LED vs CFL - My grade school level heat experiment

[CobraKai]

After participating in a discussion over heat generated by led and cfl lighting, I decided to conduct an experiment. I brought an old pot from outside into my living room. This pot is full of various outdoor trash weeds/grasses. Bonus: fire ants! I then took a cardboard box, lined it in panda film and sealed edges and top with foil tape. A hole was cut into the top of the box for access to lights and thermometer. The box was then taped quite well to the top of the pot, then wrapped in panda film quite tightly. Pretty well sealed. Two stools were inverted and pinned against the box just in case.

Here are the lights. The cfl drew right at about 20w on my kill a watt, and the 2 cheapo leds drew a combined 24w...so as close as I was interested in getting.

After the cfl was inserted, I used foil tape to seal the top hole with a piece of foam board insulation.

The cfl was left in for exactly three hours. Ambient temp of my house was 78 degrees throughout this entire experiment. After three hours, the foam board was quickly removed and temperature observed at 90F.

Next up, the two leds. Same deal for three hours.

About two hours into the leds' turn in my little fun-fest, my lady came home. Beautiful lady, "What is that? This room is a wreck!" CobraKai, "This is SCIENCE!" Quite proud of myself. Beautiful lady, "Get your science out of my living room." CobraKai, "OK, but please just another hour." The nice lady shook her head and science ruled the living room for another hour.

After the three hours was up, the foam board was quickly removed and temperature observed was 90F. Exact same temperature. Maybe not surprising to some, but I was very surprised. Ya, the leds were drawing 4w more. But this was the closest line-up that I had laying around. I was quite confident that the temperature was going to be lower with the leds. Of course, this wasn't a perfect experiment or a laboratory environment. But I think that this box was sealed up pretty well and had me shaking my head until a fire ant bit me on the foot.

So what does this prove? I have entirely too much free time on my hands and a cool ol' lady.

 

[b.real]

nice experiment. how the hell did 20 watts get so hot? I run 90s with 175+ watts. just busting your balls, but really though

 

[CobraKai]

I really did a good job sealing this sucker up! Maybe very small environment + no air in or out caused such high temps.

 

[CoNerd]

Excellent work. Quick and dirty experiments are very valuable.

The efficiency of FL and LED's producing PAR photons are actually pretty close. It's only been in the last few years that LEDs are more efficient at producing light than florescent lighting. Plants can use light across the visible spectrum, so the differences in absorption from the spectrum are pretty small relative to the total energy being expended in the system. In the end, you were trying to see a difference of a few percent when your input varied by 20%.

My own test bed is my small grow tent. I find the heat loss from evaporation to be significant. I'm drying buds above the lights and the tent runs about 5 deg F cooler when I vent on excess humidity. It's not easy keeping a real system at the desired temperature.

 

[Cruizer]

The Cfl's ballast is what gets so hot.

 

[b.real]

yup small space and sealed insulated good. well done.

the ballast probably adds a few watts but def less then the bulb itself. hid lighting is similar to fluorescent lighting.

 

[Dennise]

Great job and proud of ya b.... ya held your own.......

 

[b.real]

thanks D. I only knew this to be true cause I tested it myself. I don't just go spreading information without knowing it for sure anymore.

gotta thank cobrakai too for running a good experiment

 

[Icemud]

Love the experiment CobraKai!

I can't believe I just found this now.... definitely rep for doing this.

I know I have talked about this before on the forums, how equal wattage draw will equal same heat load to a sealed environment, and you just confirmed exactly what I read from my research Thank you for doing this.... big rep!!!! and sorry I missed this and I'm late to the party

 

[CobraKai]

Thanks Icemud, it was a fun little DIY experiment. I went into it thinking that because the LED was more efficient at producing light vs. waste heat that the plant would absorb enough of the light energy and use it that the temperature would be noticeably lower.

But with a head-to-head comparison with this small amount of wattage, that extra 4w being produced by the led constitutes an additional 20% watts with no shown temperature increase. While I was very surprised that the LED had an equal temperature, now that I'm looking at it again a few months later that extra 4w seems a little more significant than it did at first glance.

Reading through all of this really makes me want to improve on it and test 100w vs 100w after 12 hours of being sealed up with live vegetation. I've got plenty of led wattage, but will have to buy a few cfl bulbs. In a few weeks one of my leds will be out of bloom and I'll give it a go.

 

[Icemud]

Thanks Icemud, it was a fun little DIY experiment. I went into it thinking that because the LED was more efficient at producing light vs. waste heat that the plant would absorb enough of the light energy and use it that the temperature would be noticeably lower.

But with a head-to-head comparison with this small amount of wattage, that extra 4w being produced by the led constitutes an additional 20% watts with no shown temperature increase. While I was very surprised that the LED had an equal temperature, now that I'm looking at it again a few months later that extra 4w seems a little more significant than it did at first glance.

Reading through all of this really makes me want to improve on it and test 100w vs 100w after 12 hours of being sealed up with live vegetation. I've got plenty of led wattage, but will have to buy a few cfl bulbs. In a few weeks one of my leds will be out of bloom and I'll give it a go.

Yea man, it made me happy to see you take the time to do this experiment... awesome work Cobrakai!!