In a quest to become even more energy efficient, I am looking at replacing the 20W halogens in our landscape lights with MR16 LEDs. While the LEDs are incredibly expensive compared with halogens, payback through energy savings should be achievable in several years. Searching the web I found relatively little information regarding how well these units actually work in real applications. So, I thought I would see if anyone here would have some comments.
I have several concerns. First, it appears that output and life are negatively impacted by temperature. Since these outdoor fixtures are pretty much sealed except for a drain hole, conduction cooling for the higher wattage LEDs will be a problem. That caused me to rule out several of the higher output units. The design of the fixture requires a wide-angle lamp. One of the best candidates so far is this one:
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I have also been looking at the kind that have 36 to 48 individual LEDs. However, the dispersion angle isn't as wide, and they don't seem to be as bright.
Does anyone here have any experience with these units?
No personally, but there are a number of threads on Usenet. Here's one:
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aka:
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No seems to think highly of their light output as in: "while normal MR16 light output graphs will show the lux or fc levels at 1m (3 feet) through
20m (60 feet) or that sort of scale, some of these are measured out to just
25 centimetres, less than a foot, in some cases."
Yes, I did my share of Googling. I read that one, and another that claimed the photons didn't have enough pressure behind them because of the low wattage, so they slowed down. OK...
These seem to be getting better all the time. I'm going to pick up several different samples to see how well they compare with the halogens for landscape lighting.
Yes - there was some levity in that thread. I assume that gentlemen was trying to explain the difference between nearly point sources of light like LEDs versus much larger sources. Photometry is more than a little confusing because there are so many ways to measure it: talbots, candelas, nits, lumens, foot-lamberts, foot-candles, etc.
Did you post in the lighting newsgroup? I looked but I didn't see anything so I crossposted this for you. (-:
That would have been my next suggestion. From what I am reading, they've got a ways to go but for landscaping their "short throw" might not be such a liability. In your 120F degree end of the world, I'd also want to do some serious testing, like what happens if a bulb ends up running accidentally when it's full summer daylight shining on them for 8 hours at well over
That's a good point. It would probably cause rapid deterioration, and it is something I will have to protect against. Since they are under X10 control, it is easy to have the Ocelot watch for a daytime ON, and just switch them back OFF after a few seconds - leaving them on just long enough for testing.
I've been using LED's in my landscape lighting for over a year now with great success. They are switched on via an ocelot and a secu16 with an external relay and 12Vdc power supply.
A good source for LED's is
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. I've bought from them quite a few times and their shipping, even from Hong Kong, is pretty quick and the quality is pretty good. Haven't seen any other site that can compare to what they offer.
I replaced the 7 Watt bulbs (35) in my Malibu lawn lights with the T10
194 LED Inverted Bulbs and light my shrubbery with 12V MR16 Wide with
24 led's also 12Vdc.
They really have a lot of LED's for many applications AC and DC.
I too have bought from besthongkong.com and have been very satisfied with their service. They have a huge selection. I bought several flexible strips of LEDs from them and made under cabinet lights for my kitchen counter.
Thanks for the recommendation. They do have a lot of options. That 4-watt unit that quotes 245 lumen output and 150 degree dispersion is especially interesting. (The data sheet gives the lumen output as 100 to 245.) The built-in heat protection addresses my concern about getting too hot on warm summer nights. But, the cost is hard to justify. Running 4 hours a night average would save about 23KWH per year for each bulb. Unless electric rates go way up, that is a long payback period.
LEDs are all less efficient than halogen lights (of the MR16 type). If you research them you will find that they all have fewer lumens per watt than any comparable halogen. They are getting close to parity nowadays but they still aren't there yet. Also be aware that some high- output LEDs like the Luxeon-V have a significantly reduced halflife of only 1000 hours. This is much worse than any halogen. When you add in the factor of the price premium for these more exotic lighting systems it doesn't make sense to use them in any application where a halogen will work. The newer Luxeon K2 is the first with a useable lifetime that is long enough to justify the higher cost. If you're still set on going with LEDs, the only option worth considering right now is a lamp with a K2 emitter. Don't buy any lamp that you don't know for certain what type of emitter is used in it. Otherwise, you can't look up its performance on a datasheet.
I think that a lot of the misconception that LEDs are more efficient comes from the fact that they don't put out any infrared light that can be felt when you put your hand in front of them. All of the high- output LEDs, however, require significant heat sinking and this is where they dump all of their waste heat to.
The DOE CALiPER program summary reports have some very interesting data in this regard. While I agree that many LED replacement lamps are not competition for MR16 halogens, there are some that are.
A table listed 8 lm/W for a 20W halogen, and gave a range up to 13 lm/W for a 60W incandescent. So, illumination efficiency increases as incandescent bulb wattage increases. Reading throughout the latest report, I saw LEDs range from 9 lm/W up to 59 lm/W. So, it would seem that it is certainly possible for LEDs to do much better than halogens.
I have received two samples so far. One is a 4W 120V version of a MR16 with
3 high-intensity LEDs. We now have that in a hallway fixture that did have a 25W incandescent. Color temperature is similar (warm white). While incredibly bright, the LED doesn't do quite as well as the incandescent in this wall sconce application because its beam must first bounce off the ceiling, providing indirect lighting. Most of the incandescent light came directly out the side of the sconce. However, for 4W, it certainly does an adequate job in that application. The only real downside is its lack of dimming. That wall sconce lights an otherwise very dark interior hallway. While on 24/7, we normally dim that bulb down to nightlight level at night. Even set to the Leviton minimum 1.6% preset dim level, the LED is still about half its normal intensity.
The other sample is a 12V 4W wide-angle 48-bulb MR16. I installed that in a landscape light. While the lighting level is adequate, it is clearly not as bright as the 20W halogen in that application. Its color doesn't do as good a job at bringing out the warm red tones in the crushed red rock we have in our yard. However, considering it uses only 1/5 the energy, I am impressed by how well it works.
The CALiPER reports do question the estimated life for LED bulbs. They reported a couple of early failures. And some of the bulbs only make it a small fraction of their projected lifetime. While it is clear to me that some LED bulbs can provide adequate illumination levels for much less energy consumption, the big question is whether their lifespan will be sufficient to actually provide the payback promised.
The final LED MR16 sample for the landscape lighting arrived. This is the
2.6W warm-white unit with 9 surface-mount LEDs that was linked at the very beginning of this thread. It outputs a smooth wide-angle beam, which is perfect for these lights. However, like the 48-LED unit, it doesn?t do a good job bringing out the warm red tones in the crushed rock. It is also not quite a bright as the 20W halogen. But for an energy savings of 87%, it does a very impressive job.
I've been looking at various colored LEDs for use on my motorcycle. There now are extremely bright LEDs available in a multitude of colors. Most of the "white" LEDs I've seen are actually a pale shade of blue. If you want to bring out the warm tones in the brick, try adding a supplemental string of rose or even red colored LEDs. If you use red, select a lower power. You don't need much. A few manufacturers offer strings with adjustable brightness and even variegated colors. The options are surely going to increase with time.
That is a good suggestion, but not really feasible for this application. These are standard 12VAC landscape lights that accept a single MR16 bulb. I did choose the "Warm White" versions (3000-3500K). While the light looks good indoors, it must have a narrow spectrum. The red crushed rock looks a grayish yellow. However, the rock wall itself does have its natural color.
For sheer brightness, I have been very impressed by the CREE units.
If they're not too hot (they shouldn't be), you might consider placing a glass filter over them. Gels work fine indoors but they fall apart after a rain.
I'm accustomed to using different light sources, mainly theatrical fixtures. I didn't realize that LED sources were narrow spectrum until after I posted. Thanks.
Better check with your local DMV or State Police first. Some states have some pretty serious restrictions on putting colored lights on vehicles, especially those that might lead other motorists to believe you were an emergency or police vehicle. Some prohibit any changes at all to original factory equipment.
Here's one example from the first hit I found (Delaware) on Google and I know of many other states with similar rules:
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Prohibited Equipment:
Limitation in Number of Lights - Not more than four lights of 300 candlepower or more on the front of a vehicle shall be lighted at one time. Headlights must be installed no higher than 54 inches nor less than 24 inches from the center of the lamp to the ground.
Red Lights Prohibited in Front - No ordinary motor vehicle can show a red light visible to the front of such vehicle. Such lights are permitted only on emergency vehicles.
Flashing Lights Prohibited - Flashing lights are generally prohibited except on: Emergency vehicles, school buses, snow removal equipment Any vehicle as a means of indicating right or left turns Any vehicle as a means of indicating a traffic hazard (four-way flashers)
License Plate Additions - Unauthorized frames, accessories, designs, or symbols on or attached to the license plate are prohibited.
Other Lights and Original Design Change - No light, lamp or reflector that tends to change the original design or performance of the vehicle may be installed.
I did. They (FL) don't allow blue lights anywhere on the vehicle although blue tinted headlights are ok. Red lights can only be visible from the rear. All other colors are ok. Flashing lights are allowed only to warn of a traffic hazard, but pulsating brake lights are ok. I've seen a number of bikes with pulsating headlights and police seem to ignore them but technically, they're illegal here.
Which states prohibit any changes at all to original factory equipment? The one you cited doesn't.
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