Lighting How to calculate BTU's, Watts do not automatically = heat!!!

[Archaic]

As an actual scientist using BTU at all in this discussion makes my eye twitch. The BTU is a measure of heat, specifically the amount of heat required to elevate one pound of water by one degree Kelvin. It's metric analog is the calorie.

Traditionally, the BTU has been used to measure the potential heat output of a fuel, i.e. coal or natural gas. Unless we are using our LEDs to generate steam and drive a turbine, the BTU output isn't really telling us much.

Similarly, watts are a measure of work similar to horsepower. My plants are not trying to move coal up a conveyor belt and they are probably going to be a lot more interested in your lights PPFD than it's horsepower or caloric output.

Edit: don't get me wrong, watts matter and I do want to know how many watts a light consumes, but electricity does not grow plants, photons do.

 

[Black Sail]

Ok... one bowl of hash down.... so....

So it was a good point, but it was wrong because the watt went to photon and the photon went to heat... correct ?

And as an aside.... I had always thought flat white absorbed less than reflective white... Is that incorrect ?

Bowl II break.....

Yup, only a small percentage of the photons get converted into heat. A lot of the ones that hit your leaves get converted into weed:smoking:

Great question on the paint thing, honestly I've never looked into it. I'll try to find out, if you could reflect an extra 1-2% just by getting the right type of paint that would be worth knowing!

 

[Black Sail]

There's a mountain of false information about LED's that has worked it's way into "common knowledge" and it has real consequences in people's lives. I've talked to too many people who have been conned out of $1500 because they didn't have the information they needed to tell a good LED from a bad one.

There's this weird rumor going around in the cannabis growing community that the energy used to create light comes from nowhere, and that it doesn't reduce the amount of energy going to create heat (at a fixed wattage). This would violate the first law of thermodynamics! It's outrageous, and I spent a lot of time making my post a really clear explanation of why.

It's not just a theoretical argument either! This is the type of confusion that helps LED manufacturers get away with cutting corners on heat management and efficiency! How can people accurately compare lights when they can't agree on goddam Isaac Newton? Every single day our fellow growers are losing hard-earned dollars to this mess.

I put my money where my mouth is every day too. I'm selling a 240 Watt COB that gets 2.0umol/J, has a heatsink temperature of 120F at full power, a MeanWell Driver, and costs $1.45/Watt. ($349). I encourage you to do the math on that, especially dollars per watt.

I'm going to keep addressing falsehoods wherever I see them, nobody will ever stop me from doing that. But, I will try to keep it classy! This is an uphill battle in a really gnarly industry, please try to cut me some slack and feel free to let me know if you think I'm crossing the line. Thank you for your feedback and happy growing homie!

 

[Black Sail]

As an actual scientist using BTU at all in this discussion makes my eye twitch. The BTU is a measure of heat, specifically the amount of heat required to elevate one pound of water by one degree Kelvin. It's metric analog is the calorie.

Traditionally, the BTU has been used to measure the potential heat output of a fuel, i.e. coal or natural gas. Unless we are using our LEDs to generate steam and drive a turbine, the BTU output isn't really telling us much.

Similarly, watts are a measure of work similar to horsepower. My plants are not trying to move coal up a conveyor belt and they are probably going to be a lot more interested in your lights PPFD than it's horsepower or caloric output.

Edit: don't get me wrong, watts matter and I do want to know how many watts a light consumes, but electricity does not grow plants, photons do.

I completely agree man, the units aren't ideal but it's what everybody's used to. The main point I'm arguing though, is that at a fixed wattage a fixture that has a higher photon output must have a lower heat output. I'm arguing that this is Newton's First Law of Thermodynamics, as a scientist can you back me up on that? Thanks for your input brotha!

 

[Tony21]

I completely agree man, the units aren't ideal but it's what everybody's used to. The main point I'm arguing though, is that at a fixed wattage a fixture that has a higher photon output must have a lower heat output. I'm arguing that this is Newton's First Law of Thermodynamics, as a scientist can you back me up on that? Thanks for your input brotha!

You are correct in the sense that a miniscule amount of the energy is stored as chemical energy in the plant as part of photosyntheses which is an indothermic reaction. The energy is stored in the glucose molecules, ready to be used when needed.
It's nothing that makes a dolt of difference to the fact that a watt added to a closed system will eventually turn into heat.
For practical purposes it doesn't matter. A 25 w fan will add precisely 25 watt of heat that needs dealing with as well, anything electric in the system.

 

[Tony21]

Why is all the talk about efficiency rather than efficacy, that's all I care about

 

[Black Sail]

You are correct in the sense that a miniscule amount of the energy is stored as chemical energy in the plant as part of photosyntheses which is an indothermic reaction. The energy is stored in the glucose molecules, ready to be used when needed.
It's nothing that makes a dolt of difference to the fact that a watt added to a closed system will eventually turn into heat.
For practical purposes it doesn't matter. A 25 w fan will add precisely 25 watt of heat that needs dealing with as well, anything electric in the system.

How did you find out what percentage of the light energy gets used for photosynthesis? Can you post a link to the experiments/white papers you got this data from? I'd love to have some solid information on the subject. Also I don't know anyone who grows in a thermally closed system, all the walls in my growspace have a back side that transfers heat to the outside world.

I think the real question here is: How hot will my grow room get if I buy/use Light X or Light Y? It's an important question! It's on your electric bill, it's in the health of your plants, your yields and the quality of your medicine.

This sounds like the perfect time for a science experiment! So, right now I have a Cannon running at 244 Watts in a 5' x 3' x 8' closet. My only cooling comes from a fan blowing into the closet from the doorway. The temperature in the closet is 77.9F, about 4 degrees above the ambient temperature of the room.

If I understand you correctly, you're saying that the temperature in my grow room will stay the same if I switch out my 244 Watt Cannon with a 250 Watt HPS, because a watt is a watt and it doesn't matter how efficient the light is. Would that be your prediction?

I feel certain that the temperature will go up around 10 degrees Fahrenheit if I switch to an HPS fixture of equal wattage, but scientific experiments are the best way to know for sure. Plus they're fun for me because I'm a fuckin nerd! If there really is a widespread disagreement about what the result will be I'll buy a 250W HPS and do the experiment myself. What do you think brotha?

 

[Tony21]

How did you find out what percentage of the light energy gets used for photosynthesis? Can you post a link to the experiments/white papers you got this data from? I'd love to have some solid information on the subject. Also I don't know anyone who grows in a thermally closed system, all the walls in my growspace have a back side that transfers heat to the outside world.

I think the real question here is: How hot will my grow room get if I buy/use Light X or Light Y? It's an important question! It's on your electric bill, it's in the health of your plants, your yields and the quality of your medicine.

This sounds like the perfect time for a science experiment! So, right now I have a Cannon running at 244 Watts in a 5' x 3' x 8' closet. My only cooling comes from a fan blowing into the closet from the doorway. The temperature in the closet is 77.9F, about 4 degrees above the ambient temperature of the room.
View attachment 975296
View attachment 975297

If I understand you correctly, you're saying that the temperature in my grow room will stay the same if I switch out my 244 Watt Cannon with a 250 Watt HPS, because a watt is a watt and it doesn't matter how efficient the light is. Would that be your prediction?

I feel certain that the temperature will go up around 10 degrees Fahrenheit if I switch to an HPS fixture of equal wattage, but scientific experiments are the best way to know for sure. Plus they're fun for me because I'm a fuckin nerd! If there really is a widespread disagreement about what the result will be I'll buy a 250W HPS and do the experiment myself. What do you think brotha?

I didn't find out any percentages, all I said was that a minuscule amount of the energy released from the light is stored in the plant, potential energy. When you burn fossil fuel, you are burning sunlight haha, releasing heat, or infra-red radiation. How far do you think your electric bicycle will run on the energy stored in a plant, compared to how far it would run on the amount of energy, watts used to produce the plant?
I've no idea what the actual percentage is, google Photosynthesis endothermic, there's plenty to read on the subject, someone might have some calculations.

Yes, a hps light with a similar wattage will practically give you the same temperature, doesn't matter where the watts come from, but a smaller plant because the PAR output from the hps is lower, thus less energy will be stored for later release, that's why I say practically

Why do you keep using the misleading term efficiency instead of efficacy ?

I asked in a post how you propose to cool a fixture with the chip you are using running 540 w, I can't see you have replied?
Maybe best not to talk about running this chip over 200 or so watts because it's not possible without active cooling, costing wonga watts, that's what I call all watts not producing Photosynthetic Active Radiation haha
I've seen and held this chip attached to a pin fin heatsink running 500 w, it's bright and get hot, in
case anyone wondered, very much very haha, and you want to switch it off again, quickly

 

[HashMaster]

How did you find out what percentage of the light energy gets used for photosynthesis? Can you post a link to the experiments/white papers you got this data from? I'd love to have some solid information on the subject. Also I don't know anyone who grows in a thermally closed system, all the walls in my growspace have a back side that transfers heat to the outside world.

I think the real question here is: How hot will my grow room get if I buy/use Light X or Light Y? It's an important question! It's on your electric bill, it's in the health of your plants, your yields and the quality of your medicine.

This sounds like the perfect time for a science experiment! So, right now I have a Cannon running at 244 Watts in a 5' x 3' x 8' closet. My only cooling comes from a fan blowing into the closet from the doorway. The temperature in the closet is 77.9F, about 4 degrees above the ambient temperature of the room.
View attachment 975296
View attachment 975297

If I understand you correctly, you're saying that the temperature in my grow room will stay the same if I switch out my 244 Watt Cannon with a 250 Watt HPS, because a watt is a watt and it doesn't matter how efficient the light is. Would that be your prediction?

I feel certain that the temperature will go up around 10 degrees Fahrenheit if I switch to an HPS fixture of equal wattage, but scientific experiments are the best way to know for sure. Plus they're fun for me because I'm a fuckin nerd! If there really is a widespread disagreement about what the result will be I'll buy a 250W HPS and do the experiment myself. What do you think brotha?

So.....

Buy a 250W HPS and do the experiment.

I run HPS and I "think" I know what the results will show.

Or.... since I already have 1000's running, just send me equal total wattage for 1 and I can run it for ya !

 

[pop22]

Yes lets invoke censorship because that's how you promote truth.........

I think ppl get too defensive when a vendor is also our bro! You'll get there someday too especially with the info you share.

May I suggest you continue with your quest to educate but leave Sm0 out of it? Request admin for an edit? Since you also recognized that you lost your temper and ego had some to do with it? The question marks means these are just suggestions.

Its all good bro. Like you said, both your products cater to diff usage so not much conflict right? Lets all chill. I paused a good fight to post this so lets all be good lil boys!


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