by Mark Hand
Light-emitting diodes (LED) are becoming increasingly popular due to the ever-present emphasis on reducing project costs. With numbers of LED installations rising, it is imperative that architects, engineers, and specifiers are able to evaluate the benefits of LED technology.
Lighting engineers are challenged to deliver solutions on time and on budget, while also achieving maximum energy savings through reduced consumption. U.S. Energy Secretary, Steven Chu, once said, “The cleanest energy is not solar, geothermal, or wind. It is the energy saved; the energy that is never used at all.”
According to the U.S. Department of Energy (DOE), widespread use of light-emitting diodes has the greatest potential impact on energy savings in the country. Fortunately, the highly efficient nature of these luminaires, coupled with their innate ability to be controlled, make this digitally addressable light source ideal for many applications. With increased demand for LED lighting, it is essential specifiers know the details of selecting LED lighting.
Previously, specifying energy-efficient lighting was a challenge for engineers, but with the opportunity LEDs now present the lighting industry, the task no longer needs to be difficult. While the general perception of LED lighting is it is more expensive than traditional alternatives, there are ways to mitigate costs with well-written specifications.
1. Value vs. cost
LEDs are able to achieve better illumination for delivering high performance and significant energy savings. However, the perception of better illumination is it comes at a high cost. While some LEDs are more expensive, there is typically a reason. Long lifetimes, high color rendering index (CRI), tight binning, extreme ambient, control, and serviceability are often the reason for elevated prices due to performance benefits.
The important point about these features is engineers have the choice for what type of opportunities LED lighting provides. Since they typically cost more compared to luminaires with traditional sources, customers often expect a longer life, better color quality, better distribution, less energy consumption, and more control.
2. Reasonable lifetime expectations
The lifetime of LED luminaires matters to end-users because they offer energy efficiency and provide an extended lifetime. However, what is considered a reasonable lifetime for users, given there are excessive lifetimes published all the time?
Lifetimes are often inflated, because LEDs are assembled in fixtures and subjected to many adverse conditions. This includes a wide range of ambient temperatures, and drive current variations—in-rush, surge, dimming, being turned on and off several times a day, thermal shock, and various vibrations.
With that said, quality LED products can last 25 times longer than incandescent products and use 75 percent less energy. Quality lifetime for LED lighting is based on the application. For example, with applications where lighting is on for 24 hours a day, seven days a week, it is likely that 50,000 to 60,000 hours would be a reasonable lifetime.
3. Importance of CRI
CRI is a measure of a light source’s ability to show object color, which can be essential in certain settings. For instance, healthcare professionals may benefit from high CRI when conducting examinations of patients where identifying and distinguishing color is critical. In retail applications, high CRI can help highlight merchandise on shelves in a better-quality light. Product packaging colors may even look more appealing. However, it is not always critical to specify a high CRI for all applications. Even for spaces that do have a high CRI, it does not mean this criterion is as important when replacing lighting with LEDs.
A lower CRI often means a higher lumen per watt (Lm/W). It all comes down to considering price requirements, and a higher lumen per watt provides a lower cost. The lower cost is affiliated with fewer LEDs, less energy used, and better total cost of ownership. While a decent price for LEDs with a high CRI is not unheard of, lower CRI readings typically provide a better cost for projects.
It is important to only specify what is needed and not what previously existed for the CRI. Additionally, high lumens per watt do not guarantee quality illumination.
4. How to meet project needs
When specifying a new project, there are numerous factors to consider in aligning the lighting solution with the project’s needs. For example, when considering ways to mitigate prices of LED lighting, one should take into account how important energy savings is versus a high lumen per watt. While both options are available and can exist in one fixture, the end-user may not need both.
Also, it is important to consider extreme ambient conditions—temperatures above 25 C (77 F) or below –10 C (14 F). Having extreme ambient conditions could require additional costs for specialized components as higher ratings demand more thermal control.
Each application should be individually specified instead of just measuring to equivalent projects because each is different. There is typically more than one option for lumens per wattage to meet required specifications, so the design professional must consider the options and select the choice that is best for the application.
5. Benefits of controls
Initially, the use of controls with LED luminaires does mean an additional cost. However, simple controls can pay for themselves quickly and, over time, produce a dramatic return on investment (ROI). The initial increase in energy savings provides a quick ROI in LED luminaires with controls. Then, over time, those same controls allow LED luminaires to have an even longer lifespan, which saves money that would have been spent replacing traditional luminaires.
LEDs and controls are critical. Pairing LEDs with controls allows luminaires to perform at their highest ability. Dimming LED luminaires does not cause damage, and turning the luminaire on and off does not affect their life. Therefore, LED lighting integrated with controls is a simple solution to save additional energy and to create a convenient user experience.
From the cost, to the opportunity to pair LEDs with controls, there are a wide range of choices for engineers to consider. The right solution for the application can deliver energy savings, maintenance savings, and enhance the quality of light.
Mark Hand is the vice president of engineering–indoor for Acuity Brands Lighting. He has been in the lighting industry for nearly 10 years in the research, conceptualization, development, and commercialization of light-emitting diode (LED) luminaires. Hand can be contacted by e-mail at firstname.lastname@example.org.