Remaining in the vanguard, Los Angeles has begun an even more challenging, second phase. The bureau is now retrofitting some 50,000 decorative and ornamental post-tops and pendants. These luminaires come in various wattages in 400 styles; many are highly ornate poles and fixtures manufactured in the twenties, thirties, and forties. “Different fixture styles have been installed in different neighborhoods, representing the historic fabric of the city. My goal is to make sure we preserve these treasures,” said Ebrahimian. “We want to make the change to LED to realize the energy efficiency benefits without changing the look of the fixtures.”
Ebrahimian reports great results – in terms of energy savings, longevity, and light quality – from the ongoing experiment in LED cobraheads. He is often invited to speak and share the LA experience with other municipalities and institutions. BSL is moving further into cloud-based networking to more easily maintain and control the vast stock of fixtures. “We’ve been very demanding and stayed completely unbiased toward any manufacturer. I think our process has played a role in the development of LED street lighting. We demanded 63% energy efficiency, and today a city would realize even more, 70–75%. When you have a large system you can’t wait too long,” he said. All these efforts now inform phase two.
The post-top challenge.
Phase two launched in 2013 as the final cobraheads were being converted. The post-top retrofit specification issued in mid-2014 required a 10 year warranty, passive cooling, and 3000K for local streets and 4000K for thoroughfares. According to Bureau of Street Lighting Assistant Director Norma Isahakian, the city sought and continues to seek mogul-base solutions to retrofit. Hard-wired solutions take longer to install.
“Right now we’re working with two or three manufacturers that offer hard-wired bracket solutions. At these high outputs, it’s hard to control the heat and maintain the form factor that we’re looking for,” Isahakian said. She also emphasized the aesthetics of the specification: the LED array must fill the globe with light, with no clear image of the LED array or individual emitters. Kits must be adjustable to fit multiple fixture types.
The initial fixtures being converted are 200–300W incandescents on shorter poles (12–14 ft high) and 100–170W HPS and metal halide (some at higher mounting heights); being replaced with 30–40W LED retrofit kits. “As we get into higher wattage 200-400W HPS on 25 ft poles on major streets, we have limited solutions in LED,” Isahakian said.
The many districts where HPS is in place will benefit from the whiter light and improved CRI that LED retrofits provide. And because these are not spherical emitters, the LED arrays can provide directionality. House-friendly versions twist around to provide some cutoff. This modified Type III distribution projects light toward the street with less light on the house side.
In addition, less light is emitted out the top of the globe. “A lot of these are going into post-tops that don’t have refractive ability or any shielding. They’re just diffuse globes that put out a blob of light. House-friendly versions will add some cutoff to fixtures that don’t have cutoff,” said Isahakian.
“LED also minimizes uplight, compared to HID. This provides a certain level of dark-sky friendliness. They don’t achieve any dark-sky rating, but we’re lessening the upward light component.”
The jury is still out on the dark-sky benefits of LED street lighting. While the upward lumens are greatly reduced, the eye’s sensitivity to shorter wavelengths may make less light more problematic. Bluer wavelengths are also more biologically active, suppressing natural circadian cycles of rest and activity in both people and animals. On the other hand, the digital nature of LEDs could, in the future, permit networking and more controllability. Fixtures could be switched or dimmed to be used only “as needed.”
But these initial solutions being implemented suit maybe a dozen of the 400 historic fixture styles.
A thoroughly modern city, Los Angeles takes pride in its history. The streetscapes of LA have appeared in movies and television since there were movies and television. To preserve a slice of that uniquely American identity, the Bureau of Street Lighting opened a small street lighting “museum” at the BSL headquarters downtown (open by appointment).
The beautifully restored and carefully relamped fixtures at the Street Lighting Historic Museum demonstrate electric lighting in LA since 1887. Some of the luminaires archived here were saved from the “boneyard,” the last of their kind. Others can be found illuminating downtown districts and upscale neighborhoods nightly.
The Los Angeles County Museum of Art also celebrates the elaborate decorative nature of SoCal’s post-top street lights. An exuberant, large-scale installation by local artist Chris Burden, Urban Light comprises 202 restored post-tops from the twenties and thirties, assembled in ranks. Visitors can walk through the forest of fixtures and most take a selfie or two. The piece dominates the forecourt, presenting the face of the museum on Miracle Mile.
Ornate, manufactured and electric – it’s quintessentially LA.
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