A Quick Guide to LEDs
What is an LED?
LED stands for “light-emitting diode”.
Diodes are a type of semiconductor, which are materials which aren't quite as conductors (usually metals) but are more conductive than insulators (such as ceramics). Diodes essentially act as a one-way switch for current, meaning current can flow easily in one direction, but severely restricts flow in the opposite direction. As the name suggested, when current flows through an LED, it emits light.
The process is somewhat complex, and involves electrons in the semiconductor recombining with electron holes, releasing energy in the form of photons (which we see as light). The most important thing to note about the process is that it's highly efficient - LEDs produce more light and less heat than other lighting options.
How LEDs compare to incandescent and CFLs
Incandescent lighting was the most common way of generating light in the early days. Incandescent lights emit light as a result of being heated. This means that large amounts of energy are lost to heat, which makes incandescent lightbulbs inefficient, can cause them to get dangerously hot and leads to filament burnouts meaning the lights have to be replaced more regularly. About 95% of the energy is wasted as heat, with only 5% becoming light. In comparison, LEDs produce very little heat as a by-product, making them more efficient, safer and much longer-lasting.
CFL, or compact fluorescent light bulbs were another popular alternative incandescent lights to making lighting more efficient. CFL bulbs create light by passing a current through a gas-filled tube that's coated with phosphor. The gas particles excited and hit the coating, which converts the energy to light. Exciting the gas initially can take up to thirty-seconds to start, which is why it often takes a short while for fluorescent lights to light up.
While CFL bulbs are more efficient than incandescents, they can still lose up to 80% of their energy as heat. If you have incandescent lightbulbs and switch to CFL bulbs you can save around 30% of your energy usage, however, if you switch to LEDs, you could save closer to 75%. of your lighting energy usage.
LEDs last much longer.
How many people in your household does it take to change a lightbulb? With LEDs, you probably won't need to worry about the answer (for a while). LEDs have 25,000 (or more) hours of life. In comparison, incandescents only last around 1,200 hours, and CFLs perform slightly better at 8,000 hours, meaning that you'll have to replace your bulbs significantly less frequently.
All the colours of the rainbow
Common LED colours include amber, red, green, and blue. There is actually no such thing as a “white” LED. To get white light the kind we use for lighting our homes and offices, different colour LEDs are mixed or covered with a phosphor material that converts the colour of the light. The phosphor is the yellow material you can see on some LED products. Coloured LEDs are widely used as signal lights and indicator lights, like the power button on a computer.
LEDs are often the go-to solution for making your home or business lighting more energy efficient. We'll explore what makes them different from traditional lights, and how the benefits of LEDs extend beyond reducing your energy usage.
Lumen Depreciation - Useful Life
The useful life of LED lighting products is defined differently than that of other light sources, such as incandescent or CFL. This is because LEDs typically do not “burn out” or fail. Instead, they experience lumen depreciation, where the amount of light produced decreases and light colour appearance can shift over time. Instead of basing the useful life of an LED product on the time it takes for 50% of a large group of lamps to burn out (as is the case with traditional sources), LED product “lifetime” is set based on a prediction of when the light output decreases 30 percent.
LEDs and heat
While LEDs produce significantly less heat as a by-product compared to other bulb options, it's still important that the bulbs are correctly set-up to dissipate any heat they do produce.
LED lighting systems don’t radiate heat the way an incandescent or halogen light bulb does, meaning the heat produced from the power going into the product must be drawn away from the LEDs. This is usually done with a heat sink, which is a passive device that absorbs the heat produced and dissipates it into the surrounding environment. This keeps LEDs from overheating and burning out.
Thermal management is probably the single most important factor in the successful performance of an LED product over its lifetime because the higher the temperature at which the LEDs are operated, the more quickly the light will degrade, and the shorter the useful life will be.
LED products use a variety of unique heat sink designs and configurations to manage heat, so they may look very different from each other. Regardless of the heat sink design, all LED products that have earned the ENERGY STAR have been tested to ensure that they properly manage the heat so that the light output is properly maintained through the end of its rated life.
The lumen difference between tradition lights and LEDs
Traditional lamps (HID, Metal Halide, Mercury Vapour and fluorescent lamps) emit light in all directions, which means they require reflectors inside the luminaires to “bounce” as much light as possible away from the lamp and fixture components to the target area. However, not all light can be effectively redirected; typically, 40% or more of the light emitted from the lamp is trapped within the luminaire and does not reach the target area.
As a result, the stated lumen output of traditional globes tends to have a greater variation compared to the actual number of lumens coming out of the fittings. Most companies will supply a LOR (light output rating - this may have D or U in front of it for Downward or Upward light) for their fittings (expressed as a percentage), that will tell you what the minimum amount of lumen loss is. It is worth noting that this is done with new clean reflectors, and the actual amount of lumen loss will get higher as the fitting ages due to corrosion and dust reducing the efficiency of the reflectors.
LED lights deliver the majority their light in a reduced beam angle and usually do not require an external reflector for the light so they have a higher LOR.
This means that the amount of lumens shown is usually what the fitting will actually deliver. It's worth noting that there are some companies that promote “Chip LUMENS”; this means the number of lumens that the chips actually produces and does not take into account any losses due to clear covers etc. that may be put over the fitting to protect the LED chips (even clear glass will reduce light by 4% plus).