Lunar Resonant Streetlights

All street lights have a photosensor on top of their fixture designed to turn the lamp off during the daylight hours. When the Sun rises, the photosensor turns off the lamp and it stays off until the Sun sets again, at which time, the lamp turns on.

A design company in San Francisco just won a $10,000 prize for their “innovative, energy-saving urban outdoor lighting concept”.

Here’s a definition from ArchNewsNow:

Lunar-resonant streetlights respond to ambient moonlight, dimming and brightening as the moon cycles through its monthly phases, as well as clouds and atmospheric conditions. Simple technology: sensitive photocells detect ambient light levels and electronically adjust output; high-efficiency dimmable white LED clusters replace standard sodium bulbs.

Supposedly, this will save lots and lots of energy and reduce our carbon emissions dramatically. Here’s a schematic:

Illustration Credit: Civil Twilight Collective

If I sound skeptical, well, it’s because I am. Installing these more sensitive photosensors and LED clusters is a HUGE effort. There are hundreds of thousands of mercury/sodium vapor streetlights in the U.S. and even replacing a fraction of them involves a cost I don’t see anyone accepting. Light pollution in this country is simply not a priority, nor do I see it becoming one in the near future.

I like the idea of using LED clusters to dim the lamps because that alone will save lots of energy and LED’s generally last a lot longer than bulbs. This idea looks extremely promising.

This doesn’t really get us back our dark skies though. Even though the website mentions that we are losing our dark skies and makes noises that this could help with that problem, I think this is aimed more at saving energy than reducing light pollution. When the moon is full, I can’t see the stars well anyway, so dimming the streetlights during a bright moon won’t give me a better sky. To do that, they’d need to dim the lamps when there is no moon. (Now, if the photosensor responds to when Betelgeuse or Vega is up, well then…)

I think this solution would be great so long as the LED’s are astronomy-friendly, meaning the light can be filtered easily with standard optical filters, and they are installed in full-cutoff fixtures that focus all of the light straight down on the ground where we need it and not in my face.

It’s a fun idea, and I’m really happy there’s someone out there thinking about the problem, I just wish there was some motivation out there to implement it.

Photo Credit: Civil Twilight Collective.

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