Fact or Fiction:
Setting the Stage
Energy Savings
Luminous Efficacy
The Scotopic Reality Shining Light on Scotopic
Screw-In LEDs Replace Bulbs
Solar Energy - Free and Friendly
NEMA and Functional Standards
IES Standards
Long Life
LEDs and CRI
Candela or Lumens?
Meeting the Standards
Checking out a Company
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Table of Contents
Setting the Stage Here we discuss a few hopeful ideas or rumors, and some of the reality to support or dispel them. Two of the most popular myths are shown in this opening section. If you are new to LED technology, see "About LEDs" for a basic overview.
As you read here, keep in mind that LED justification and ROI (return on investment) are different between indoor and outdoor lighting.
When you have prices and specifications for LED products with comparable and adequate lighting capability, use this Payback Calculator to determine if it's right for your application.
The LED manufacturer rates lumen output at a specific junction temperature, typically 25°C, and some luminaire marketing will use that lumen figure to promote a new LED light. Few LEDs perform in the real world as they did in laboratory tests. LED marketing has become clever; the Department of Energy (DOE) states that about one-third of the products they test have accurate manufacturer specifications. Not surprisingly, they report that about one-third vastly overstate performance by as much as 100%. Consequently we require LM-79 and LM-80 testing to validate claims on the end product. Back to Top ~~~
Energy Savings
"LED Lighting means huge energy savings"
That seems like a practical statement since LED traffic signals saved over 80 percent when they came on the scene. But beware. LED traffic signals saved energy because the signals are monochromatic (single color). The extra color spectrum generated in incandescent bulbs was absorbed in a filter (colored lens) and LEDs naturally emit only a single color so there's no extra light generated to throw away. http://www.nrel.gov/docs/fy04osti/35551.pdf The issue of saving energy with LEDs comes down to producing only what the task requires, AND using all the light that is produced. Competing technologies may produce higher lumens, but it's not easy getting all that light where it's needed, and usually any extra light is just masked. A typical bulb type luminaire may be only 60% effective, or in other words, a lot of the light it produces doesn't go to the intended target (it becomes light pollution or it can't get out of the luminaire). And, the higher efficacy HID bulbs require a ballast to start the arc and regulate the gas ionization. The ballast may consume more than 20% of the electrical energy going into the luminaire. That's 0.6 × 0.8 = 0.48 or Metal Halide = 80 lumens/watt × 0.48 = 38 delivered lumens per watt. In contrast, the LED luminaire may be 90% effective with a power supply that's 90% efficient. That's 0.9 × 0.9 = 0.81 or LEDs = 70 actual lumens/watt × 0.81 = 57 delivered lumens per watt. Metal Halide is shown because of comparable color temperature. The LED will not easily pay for itself with energy savings alone when equal illumination is required. Use a Payback Calculator to be sure. High lumens are not always required for certain tasks, just because older luminaires were so inefficient. Where have all those lumens been going, and at what cost to the consumer? Is this deceptive? You bet it is. This I call the "Lumen Legacy." See this breakdown on Sodium Lighting effectiveness. Back to Top ~~~
HID Efficacy Table
LED chip manufacturers are boasting of 100+ lumens per watt (at 25°C TJ of course).
*Neutral is now used by LED manufacturers for a range between warm white and cool white. Outside the laboratory, in the real world, LEDs rarely deliver over 70 lumens per watt. The barrier to keep an eye on in the LED illumination business is not the efficiency, it's the LED's high cost per lumen. HID bulbs can jump in increments of ten thousand lumens for mere dollars, whereas LEDs cannot. Back to Top ~~~
The Scotopic Reality Several LED luminaire suppliers are trying to use a Scotopic Advantage when promoting less footcandles to do an equivalent lighting job. There will be lots more to come on this subject, so check back for updates. In the meantime, here is a LRLL white paper that shines some light on the OUTDOOR Scotopic issue. Beware the pitch for indoor lighting that promotes LEDs to replace Metal Halide and Fluorescent for factory assembly work areas, claiming less footcandles are acceptable due to that Scotopic Advantage This couldn't be more misleading since detailed assembly work requires good full spectrum coverage AND at least 30-50 footcandles. This Scotopic Advantage is possible only when new lighting at least improves spectral content. Standard white LEDs usually offer no spectral advantage when replacing fluorescent or Metal Halide without some red enhancement. Visual work requiring direct focus and high color rendition relies upon the cones, Foveal Vision, which allows NO Scotopic Advantage. Scotopic vision is a matter relating to outdoor lighting, but even some of those applications don't fit these claims. See these Outdoor Lighting tables and you decide. Another case of buyer beware, and a potential black eye for LED sales people. See Scotopic Spin Back to Top ~~~ Screw-In LEDs Replace Bulbs Now A 20-Year Light Bulb
Entrepreneurs may need to re-write a few laws of thermodynamics when showing screw-in LED light bulb replacements. These inventions need more thought to live up to claims. Will the consumer settle for less light because it's a novel gadget? Reducing their lighting requirements will itself save energy, but is that what they intended? This leaves the market open for a rude awakening - buyer beware? LEDs produce more light per watt than an incandescent bulb. But most of the watts they consume is still converted to heat, and if not dissipated, will drastically shorten their life. Heat doesn't radiate from an LED, so it must be conducted away, usually into an exchanger to free flowing air. The LED junction must operate below about 85°C. A light bulb is fundamentally a heater that just happens to send out a little visible light. Yes, a heater, and the socket it's screwed into is designed to protect the base and wiring from all that heat. In other words, the socket is a very poor thermal path for cooling that screw-in LED light bulb. Something must cool the LED, and cooling will not happen through the socket. Each watt of LED power needs about 6 square inches of surface area in free air for cooling. That 3" post-it-note on your desk is 9 square inches. Roll it up, fold it & shape it to get an idea of the size neded to convection-cool about 1.5 watts. If the LED has twice the efficacy of incandescent, then lumen for lumen, a 60-watt light bulb replacement must dissipate 30-watts of heat. That's about 180 square inches of surface metal attached to that screw-in LED device. To get the lumens and keep the life, you gotta cool that thing. Of course an alternative is forced air with a fan. Back to Top ~~~ On the surface that statement is partially true. We don't get a monthly bill for using the Sun's energy, and the process of converting the Sun to electricity produces no harmful side effects. However, lighting is needed at night when the Sun is not around, so our night lighting is powered by energy stored during the day in batteries. Batteries contain materials that aren't land-fill friendly, and they must be replaced every few years, so costs are quite high. Photo-voltaic cells are the key to harnessing the Sun's rays, and those cells are not cheap. The solar panels may cost 2 or 3 times that of the light they power, and the amortization may be 30 or more years. Solar powered nighttime lighting can be justified only when there is no electrical service, or, when complete independence from the utility company is essential. Solar power isn't likely to win if the competing power source is hydroelectric. Back to Top ~~~ Luminaires are no longer a simple bulb and ballast Technology has come into the equation, and with that comes many ways to measure performance and even ROI. Electronic controls are now involved that can inform the owner of pending failure or lumen depreciation, they can allow remote control of your luminaire. Can you imagine a communications protocol between streetlights and your central office? It's here. Now you need interchangeability, and NEMA can drive manufacturer functional compatibility. Spreadsheet generated Photometric files are here too. NEMA can draft appropriate performance Standards, and possibly find ways to police deceptive practices. We used to expect the Photometric file came from an independent lab, but until there are NEMA Type numbers for Luminaires, you should insist on Certified Independent IES Files and Test Lab Report before committing poles and luminaires. We can hope that NEMA will raise Manufacturer Standards and Ethics. Leave your comments here. Back to Top ~~~ "Meets IES Standards"
Claims like this will make skeptics of us all. A particular IESNA (Illuminating Engineering Society of North America) "Standard" must be identified by number, e.g. RP-1, RP-8, RP-20, etc. IES LM-63-95 is the IESNA Standard File Format for Electronic Transfer of Photometric Data. This is a photometric file; a tabular format representing typically a 180° x 360° plot of candela measurement. An LM-63 photometric file along with layout software, can determine the quantity, location and spacing for luminaires to provide lighting levels and uniformity based on your selection. Your luminaire manufacturer must provide this photometric file for the luminaire. Type Classification The IES roadway classification system is based on the position of a half-maximum candela line plot. Any luminaire, indoor or outdoor, can be classified regardless of style, technology or lumen output. Click here to see the real IESNA Outdoor Lighting Requirements Back to Top ~~~
LEDs have a reputation for long life, but they are also easily abused. Light Emitting Diodes are more fragile than some designers are aware, but electrical or thermal deficiencies in their fixture design will not often cause a sudden failure. Too much current or too much heat, for example, could result in a 50,000 hour part lasting only 10,000 hours. High quality, high output monochromatic LEDs can provide 70% of their original lumen output at 100,000 hours IF they are not abused. Note that Monochromatic is stipulated because the Phosphor in PC (Phosphor Converted) white LEDs can degrade faster than the LED junction. This can be caused from thermal overload, excessive ultra-violet exposure or moisture. Most manufacturers have overcome these problems, now the integrator must adhere to good science. See the previous section here Screw-In LEDs Replace Bulbs.   As an example, I have tested this Journée Lotus product, and found the heat sink section to exceed 65°C with a room ambient of only 24°C.
A rise this high will surely limit the LED life to far less than the manufacturer's claim of 40,000 hours. The phosphor output shifts through several colors while the assembly is stabilizing, which is a good sign the phosphor is not very happy. But as an office or desk lamp, if you don't leave it on all night, how many years is 10,000 hours, really?
So you need to be careful not to burn yourself, because it will leave a welt. Time will tell.
Back to Top ~~~
Back to Top ~~~ Which measurement shall I use: Candela or Lumens?
Beware the conversions that simply multiply candela by 12.57; they don't account for angle. This simplified calculation works only with a candle, it does NOT work with a lensed LED. Be very cautious of such information on a site with a shopping cart, e.g. http://www.theledlight.com
~~~ Meeting the Standards The user community, contractors, agencies and municipalities, have established lighting criteria so they can maintain a quality of illuminance through time. Specifying a lighting fixture by lumens is merely requiring a power consumption and not a lighting criteria. Indoors: Dimensions of an area illuminated does define minimum delivered lumens, but lightmeters measure footcandles or lux. Calculate the minumum delivered lumens required: (square ft. × footcandles) + 10% NOTE - this is an approximation that will depend on fixture placement, mounting height and angles, and when estimating, add at least 10%. It may help you get into the ball park. Outdoors: Properly managed LEDs in a suitable luminaire have been field-measured as placing 3-times more footcandles on the ground per watt than other technologies, partly because they can be directed where most suitable, and partly because they produce light only where needed. Be careful of the Lumen Legacy. Select fixtures based on application footcandles or lux rather than lumens. Now we have LEED certification to ensure Green. Back to top ~~~ Checking out a Company The popularity of LED Lighting brings a lot of wannabe experts to the scene. Even with poorly designed products lacking quality control in production, LED products may survive the warranty period and never give the R.O.I. you paid for. Your LED product should be built to at least ISO 9001:2008 certification. Also see ISO-9000 Defined Is the manufacturer listed as an Energy Star Partner? Begin with a Google or Yahoo Search. Type in the company name or product (within quotes if more than one word) followed with keywords, e.g. failure, fault, recall, etc. Next search financial records and duration in business, then see if their state of filing records are up to date. Today, it's a red flag if LED Lighting companies haven't shown reasonable growth (at least 25%) within the first two years. There are several sites on the Internet that make this research an instant reality. Manta is a free business record service, you register to use. Hoovers a free trial D&B Business Search Service Free Public Records Finder Experian Business Reports for a fee Next, check their status in the State where they filed for incorporation. You can search for any state with SOS (Secretary of State) Business Entity Search. Here are a few links for example. Alabama, Arkansas, California, Florida, Georgia, Illinois,
Kansas, Minnesota,
When you find the company, hope to see "Active" rather than "Default" or especially "Revoked" or even "Permanently Revoked".
Missouri, Nevada, New Jersey, New York, Ohio, Oklahoma, Oregon, Tennessee, Virginia (Note that some companies file in Nevada regardless of residence.) Back to Top ~~~
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