With its combination of energy savings, durability and low profile construction, the light-emitting diode (or LED) has quickly become the lighting technology of choice. The fast and furious way in which it came to market—without giving pause for the industry to develop standards—has resulted in some missteps that have caused problems with premature failures, flicker, and poor color quality.
The industry has responded by developing new standards which most, but not all, manufacturers have embraced. It is important to specify products that are tested in accordance with industry safety (UL) and performance (IES) standards. This article is intended to help laboratory managers, equipment vendors, and specifiers understand some criteria that should be considered when incorporating lighting into the laboratory environment.
The potential for energy savings and lower maintenance costs has brought LED lamping to the forefront of design conversations with building owners. The U.S. department of energy reports, “Widespread use of LED lighting has the greatest potential impact on energy savings in the United States. By 2027, widespread use of LEDs could save about 348 TWhr (terawatt-hour) (compared to no LED use) of electricity: This is the equivalent annual electrical output of 44 large electric power plants (1000 megawatts each), and a total savings of more than $30 billion at today's electricity prices” (www.energy.gov). With so much potential energy savings available, it is clear why owners and facility managers are turning to LED technology to lower operating costs and reduce the related demand for fossil fuels.
A closer look at LED performance
Photopic human vision is quite sensitive to variations in color. It is estimated that the eye can differentiate approximately 10 million colors when making side-by-side comparison. Human vision’s color discretion is dependent upon the spectral power distribution of the light. Unlike prior lamp technologies, spectral power distribution curves for LED products vary greatly. Consistent, accurate color rendering throughout the laboratory environment (across work tops and within hoods) can be critical in the research process, especially where test strips and sample evaluations rely on color assessments. It is important that the color quality and color consistency of electric lighting is addressed when designing and servicing light fixtures in these environments.
The wide variations in color quality produced by LEDs exposed limitations with the lighting industry’s traditional color metrics: Color Temperature (measured in degrees Kelvin) and Color Rendering Index (CRI). CRI is used to predict accuracy of color discrimination based on a reference source of the same color temperature. As a result, two new color rendering metrics, color fidelity (Rf) and color gamut (Rg), have been developed to better represent color rendering performance. Color fidelity is very similar to CRI but averages color discernment between 100 various colors instead of only 8. Color gamut tests for vividness, or color saturation, and can indicate when lighting is being used to artificially enhance a particular color. The IES (Illuminating Engineering Society) TM30 standard defines these metrics and the IES LM80, LM84, and LM86 standards defines the testing and measurement requirements. All LED products should be tested and specified using these standards—it is the only way to assure accurate and consistent color rendering ability.
LED module manufacturing cannot guarantee color characteristic consistency between LEDs made in different production lots. In response, the industry has adopted a process referred to as “binning,” which segregates LED modules by color metric testing with a defined standard of deviation acceptability. When publishing color metric values, manufacturers should also publish the acceptable deviation value. Laboratory equipment manufacturers have to determine if they will purchase UL recognized lighting components and perform this work and safety testing themselves, or purchase and incorporate UL listed luminaires from quality manufacturers who perform this testing prior to sale.
LED modules are very small, very bright point sources that are incredibly uncomfortable for direct viewing. It is important that a luminaire lens be specified as either diffuse white glass, acrylic, or polycarbonate when LED modules may be directly viewed. Environmental conditions determine the best material; regardless of material, it should be a diffuse white.
Laboratory applications for LED lighting
Laboratory lighting involves more than simply specifying LED light fixtures to save energy. Light levels needed on laboratory benchtops can often provide sufficient illumination for adjacent service corridors without the need for additional fixtures. Lighting designers refer to this design approach as task-ambient design. This design method is extremely effective in laboratories where high illumination levels are needed in select, defined zones that are typically adjacent to corridor zones with low illumination needs. Using fewer fixtures not only saves energy, but reduces first and maintenance costs. Lighting design professionals will also determine if both the horizontal illumination on the bench and vertical foot-candles on the shelving comply with corporate standards and IES recommended practices.
Energy codes often require occupancy sensing controls, but special care must be taken when applying this technology to laboratory environments. Proper detection is key, as small motor movements are common and often occur inside a hood or other device. Lighting professionals familiar with laboratory environments should work with the client, laboratory planners, and mechanical engineers to determine appropriate control solutions. Collaboration often results in the status of the lighting system occupancy sensors being shared with the Building Automation System which controls the occupied/unoccupied set-back for the HVAC system.
Lighting designers should also specify color characteristics for lighting equipment to assure that appearance is consistent throughout the space, and that the color rendering quality is high (refer to new metrics discussed in “color quality”).
Supplemental task lighting
Proper overhead general lighting can often eliminate the need for supplemental task lighting. Where task lighting is required, LED technology allows for very slim profile luminaires that tuck nicely onto the underside of shelving. All task lights should be UL listed fixtures. UL recognized components are tested for use as componentry. They have not undergone complete safety testing for stand-alone lighting equipment. It is important that the color metrics match those of the overhead general lighting and that controls assure lights will not be left on when not in use. If this task lighting is provided by the casework or shelving vendor, they must have the ability to adhere to the color metrics and control methods specified. Casework vendors who use reputable luminaires from manufacturers offering a diversity of products that are tested to industry standards will avoid the time and expense of testing luminaires on their own.
Integrated equipment lighting
Laboratories often contain large equipment such as fume hoods, biosafety cabinets, and CTCH rooms which are typically manufactured with lighting. Like the supplemental task lighting above, adherence to UL listing and the color metrics and control methods included in the project specification is the responsibility of the submitting contractor/manufacturer. This can become burdensome if the metrics for the integrated luminaires are unavailable.
Physical integration of the LED luminaire within the lab equipment is important. Ventilation and heat sinks are important for conducting heat away from the LED module. Although service access is not as frequent, it is still needed. Access should be designed with personnel safety in mind. Consider using quick connect wiring components for LED drivers and modules so that small connections do not need to be performed inside a small housing without task illumination.
Luminaire housings must be structurally supported within equipment, taking into account potential vibration sources. Clearly visible luminaire labels which identify manufacturer replacement part numbers help owners order and manufacturers provide replacement parts prior to disconnecting the light to perform maintenance.
LED technology does well in cold environments, making them particularly well suited for refrigerated cases, freezers, and cold temperature CTCH rooms. LED technology does not perform well in very hot environments and will prematurely fail if operated under very hot conditions. This can also occur in environments that are not excessively hot, but have not provided a proper heat sync for the LED modules. Manufacturers should use IES LM82 standard to define photometric performance as a function of temperature. Establishing and publishing ambient operating temperatures that will void a warranty is important with LED technology. Specifiers should always require a minimum 5 year product warranty for LED lighting.
What many people do not realize is that the published life of an LED product is the time it takes for the light produced to decrease 30 percent. This means that if LEDs with a published life of 50,000 hours are used to provide 100fc, at 50,000 hours they will only be producing 70fc. Although they are still operating, they will not be providing sufficient illumination and should be replaced. Facility managers and maintenance technicians need to replace LED modules that are still operational if illumination levels are to be maintained. Where an illumination loss of 30 percent is acceptable, an LED fixture with a 50,000hr rated life operated continuously will need to be replaced in 5 years; if operated 10hrs/day, 5days/week, 52weeks/year, it will need to be replaced in 19 years.
It is important for equipment manufacturers to realize that they will need to provide replacement LED modules for servicing at the end of life. Unlike incandescent and fluorescent lamps that can be purchased at any distributor and work in any luminaire, LED modules, drivers, and control methods are all different. It is important to get replacement parts from the luminaire manufacturer. It is very unlikely that the LED modules produced 10 years from now will be the same as they are today, but the manufacturer knows the physical attachment and operating characteristics of the existing components and must be able to supply a compatible replacement. They should keep records to assure that replacement modules match the color quality and delivered lumens of the original LED modules.
It is difficult to overstate the impact that LED technology has made in such a short amount of time. This relatively new technology has also introduced new lighting metrics and maintenance protocols. As the breadth of product continues to grow, continued emphasis on standardization will lead to environments with cohesive lighting strategies, contributing to the laboratory mission.
It is important that lab managers work with lighting professionals who understand the LED paradigm shift. These professionals can help navigate purchasing and maintenance protocol decisions that will work for your organization moving forward. The NCQLP administers testing and continuing education re-certification for lighting professionals; a current list of LC certified professionals can be found on their registry website, https://www.ncqlp.org/Registry.
Fred P. Mason, Jr., RA, LEED AP, and Karen P. Murphy, LC, IALD, LEED AP, are with HDR.