installers can achieve superior uniformity, with minimal light trespass and low power density by selecting luminaires with the best photometric control. Energy savings can be further increased by about 50% by selecting lighting with wireless embedded controls.
Blue light can obscure the view of the sky and it can impact human health and wildlife. For instance, blue light in sea turtle nesting areas can confuse hatchlings and prevent them from heading back into the ocean after hatching.
“Not all LED products measure up in terms of efficiency and light quality, even when lumens per watt ratios are similar or equal,” said Husnain Fareed, Eaton regional sales manager.
Ultimately, solving light pollution can be complex, Fareed added.
“There are many parameters to address that are impacted by light pollution,” including application scenarios, operational safety, reliability and maintenance objectives, enhanced efficiencies and community concerns, he said.
Deployments that are dark-sky-friendly by design can help, but they only partly solve light pollution challenges, according to Fareed and Rivas.
“Fundamentally, every lighting scenario is unique and lighting pollution does need to be considered,” Rivas said.
So, while lighting designers have technology available to enhance customer and community experience, these must align with design objectives, Fareed said.
There are many ways to reduce light pollution, and the time to address that issue is now, Rivas said. Dark-sky ordinances are being applied across the country to new construction and retrofits, although some such ordinances grandfather in legacy products. LEDs last for a long time, so it’s essential to address light pollution in the design process, rather than following an installation.
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