The city of Bakersfield, California considers itself enlightened – enlightened by LED streetlights, that is.
The city, the 9th largest municipality in the state of California, recently completed a huge public works program with PG&E to upgrade no less than 12,865 of its 17,500 old “cobra head” sodium vapor streetlight fixtures with brand new LED lighting.
The replacements, completed by June 30th, 2018, were mostly on major city streets and residential areas.
Sodium Vapor VS LED
Bakersfield’s old streetlamps were High Pressure Sodium Vapor (HPS), gas-discharge lights, with an arc tube made of aluminum oxide requiring a voltage pulse to cause a spark for them to light up. The sodium is combined with elements like Mercury to counter-balance its natural yellow glow with some white/light blue emissions. Still, the light that emanates from these bulbs is decidedly more yellow in color. The lights take some time to “warm-up”, as the internal gas is evaporated into plasma, and once warmed, require even more voltage to keep running.
The older sodium vapor lights get, the more voltage needed to produce the same amount of light, making them progressively less efficient (and dimmer) over time.
Meanwhile, LED (or Light Emitting Diode) lights have two electrodes through which electricity flows – in through the anode, and out through the cathode. The diodes are usually semiconductive materials like silicon or selenium – solid state substances that conduct electricity in some circumstances and not in others (e.g. at certain voltages, current levels, or light intensities).
When current passes through the semiconductor material, the device emits visible light immediately. In simple terms, it’s the exact opposite of a photovoltaic cell.
Single LEDs don’t produce much light, but an array of around 20 (as found in a street light) produces a very bright, crisp light.
LEDs, in addition to having a very high light quality, also have an extremely long lifespan relative to every other lighting technology on the market. They can last up to 100,000 hours (15-20 years) which makes for some serious savings when it comes to maintenance.
Compared to their predecessors in Bakersfield, the new LEDs use 50-75% less energy and last about four times longer. They don’t waste a load of energy as infrared radiation and can emit light directionally over 180 degrees as opposed to 360 degrees, so less light needs to be redirected. This means greater visibility, less glare, fewer dark spots, more direct and natural night and an overall improvement in public safety.
Bakersfield by the numbers
How many PG&E crews does it take to change 12,865 lightbulbs, then? Just four. Or approximately 32,216 lightbulbs per crew. Proof that it doesn’t take TOO many hands to make light work.
That said, City maintenance staff and PG&E workers didn’t take the task lightly. They first had to visit and analyze all 13,000 “cobra head”-style fixtures targeted for replacement, “to determine their condition, power source and other data essential to preparing for this gargantuan undertaking.”
The project was funded with a no-interest loan, which PG&E is offering to municipal customers who invest in energy efficiency projects.
A City of Bakersfield spokesperson said the changeover would translate into $710,000 worth of savings, from a reduction in energy usage and less yearly maintenance. Indeed, he said, it would only take six years for the project to pay for itself.
“LED lights will make our streets safer and offer significant long-term savings to the taxpayer,” said Nick Fidler, public works director for the City of Bakersfield.
Before the big LED light switch, Bakersfield was having to replace around 2,500 conventional, high-pressure sodium vapor lights a year. “The LED lights require less maintenance than traditional street lights, which will allow city crews to address other critical needs throughout the community,” added Fidler.
“Our customers and the city will see an immediate benefit from this upgrade project,” said Kristen Doud, a public affairs representative for PG&E.
The new fixtures are also futureproofed in that they are “adaptable and equipped to handle developing technologies such as automated dimming for more cost savings, and Wi-Fi connection that sends an alert the instant a fixture burns out, enabling quicker replacement.”
Night Lights, A History of Greater Security
Since early civilization, well-lit streets have been known to provide more safety. From lamps to lanterns to fireflies in jars (used by the ancient Chinese), lights have helped prevent people from falling flat on their face in the dark, or worse, being robbed or assaulted. Greek and Roman civilizations predominantly used oil lamps, and the Latin word ‘lanternarius’ was a term for the slave responsible for lighting the oil lamps in front of noble men’s villas.
Before incandescent lamps, major cities spent a fortune on candles, which required nightly lamplighters. In 1802 coal gas made its appearance, followed by Electric arc lamp streetlights and now LEDs.
In modern times, streetlighting is predominantly geared at automotive safety. In fact, a recent UK survey found that while only a quarter of all car travel takes place between the hours of 7pm and 8am, this period accounts for 40 percent of fatal and serious injuries to the same group. Not to mention the risks to pedestrians and cyclists in hours of decreased visibility. For Bakersfield’s approximately 384 thousand residents, the new lights are, therefore, a huge boon.
Bakersfield Vice Mayor Bob Smith, said in a press conference he’s proud of city staff’s efforts to improve public safety while reducing costs to taxpayers.
Night Light Too Bright?
While most in Bakersfield seem pleased with the new lights, some residents are not. “These are flood lights like you see in a Walmart parking lot. They are extremely bright and are a form of light pollution,” said resident Peter Roth.
“While LED lights are a wonderful idea from an energy efficiency standpoint, cities need to be very careful to choose the correct type of LED light,” cautioned Dr. Michelle Jonelis, a sleep medicine specialist.
The vast majority of the LED street lights emit a significant amount of blue light, which, Dr. Jonelis said, is potentially harmful to humans and other living organisms. That’s because our brains interpret blue light as sunlight, which disrupts our internal body clock. “The blue light detection cells in our eyes are exquisitely sensitive,” said Jonelis, adding that even the presence of very small amounts of blue light in our environment late in the evening and night reduces our brain’s ability to produce melatonin. Without the proper amount of melatonin in our system our sleep quality is reduced.
“Research also suggests that the presence of blue light at night may be associated with an increased risk of cancer, diabetes and cardiovascular disease, she added.
Does that mean we should stop using LED lights? No, said Jonelis. “It is very possible to use energy efficient LED street lights AND minimize their impact on humans and wildlife. The way to do so is to choose the proper color of lighting and implement adaptive dimming.”
The ideal color of light to minimize negative effects on wildlife turns out to be a yellow color which is free of all blue light and also emits minimal red light. “This is the color of light that should be used by cities.”
Additionally, said Jonelis, LED streetlights should be equipped with motion sensors that allow them to dim, or, even better, turn off when no cars or people are around them. Several European countries have already implemented this type of dimming strategy.
LED lights have the potential to be beneficial to the environment in many ways, and Bakersfield is lighting the way for its neighbors to make similar energy efficient changes, but careful thought must go into designing and using them.