Day: September 25, 2020

How are LEDs evolving and impacting businesses? With the New Year comes new opportunities and this is certainly true with LEDs. There are now high quality LED luminaires for street, area and landscape lighting; down lighting; track lighting; shelf and display lighting; decorative fixtures; 2X2 and 2X4 recessed luminaires for general ambient light; even high brightness high bay luminaires. The directional nature of LED sources allows for more of the lumens generated to be emitted from the luminaire compared to traditional light sources making these luminaires extremely efficient. The advancements in LED technology has lead to higher efficacy and higher lumen LED chips, as well as chip on board technology minimizing or eliminating heating sinking requirements, enabling the development of luminaires for general ambient lighting  that deliver more than 100 lumens per watt.  Most indoor luminaires typically have a rated life of 50,000 hours (L₇₀), but there are many street and area lighting luminaires with life ratings in the 70,000 to 100,000 hours range. Color consistency fixture-to-fixture and color stability over life is being address with “hot binning” of LED chips or the incorporation of intelligent active color control into the LED system to maintain the color within a two-step or three-step Macadam color ellipse minimizing perceptual color differences. There are also a variety of phase cut, 0-10 V, DALI and wireless lighting controls that have been developed for dimming of LED lamps and luminaires down to 5 to 20 percent.

Boston Interiors Photo Credit: Shannon Creeden

One example of LED technology making a difference for businesses is Boston Interiors, a family owned and operated furniture retailer with seven locations throughout Massachusetts that sought to reduce operating costs at its retail locations. Having identified lighting as an area that could offer significant savings, it was also critical to Boston Interiors that its lighting provided excellent color rendering to highlight its quality furniture and catch customers’ eyes.  Boston Interiors selected its retail store in Stoughton, Mass. as the pilot location for upgrading the lighting to LEDs. Having selected OSRAM SYLVANIA’s ULTRA High Performance series PAR38 LED retrofit lamps to replace the existing 60-watt halogen lamps throughout the store, Boston Interior was very satisfied with the quality of light and color rendering of the ULTRA High Performance Series LEDs.

As a result of the retrofit to LED lighting, Boston Interiors will save more than $8,000 annually in energy and maintenance costs at its Stoughton store. Over the lifetime of the lamps, the savings will total nearly $100,000 over approximately 12 years. In addition to the energy and maintenance savings, Boston Interiors has also noticed savings in cooling the Stoughton store. Because OSRAM SYLVANIA’s LED lamps produce far less heat than halogen lamps, Boston Interiors has not needed to rely on its HVAC system quite as much since the LED lighting was installed.

In addition to cost savings, the LED lighting has enabled Boston Interiors to reduce its carbon footprint, as the company is committed to green initiatives. The retrofit is a major contributor in helping reduce the store’s energy consumption by 48,315 kWh, the equivalent of 74,163 pounds of carbon dioxide.

The advancements in LED technology and more reasonable price points for LED luminaires definitely makes LED lighting solutions worth looking at. Remember, not all LED solutions are alike and requires doing your homework. Before deciding on an LED solution, it is best to install a few luminaires and evaluate its performance before making a final decision.

LEDs are very good at producing light and heat. Unfortunately they are slightly better at the latter than the former and as each generation improves, more Lumens for every Watt of electrical energy are produced.

Indeed, LEDs have now become so good at producing light that they are rapidly replacing other types of light source for a wide range of applications including automotive lighting, domestic “light bulbs” and industrial luminaires (e.g. ‘high bays’). The one thing these applications have in common is that it is the manufacturer’s responsibility to prove the product is safe and performs as advertised. Both are accomplished through testing. Often these tests are defined by standards.

While passing a test is highly desirable, it does not guarantee that an LED light is suitable for an application or will survive long in service. There are two reasons for this:

1. The manufacturer often has little control as to how or where the LED lights are installed
2. There is Mother Nature to contend with.

Consider, for example, the thermal management of LEDs. Due to the production of heat (alongside photons) LEDs must be cooled to keep the junction temperature within safe limits. Ideally LEDs will run at the lowest practicable temperature since virtually every performance metric of LEDs efficiency, stability of hue and lifetime all decline as the temperature increases. LEDs are cooled by conduction so it is important to use circuit boards with very low thermal resistance between the semiconductors and the heat sink. It is for this reason that high brightness and high intensity LED light sources use various forms of metal-back PCBs on which to mount the LEDs. A metal board is able to spread the heat and conduct it through to a heat sink that dissipates it to ambient air.

A well-designed LED luminaire will keep the LEDs comfortably warm at around 70-90°C and the heat sink at a pleasant 30°C or thereabouts. However that very design assumes the luminaire will be used in a temperate climate where the ambient air is around 20°C. More importantly, LED lights are often tested in just that sort of environment. In some parts of the world, night time minimum temperatures can be as high as 40°C – and that is outside in a nice “cool” breeze. Typically luminaires are installed on or in ceilings. Now given hot air rises and the ceiling air is relatively stagnant (particularly if the LED light is installed in a closed void) the operating environment can easily reach 50°C or more.

Traditional metal finned heat sinks that transfer thermal energy to air function by having lots of surface area.  As such the LED luminaire sent for testing will, in all probability, have a pristine heat sink that will function at maximum efficiency. Now fast-forward five years and some heat sinks will be covered in a thick layer of dust and cobwebs (when did you last clean your light fittings?). Indeed, it is not uncommon for larger high bay lights to be used as nesting sites by a variety of lesser and more endangered bird species! Cutting the efficiency of the heat sink has only one outcome, which is to raise the operating temperature of the LEDs and inevitably shorten their lifespan.

While the construction of a birds nest on an LED heat sink is not part of standard tests, some allowance for product aging should be included in the thermal design.