Author Topic: EEVblog #664 - Peltier TEG Energy Harvesting Experiments  (Read 24760 times)

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EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« on: September 22, 2014, 12:26:55 am »
Dave plays around with an energy harvesting kit to see how much power he can get out of a Peltier device used as a Seeback effect module to generate power from temperature differentials.
Bonus white board tutorial of how Peltier devices work as heat pumps.
 
Wuerth Elektronik Energy Harvesting Kit: http://www.we-online.com/web/en/electronic_components/produkte_pb/demoboards/energy_harvesting/energy_harvesting.php
Linear Technology: http://www.linear.com/solutions/1834
DC2080A Demo Manual: http://cds.linear.com/docs/en/demo-board-manual/DC2080AF.PDF
LTC3108 Energy harvesting chip datasheet: http://cds.linear.com/docs/en/datasheet/3108fc.pdf

Measuring microcontroller sleep current using integration on an oscilloscope:


 

Offline AlfBaz

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #1 on: September 22, 2014, 03:59:29 am »
Thanks for posting this. I recently bought a stack of Peltier cells with the aim to experiment harvesting energy from wasted heat from cooling systems and these "Peltier specific" voltage regs look nice.

The one thing I've been meaning to look at is the availability/manufacturability of odd shaped Peltiers, more specifically curved ones, given that for what I'm looking at most of the wasted heat is contained in pipes/hoses.

At this stage, since the cheap plain rectangular cells are the only practical option, inserting a rectangular tube in existing systems seems the only way forward which is a shame because you are limited to the size of the inserted heat exchanger.
 

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #2 on: September 22, 2014, 04:00:51 am »
The one thing I've been meaning to look at is the availability/manufacturability of odd shaped Peltiers, more specifically curved ones, given that for what I'm looking at most of the wasted heat is contained in pipes/hoses.

I'm ultimately after a curved one too.
If anyone knows of any, please let us know.
 

Offline Alexei.Polkhanov

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #3 on: September 22, 2014, 04:22:04 am »
Hmm, I think having curved Peltier cells is not how you solve this. You better off by using some kind of liquid to collect the heat and then recover the heat from the liquid. Same idea as with engine coolant or heat transfer liquid (Potassium, Led etc.) in nuclear reactors and so on. Maybe this is how these ring shaped ones meant to be used: http://www.digikey.ca/product-detail/en/71062-514/926-1217-ND/2269577
 

Offline miguelvp

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #4 on: September 22, 2014, 04:58:00 am »
I can't find my peltier to play along :(
 

Offline steves

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #5 on: September 22, 2014, 05:26:15 am »
Given the low power, I guess that you'd have to have a good reason to not use a battery. In what types of applications might these devices be advantageous?

Thanks.
 

Offline casper.bang

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #6 on: September 22, 2014, 05:52:13 am »
Given the low power, I guess that you'd have to have a good reason to not use a battery. In what types of applications might these devices be advantageous?
Remote sensing applications comes to mind, never having to replace battery... we (well the electronics engineers) did a bunch of research of this at my former job.

I wonder about the law of thermodynamics (preservation of energy). Since you essentially remove/transfer energy away from the Peltier element as electrons, does that mean that you also remove heat (read: cool)? Will a connected Peltier element exhibit different physical characteristics than a disconnected element?
 

Offline AlfBaz

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #7 on: September 22, 2014, 05:54:18 am »
Adding a heat transfer medium only compounds an already lossy energy conversion method. Having said that I have contemplated mounting these flat peltiers on square block of aluminium, drilling a hole in the middle to suite the size of the pipe and then cutting them in half so that they can be clamped onto the pipe
 

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #8 on: September 22, 2014, 05:55:17 am »
Since you essentially remove/transfer energy away from the Peltier element as electrons, does that mean that you also remove heat?

Yes. that's how it works. You "pump" heat from one side to the other. Without that heat flow you get no power out of it.
So it becomes a thermal dynamics problem, one side must lose heat, the other must gain it.
 

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #9 on: September 22, 2014, 05:57:39 am »
Adding a heat transfer medium only compounds an already lossy energy conversion method. Having said that I have contemplated mounting these flat peltiers on square block of aluminium, drilling a hole in the middle to suite the size of the pipe and then cutting them in half so that they can be clamped onto the pipe

Don't forget the free air side will likely need a suitable heatsink so it can radiate to ambient as efficiently as possible.
 

Offline ckambiselis

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #10 on: September 22, 2014, 09:15:51 am »
Finally the episode I've been waiting for!

Been thinking about making a large TEG over a year now, the idea came when I realised that the temperature difference between room temperature and outside winter tempearature in Finalnd is around 40-50 C . So I was thinking to make a large seebeck panel (at least 50x50cm) out of many 40mmx40mm peltier modules found cheaply around Ebay, between 2 aluminum plates, stick one side of the panel to the chimney and other side facing free towards the outside cold air, maybe some insulation around the panel to keep each side at each own temperature.

From a quick test with one of the modules (TEC1-12706), using just my hand pressed on one side and the other side just sitting on a small CPU heatsink (around 20C ambient temperature), I was able to get 170mV and 40mA, measured with my Fluke 287 so I'm sure it's pretty accurate measurement, even though last calibration was in 2008.

So a few questions since I haven't played around with the modules many times.

1. Can they be connected in serial/parallel?
2. If they can be connected both ways, what would actually be preferable, connect them in series to get the desired voltage or connect them in parallel to get high amps and run it through a step-up circuit to get the desired voltage (Vout of the TEG 12V)?
3. Is it better to use even larger modules, are they more efficient?

Thanks for all the amazing videos Dave!!!
 

Offline AlfBaz

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #11 on: September 22, 2014, 09:37:32 am »
Don't forget the free air side will likely need a suitable heatsink so it can radiate to ambient as efficiently as possible.
Hard to draw freehand with a mouse :)

In actuall fact the idea was to sandwitch the peltier with 2 of those units, cooling water in pipe in one unit heated water out in the other
 

Offline max_torque

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #12 on: September 22, 2014, 11:48:44 am »
Although these thermoelectric generators are interesting, and maybe solve a limited number of specific issues, for example powering a remote, high reliability ultra low energy consumer, like a sensor or something, i can't see any real use for them?

They don't have sufficient energy density or cost parity to any other power source i can think of?

(cheapest unit i can find in the uk is on Ebay for £1, for that, you could have pretty much 7 kWhrs of electrical power delivered to your home or place of work.  As the TEG puts out only several mW peak (at max DeltaT), you'd have to leave it running for a LONG time to harvest the same amount of power.......)

Certainly, any "green" useage is foolish (attempts to harvest heat flux from hot houses or something) and you'd be several hundred times better off to just spend the same amount of money on more insulation to prevent the heat escaping in the first place.
 

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #13 on: September 22, 2014, 12:07:51 pm »
Although these thermoelectric generators are interesting, and maybe solve a limited number of specific issues, for example powering a remote, high reliability ultra low energy consumer, like a sensor or something, i can't see any real use for them?

You aren't wrong. They are for niche applications only.
Even for remote sensors it can be better to simply install a large long life lithium primary cell. 10 years life is easily doable.
 

Offline ggchab

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #14 on: September 22, 2014, 12:41:05 pm »
Been thinking about making a large TEG over a year now, the idea came when I realised that the temperature difference between room temperature and outside winter tempearature in Finalnd is around 40-50 C . So I was thinking to make a large seebeck panel (at least 50x50cm) out of many 40mmx40mm peltier modules found cheaply around Ebay, between 2 aluminum plates, stick one side of the panel to the chimney and other side facing free towards the outside cold air, maybe some insulation around the panel to keep each side at each own temperature.
You can't "create" energy. You will cool your room (move heat from inside to outside) to produce electricity   ;)

Nice video :)
 

Offline Artraze

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #15 on: September 22, 2014, 03:30:12 pm »
Adding a heat transfer medium only compounds an already lossy energy conversion method.

The law of conservation of energy disagrees.  The heat can go through anything and everything, but as long as it ultimately flows through your peltier(s) you won't lose anything.  Of course, adding a heat transfer medium may increase thermal impedance, but whether that makes the system more or less efficient will depend on every tiny detail of the system.
 

Offline max666

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #16 on: September 22, 2014, 05:47:03 pm »
Thanks for going over the block diagram in such detail, Dave.
Every minute well worth spent.
 

Offline Maxlor

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #17 on: September 22, 2014, 07:04:04 pm »
Really interesting stuff, thanks for taking the time to explain and show us. I feel my fingers itching to play with peltiers now... if only I had the time :(

A comment about the audio for the whiteboard bit at the beginning: it varies in volume and tone as you turn your head left and right. It can't be avoided with that kind of microphone I suppose. Here's one thought though: With the microphone on the left side of your collar, your voice becomes louder and clearer when you turn your head away from the camera, which feels a bit weird. Maybe try mounting it on the camera-facing side of your collar?
 

Offline resistor

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #18 on: September 22, 2014, 07:10:53 pm »
I don't understand how one can generate (semi-)consistent power with a device like this.  As Dave pointed out, current only flows as long has heat is being pumped from one plate to the other.  But, as the heat is pumped, the temperatures reach equilibrium and the current stops.

It seems like you need some kind of situation where the temperature polarity of the plates oscillates over time, so that you're shifting heat back and forth?  That seems like a fairly unusual circumstance...
 

Offline SeanB

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #19 on: September 22, 2014, 07:49:24 pm »
Consider one plate has a source of low grade heat, like a burning candle, while the other plate has a heatsink exposed to air so it can be cooled by convection. As long as the candle burns you get power.
 

Offline ckambiselis

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #20 on: September 22, 2014, 09:08:29 pm »
Been thinking about making a large TEG over a year now, the idea came when I realised that the temperature difference between room temperature and outside winter tempearature in Finalnd is around 40-50 C . So I was thinking to make a large seebeck panel (at least 50x50cm) out of many 40mmx40mm peltier modules found cheaply around Ebay, between 2 aluminum plates, stick one side of the panel to the chimney and other side facing free towards the outside cold air, maybe some insulation around the panel to keep each side at each own temperature.
You can't "create" energy. You will cool your room (move heat from inside to outside) to produce electricity   ;)

Nice video :)

The heat used is wasted heat that is produced anyway, it only works as a heat pump when you power it not in "seebeck mode", if I'm not mistaken.
 

Offline ckambiselis

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #21 on: September 22, 2014, 09:22:19 pm »
Although these thermoelectric generators are interesting, and maybe solve a limited number of specific issues, for example powering a remote, high reliability ultra low energy consumer, like a sensor or something, i can't see any real use for them?

They don't have sufficient energy density or cost parity to any other power source i can think of?

(cheapest unit i can find in the uk is on Ebay for £1, for that, you could have pretty much 7 kWhrs of electrical power delivered to your home or place of work.  As the TEG puts out only several mW peak (at max DeltaT), you'd have to leave it running for a LONG time to harvest the same amount of power.......)

Certainly, any "green" useage is foolish (attempts to harvest heat flux from hot houses or something) and you'd be several hundred times better off to just spend the same amount of money on more insulation to prevent the heat escaping in the first place.

Well I'm not really sure about that, there must be better versions or something, I mean the Curiosity Rover produces about 125W form 2kW of heat, or about 2,5kWh per day (yes I do have in mind that it is million dollar system, but it is still possible, same as solar panels, it will become affordable at some point), yeah it's still less than your typical solar panel system but there are months with only 4 hours of sun here.

Think it more of a part of whole bigger power generation system, not just by its self.
 

Offline MrsR

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #22 on: September 22, 2014, 10:01:29 pm »
Back in the 1980s my brother was playing around with these units. He bought them from CAR-VAN SUPPLIES in Sydney.

He was making little Fridges for campers ended up using two to get any reasonable useful Fridge.
They ran on 12v. I think he had to put fans on the Heat side to get them to work.
I think CAR-VAN still exists and they might still have them, they still had them listed in the late 90s.

Rachael :-+

 
 

Offline steves

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #23 on: September 22, 2014, 11:43:09 pm »
I'm still struggling to come up with an application: temperature sensor at the top of a very tall chimney at extreme latitude in winter is my best so far.

How much power would be available if a temperature difference of 70C or 80C could be maintained? Thanks.
 

Offline allikat

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #24 on: September 22, 2014, 11:55:33 pm »
This video shows the reason why electric and hybrid vehicles aren't covering every heat producing part in a layer of these Seebeck generators.  The sheer mass of them required to produce any meaningful output would be prohibitive even when you're just adding them between hot devices and the fins that are cooling them anyway. 

Highly informative video, thanks!
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1: Coffee, 2: Escaped magic smoke, 3: Bullshit
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