The first incandescent light shed its initial photon in 1802 - forty-five years prior to the birth of Thomas Edison. It took three-quarters of a century to make a marketable electric light bulb - that's the one that Edison patented in 1879, whose basic design has "turned night into day" for over a century.
The light emitting diode (LED) was invented in 1962, and while it soon found a niche as an instrument panel indicator light, the LED - which is far more efficient than its glowing grandparent - is still a toddler with respect to illuminating our streets, offices, and homes. Several independent consortiums are working to make LED lighting a mature and sustainable technology, so let's shine a little light on their endeavors.
Modular Lighting Designs for Sustainability
When we think of the advantages of LED lighting, the first thing that comes to mind is energy efficiency, which helps reduce electric bills and CO2 emissions. But carbon footprint is a complicated issue since we also have to take into account the energy needed to manufacture the product. Overall sustainability involves the efficient use of all resources, including energy and materials. To that end, the European Repro-Light consortium is developing the "Luminaire of the Future," a lighting fixture that can be reconfigured, repaired, refurbished, recovered, and recycled.
The group is promoting designs that are modular, enabling service personnel to customize standard light fixtures for particular applications, upgrade luminaries as newer technology and software becomes available, replace failed components, and ensure that the fixtures spend most of their time in a ceiling rather than a landfill.
When an LED bulb fails, it's rarely due to the diodes themselves; most failures are in the driver - the electronic circuit that converts the electrical input into voltages and currents that the LEDs can handle. For this reason, the consortium separates luminaries into three distinct modular components: LED module, driver, and network transceiver, all of which can be swapped out or repaired. When the components become obsolete or too costly to repair, they can be harvested for parts and materials, reducing landfill usage and the need for virgin stock.
In addition to cutting waste, modular designs will provide jobs for skilled service personnel. The old joke, "How many _______ does it take to change a light bulb?" just got a bit more complicated.
Efficient, Reliable, and Tunable Lighting
The North American DesignLights Consortium® (DLC) works with engineers, manufacturers, lighting designers, and government agencies to promote the widespread adoption of high-efficiency LED lighting. The group's efforts include establishing standards for color tuning, networked lights, direct current (DC) lighting systems, Power over Ethernet (PoE) lighting, and flicker control. Let's see why these issues are important.
Color tuning allows lighting designers to create light fixtures that provide the best hue for the application. For example, cool, natural daylighting - more toward the blue end of the color spectrum - lends itself well to a work environment because it promotes alertness. Warm, soft lighting has a slightly reddish tint that encourages relaxation. Single-purpose lights have one color temperature, while more flexible lighting fixtures allow the color temperature to be adjusted. Here's a video with more about color temperatures for different applications:
Video: US Department of Energy
Intelligent light fixtures contain sensors to detect occupancy, ambient light, and temperature. They can communicate with each other and with a central controller in a networked environment, automatically maintaining an optimal environment for the conditions, which could lead to a significant reduction in energy use by HVAC and lighting systems.
LEDs are DC (direct current) devices - they conduct electricity in one direction but not the other. Our wall outlets deliver AC - alternating current - which changes direction periodically. Incandescent and fluorescent lights work with AC, but LEDs require a driver circuit to convert the AC into a proper DC voltage and current. The driver is not only a common source of failure, it also uses electricity, which cuts into the energy savings that an LED light provides. DC lighting systems, including Power over Ethernet (PoE), are becoming popular in new constructions and retrofits, reducing energy use and increasing LED fixture reliability.
LED brightness is controlled by pulse-width modulation (PWM), where the controller delivers power to the LEDs in bursts - the longer the burst (engineers call it the "duty cycle"), the higher the average power getting to the light, and the brighter the light appears.
Essentially, PWM turns the light on and off repeatedly, causing the light to flicker. Since it happens very quickly, our eyes don't notice it, but there is evidence that some people are sensitive to flicker, so engineers must work to minimize the effects.
DLC's efforts have already resulted in several sites that demonstrate advanced lighting systems. You can read some of their case studies here.
The three Rs of sustainability used to be Reduce, Reuse, and Recycle, but today's engineers have a few more Rs to consider. I think they're bright enough to handle it.
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