Light Bulbs

[RobbieB]

It's not a lot of energy (a lot of watts but very little time) so not too important.

The important thing is they have these new tiny LEDs that will go where those small appliance bulbs go and provide better light. It really is brighter in the fridge now and easier to see stuff. Adding less heat to the cooled space in just gravy.

 

[meierlde]

Note that newer fridges (even fairly low end side by sides now have led lights installed from day one. At least with Whirlpool.

 

[AllDone]

Oh, and as for my electric bill? Well, this is the first project I've done on the house that materially and significantly reduced my electric usage. More than my new fridge. More than my new A/C unit. As a libertarian leaning voter, I have to admit, that the government regulation provided the kick in the pants to the manufacturers to move this LED project along.

One of my first arguments on this forum was with someone who insisted that I couldn't have reduced my electric bill that much by changing to LED bulbs. We actually pay a small monthly penalty to the electric company because we don't use the minimum amount of power. That pisses my husband off in a big way, but I refuse to put an old refrigerator in the garage just to burn off some more electricity. We're on the waiting list for the new Tesla, anyway.

 

[RobbieB]

Amazing.

Filament bulbs operate at 5% efficiency compared to ~50% for LED. An order of magnitude.

Summer even more with AC working heat load, winter, not so much.

I prefer making light for less and using gas for heat. You guys remember the "easy bake oven"? Yup, used a light bulb to bake a cake.

 

[NW-Bound]

I saw that the theoretical limit of a white LED is about 44% efficiency. This corresponds to 300 lumens/W, as 100% efficiency is 683 lumens/W.

Current light bulbs still fall short. The 100W-equivalent Costco bulbs I bought were 1,600 lumens for 17W. That's only 94 lumens/W, or 2/3rd of the theoretical LED.

That means the bulbs can still get a lot brighter for the same wattage.

 

[RobbieB]

Oh yeah, I've been buying them for a while now and there is a big difference in light and color and dispersion and size and cost and...

Gotta love hi-tech, it keeps getting better and cheaper all the time -

 

[NW-Bound]

Improvement in electronics is amazing.

Now, how about an LED that puts out more optical power than it consumes in electrical power? Higher than 100% efficiency!

When I read this, I asked "what kind of BS is this?" Is it the same as a perpetual motion machine?

Well, it turned out that this LED additional optical output comes from its own thermal energy, in addition to the supplied electrical energy. The LED cools itself down!

Son of a gun! So, we can have light, and solid-state cooling at the same time? Hallelujah!

Well, they have been able to demonstrate it with a tiny device. It takes in 30 picowatts of electrical power, and puts out 69 picowatts of light. A picowatt is one trillionth of a watt.

Oh well, everything starts out small before it can become useful.

 

[ERD50]

Amazing.

Filament bulbs operate at 5% efficiency compared to ~50% for LED. An order of magnitude. ...

Amazing yes, but not that amazing.

An 800 lumen filament bulb is 60W, ( ~ 13 L/W)
An 800 lumen LED bulb is 13W, (~ 61L/W)
~ 1/5th the power for the same light.

Some more searching shows that the 683 lumen/watt reference that NW-Bound posted is for a monochromatic light source. We don't use those for lighting, you want something closer to white light. Seems like a white light 100% efficiency number is ~ 250 lumens/watt.

That would make filaments ~ 5.2% efficient, and LEDs ~ 24.4% efficient.

http://physics.ucsd.edu/~tmurphy/papers/lumens-per-watt.pdf

But since LEDs are monochromatic by nature (they generally use phosphor to convert UV to white-er light), they are super efficient where you want red or green or yellow (red + green). So they are great for brake lights, turn signals and traffic lights (except they don't produce enough heat to melt ice & snow!).

-ERD50

 

[NW-Bound]

OK. I missed that part about the 683 lumens/W being at the wavelength of 555 nm. What happens is that lumen is a measure of brightness as perceived by the human eye, which is most sensitive to green light. Lumen is not a measure of radiated power.

The 250 lumens/W limit for white light is low, because back in 2014 Cree already claimed a number of 300 lumens/W, for an LED which was quite white at 5150K color temperature.

See: http://www.cree.com/News-and-Events/Cree-News/Press-Releases/2014/March/300LPW-LED-barrier.

 

[NW-Bound]

Speaking of progress on LEDs, here's something I recently discovered.

I needed an LED to use as a power indicator in an electronic project. I have had some LEDs in my part bins for a long time (>30 years), so reached in to grab them. One after another came up dead, or very dimmed. Out of a couple of dozens, I got about 3 or 4 usable. So, I ordered some on eBay, paying $1 for 100.

When they arrived, I was shocked as to how good the new ones were. Used to be that you had to put about 10mA through one to get decent brightness. These 1c LEDs are usable with 1 or 2mA. Son of a gun!

 

[ERD50]

OK. I missed that part about the 683 lumens/W being at the wavelength of 555 nm. What happens is that lumen is a measure of brightness as perceived by the human eye, which is most sensitive to green light. Lumen is not a measure of radiated power.

The 250 lumens/W limit for white light is low, because back in 2014 Cree already claimed a number of 300 lumens/W, for an LED which was quite white at 5150K color temperature.

See: Cree News: Cree First to Break 300 Lumens-Per-Watt Barrier.

Yes, I'm not sure exactly how to parse all those different terms. I think I read that a filament bulb could be considered to be near 100% efficient in converting electricity to electromagnetic radiation. But much of that is not visible to humans, and is not generally considered 'light'.

I guess you can say all light is electromagnetic radiation, but not all electromagnetic radiation is light.


-ERD50

 

[RobbieB]

I have heard that it converts 5% to visible light and 95% to heat (infrared)

Which is usually not a problem in the winter, but a double problem in the summer with the AC on.

And even in the winter, my gas furnace is 95% efficient. I believe in making heat with stuff that was designed to make heat and light with stuff that is designed to make light.

 

[NW-Bound]

For the inquiring minds that just have to know, the caption of the graph below reads:

"Based on the human eye's perception, equal powers of green 532nm light is 20 times brighter than blue 445nm light, 8 times brighter than red 650nm light, and 190 times brighter than purple 405nm light".

So, for the frugal minded, one should use green LEDs for lighting. It will not make your dinner look very good, but for reading, it should be OK. No?

 

[RobbieB]

By all means, frugal people should use green LED's and nothing else.

 

[CDRE]

Thus, green LEDs = green money!

 

[mathjak107]

not all led lamps can be used in enclosed fixtures. led's radiate quite a bit of heat despite the fact the glass feels cool .

they will over heat in enclosed fixtures unless specifically not marked not for use in enclosed fixtures .

 

[NW-Bound]

True. LEDs run a lot cooler than incandescent bulbs, but without ventilation the rise in temperature may be too high still for their internal electronics.

 

[CRLLS]

Since we are entering the Xmas lighting season, I think this is appropriate......

DW loves the old C9 string of colored C9 bulbs around our rear deck railing. They are big and colorful and consume a lot of energy. Saturday we were in a Big Box Store and they had the LED equivalent of C9 Xmas lights on sale for 6.99(@25 bulbs per string), So we bought 6 boxes. Running thru some rough calculations, the cost of a new string of LED bulbs now costs less than the cost to run out old C9 bulbs for just one Xmas season! Cost of new LED's = $6.99. The cost of running a string of the old lights for the entire Xmas season worked out @ $8.50 per string. The cost of LED's (@2.4Watts per string) is 10 cents per string. I only hope that we will like the new LED lighting effect.

Now, if I can only find a similar low cost deal on the LED version to replace our incandescent icicle lights on about 175 ft of fencing!

 

[JoeWras]

Speaking of progress on LEDs, here's something I recently discovered.

I needed an LED to use as a power indicator in an electronic project. I have had some LEDs in my part bins for a long time (>30 years), so reached in to grab them. One after another came up dead, or very dimmed. Out of a couple of dozens, I got about 3 or 4 usable. So, I ordered some on eBay, paying $1 for 100.

When they arrived, I was shocked as to how good the new ones were. Used to be that you had to put about 10mA through one to get decent brightness. These 1c LEDs are usable with 1 or 2mA. Son of a gun!

It has been a while since my physical electronics class, and even then, I hated the subject so I'm no expert! Is there some physical effect of some semis? Metal or phosphor migration and some such?

That said, the new LEDs are just better. I recently got a flashlight that has one LED element. The flashlight is powered by 3 AA batteries. If you look at the flashlight from a close distance, it will leave an imprint. The packaging even has a warning. Holy cow, this thing is BRIGHT.

 

[Amethyst]

LED flashlights are wonderful.

LED Christmas lights, on the other hand, are chilly and garish. I miss the old warm lights, and so does the cat (the incandescent lights make a tree into a warm haven to sleep under).

 

[ERD50]

Since we are entering the Xmas lighting season, I think this is appropriate......

DW loves the old C9 string of colored C9 bulbs around our rear deck railing. They are big and colorful and consume a lot of energy. Saturday we were in a Big Box Store and they had the LED equivalent of C9 Xmas lights on sale for 6.99(@25 bulbs per string), So we bought 6 boxes. Running thru some rough calculations, the cost of a new string of LED bulbs now costs less than the cost to run out old C9 bulbs for just one Xmas season! Cost of new LED's = $6.99. The cost of running a string of the old lights for the entire Xmas season worked out @ $8.50 per string. The cost of LED's (@2.4Watts per string) is 10 cents per string. I only hope that we will like the new LED lighting effect.

Now, if I can only find a similar low cost deal on the LED version to replace our incandescent icicle lights on about 175 ft of fencing!

Yes, the old incandescent big bulb C9 style ( ~ 7W each, 20 ~ 175W for a 25 light string)) consume much more than the LED equivs, I checked your numbers and they seem about right @ ~ $0.11 kWh.

Not so much of a difference with the old mini filament lights, but I've been very happy with mine in terms of durability. Every year I struggled with the old mini-lights, trying to find a bad bulb in the string that didn't 'bypass' properly when it burnt out, and throwing many of them out over the years. And replacing the burnt out ones that did 'bypass', as that puts higher power into the remaining bulbs on the string, shortening their lives.

So far, not a single failure on any of our many strings of LEDs.

-ERD50

 

[NW-Bound]

It has been a while since my physical electronics class, and even then, I hated the subject so I'm no expert! Is there some physical effect of some semis? Metal or phosphor migration and some such?

That said, the new LEDs are just better. I recently got a flashlight that has one LED element. The flashlight is powered by 3 AA batteries. If you look at the flashlight from a close distance, it will leave an imprint. The packaging even has a warning. Holy cow, this thing is BRIGHT.

Electromigration does cause solid-state devices to degrade with time, and the effect is accelerated with temperature. At room temperature, they should last decades. These LEDs that I had sitting in the part bins degraded terribly, compared to the other old devices I have like diodes and transistors that show no effect. Not a solid-state guy, so I do not know if or why LEDs should be more susceptible.

About brightness, yes, the new LED flashlights are incredibly bright.

When the 300 lumen/W LEDs that Cree claims to have built hit the market, we are talking about a bulb as bright as the old 100W bulb (1500 lumens), while consuming about the same power as a night light (5W).

 

[JoeWras]

Some new "warm" Xmas LED sets have hit the market this year.

They are pretty good. About 90% there. Enough for me to give them a shot.

 

[Sunset]

Since we are entering the Xmas lighting season, I think this is appropriate......

DW loves the old C9 string of colored C9 bulbs around our rear deck railing. They are big and colorful and consume a lot of energy. Saturday we were in a Big Box Store and they had the LED equivalent of C9 Xmas lights on sale for 6.99(@25 bulbs per string), So we bought 6 boxes. Running thru some rough calculations, the cost of a new string of LED bulbs now costs less than the cost to run out old C9 bulbs for just one Xmas season! Cost of new LED's = $6.99. The cost of running a string of the old lights for the entire Xmas season worked out @ $8.50 per string. The cost of LED's (@2.4Watts per string) is 10 cents per string. I only hope that we will like the new LED lighting effect.

Now, if I can only find a similar low cost deal on the LED version to replace our incandescent icicle lights on about 175 ft of fencing!

We used LED's outside last year on a timer as usual, our electric bill was $10 cheaper than the year before, pretty big effect considering it was replacing just 2 strings of light.

This year we are going to replace the lights on the tree with LED's.

 

[NW-Bound]

You will save even more by using only green LEDs for Xmas.