On Thu, 30 May 2019 12:51:20 -0700 (PDT), Tim R
wrote:
On Thursday, May 30, 2019 at 1:36:48 PM UTC-4, Jeff Liebermann wrote:
Maybe. LED's are certainly more efficient.
Lumens/watt
LED 100
CFL 60
Incandescent 16
For equal amounts of light output (lumens), a CFL lamp takes 1.7 times
as much power to produce that light as does an LED. That's a big
I doubt that's true. Flash power, the first 3 seconds of operation
for an LED, might be 100 lumens per watt, but I think 60 is more realistic.
That's correct, if you include:
1. Losses through any lenses or reflectors.
2. Losses in the switching power supply.
3. Losses in any power factor correction circuitry.
4. AC power is power factor corrected.
Easy enough to measure. I have enough junk from my flashlight
tinkering to measure lumens, but not with any great accuracy. Here's
how I do it with flashlights, bicycle headlights, spot lights, and any
light that generates a round spot on a wall.
https://groups.google.com/forum/#!original/rec.bicycles.tech/UJdJQFTDgl8/NgOZUloVCwAJ
I found new LED "flood" light in my collection.
https://www.feit.com/products/bulbs/flood-and-spot/led_lampsreflectorr_ledsrr_and_brbr30-927-led-can/
750 lumens 12.5w
Notice that there's plastic diffuser in front of the LEDs.
Plugging it into my Kill-A-Watt watt-guesser, I measu
12watts 15VA 0.78PF (power factor)
which seems about right.
Luminous Efficacy = 750lumens / 12watts = 63 lumens/watt
So, you're correct if I include all the losses.
However, the numbers I provided were for the raw LED at room
temperature and does NOT include all the losses.
Might as well grind the numbers for CFL.
I found one of these in my collection:
http://www.greenliteusa.com/en/lights/1684-26w-t2-ultra-mini-spiral.html
1700 lumens 26 watts
Measuring with the Kill-a-Watt meter:
26watts 37VA 0.70PF
Luminous Efficacy = 1700lumens / 26watts = 65 lum/w
Hmmm... looks like the LED (with the diffuser) is almost as bad as
CFL. I suspect the diffuser loss is what's causing the lower efficacy
for the LED, but I don't have LED bulb handy to prove it. I'll see if
I can find or borrow one, at least with a glass lens, not plastic.
According to this chart:
https://en.wikipedia.org/wiki/Luminous_efficacy#Lighting_efficiency
the LED floodlight should have been about 100 lum/W.
Surface area makes a difference for both radiation and convection, but
the temperature difference is what really drives the heat transfer.
The plastic globe area of an LED equivalent lamp runs much hotter than
the curlicues of a CFL. (I haven't measured, but that's what my
fingers tell me when changing both while hot.) (and that's probably
because an LED doesn't have vacuum inside the globe, it has air
that's in contact with the emitters)
Temperature (C or F) is not the same as heat (calories) which is not
the same power (watts) which is not the same as energy (joules or
watts/second). Also, there are several different types of
efficiencies and efficacy:
"Energy Efficiency of White LEDs" (2009)
https://www.fcgov.com/utilities/img/site_specific/uploads/led-efficiency.pdf
https://en.wikipedia.org/wiki/Luminous_efficacy#Lighting_efficiency
Overall luminous Overall luminous
efficacy lum/W efficiency
LED screw base lamp (120 V) Up to 102 Up to 14.9%
9- 32 W compact fluorescent 46 - 75 8 - 11.45%
(with ballast)
Kinda looks like the LED produces about twice the light output of the
CFL, for the same amount of input power. However, my measurements say
they're about the same.
I don't think the majority of the heat dissipation from a CFL is from the curlicues. But if even a portion is, then the orientation will make no difference. Air will flow through them base up or down about the same.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558