A small piece like this will not do justice to the complexity of the lighting plan for Galveston that council members are discussing. Many of us understand from this discussion that light-emitting diode lights, better known as LED, can be 50 percent more energy efficient than the street lights that they replace.
The bulbs are less costly and last for 15 to 20 years instead of two to five. So, LED lighting seems the way to go. But the meaning of the K value of LED lights is central to the discussion and needs some thought.
Clueless as I am in matters electrical, when I first heard about the “4000K” lights being considered, I thought folks meant kilowatts. Not so. The K here refers to a value on the Kelvin scale that measures the color temperature of lights. The higher the K value, the more intensely bright and blue the light.
Large cities such as Houston, New York, and Seattle have installed 4000K LED streetlights with brightness as strong as midday light. Smaller town Davis, California, installed similar ones, but distressed citizens demanded that the bulbs they experienced as spotlights be replaced at great cost.
The 4000K lights cause concern significant enough that the American Medical Association adopted an official statement about the intensity of nighttime lights. In a nutshell, the message is to cool and dim them, because there’s a close connection between light and human health.
The AMA strongly cautions against outdoor lighting above 3000K. The 4000K lights cause severe glare, and sufficient levels cause retinal damage. Although it’s doubtful that anyone in Galveston will stare at these bulbs to cause such damage, it’s equally doubtful that glaring lights will make driving or walking safe at night.
Lighting the night brightly with blue-white light can also disrupt sleep in people and animals. It’s part of a concern that some call light pollution. Disturbed sleep and waking cycles affect hormone production, especially in teens, and can be associated with health conditions such as breast cancer and cardiovascular disease.
Engineers have proposed design solutions to lessen the negative impact of highly intense light. These include shields that make less of the bulb visible and use of the dimming function that’s possible with LED lights. The AMA advises that communities dim even 3000K lights after peak usage. Cambridge Massachusetts does so after midnight.
Experts who support the growing trend toward installing LED lights cite the legitimate need for energy efficiency. But they also stress the need to lessen human risk from overly intense lights. Installing 3000K LED bulbs, just 10 percent less efficient than 4000K, can meet both needs.
Now less clueless about the meaning of the K value, I hope to avoid being sleepless. And in case anyone wonders, as I did: The Kelvin scale for color temperature is named after engineer William Thomson, 1st Baron Kelvin, who lived decades before the scale would become central to our discussion.