Thermoelectric Generators - Converting Waste Heat To Electricity

[fearnoevil]

So in my musings on the heat generation of COBs, it occurred to me that there should be a way to convert heat back into electricity (sans the need for high temp/pressure generators like steam turbines, moving parts etc). I imagined something like a solar panel but that used thermal energy instead of photons. So upon googling it I find there's something called the Seebeck generator which does just that, and once again another idea stolen, albeit 135 yrs before I was born(how's a guy going to invent anything when people keep beating you to the punch, lol).

SO, is anyone using these, and can they generate enough juice from say a few COBs to run a fan to cool it? Seems like a neat trick to turn an active cooling system into a quasi-passive system, at least one that doesn't use any external energy.

I haven't had time to really look into these, and of course the added expense could tip the efficiency scale, at least concerning costs, but I thought it worth looking into. Of course this could be old news, lol, and I'm just discovering it (day late and all ;?).

 

[fearnoevil]

I found these TEG units on eBay, 40mm x 40mm, for $22

http://www.ebay.com/itm/THERMOELECTRIC-POWER-GENERATOR-TEG-MODULE-NEW-USA-/310148993913?_trksid=p2141725.m3641.l6368

but can't figure out how much juice one of these might produce in a heat sink, and I suppose that's dependent on the heat produced by a particular COB.

 

[fearnoevil]

Here's a video os a simple project showing how these work, although at the end he does mention that it's a TEC instead of a TEG (interesting that it was removed from the heat sink of a water dispenser). But the principle of generating electricity from differing temperatures is obvious.

 

[fearnoevil]

Found this at Science Direct, but I'm not paying $31.50 for the paper (beyond my comprehension/pay grade, lol), maybe someone here has access though an institution if they're interested.

http://www.sciencedirect.com/science/article/pii/S2213138816300522

Abstract
The waste heat of high-power light emitting diodes (LEDs) is well localized and can be efficiently harvested in contrast to incandescent or fluorescent light sources. Compact thin film thermoelectric generators can accumulate the high-density heat flux from the LED chip and convert it into usable electrical power. We designed and analyzed a thermal management setup with high power LED and embedded thin film thermoelectric generators. The available thermal gradient of approximately 50 K allows conversion of the LED waste heat with an overall efficiency of 1%. We present an application of the active cooling powered by the harvested waste heat. The compact flat shape of the thin film thermoelectric generators allows an instant upgrade of the existing LED-based luminaries available on the market.

 

[fearnoevil]

So it this just old news or has this been tried without success on COB builds???

 

[CobKits]

havent checked your links yet but my gut tells me if its on the same level of peltier coolers what they do is cool but how efficiently they do it may be the deciding factor

 

[PhotonFUD]

Yes, no, maybe. Sorry, but all apply.

Yes technically they could work. But you would get better efficiency just running the emitters lower.

No, they won't work because if you run them hard, like CPUs for example, you will have to drive power to the TECs to transfer heat across.

Maybe, you could use them to cool cobs ala peltier. If you wanted to reclaim the heat energy, sure you could but you need active cooling still on the other side. What the heck, why not.
it is a DIY project.

 

[resinhead]

I like your thinking! Check out the last two sentences in the abstract section in this link. It says your ideas are validated, and that it cools while improving illuminance!

I think the last couple guys posting are missing the point that it's waste heat recovery, so it can't negatively impact efficiency.

http://www.sciencedirect.com/science/article/pii/S0196890416302151

 

[Isawthelight]

I'd rather have a Stirling Engine running off the COB's waste heat. The Stirling Engine could directly drive plant cooling fans and air & water pumps, and make somebody's steam punk dream a reality.

 

[PhotonFUD]

I'd rather have a Stirling Engine running off the COB's waste heat. The Stirling Engine could directly drive plant cooling fans and air & water pumps, and make somebody's steam punk dream a reality.

Talk about old school

But the past has lots of usefull stuff.

 

[fearnoevil]

I like your thinking! Check out the last two sentences in the abstract section in this link. It says your ideas are validated, and that it cools while improving illuminance!

I think the last couple guys posting are missing the point that it's waste heat recovery, so it can't negatively impact efficiency.

http://www.sciencedirect.com/science/article/pii/S0196890416302151

I tend to agree, TEG's are different or have a different purpose than TEC's, the former is used to generate electricity from waste heat, which is what I was considering, not so much to cool COBs.

As I understand it, you would mount the TEG between the COB and the heat sink, and depending on how much current is generated, it might be possible to run a fan off a few COB's, making your active cooling system as energy efficient as a passive one. Of course the problem is the initial cost of these, and my guess is that with the current (NPI ;?) state of the art, it isn't really practical. Yet. ;?)

 

[Danielson999]

You can also have solar panels collecting stray photons which would then power fans, pumps etc. Your fans would just kick in as soon as your lights turned on and any extra energy would get saved in a battery so you could use power even when the lights are out.

 

[fearnoevil]

I'd rather have a Stirling Engine running off the COB's waste heat. The Stirling Engine could directly drive plant cooling fans and air & water pumps, and make somebody's steam punk dream a reality.

SE's are cool, but they are bulky and I don't think they would be as efficient at converting the waste heat if you had to move it from the COB's to wherever the SE was located, and then use the SE to power a small generator, I presume.

 

[fearnoevil]

You can also have solar panels collecting stray photons which would then power fans, pumps etc. Your fans would just kick in as soon as your lights turned on and any extra energy would get saved in a battery so you could use power even when the lights are out.

Lol, I was thinking the exact same thing, but I'm not sure how many solar panels you could fit in your grow room, especially as the canopy started to fill in. And if mounted on the walls, they would absorb rather than reflect, which could essentially rob your plants of some small amount of light thus lowering the efficiency, I think.

 

[resinhead]

It might be hard to find a fan that will run off such small amperage. It might take a few led units to power one fan. I hope to conduct some experiments soon to see how much power each diode can create!

 

[MeGaKiLlErMaN]

Since a pelltier device/ thermal generator takes the difference from the temps to create electricity or electricity to make two different temps, it's possible and in the winter proabably profitable. But I haven't seen any that are either the money, but that could change with DIY.