While LED technology evolved from early experiments in electroluminescence in the early 1900’s, the first practical, visible-spectrum (red) LED was developed in 1962 by Nick Holonyak Jr., while working at GE in Schenectady. Still, it has taken 50 years for this product to work its way to the practical residential market and it still has a long way to go to achieve its full potential. The good news is that there are products on the market today that can save a lot of energy in residential lighting.
I attended Ulster Community Colleges’ evening class on LED Lighting Fundamentals last month. This class was excellent, covered a lot of ground in a short period of time, and was presented by two very experiences instructors: Jean-Claude Fouere (JCNETech@gmail.com) an electrical engineer with NE Technology Associates and Michael Stiller a lighting designer with Michael Stiller Design (www.michaelstiller.com). Well worth the price of admission! I’ll try to convey some of the main points I took away about this emerging technology.
First, LED lighting is different from incandescent and florescent lighting. It is more efficient, which I’ll get to in a minute, but it also emits light in a different manner. An incandescent light “heats” a filament and light is emitted 360 degrees around the filament. Florescent lights are similar in that they emit light in 360 degrees, except the process is to excite mercury vapor that causes phosphors to emit visible light.
An LED doesn’t heat or burn anything but rather passes current through a semiconductor’s p-n junction and when electrons “fall into holes” some photons of light are emitted. The efficacy (amount of light per watt - lumens) and the color of the emitted light depends on the semiconductor materials involved – different materials produce different colors with more or less light. But another result of the process is that light is emitted directionally or 180 degrees from a small flat semiconductor chip. This difference requires lighting fixtures to be redesigned to produce light in the manner we are accustomed to – pleasant and effective.
The desire to project light downward is being shown as an advantage with more lumens where you can use them, using the GeoBulb shown above (see Lighting Facts for this bulb below). Cost $25 at www.CCrane.com.
The second main take-away I took was that an LED lamp is a system made up of several components that must be integrated and must work well together to be effective: the LED chip and its driver to regulate current and voltage, a reflector, a lens, and a heat sink to dissipate as much heat as possible away from the LED chip. Plus, if you want dimming capabilities it is important to match the dimmer with the LED driver.
Heat is the enemy of both the LED and components in the driver, so heat must be managed. The main point here is to install according to manufacturer’s directions. For example, a lamp designed to operate in the open should not be put in a recessed fixture. While LEDs can last many times as long as incandescent and florescent bulbs, excess heat is the primary cause for light emission efficacy degradation over time and/or hard failures.
LEDs have far greater efficacy in generating light than incandescents. However, there are a lot of variables that go into the final light output and this can reduce their efficacy to about the same lumens per watts as tube fluorescents. Still other applications can be provide up to 85% energy savings over incandescents and approximately 50% over CFLs. Do not just assume that LEDs are much more efficient – check the numbers for your specific application.
There is no such thing as a “white” LED. White light is obtained by using multiple LEDs of different colors so the combined light appears white, or by using phosphor coatings that emit white light when excited by the appropriate blue or ultraviolet LED. Also, the “white” rendition can vary. The color white can range from a blue/cold to a warm/red. The color white is indicted by its temperature Kelvin (K), which runs between 2700 for warm to 4500 for cool white light. Another parameter often given for lighting is the Color Rendering Index (CRI) – this shows how well various colors are seen using the light. CRI ranges from 0 to 100, where 80+ is generally consider “good.” The CRI is not perfect for evaluating LEDs, so a new measure is being developed. Still, the best way to evaluate a light is to turn it on in the environment you want to use it and judge for yourself. This can be expensive with LEDs, unless you can borrow them to test or return those that are unsatisfactory.
Philips award wining bulb here uses yellow phosphor and an ultraviolet emitting LED to generate very pleasant white light (K-2700, CRI-92, Average Rated Life=30,000 hrs, 10 Watts, 940 Lumens, $60 at www.Bulbs.com).
LEDs are still seem expensive, but can look to be cost effective when you calculate total costs (initial purchase cost + operating cost) over the expected longer lifetime of the LED light. The more hours a day the lighting is used tips this calculation in LED’s favor. One of the keys to having this calculation prove correct is the actual life of the unit. As mentioned earlier, heat can reduce life expectancy. Also poor design and low quality manufacturing will impact LED light life. Buying LED lights from reputable manufacturers should translate into LED light expectancy that will be close to what is advertised. Time and independent testing agencies will provide insight into this very important factor.
There are many manufacturers getting into the LED lighting business today. One way to select quality players is to look for a DOE Lighting Facts label on the packaging: http://www.lightingfacts.com/ . Those manufacturers using it have committed to testing products and reporting performance results according to industry standards. Having this label is not an indication of a great unit – you still need to check the numbers for your application – but you can be pretty sure the numbers are accurate for your comparisons.
A final take-away, it was recommended when specifying LED lighting, especially on more complex installations, that you or your lighting designer consider the following:
- What are their thermal management capabilities?
- Can they be enclosed or recessed?
- What kind of driver is used?
- Are they “dimmable” and if so, how?
- Do they suit the fixture they are to be used with?
- What is the min and max number of lamps that can be used on a specific dimmer? Consider the inrush current.
- How will they work with transformers integral to the fixtures in which they are being installed?
- Must the whole unit be replaced or are there field replaceable components?
Because these units can represent quite an investment, I highly recommend that when you install a bulb or fixture mark its purchase date on the base and file all receipts and warranty details by date! Also, be sure to look at the warranty: while the packaging may say the unit has an expected life of 22 years, it is probably only warranted for 6 years.
It was a great class – a lot more details flew by but I think I covered the main points. There is a lot we need to learn to make the best use of new LED lighting. One of the best ways is to compare a few, buy one and try it out in different settings. Buy more where the light is used a lot and the units work well.
Note: Both instructors are available for consultation. You can reach Michael Stiller through his website www.michaelstiller.com and Jean-Claude Fouere can be reached via email at JCNETech@gmail.com. We are also looking for businesses that sell and install LED lighting in our area – if you are one or know one please let me know.
Dan Gibson is the Reporter and Chief Coordinator of Our Energy Independence Community (www.OEIC.us). Previously he was a participating contractor in NYSERDA’s Home Performance program and a rater in the New York ENERGY STAR Home program. He is currently building a 100% Solar Home. He can be reached at DanG@OEIC.us