# FYI Saving energy using small lights?

Discussion in 'Electrical Forum discussion & Blog' started by Bill Arden, Dec 19, 2007.

1. ### Bill ArdenComputer Programmer

Joined:
Sep 30, 2006
Occupation:
computer programmer
Location:
MN, USA
Summary of Saving energy using walkway "guide" lights.

I've been trying to find ways to reduce the number of times I have to turn all my lights on in order to both reduce the failure rate of the CF bulbs and to conserve electricity.

Recently I installed four 4W T5 (under cabinet) lights to allow me to walk around without all of the main lights on.

Some figures

Power consumed by "guide lights"
4 * 4W * 24 hrs = .38 kWh (~\$1 per month)

Power used by main lights. (22 CF + two 4 foot T12)
(22 * 13W) + (2 * 40W) = 366 watts

Average power consumed by main lights during normal??? work day
366 watts * 8 hours = 3kWh (~\$9 per month)

Time needed to leave lights off per day for energy "break even".
384 watt hours / 366 watts = 1 hour.

I'm not sure how to calculate the bulb replacement costs since I have not kept accurate figures as to how often the lights are turned on and off. I just know that some days I turn on the lights in the CF section and forget them on till the next day!

I also have to find where the rest of the 870kWh per month is being used.

2. ### Bob NHIn the Trades

Joined:
Oct 20, 2005
Location:
New Hampshire

4. ### rdtompkiNew Member

Joined:
Dec 21, 2005
Location:
Iowa
I know there is a big push to CFLs which clearly are more efficient than incandescent light bulbs, but many of us have recessed lighting on dimmers which we are loath to replace with CFLs. Dimming is not all that efficient, but better than nothing as they say.

Won't be too long before we have affordable LED-based direct replacements. LEDs have surpassed CFLs in efficiency, will be dimmable and don't contain any mercury. Even if they are as expensive as the ridiculous Par16s and Par20s they'll be well worth it. Shouldn't ever have to replace these in most applications.

Of course LEDs make possible all sorts of different lighting configurations, but the big, short term market is in the direct replacement area.

BTW, I'm tired of staying in hotels where they have replaced the incandescents will very low wattage CFLs which give off absolutely no light

Rick

5. ### jimboPlumber

Joined:
Aug 31, 2004
Location:
San Diego, CA
Right on!! Before CFL's, a lot of hotels were fond of putting 25 watt bulbs in the reading lamps! I got in the habit of taking a 100 watt bulb with me when I traveled.

I believe you are also right on about the LED. I have seen some obscure reports that the US Energy Dept. is putting research money in the LED arena, with a goal of replacing all incandescent AND fluorescent by about 2025. These things get very political, as various factions get involved, but it is coming.

Here in San Diego, about 5 years ago they started replacing traffic signal bulbs with LED. Supposed to last 10years+. Turns out there is a problem with green. They are dropping like flies. The signal lamp is composed of many small segments, but if one individual LED dies, it takes out a larger segment with it. So you see a bulb that looks like a rat has beeb chewing on it! They say the present day technology is now better.

6. ### Bill ArdenComputer Programmer

Joined:
Sep 30, 2006
Occupation:
computer programmer
Location:
MN, USA
1. The building has no windows and therefore the Light sensor would be a waste of energy. I have looked into installing Sun tubes to add sunlight.

2. It does not specify the light output, but I am guessing that it would be too small to mount on the ceiling and light each isle.

-
In other news I had a really strange CF bulb failure.

A welding ball/spark landed on the base of the glass part and the ball caused a small hole in the glass.

-
Right now I am looking at all my power usage and the computers and equipment still uses the most power.

I did manage to reduce the power the one unit draws from 9 amps to 6 amps by reducing the line voltage to 90 volts AC. The suction blower fan runs in a blocked state and therefore does not need full power.

Last edited: Dec 19, 2007

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Oct 7, 2005
Location:
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8. ### MortNew Member

Joined:
Jan 10, 2007
Location:
CA
I figure the biggest draw in my house is the fridge (outside of the air conditioner) Replacing 90% of my bulbs with CF hasn't affected my electrical usage in any meaningful way that I can tell.......and I ain't givin' up a cold beer now and then just to save the planet

Mort

9. ### rdtompkiNew Member

Joined:
Dec 21, 2005
Location:
Iowa
LEDs

Flat panel televisions have been using CFL's. These are migrating to LEDs.

Notebook computers use CFL's. These are migrating to LEDs.

Even the short-lived arc lamps in projection television are being replaced by LEDs.

LED companies have been acquired by large lighting companies. Philips bought LumiLEDs. OSRAM bought someone (can't remember the name).

I think the biggest problem with LED "light bulbs" is the change in business model. What would a consumer pay for an efficient light bulb that lasted 20,000 hours? Worth ten bucks at least, but will we pay it? Which light bulb manufacturer wants to be the first? On the other hand you don't want to be stuck with a warehouse full of 20,000,000 or so obsolete light bulbs!

Ain't technology grand?

Rick

10. ### CassPlumber

Joined:
Nov 12, 2005
Location:
Ohio
Interestingly I did the math on LEDs and if you get 100,000 hours out of one and use it 10 hrs. a day it should last about 27 years.

I am skeptical about that. Seems like if they did it would put the bulb Mfgs. out of business.

Even if they lasted 1/2 that long it wouldn't be good for them.

11. ### jadnashuaRetired Defense Industry Engineer xxx

Joined:
Sep 2, 2004
Occupation:
Retired Systems engineer for defense industry.
Location:
New England
That's the conundrum...you build a product that lasts almost forever, and once everyone has one, you don't sell any more, so, what do you charge for them in the first place since the replacement market is so poor?

There was another technology being investigated...almost like a CFL, but the core caused nobel gases to glow, sort of like a neon lamp, rather than phosphors. Don't have a clue where that went.

BTW, researchers at Stanford came up with a way to extend the power of a lithium ion battery up to 10x by the use of nano-silicon wires. Think about it...a battery that lasted say a day in your cellphone now would last 10-days, or it could be 1/10th the size. Hope they figure out how to mass produce these soon...

Last edited: Dec 21, 2007
12. ### Bill ArdenComputer Programmer

Joined:
Sep 30, 2006
Occupation:
computer programmer
Location:
MN, USA
They could make LED's so that they fail.

I worked with a large company that had a large number(think millions) of units fail due to the (AlGaAs) LED's failing from a defect after about a year of use.

Interestingly the failure rate was based on time and not usage due to the way the defect would grow across the die.

I've also heard about how the really high power LED's have a faster burn out rate. At the high power levels they have the same problems that most other light types have in terms of "Thermal cycling" and "Oxygen corrosion".

I believe that the trade-offs will put the cheep LED's in the 10,000 hours range.

Edit:
The big improvement with LED's will be the ability to turn on and off the lights faster.

I wonder how well W-mart's T9 lights with motion sensors that in there frozen foods isle will last?

Last edited: Dec 22, 2007
13. ### alternetyLike an engineer

Joined:
Apr 2, 2006
Location:
Washington
There are indeed some LEDs that have exceeded the efficiency of CFLs. I am not sure they are in volume production or still being developed.

The difficulty with LEDs for general lighting is the dissipation of heat. Unlike most of the other technologies, the waste heat is almost a "point source", and needs effective cooling. When junction temperatures go up, lifetime goes down (or it melts). Put a bunch of 5W LEDs in a cluster to get usable room lighting and cooling gets tricky.

A CFL using 15 watts and yielding an incandescent equivalent of 60 watts is probably marked to not use it in ceiling cans. Look at the total area of the ceramic base (where the electronics live) and the bulb surface area. This is the area available to dissipate heat. Make this a multi die LED source and you have about 1 sq inch. And the point loads where the diode are actually mounted has quite a bit higher thermal density. The bulb has all that dissipation area and the LED has a square inch or so, before the addition of heatsink/dissapation mechanisms. Heat sinking adds to the cost of an LED and makes it more difficult to use existing light bulb form factors.

One thing that will help is the acceptance of new form factors for bulbs. But retrofitting the 7.6235 gazillion (yes that is an exact number and the result of massive research) existing sockets will slow overall installations.

There are some competing technologies (there is some sort of radio frequency excited bulb as I recollect), but solid state would seem to be the future. And it is advancing fairly rapidly.