Categories LED

Avoiding LED Glare Bombs

If you’ve ever looked directly at a retrofitted LED luminaire in a parking structure or gas station canopy, chances are you were blinded by the glare. And when you looked away you probably saw those black spots reminiscent of antiquated flash cameras.  This happened to me just last week. As a lighting product manager and mechanical engineer I often look up at the lighting source; try as I might, I simply can’t avoid it! Since you’re reading LED Journal, you undoubtedly do this too.

So why do covered ceiling and area light luminaires have exposed LEDs? Such a design model virtually ensures glare. Yet as a lighting professional, I often wonder why LED fixtures are being developed with such little regard for glare control. While there is no clear answer, I’d suggest two strong possibilities: the first is that lighting manufacturers were initially so consumed with lumen output that a feature that would lower light output was not part of the discussion. Lighting specifiers were skeptical, at best, that a parking garage could be properly illuminated with a 3,000 to 4,000 lumen fixture, costing $700 and lasting only 50,000 hours—so where was the value proposition? The manufacturers were making seemingly outlandish statements that only delivered lumens mattered, and a parking garage could be magically illuminated with what appeared to be ¼ the total amount of light output from the luminaire.

The second reason, in my opinion, is that manufacturers and specifiers both believe the new designs are an improvement over the old shoe-box designs normally used in area light applications. Post-top mounts were certainly more attractive, but new stray light ordinances have slowed their sale so many specifiers perceive these designs as new and fresh.

Standards -Yes, fresh design aesthetics are definitely appealing! That said, I don’t believe that modern LED luminaires should be held to a lower standard regarding glare control or that modern LED luminaire designs should be exempt from the standards and practices meticulously developed over the last 100 years.

Measuring Glare – Since glare can be quantifiable through a standard luminance measurement, this issue is far more significant than one person’s opinion versus another’s. As you may know, luminance is the photometric measure of the luminous intensity per unit area of light travelling in a given direction. Luminance describes the amount of light passing through a specific area that falls within a particular angle.

A common mistake in measuring LED luminaire luminance is measuring the entire fixture. Luminance must be measured at the luminous opening, in other words at the smallest point (without any breaks) that emits light out of the fixture. If one were to measure the entire LED luminaire, it would not account for the “shards” of light emitted from each individual LED. The light emitted from individual LED luminaire designs is more akin to a series of laser beams in contrast to the homogenous output of a traditional luminaire.

I don’t want to dive too deep into the mathematical equations or the comparison of luminance values, since not everyone following this blog is an engineer.  However, it’s important to point out that in controlled tests, results showed quantitatively that a shielded LED luminaire yielded an eightfold reduction in glare.

LED Luminaires Redesign Needed – Most LED luminaires designed today do not address the issue of glare. To the contrary, glare is often completely ignored. Clearly, as was done with traditional light sources, manufacturers should address LED glare, because high efficacies and quality distributions can be maintained while controlling both discomfort and disability glare.

I believe glare is just as important an issue today as it was 20 years ago. Unfortunately, with the impracticality of physical testing, there is no easy way to compare one luminaire to another when specifying fixtures for a project. However, there is one important point I’d like to make and that is, as with incumbent lighting technologies, new LED luminaires should not be designed with unshielded lamp sources. Effective shielding of LEDs can be achieved, while still providing excellent performance and a dramatic reduction in glare.

You may have a different opinion and I welcome your comments and feedback.

Categories LED

2021- New Year, New Possibilities for LEDs

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.

Categories LED

LEDs Cook Eggs

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.

Categories LED

All LED Luminaires Are Not Created Equal

As readers of LED Journal you know that both interior and exterior conventional lighting is rapidly being replaced by LEDs with intelligent lighting management. End-users are reaping the myriad benefits of this technology in reduced energy consumption and costs, and the virtual elimination of lighting maintenance. These benefits provide an incentive to help vigorously drive the ongoing development and implementation of LED technology. However, when considering this technology, it’s important to assess factors that contribute to the lifetime of an LED luminaire.


Kenall's TekDek engineered with a systems-approach. Photo courtesy of Kenall Lighting

Given that the LED luminaire is a system, it is vital to recognize all aspects [of the system] and not just individual components that can affect or limit lifetime. Luminaire manufacturers are learning how to better account for the lifetime behavior of the many components that are used when designing an LED fixture, including drivers, optics, mechanical fixings and housings. Each of these is a factor in determining the lifetime of a luminaire. The primary factors in the lifetime of a LED luminaire are the LED source selection and the durability of the power electronics.

An effective, long-lasting luminaire design combines the most advanced LED sources, driver technologies, optics and form into each product. Let’s examine a few of these components to really get a feel for what engineers need to consider in designing an LED luminaire. The entire luminaire must be built to last for the lifetime of the application.

In the Lighting Industry Liaison Group’s 2011 Guidelines for Specification of LED Lighting, the following criteria provide excellent considerations when determining what factors should be considered for the length of an LED luminaire.

LED Source Selection – When selecting LEDs, it’s important to consider the color, color temperature (if selecting white LEDs), the viewing angle and CRI.  But one of the most important factors is the application: what is the area to be illuminated – spot or area? Optics – diffuser, reflector, lens? Thermal density and heat removal? Size and lit appearance?  Also, does the manufacturer’s LM-80 test data support the lumen depreciation requirement?

Power Electronics’ Durability – The electronics affects almost every performance aspect of an LED design. High quality components – not using electrolytic components when possible and not running at maximum capacity or temperature– help to ensure the luminaire’s reliability and lifetime.

Optical Performance – LEDs are directional light sources, giving the lamp or luminaire designer new challenges when compared to existing lamp technology. The use of reflectors, lenses and diffusers, or a combination thereof, allows a designer to direct light in many different ways. The efficiency of the optical system must be considered and factored into the overall efficiency value of the lamp or luminaire.

PCB – A PCB is the electrical carrier as well as the interface between the LED and heat-sink that carries with it a thermal resistance value. The higher the resistance, the less efficient the system is at wicking away heat from the LED, this may well impact the LED lumen output performance and, ultimately, the life, lumen maintenance and/or catastrophic failure of the LED.

Finish – The paint finish/color may affect the heat dissipation from the luminaire, but more importantly, plays a significant role in the long-term integrity of the luminaire enclosure.  As the finish degrades, the base material of the enclosure may become susceptible to corrosion.  Different applications require different levels of corrosion protection.  Tunnel lighting, for instance, requires one of the highest levels of protection while indoor office lighting, the one of the lowest.

Mechanical – The mechanical integrity of a luminaire is important in several different areas, including: ingress protection ratings suited to the application,  gasketing that will not become compromised with time and/or lack of maintenance, chemical compatibility with all materials used within the luminaire, UV resistance of polymeric materials when used outdoors and vibration resistance.  While solid state lighting sources are inherently vibration resistant, that in itself is not enough to ensure the long term integrity of the remainder of the luminaire, in an application such as street lighting or parking structures, where constant vibration is commonplace.

Thermal Management – The performance of an LED is dependent on its temperature during operation. The design of the luminaire will influence its operating temperature. Heat management is a critical factor that affects LED luminaire performance and the LED lifetime.

Housing – LEDs allow new luminaire design freedom to lighting manufacturers and engineers. Innovative form factors not possible with incumbent lamp sources can be used both for styling and function.  Even though it should be infrequent, design consideration should be given to the maintenance of the LED light source and all power electronics, because even the most well-designed luminaire will eventually no longer meet its expectation of light production.

All LED Luminaires are Not Created Equal – While it’s easy to get caught up in the LED revolution, it’s critical to understand the application as well as manufacturers’ luminaires’ designs. Does screwing in a replacement LED bulb provide the same quality illumination as a well-engineered, from-the-ground-up fixture? As we head into one of the industry’s largest tradeshows, LightFair, take the time to consider the system components I’ve briefly addressed above; these provide metrics for the quality and lifetime of an LED luminaire.

Categories LED

To Ensure Accurate HBLED Testing, Start with the Fundamentals

Ensuring the performance and reliability of HBLEDs demands accurate testing at every phase of production. Many HBLED tests require sourcing a known current and measuring the resulting voltage or vice-versa, so instruments that combine and synchronize these functions, such as source measure unit (SMU) instruments, can speed system setup and enhance throughput. Testing can be done at the die level (both wafer and package), or the module/subassembly level. At the module/subassembly level, HBLEDs are connected in series and/or parallel; therefore, higher currents are typically involved, sometimes up to 50A or more, depending on the application. Some die-level testing can be in the range of 5 to 10 amps, depending on die size.

A forward voltage (VF) test verifies the device’s forward operating voltage. When a forward current is applied to the diode, it begins to conduct. During the initial low current source values, the voltage drop across the diode increases rapidly but levels off as drive currents increase. This region of relatively constant voltage is where the diode normally operates, so this test provides useful information. Results are often used in binning devices because an HBLED’s VF is related to its chromaticity (the quality of color characterized by its dominant or complementary wavelength and purity taken together).

Forward current biasing is also used for optical tests because current flow is closely related to the amount of light an HBLED emits. A photodiode and integrating sphere can be used to capture the emitted photons to measure optical power. This light is converted to a current that’s measured using an ammeter or one channel of an SMU instrument.

A negative bias current applied to an HBLED allows probing for its reverse breakdown voltage (VR). The test current should be set to a level where the measured voltage value no longer increases significantly when current is increased slightly. At higher voltages, large increases in reverse bias current produce insignificant changes in reverse voltage. The VR test is performed by sourcing a low-level reverse bias current for a specified time, then measuring the voltage drop across the HBLED. Results are typically in the tens to hundreds of volts.

In leakage current testing, moderate voltages are normally used to measure the current that leaks across an HBLED when a reverse voltage less than breakdown is applied (IL). In production testing, it’s common practice to ensure only that leakage doesn’t exceed a specified threshold.

Minimizing HBLED Testing Error
Junction self-heating is among the most significant error sources in HBLED production test. As the junction heats over time, the forward voltage drops and the leakage current increases, so it’s crucial to minimize test times. Smart SMU instruments can simplify configuring the device soak time (which allows any circuit capacitance to settle before the measurement begins), as well as the integration time (which defines how long the A-to-D converter acquires the input signal). Some of these instruments, such as the Keithley Model 2651A (Figure 1), have digitizing A-to-D converters, which can sample at speeds up to one million samples per second, which is up to 50 times faster than high-performance integrating A-to-D converters. These higher measurement speeds further improve overall test times.


Figure 1. Model 2651A High Power System SourceMeter instrument.

The use of pulsed measurements minimizes test times and junction self-heating. Modern SMUs with high pulse width resolution ensure precise control over how long power is applied to the device. Pulsed operation also allows these instruments to output current levels well beyond their DC capabilities.

Categories LED

Testing High Power LEDs? Watch Out for Inrush Current!

As an instrument applications engineer, I talk to a lot of design engineers who work with high power LEDs. All too often, they overlook the risk of inrush current, which they can apply inadvertently during testing. This post explains what happens, why it’s a problem, and how to prevent it. First, let’s review a few basics.


Figure 1. Typical I-V curve of a diode.

An LED is a two-terminal semiconductor device. A diode turns ‘on’ at a characteristic voltage (Vd) in the forward bias operating region when an avalanche of electrons and electron holes start to recombine. During this recombination process, one of the properties of an LED is the release of energy in the form of photons, which cause the LED to illuminate. The I-V characteristic of a diode in the forward bias region is depicted in Figure 1, where Vd is the on-voltage of the diode.

Although LEDs can be driven with either voltage or current, current is the preferred method because LED brightness is proportional to its drive current. As the I-V curve in Figure 1 indicates, a small change in voltage results in large variations in current, which will lead to drastic and undesirable variations in LED brightness. In addition, temperature and aging can cause Vd to drift over time. Again, this small voltage drift will likely cause unwanted current variations. Furthermore, driving LEDs with excessive amounts of current can result in irreversible damage and lead to much shorter device lifetimes. Therefore, regulating the drive current at appropriate levels in LEDs is critical.


Figure 2. Test system schematic.

Inrush current is a common phenomenon that overstresses LEDs. An LED can be modeled as a parallel R-C network; as a result, the device is instantaneously a short circuit when a voltage is applied across the device’s terminals. This instantaneous short circuit results in an inrush current, a short-duration startup current, that is of a much greater magnitude than the LED’s steady state operating current. For example, introducing an LED to an energized circuit or “hot switching” the LED may lead to an inrush currents of damaging magnitude. Figure 2 shows that when the switch is open, the voltage at the power supply is maintained at the rated voltage of the LED. As soon as the switch closes, the charge stored at the output of the power supply and the wires flows rapidly into the LED until the power supply starts to regulate. The transient current peak is shown by the blue line in the oscilloscope view in Figure 3(a).


Figure 3. LED turn on voltage (yellow) and current (blue) waveforms when powered by a power supply in the traditional constant voltage (CV) mode (Figure 3a) and the constant current (CC) mode (Figure 3b).

When testing LED designs, engineers typically use a benchtop power supply to drive power to the device precisely while they are taking measurements. Too often, engineers have the settings wrong or they use a power supply that isn’t fully controllable, and end up destroying their devices. But this doesn’t have to happen to you.

A growing trend in power supply design is the addition of a constant current (CC) mode beyond the traditional programmable constant voltage (CV) mode. When a supply operates in the CV mode (Figure 3a), the voltage is regulated while the current may vary. Unlike traditional powers supplies, this new breed of power supplies can be put in a constant current mode independent of the load value. This results in the behavior captured on the oscilloscope in Figure 3b. When the power supply is operating in the CC mode, the current is regulated and supplied to the load while the voltage output may vary. This mode eliminates the need for external controlling circuitry and simplifies the approach to “soft start” a LED. The power supply itself is capable of keeping the current input to the LED under control until the LED reaches the ON-voltage. Removing the possibility of transient inrush current protects the LED from related damage.

Categories LED

Innovative AC LED: Ready for Prime Time

There has been a lot of exciting talk about AC LEDs. The ability to bypass costly AC to DC LED drivers, reduce systems size and cost, all while still providing leading edge light quality is an attractive proposition for luminaire manufacturers, lighting designers and specifiers. In the past, however, there have been necessary sacrifices in order to reap these benefits. But, recent advances have made this technology a winning proposition. By using AC to directly drive the LED light source, the system will greatly simplify the application programs, making the system reach 90 percent efficiency. Let’s explore this.

The Technology
As you may know, in conventional LED lights a driver is required to provide a regulated constant voltage or current to the LED light engine. However, the converter circuit not only increases costs but also shortens the lifespan of the LED lights. In the report, Solid-State Lighting Product Quality Initiative, by the DOE and Next Generation Lighting Industry Alliance, drivers are responsible for a 52 percent failure rate of the luminaires tested.

However, AC LEDs can be connected directly to 120V or 230V line voltage and do not require a driver. The sinusoidal waveform circuit means that at each particular time half the LEDs are off while the other half is on, emitting light. This stage is reversed and repeated continually, producing a constant stream of light.[1]

With AC, power is transmitted and used much more efficiently. Basically, by putting LEDs directly on the end without having to include complex electronics to convert AC back into DC, the power is distributed efficiently and delivered more effectively without intervening electronics.

Eliminating the Driver
A LED driver is a power module to generate the voltage or current to driver LED module from AC mains. However, an AC LED doesn’t need to have LED driver. Let me explain. By eliminating the LED driver and operating the light source from direct mains voltages (120VAC/60Hz in the US and 240VAC/50Hz in the Eurozone) the system is more reliable, it offers greater design flexibility and the failure rate is lessened.

The thermal management requirements are slightly reduced as drivers are not efficient and generate excess system heat as a result.  An additional benefit of the removal of the external driver is space saving and weight.  A typical 20-watt LED driver takes up nine cubic inches of space and often requires an enclosure or junction box of some kind for agency approvals.

Additional Advantages

  • AC driven without converter or driver
  • Simplified circuit design
  • No conversion loss
  • Reduced costs
  • No lifespan reduction by secondary components
  • Dimming available
  • No power supply to clog thermal path

With the introduction of LED modules with a driver IC integrated for current control that is designed to be used in any 24V system and AC LED modules that allow LEDs to be driven from direct 120V AC without using any capacitors, coils or resistors, manufacturers don’t have to give up anything but cost and complexity.

Thermal Management
When designing with a direct AC input LED light source the design does not need to accommodate the driver but still must properly manage the thermal requirements and optical outputs. In many cases the existing luminaire will have adequate exposed surface area to the ambient to afford a much smaller heatsink or allow for the elimination of one altogether.  As a rule of thumb, four exposed square inches of surface area to ambient per watt is all a system needs to keep the operating temperature in the safe and optimal range.  This allows for lower profile fixtures such as wall sconces, four and six inch down lights, track light heads and pendant mount luminaires.

In a research paper, “Issues of Thermal Testing of AC LEDs,” the authors provide an excellent description of thermal management with AC LEDs. According to the paper, in the case of AC driven LEDs the sinusoidal AC mains voltage results in a periodic waveform of the actual heating power, after an initial transitional period while heating up the LED junctions. Once the shapes of the waveforms of the heating power and the junction temperature do not change any more we can say that the AC LED is in a stationary state. As our systems are nearly linear in the thermal domain the thermally stationary situation can be treated similarly.[2]

Dimming Challenges
An important element of AC LEDs is the dimming feature, which is compatible with phase-cut dimmers. A good dimming system should only lower the light output without sacrificing the color accuracy, unless that is the manufacturer’s desired result. A dimming rate of two percent is ideal, however it is not easily achieved, resulting in the CCT going from 4000K to 2000K. A more realistic dimming rate is five to 10 percent. However, while dimming performance varies significantly across many types of commercially available LED sources, less-than-ideal behavior shows up most frequently when integral LED replacement lamps are installed on circuits controlled by phase-cut dimmers.

It’s important to remember that dimming problems are not caused by any shortcomings of SSL technology. Rather, they’re due to the fact that almost all of the existing dimmers in this country were designed for traditional lighting fixtures. Nearly the entire installed base of traditional line-voltage (phase-cut) dimming controls was designed for incandescent light sources. There can be compatibility issues between these controls and an LED light source’s driver. That said, well-designed SSL products will work with existing dimming control systems without adding unwanted flickering.  Additionally, there are also many dimmers designed for specifically for LED products and are currently on the market.

Light Flickering
One of the main drawbacks of the AC LED is light flicker. Because it is directly driven by AC line voltage, which oscillates at 60Hz (or 50Hz), the AC LED produces light flicker at twice the frequency of the AC line frequency (e.g., 120Hz in North America). According to past research, even the perception of light flicker is undesirable in lighting applications.

Studies have linked flicker to health problems. So, even though flicker at these frequencies may not be visible to the naked eye, there is evidence that the human brain can detect light flicker frequencies as high as 200Hz. Potential problems include headaches, eye strain, impaired visual performance or, in extreme cases, epileptic seizure.

The ENERGY STAR requirement for lamps, due to go into effect Sept. 30, 2014, specifies that the highest percent flicker and highest flicker index be reported, but does not specify a maximum allowable limit for either.[3]

In a lighting system, a good solution should reduce light flicker without sacrificing power factor and power efficiency. But what is a good solution to this problem? One is to add components that will shorten the “off” time. Another is engineering a circuit board that uses a separate AC power and control signal. Unfortunately, it’s difficult to define the “safe” amount of flicker to the overall population because it’s perceived as a matter of human recognition.

Ready for Prime Time
There is no longer the need to sacrifice power factor, luminous efficiency, or light quality to gain the benefits of using AC LED lighting technology. These lights are a compelling platform for retrofit lamps, architectural and landscape lighting and other general lighting applications. This technology offers tremendous benefits over more traditional DC LED lights.

Categories LED

LEDs and Movie Stars

One of the many virtues of LEDs is that they have an exceedingly long life span. Perusing a few data sheets will show an oft-cited figure of 50,000 hours. Indeed, if installed in a domestic setting like a kitchen or lounge where the lights are mostly on after dark and used on average, say, 6 hours per night, this means the LEDs should last for 23 years. But what does “last” actually mean? At the end of life, tungsten bulbs simply cease to operate when the filament ruptures, so it is quite obvious when one has blown. Fluorescent bulbs tend to flicker and flash when the tube is no longer able to sustain conduction and replacement is then necessary due to the nuisance factor. LEDs on the other hand simply fade away.  They just get progressively dimmer, as though running on batteries that are very slowly running out.

There are various definitions of how dim an LED can become before it is considered to have reached end of life. For general lighting applications research has shown that most people will be oblivious to a reduction in illumination of up to 30 percent, particularly if it occurs gradually. For this reason the useful life of a high brightness LED is often defined as the point at which light output has declined to 70 percent of initial lumens. For an indicator LED on an instrument panel a 50 percent reduction might be acceptable, while in a scientific instrument it could be 5 percent or less.


By far the largest factor causing LEDs to dim is its time at temperature. High temperatures in LEDs cause a variety of undesirable processes to occur that are irreversible and reduce the ability of the device to produce light. This means that to achieve long life special attention must be paid to the materials used to conduct heat away from LEDs. A good slab of aluminium with a thin coating of Nanoceramic as the thermally conductive dielectric is a good choice, and the difference of just a few degrees can have an enormous, exponential knock-on impact on the lifetime of the LED.

A recent study by the Lighting Industry Association Laboratories showed that high brightness LEDs mounted on Nanotherm Nanoceramic PCBs operated 5 percent cooler than the nearest commercial competitor substrate. But don’t be tempted to think that just because 5 percent of 100°C is only 5°C that such a reduction is not worth bothering about, the underlying physics begs to differ. It turns out that the reduction in lumens of an LED is an above unity exponential function of the LED temperature. So a small difference in temperature makes a huge difference in the time it takes an LED to reach a particular level of dimness.

LEDs are quite like movie stars. They start as bright starlets and the hot ones burn out early, while those that stay cool have long careers and fade slowly from the limelight. As limelights in theaters have been replaced by LEDs, modern movie stars can now stay in the LED spotlights and wait for them to fade over 50 years instead!

Categories LED

LEDs Bring Big Savings to Retail Centers

Almost every industry, business and municipality has a parking lot that needs night-time illuminating. As energy costs continue to soar and strict energy mandates are enforced, municipalities and private property owners are looking for ways to cuts costs.

Fortunately, energy is a very controllable operating expense; by prudent, energy efficiency investments, operating costs can be reduced. One key to making day-to-day operations more energy efficient and more sustainable is through the installation of exterior LED luminaires.

Retail Centers – Retail stores, shopping malls and entertainment complexes are major energy consumers. Malls, “big box” mega-stores and retail outlets are not usually considered energy intensive on a square foot basis, but because of their large size and long hours of operation, they often run up extensive energy bills.

The parking lots for these facilities represent a challenging environment for lighting solutions. The lighting must accommodate vehicular and pedestrian traffic, endure harsh environments and address public safety considerations.


Image depicts TopDek in a typical retail parking application

Parking Lots and LED Luminaires – Going green is an initiative that nearly every industry is being forced to consider. The desire to incorporate new technologies to meet green initiatives and lessen costs is driving unprecedented change. Outdated light fixtures are being replaced with parking lot luminaires designed specifically for energy efficiency and sustainability. And while the upfront cost of LED luminaires is typically more than traditional lighting systems, it will be paid back to owners in lower electric bills, reduced maintenance and disposal fees.

Many parking lots are illuminated with high intensity discharge (HID) lighting sources. Because this type of lighting is not suitable to frequent switching, this lighting is typically operated the entire evening, even when the parking lot is mostly or completely empty. LED luminaires, however, are amenable to control systems such as motion sensors to further reduce electricity consumption.

The opportunity for savings is enormous, in part because LED luminaires have the potential to control the LED source emission more precisely than traditional HID luminaires, reducing waste light and limiting glare.

An innovative program, the Partners in Project Green in partnership with the University of Toronto’s Center for Landscape Research, offers companies (in the Pearson Eco-Business Zone) a Green Parking Lot Program. Specifically, it provides companies assistance in the (re)design of their parking lots and landscaping to include green features that can help them reduce costs, enhance safety and enrich the aesthetics of the facility, while improving local air and water quality. Installing LED luminaires is an excellent complement to this forward-thinking program.

Exterior lighting has three primary functions – safety, security and ambiance. With sustainability and design now complementing each other, LED luminaires for outdoor general lighting provide a win for everyone and retail properties retain their aesthetic integrity while saving on energy and maintenance.

Importance of Color Rendering and Distribution – Mall parking lot lighting represents a critical component for a business to achieve a high retail sales volume. Businesses must provide shoppers with safety and optimal visibility.
Color rendering should be considered as an important lighting performance element to showcase a business’ storefront displays, outdoor exhibits and landscaping features that create an aesthetically pleasing environment throughout the general grounds surrounding the mall itself.

Parking lots around malls experience a high volume of pedestrian traffic, and vehicular traffic tends to increase as closing time approaches. It is necessary for a business to provide appropriate lighting performance to insure a safe and comfortable environment is maintained.

Many cities have lighting mandates for parking lot illumination that identify a specific set of lighting performance metrics. Unfortunately, many businesses might not be aware if their parking lot lighting performance levels have fallen below minimum acceptable levels, which happen when lamps deteriorate over an extended period of time.

Distributing light and containing it within the property’s boundaries are essential components to remaining in compliance with regulatory codes pertaining to dark skies and energy efficiency.

The size and layout of the parking lot determine the specific lighting performance requirements. For example, if the parking lot is asymmetrical and located in a less safe part of town, the need for security may require a bright perimeter of light that is focused on the edges and corners of the lot while simultaneously contained within the property line.

Parking Lot Safety – Security professionals have long known that locations where people and their valuables are together, such as in parking lots, are criminals’ favorite targets. A key element of security in most surface lots is visibility – for employees, customers and passers-by; and a significant part of visibility is lighting.

According to Witherspoon Security Consulting, the exterior lighting should enable parkers and employees to see individuals at night at a distance of 75 feet or more and to identify a human face at about 30 feet. Employees who are working after-hours or visitors entering the building at night need to have efficient parking lot illumination fixtures so they can safely return to their vehicle.

Proper lighting creates better security and the perception of security, which can increase patronage of the parking facility, individual stores and the area in general.

Mindwave Research of Austin, Texas, conducted a survey, which showed that LEDs’ bright white light can help improve public feelings of safety in city spaces. After the addition of LED luminaires in a Raleigh, NC, municipal parking garage:

  • Both men and women felt significantly safer post-installation: 74 percent rated the garage as feeling “very safe,” while only 2 percent did not feel safe.
  • These figures contrast with the pre-installation numbers: Only 42 percent felt “very safe” with the original lighting, and 13 percent did not feel safe.

Opportunity – In the United States alone, it’s been determined there are more than 20 million parking lot lights, providing an excellent opportunity to retrofit with LED luminaires for increased security, reduced energy consumption and lowered maintenance costs.

Categories LED

High-Quality LED Luminaires Make Dramatic Improvement at Car Dealership

Car dealerships use a lot of illumination. While these lights serve a dual purpose of attracting potential customers and as a 24/7 security system, they devour energy, which is the third-highest overhead expenditure for dealerships, so reducing electricity consumption is a major consideration. By living and working sustainably, dealerships can reduce costs, increase their brand recognition, and attract more customers.

Including this extensive use of lighting, auto dealerships consume on average more energy per square foot than a typical office building: using about 110 kBTU/sq-ft compared to prime office space at 93 kBTU (source: National Automobile Dealers Association). This can mean thousands of dollars in energy costs for the typical dealership each year.

Chevrolet and Sustainability
Chevrolet’s dedication reaches further than compliance with the law to encompass the integration of sound environmental practices into business decisions. Guided by environmental principles, the company considers the environment throughout all aspects of their business, from supply chain, to manufacturing, to the vehicles on the road. These are the principles that help frame Chevrolet’s planning and decision-making for the company’s future.

Love Chevrolet | Columbia, South Carolina
Love Chevrolet is a family owned business that was established in 1961. Love Chevrolet is a member of the Love Automotive/RV Group that also represents Buick, GMC Truck, Mitsubishi, Hino Trucks and multiple RV brands.

As a customer-focused and forward-thinking business, Michael Love, president of Love Automotive/RV, is always looking for ways to reduce costs and increase operational efficiencies while promoting sound sustainability practices. To that end, Love Chevrolet recently completed a LED lighting upgrade.

In a one-for-one replacement, (148) 1,000W metal halide (MH) fixtures on the dealership’s primary and secondary sales lots, back lot and driveway were upgraded to 120W, 240W and 300W LED area light luminaires. Additionally, (100) 400W MH fixtures were upgraded to 120W high bay LED luminaires in the service check-in area and service bays, and (25) 400W MH fixtures were upgraded to 70W low bay LED luminaires in the detailing shop. Also retrofit were nine 250W MH fixtures to 60W LED wall packs and (18) 400W MH fixtures to 90W LED canopy lights in the primary sales lot.

This replacement is reducing the dealership’s electricity energy consumption by almost 50 percent. Prior to the LED installation, the monthly electric bill was $14,270, since the upgrade the monthly bill is averaging $7,000, while also increasing the foot candles – light on the ground, and the light uniformity increased.

The previously installed MH fixtures would regularly burn out. However, at the cost of $50 to $70 each light plus labor hours the dealership delayed repairing them until sections were poorly illuminated because they needed to rent a bucket truck to change lights. Unfortunately, as soon as a group of lights were repaired, other fixtures would burn out – the dealership never experienced all fixtures working at the same time. Also, as the lights aged, the quality of light decreased causing different color lighting in various areas. Now, the new LED luminaires are virtually maintenance free and come with a five year warranty.

“These lights make our inventory show better and stand out more from the street,” said Ben Hoover, general manager Love Chevrolet. “Additionally, we anticipate these new lights will last three times longer than the old fixtures and, the best part, eliminate maintenance and the need to move cars to accommodate the rented bucket trucks to change out the burned out lamps.”

The automobile dealership industry, like many businesses, typically only has one chance to make a positive impression with the customer, so it’s important to show products as best as possible. The luminaires’ uniform lighting eliminates dim areas between lamp poles, improving the automobiles’ vibrancy.

The new LED lights have also made a tremendous difference in the service drive and repair shop.  On the first day of installation, only one out of five rows of lights was able to be mounted. Yet those fixtures alone made a dramatic improvement and clearly showed the distinction between the two technologies. The LED luminaires provided brighter illumination without any shadows, which the technicians noticed it immediately.

“The upgraded luminaires deliver crisp, uniform illumination across the shop floor, detail bay and parts department,” said Mark Williamson, service and body shop director. “Additionally, the service technicians previously used fluorescent drop-light bulbs to see underneath the vehicle, these are now almost eliminated with the addition of the LED lights, which have improved technicians’ productivity, safety and morale.”

Customers also have noticed the difference in the service drive area, and have positively commented on this and inquired about the changes.

After seeing the product, learning about the energy savings and SCE&G EnergyWise incentives, and determining that the dealership would have only a two year ROI on the $250,000 total investment, it was an easy decision to retrofit. The LED luminaires provide consistent light levels, reduce hazardous waste disposal and provide dramatically more efficient light distribution than the MH fixtures.

“When we looked at the energy savings we’re getting, and that it’s really the right thing to do for the environment, it’s just a win-win for everybody,” Hoover explained.

”These lights absolutely provide the level of illumination we were looking for to make our location bright and secure,” Michael Love, president of Love Automotive/RV said. “And, as the guy paying the bills, I’m impressed with the tremendous energy savings and payback.  My only regret is that we didn’t do it sooner.”