LEDs are used in many different types of outdoor applications, from colorful decorative architectural lighting to high-power white-light applications like street lighting. Though using more light to create colorful decorative fixtures cranks up the usage numbers, the overall light pollution caused by lighting will decrease if LED lighting is employed in higher power, white-light applications. Why? It all comes down to the utilization factor.
The overwhelming majority of light generated by humans gets wasted because no one is present to use it! Given that power for lighting is 20% to 30% of total electricity consumption, this simple fact points to lighting as one of the most wasteful contributors to global warming in our world. Some examples are building wall packs, parking lots, and even many street lights that are either being used very little or not at all throughout the evening.
These applications typically use high-intensity discharge (HID) lamps such as low-pressure sodium, high-pressure sodium, and metal halide lamps. These lamps can’t be easily or very effectively modulated— either dimmed to low levels or shut completely off—when not in use. Most HID lamp manufacturers suggest only dimming them to a minimum of 50%, at which point they still consume approximately 60% of their full output power. They can’t be shut off completely because of their inherently long restrike times.
In contrast, LED-based lamps are extremely easy to turn on and off, and they dim down to 1%. New lighting systems are already being deployed that implement increased levels of intelligence, such as ambient light and motion sensing and remote control via radiofrequency (RF) communications.
These systems can be dimmed to low levels or even shut off when the system “knows” no one is present to use the light. Due to the significant increase in the utilization factor, overall lighting levels at night will see a sizable net decrease when these systems are more widely deployed.
Finally, in contrast to most traditional light sources, including HID lamps, LEDs provide extremely directional light rather than emitting light in all directions. These beam patterns can be finely tuned via secondary optics to only provide light where it’s useful, increasing overall system efficiency and further decreasing light pollution.
