Wal-Mart saves $2.6M with LEDs over fluorescents

The massive US-based retail chain will install LED lights in 500 stores, saving $2.6 million annually in energy costs.

Wal-Mart Stores is to deploy LED lighting from GELcore in low- and medium-temperature refrigerated display cases in over 500 U.S. stores. The retailer expects that energy cost savings of a 500-store retrofit -- one of the top energy-saving initiatives that it will pursue in 2007 -- will exceed $2.6 million annually.

Of note:
"In stores where the new GE LED products will be put to work, Wal-Mart expects to net up to 66 percent energy savings, compared with incumbent fluorescent technology."

And

"The combined environmental impact of a 500-store installation represents an annual 35-million pound reduction of carbon dioxide emissions. It also equals the good that comes from planting over 4,464 acres of trees or removing over 3,143 cars from the road for every year the LED lighting operates in place of fluorescent lighting."

http://ledsmagazine.com/articles/news/3/11/16?alert=1


Related stuff:

-Folks prefer LED lighting:
"The lighting within the display case was much more uniform with the LED lighting system compared to the traditional fluorescent system. The results from the human subject experiment show that subjects strongly preferred the display case with the LED lighting. Considering the luminous efficacy of white LEDs presently available in the marketplace, it is possible to develop a LED based lighting system for commercial refrigerators that is competitive with fluorescent lighting system in terms of energy use. The LED based lighting would provide better lighting than traditional fluorescent lighting"
http://www.lrc.rpi.edu/programs/solidstate/completedProjects.asp?ID=52

See page 44 for the scores:
http://www.efficiencyvermont.com/pages/BBBD2006/docs/Leslie-Lighting Matters_ Results.pdf

From GelCore:
"Primary benefits of GE's RoHS-compliant, UL-approved LED Refrigerated Display Lighting solution include:
• Improved product visibility with reduced light-source glare on products and floors
• Hidden light source provides better access to products for stockers and consumers
• More robust and better for the environment than fluorescent lamps because it doesn't contain glass or mercury and it doesn't produce UV or infrared light
• Up to 78 percent energy savings compared with VHO fluorescent lamps in a 5-door fixture
• Over two times the life of fluorescent lamps in a cold environment reduces maintenance costs and hassles (50,000 vs. 18,000 hours)
GE's LED Refrigerated Display Lighting solution also saves watts by lessening the load on the compressor. For every light watt reduced in a frozen food case, the compressor works less hard, saving ~ 0.45 watts. On a 5-door case, the additional energy savings from a reduced load on the compressor, can reach 70 watts vs. T8 fluorescent; 134 watts vs. HO fluorescent; and 330 watts vs. VHO fluorescent."
http://www.gelcore.com/literature/GELcore_WalMart_refrig_announcement_DE_FINAL_111406.pdf


The product that is utilized:
http://www.gelcore.com/product.php?id=51


And on top of it all, the LEDs they are using don't have very high efficiencies!

1280 lumens/41 Watts = 31.22 lm/W
http://www.gelcore.com/literature/RefrigSpecSheetWEB7_7_06.pdf

Also to consider with fluorescent lamps, most don't realize the large losses in fluorescent fixtures, plus the additional losses in the ballast, that cause the usable lm/W to drop quite significantly, from what everyone runs around touting. Additionally, in this case, the cool environment also comes into play, which benefits LEDs. But with fluorescent lamps it requires extra power input into the fluorescent bulbs to keep them warm, which also loads down the refrigerator cooling system, for even more losses.
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Neat And that is just refrigerated cases! Imagine if they did the whole store.

Wow, that sounds very interesting. Thanks for sharing.

Hopefully the 'standard light bulb" type leds will come down in price soon. If I could get them at the right price my whole house would be using them.

Interesting post BTW.

Very cool!

I wonder if they can mount the LED's on heat sinks that carry the heat to the outside air instead of dumping it inside the fridge where the compressor has to get rid of it.

paulr said:

I wonder if they can mount the LED's on heat sinks that carry the heat to the outside air instead of dumping it inside the fridge where the compressor has to get rid of it.

Click to expand...

Might be tough in the refrigerator case retro-fit market, but you might have a real winner there for new cases. Imagine, heated door handles... But then again, you get into building cooling requirements if you do that. Might help in the winter though.

Makes sense since fluorescents don't like the cold.

havand said:

Neat And that is just refrigerated cases! Imagine if they did the whole store.

Click to expand...

It is great to see companies like Wal-Mart using high tech to reduce energy consumption. I wonder if we will see anyone else adopt similar approaches.

NewBie said:

Might be tough in the refrigerator case retro-fit market, but you might have a real winner there for new cases. Imagine, heated door handles... But then again, you get into building cooling requirements if you do that. Might help in the winter though.

Click to expand...

I think the building cooling is likely more efficient than the fridge, because the temperature gradient between the inside and outside of the building is smaller than the gradient between the inside and outside of the fridge, except maybe in extremely hot weather. Of course they should turn off the fridge lights at night when the store is closed.

As far as building lights, they already have very efficient electronic ballasted T8 sized tubes, about the best you can do for high lighting like that. They also dim them when it's sunny outside since they have lots of skylights to provide natural light when it's available.

So on a sunny day they only run the tubes at half brightness or less anyway then in the evening turn them up.

So I doubt with the current generation of LED's that there would be any significant savings with doing the actual store lighting with LED's of any kind. But that will change in another few years as teh LED's get better and better!

So we've found another niche for LED lighting products where they outperform their gas and glass counterparts! Thats terrific!

light_emitting_dude said:

Hopefully the 'standard light bulb" type leds will come down in price soon. If I could get them at the right price my whole house would be using them.

Interesting post BTW.

Click to expand...

I completly agree on both points.

NewBie said:

Might be tough in the refrigerator case retro-fit market, but you might have a real winner there for new cases. Imagine, heated door handles... But then again, you get into building cooling requirements if you do that. Might help in the winter though.

Click to expand...

Seems to me I would only have to evacuate the heat from the building instead of have the compressor evacuate the heat from the fridge first... I really like the idea of heat piping the therms to the handle, of course making sure they dont cross into a startlingly warm state.

James S said:

As far as building lights, they already have very efficient electronic ballasted T8 sized tubes, about the best you can do for high lighting like that. They also dim them when it's sunny outside since they have lots of skylights to provide natural light when it's available.

So on a sunny day they only run the tubes at half brightness or less anyway then in the evening turn them up.

Click to expand...

In my local store, I've noticed that they turn most of them completely off during the middle of the day. The skylights provide virtually all of the area lighting - and it works just as well as artificial lighting.

James S said:

As far as building lights, they already have very efficient electronic ballasted T8 sized tubes, about the best you can do for high lighting like that.

Click to expand...

Thats great, until you realize that you loose 10% in the electronic ballast, and another 20-45% of losses in the fixture itself (and the fixtures are definitely not all created equal).

So, you end up with a 30-55% lm/W loss, right off the top. Then the tubes age, and you loose even more.

Sorry, but they don't even get close to 80 lm/W once they are fixtured.


Take one of the super duper high efficiency lamps from GE (usually they are very hard for consumers to obtain unless you go to the right places):
28 Watts
48"
P/N F28T8/SP30/UMX/ECO
life 24000 (with 12 hours ontime minimum, shorter with less on time)
Initial lumens 2750
Mean Lumens 2585
Color temp 3000K
CRI 85

Take the mean lumens of 2585 and divide it by 28 Watts:
92.32 lm/W

10% efficiency loss for the electronic ballast so multiply by 0.9:
83.09 lm/W

Use a very high end fixture (rarely seen) and get an additional lumen loss of 20%, so multiply by 0.8:
66.47 lm/W

Or take a average fixture with 35% losses, so multiply by 0.65:
54.01 lm/W


Funny how things get so hyped up and folks only consider initial lumen peak efficiency, no ballast losses, and no fixture losses. Together, the impact can be very significant.


Doing the same for the special 8':
8' T8 XL EXTRA-LIFE WATT-MISER® PLUS ENERGY SAVING LAMPS
54 Watt
P/N F96T8/XL/SP30/WMP
Life 29000 (with minimum 12 hour on time)
Life 24000 (with minimum 3 hour on time)
Initial Lumens 5800
Mean Lumens 5450
Color temp 3000K
CRI 84

5450 lumens / 54 Watts:
100.93 lm/W

10% Ballast losses:
90.83 lm/W

20% high end fixutre losses:
72.67 lm/W

35% average fixture losses:
59.04 lm/W


Total system losses can be astounding, once you look into them...

Just noticed our walmart got rid of all the mercury vapor (I'm guessing thats what they were) globes, and went to TONS of rows of florescent lights. This is a large supercenter, one of the first ones built.

man... if walmart used Cree XR-E LEDs you might be able to add another 1M to the savings? ...

thanks newbie for your post on flourscent tube eff's... I bought a 2xT8 fixture that has a curved reflector and it claims 20% more lumen output vs. standard fixtured... it seems a lot better than horriable cheap fixtures... so you are correct that not all fixtures are made the same ... it was only $10 more than a typical fixture too!

http://images.lightinguniverse.com/img/l/225/147995_family.jpg

NewBie said:

Funny how things get so hyped up and folks only consider initial lumen peak efficiency, no ballast losses, and no fixture losses. Together, the impact can be very significant.

Click to expand...

Same goes for LEds. Even worse for LEDs I would say.

LEDs might be more efficient in refrigerated cases than fluo tubes, but I doubt they currently would in general lighting usage...
A good save would be to remove 30% of tubes, stores are generally over illiminated IMHO. Also, another 20% could be won with better lighting paths (reflectors, fixture, building architecture, ceiling and wall colors, etc) and maintenance (cleaning).

First: WOW! I'm very impressed by Wallmart's decision. I've always thought that LEDs would be home in a fridge.

Second: Newbie, what are fixture losses and how are the high end ones better than the low end ones?

Thanks.

Basically, the ultra high end fixtures will have a rather expensive paint that is 94% reflective, or a miro protected silver metal- both of which are rather rare, but can be found if one digs hard enough.

For the good quality ones, you'll see them using 85-90% reflective paints, or one of the lower reflectivity metals.

I've unfortunately purchased lower cost fixtures (~30 dollars) that measure 70% reflectivity for the paint.

So, why does this matter? Well, just like in a flashlight reflector, a portion of the light hits the reflector for it's first bounce. In this case, you'll typically see 60% of the fluorescent bulb light output hitting the reflector first. There is your first loss factor.

This is much like the 65% reflector losses number that has shown to be rather accurate with our incandescent bulbs in our flashlights.

The next factor is the diffuser that is placed over the bulbs. Here, you will often see a 70% diffuser, which causes an additional 30% of your loss, right off the top. Then there is a good amount of that light that is kicked back at the fixture coating, which causes additional losses once it hits the paint, and then it takes more losses going back thru the diffuser. There are special diffusers, that have lower losses, but as you reduce the losses, they get expensive pretty quick.

Another technique that has lower losses, is a mirror metal grid.

Then there are the ballast losses. A normal ballast can easily have 20-30% losses. Some of the higher end versions of the electronic ballasts only have 10% loss, and I believe I have seen one brand that only had 7% loss.