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Author Topic: More retail businesses using CMH than LED  (Read 12900 times)

Offline Anders Hoveland

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More retail businesses using CMH than LED
« on: December 19, 2014, 10:53:25 pm »
I have begun to notice ceramic metal halide (CMH) spotlight fixtures appearing more and more in numerous different stores.
 (Just to be sure it is CMH, I hold up a compact disc to the light to see the characteristic spectral lines)

 There was a clothing store, mostly lit by fluorescents but had a few 3000K CMH spotlights, some shining on merchandise, others over the display counter. There was an upscale supermarket. Most of the aisles were lit by fluorescents, but there were CMH built into the ceiling over all the interesting stuff, and surrounding the perimeter aisles with all the fresh things. I think these must have been 3500K. The market also had a much smaller number of little LED spotlamps (high CRI), obviously replacement for halogen, shining over a bread display and at the meat counter. Lastly I saw a floral gift shop and picture frame store had lighting tracks with CMH, but there were a few high CRI LED floods mixed in on these tracks. The CMH and LED were both screwed into fixtures, and were difficult physically to tell apart. I found this interesting because CMH requires much higher voltage power supply than retrofit LED. Perhaps the CMH bulbs were self-ballasted, not sure, not sure how they did it. But the two looked like the same type of lighting.

 I have also seen CMH as the main lighting for a jewelry store and fine suit store.

 Now, with commercially available LED technology making so many advances, I am wondering why these stores are using CMH. Ceramic metal halide really only became commercially available in the 1990's, a relative late-comer, though available earlier than LED lighting. CMH is not cheap. The bulbs themselves are fairly expensive, but the real expense is the high voltage power supply. Though they use the same size base, one cannot just screw in CMH into a regular socket, it will not work. Retrofit LED floods are now available cheaper than a CMH flood, though of course we are not talking high CRI here.

 As for CRI, ceramic metal halide tends to have higher CRI at higher correlated color temperatures. To get the warmer color temperatures, they add sodium salts into the mix, giving a characteristic yellow-orange line prominent in the spectrum. This takes away from CRI a little. 4000K is available with 95CRI, but if one gets 3000K the CRI goes down to 85. Ceramic metal halide is basically a high pressure version of metal halide, a similar comparison can be made between sodium vapor lamps and high pressure sodium lamps. They are more expensive because the inner bulb must be made of fused alumina to withstand the more intense heat. The spectrum from CMH does contain violet light that activates optical brighteners in white clothing. This might be one possible reason stores could prefer CMH over LED (though I doubt it). Philips has developed "CrispWhite" LED technology which basically just adds a 430nm emitter to address this issue for retail.

 Now there are unique differences in the spectrum between high CRI LED and CMH, it is not the same quality of light, regardless of given CRI values (CMH generally has better coverage in the cyan and blue part of the spectrum than LED, though normal high CRI LED has better coverage in the warm colors). In terms of exact color rendering and subjective feeling of the light, there are subtle differences, pros and cons to each. But I doubt most businesses buying lighting are taking any of these finer details into consideration.
 The traditional wisdom in the lighting world was that LED was too expensive if one needed large amounts of light from each fixture, but today this is no longer true. High power LED lighting fixtures are available and the price has greatly fallen. Perhaps for sporting illumination where huge amounts of light are required, but I cannot see any indoor application where reasonably priced LEDs could not provide enough light. It is possible CMH could also be used in place of halogen, where high quality of light is desired, but where there is an attempt at energy savings. However, this is not what I have observed. None of these businesses which have recently installed CMH had halogen in those places before.

 So back to why stores are choosing CMH. I have seen a few stores convert to mostly LED. But not many. There are more stores that have converted a substantial amount of their lighting to CMH than stores that have converted a substantial amount over to LED. I have to think that higher power high CRI LED products have just not become as prevalent in the market place, and that is why CMH is more popular, because it has had more time to establish itself in the market place.

There are many stores using some LED fixtures now, but virtually no stores using mostly LED. I just meant to say that when it comes to generating 30+% of the general lighting in the entire store with something other than fluorescent, more businesses are using CMH. So if we counted it all up by the wattage or lumens, the thesis of my thread is basically that the average store uses CMH more than LED.

 I know some of the responders to this thread are going to claim how much superior LED is over CMH, but could there possibly be some potential advantages of CMH that current LED lighting products in the market place are not providing? CMH is definitely not cheap. If anything, it is more expensive than LED. So why are all these businesses converting to CMH instead of LED ?

 What are your opinions about this? Why are businesses going with CMH ?

The higher end retail stores are using a combination of CMH and halogen spot, the less high end stores are using a combination of fluorescent and medium-sized LED floods.

 Just what I've noticed, when a retail store uses a large LED fixture, it usually seems to be about 90-92 CRI.
 Sure the smaller LED spot lamps may be 95 CRI, but these only provide a small fraction of the overall store lighting. I have to think that the reason retail stores are not using 95 CRI more frequently has to do with efficiency and price.

 The typical design used to achieve 95 CRI (simply modifying the phosphor composition) makes the LED significantly less efficient (about 30%). This effectively makes CMH more efficient than LED for a comparable quality of light. Not a big consideration for those little spotlights, but it is for the big fixtures lighting up the whole area.

 And for some reason, all the 95 CRI LEDs on the market are substantially more expensive. I suspect it's not inherently that much more expensive to manufacture a 95 CRI LED, since it's just a variation in the type of phosphor used. Rather I suspect these big companies are simply charging a hefty premium for what is perceived to be more of a luxury product. In economic terminology, a perfectly discriminating monopolist, where the seller can target products to different buyers, and charge the different buyers based on their ability and willingness to pay. Huge automotive companies do it all the time. That sports car they make does not cost them that much more to make, but they jack up the price, knowing that someone wanting to buy a sports car probably has more money he is willing to spend.

 It seems in the lighting industry, there is still a view that CMH ranks ahead of LED when it comes to excellent quality of light, while high CRI LED is only for very small scale accessory lighting.
« Last Edit: December 19, 2014, 10:58:59 pm by Anders Hoveland »