Lunar-Resonant Streetlights Win Metropolis’ Next Generation Competition

This year’s Next Generation winner looks to remake our urban spaces and skies by harnessing the illuminating beauty of the moon.

The picture shows a familiar landscape: the horseshoe of the San Francisco Bay, the arms of the city and Marin County reaching out to meet each other, clouds obscuring the famous bridge that connects them. What’s odd is that it’s nighttime, and all of the landmasses are visible—yet where the city should be, there’s only darkness. The brightest elements are the full moon in the sky and its reflection on the water. Here is what the Bay Area, population 6.7 million, would look like without electric light.

This computer-generated image is the vision of Civil Twilight, a design collective based in San Francisco’s Mission District. With its concept for a new approach to outdoor lighting, the group asks: What if streetlights could respond to ambient moonlight, dimming and brightening each month as the moon cycles through its phases? On clear nights when the moon is full, streetlights might even turn off completely. The scheme, which they call “lunar-resonant streetlights,” could save as much as 80–90 percent of the energy used in streetlighting while bringing back the experience of moonlight and stargazing to urban areas.

The concept, a small and simple intervention that could impact light pollution and energy use on a global scale, won this year’s Metropolis Next Generation ideas competition. For the first time, the four-year-old program took up a theme: energy—its uses, reduction, consumption, efficiencies, and alternatives. Runners-up included an LED display for faucets that makes people aware of water usage; a multistory residential unit that generates renewable energy and treats waste; thermo-responsive architectural cladding that expands and contracts to regulate building temperature; and a highway sound barrier that absorbs airborne pollutants.

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The proposal for lunar-resonant streetlights captured the jurors’ imaginations with an inspiring combination of poetry and practicality. Its goals may be lofty, but the implementation would be simple: retrofit existing streetlights with dimmable LED bulbs and a highly sensitive photo-sensor cell that could detect and respond to moonlight. Civil Twilight member Anton Willis says the idea evolved out of his master’s thesis for the architecture school at the University of California, Berkeley. Inspired by the work of the artist James Turrell and by ancient astronomy-based architecture, Willis studied ways that the developed environment could respond to lunar and tidal conditions. After graduating, he came away wanting his admittedly esoteric project to have a broader cultural impact—the way the moon itself once did before the advent of electric light.

To flesh out his idea, Willis enlisted his friends and collaborators Kate Lydon and Christina Seely. Lydon, who is currently finishing the graduate architecture program at Berkeley, is also a graphic designer and had worked with Willis on a design charrette for the adaptive reuse of a famine poorhouse in Ireland. Seely, a photographer, was pursuing an ongoing project called “Lux,” in which she documents the glow of artificial light produced by cities in the three brightest regions in the world. All three trace their interest in sustainability and energy issues back to their earliest experiences. Willis is from a small Mendocino County logging town, where stars and moonlight were part of everyday life. Lydon and Seely grew up in Berkeley, steeped in both environmental politics and a stunning natural landscape. “You cannot grow up here without an awareness of the land and the water and the light because of the way the bay is formed and how dominant the sunset is,” Seely says. “You’re tied into the rhythms of nature, even in a highly urban area.”

Expressing sustainability as a personal connection with nature is one of the proposal’s key ideas: Would we feel closer to nature if we could see the stars and moon from urban rooftops and backyards? How much energy would we save if we relied on the moon, when we could, for nighttime lighting? Civil Twilight’s research indicates that streetlights account for 38 percent of the electricity used for lighting in the United States—that’s close to 300 million tons of carbon emissions a year. They’re also the top source of light pollution, preventing two-thirds of Americans from seeing stars at night. The collective estimates that switching to dimmable LEDs and more responsive sensor cells could save the majority of that energy and bring the night sky back into the lives of urban dwellers.

Perhaps the most fascinating fact that the collective’s research revealed, however, is a little-known detail about the history of electricity: in the 1930s, with the spread of electrification and the consolidation of utilities, streetlights became a convenient way to off-load excess energy from the grid at night, when power demands dropped significantly. This intentionally inefficient system determined the norm for nighttime outdoor lighting levels, a standard that has not been revised since, even though the need for off-loading ended in the 1970s. What we now assume is a safety measure is in fact the forgotten remnant of an obsolete energy practice. Next Gen juror Fred Dust, head of IDEO’s Smart Space design practice, says the jury found this part of the proposal both shocking and compelling. “It’s such an archaic concept that it seems like science fiction,” he says.

Questioning current lighting standards and asking what level of illumination is actually necessary brings some sur­prising answers. Willis explains that the human eye, with its com­-ple­mentary systems of rods and cones, evolved to adapt to both full-sun days and moonless nights. “We can see an incredibly broad range of intensities,” he says. “The difference between sunlight and starlight is something like a hundred thousand orders of magnitude.” Bright moonlight is in the transitional part of this range, when both rods and cones are active. “It’s a natural biological benchmark,” Willis says, “because we evolved with it.” Meanwhile, the Institute of Electrical and Electronics Engineers’ recommendations for artificial lighting are only about ten times brighter than full moonlight—almost nothing compared to what the human eye is capable of seeing and yet significant in terms of our ability to appreciate the night sky.

So what are the current standards based on? Comfort levels and perceptions regarding nighttime safety. Since the off-loading days of the 1930s, we’ve become accustomed to the feel of brightly lit streets and parking lots. But ironically, studies have shown no link between outdoor lighting intensity and crime or accident rates. What’s more dangerous, Willis says, is the drastic variation in light levels within an urban area. As you drive, for example, from a well-lit major thor­oughfare to a darkened residential street, your eye does not have time to adjust, and your vision is impaired. Moonlight is much more even, he explains, and that makes it more effective for human vision. By filling in only what light is needed, lunar-resonant streetlights would help restore this evenness and actually improve nighttime visibility. “We’re interested in the question of standards,” Willis says. “Do you need to be able to read a newspaper in the middle of the night outside, and is that really worth all of these other things we’ve lost?”

As Seely points out, another thing we’ve lost is an appre­ciation for electric light itself. “The evolution of streetlights was partly decorative,” she says, “and this project is in some ways about getting people to reappreciate light where it’s spectacular, tapping into the wonder of how beautiful it is.”

As her photographs show, the gradual ratcheting up of artificial lighting means that spectacle is harder and harder to achieve. Her 2006 photograph Metropolis: 36°10’N 115°8’W, taken from the desert outside Las Vegas, makes the city look dangerously radioactive. A light beam shooting from the top of the Luxor hotel pyramid looks like it would be visible from space, raising questions about what its competitors will do to top it—and how long ago it was that Las Vegans last saw a star in the sky.

The implication that lunar-resonant streetlights could correct a loss reinforces the inspirational qualities of the project. The new fixtures would be so sensitive to light condi­tions that even passing clouds would cause them to turn on or off. On cloudy moonlit nights, airplane passengers and high-rise apartment dwellers could observe pools of light flickering across a city in reverse of cloud patterns. Willis, Seely, and Lydon envision cities—hikes, performances, and fes­ti­vals. It’s this quality of the project that makes it so appealing—tapping into what the group calls the “wonder and awe” of the natural world as a way to motivate sustainable behavior. “We like to appeal to people’s irrational aspirations as opposed to their rational, guilt-driven reactions,” Willis says.

Dust says the project’s “magical quality” is part of what pushed it into the winning position. “Sus­tainability is such a significant design issue for us now that to some degree we’ve sucked the joy out of how to explore the problem,” he says. “We sometimes forget the importance of poetics to inspiration.”

The proposal’s underlying strength, however, is its practicality. Most of the necessary parts are available off the shelf. The standard cobra-head streetlights that we see on most American streets use a sodium-vapor bulb hooked to a photosensitive cell. The cell detects when the ambient light drops below a certain level (i.e. at sunset), and turns on the bulb. At sunrise the sensor perceives the increased light level and shuts the bulb off. The new sensor Civil Twilight has conceived would still respond to light levels but would be much more sensitive—enough to respond to light from the moon. Because sodium bulbs are not dimmable, Civil Twilight’s project would replace them with a cluster of white LEDs, which are also more efficient and require less maintenance. Currently the collective is applying for a patent on the light and working with an engineering student at Berkeley, who will build a prototype.

Working collaboratively—with their engineer and other advisers—is the preferred methodology for the members of Civil Twilight. They insist that they don’t really think of themselves as a group of three but as a larger, more loosely defined collective. Other collaborative projects in the works include a concept for the adaptive reuse of a 1970s strip mall in Marin County and an urban-farming scheme that would put dilapidated wooden buildings to use as a medium for growing mushrooms, eventually generating compost as the wood decomposes. “All of our projects deal with some question of the built and natural environments interacting or cohabiting,” Willis says. “Not equating urban nature with parks and greenery necessarily, but looking for deeper, more investigative ways to bring them together.” The name Civil Twilight, taken from the legal term for the hour of semidarkness just after sunset and just before sunrise, suggests a bridging of the built and the natural, the civic and the personal—as well as a fascination with in-between areas in general.

For lunar-resonant streetlights to have the impact that Civil Twilight’s proposal suggests, they would have to be adopted on a global scale. While Seely, Willis, and Lydon admit that it may be a hard sell with municipal utilities, they see small independ­ent entities like colleges or corporate campuses as likely early adopters. One potential partner is the International Dark-Sky Association (IDA), which encourages cities around the world to adopt “dark sky” ordinances to limit light pollution. To start, Civil Twilight is particularly interested in settings with a didactic or educational mission, where passersby can interact with the lights and learn about the goals of the project. Willis’s dream would be an installation at the new California Academy of Sciences, in Golden Gate Park. Seely suggests the parking lot at Google. “We don’t see this as universal,” Lydon adds. “Some places [like commercial districts and thoroughfares] would need a lot of light all the time.”

Thinking about when and where outdoor lights are appropriate raises the question, What would happen if we could remove all of the artificial outdoor lighting already in place and start over? Lydon theorizes that in developing countries lunar-resonant streetlights could spread in the manner of the cell phone, which immediately became the telecom standard in parts of the world that never had landlines. “It would be amazing if developing countries skipped over the stage of energy wasting and overconsumption, and just went straight to the standard that’s closest to natural,” she says. Perhaps the collective’s computer-generated image of a modern city illuminated by moonlight isn’t as fantastical as it seems—if we imagine it not in California but in China or Africa.

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