Author Topic: EEVblog #664 - Peltier TEG Energy Harvesting Experiments  (Read 23663 times)

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Offline EEVblog

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EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« on: September 22, 2014, 10:26:55 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, 01:59:29 pm »
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.
 

Offline EEVblog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #2 on: September 22, 2014, 02:00:51 pm »
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, 02:22:04 pm »
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, 02:58:00 pm »
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, 03:26:15 pm »
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, 03:52:13 pm »
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, 03:54:18 pm »
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
 

Offline EEVblog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #8 on: September 22, 2014, 03:55:17 pm »
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.
 

Offline EEVblog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #9 on: September 22, 2014, 03:57:39 pm »
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, 07:15:51 pm »
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, 07:37:32 pm »
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, 09:48:44 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.
 

Offline EEVblog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #13 on: September 22, 2014, 10:07:51 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, 10:41:05 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 23, 2014, 01:30:12 am »
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 23, 2014, 03:47:03 am »
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 23, 2014, 05:04:04 am »
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 23, 2014, 05:10:53 am »
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 23, 2014, 05:49:24 am »
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 23, 2014, 07:08:29 am »
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 23, 2014, 07:22:19 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.

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 23, 2014, 08:01:29 am »
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 23, 2014, 09:43:09 am »
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 23, 2014, 09:55:33 am »
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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Offline max666

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #25 on: September 23, 2014, 11:07:33 am »
...
How much power would be available if a temperature difference of 70C or 80C could be maintained? Thanks.

Like Dave explained so marvellously in his video, stating a mere temperature difference doesn't tell you squat about the power you can expect.
Depending on your system you will have a certain thermal resistance from the medium providing the heat, through the Peltier device, into the medium dissipating the heat. That thermal resistance will determine how much heat (as in watts) will flow through the Peltier device at a given temperature difference. And if we assume an efficiency of 5%, then 5% of that heat flow will be converted into electrical power.
 

Offline steves

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #26 on: September 23, 2014, 11:50:59 am »
...
How much power would be available if a temperature difference of 70C or 80C could be maintained? Thanks.

Like Dave explained so marvellously in his video, stating a mere temperature difference doesn't tell you squat about the power you can expect.
Depending on your system you will have a certain thermal resistance from the medium providing the heat, through the Peltier device, into the medium dissipating the heat. That thermal resistance will determine how much heat (as in watts) will flow through the Peltier device at a given temperature difference. And if we assume an efficiency of 5%, then 5% of that heat flow will be converted into electrical power.


Okay, I was picturing like an electrical resistor with an constant potential difference across it, but this is not a valid analogy?
 

Offline sacherjj

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #27 on: September 23, 2014, 12:55:55 pm »
We are researching making some of our own TEG modules to provide power in places where there is no electricity and the forest canopy and/or rainy seasons make solar impracticable.

Some of these modules can provide 30 W of power with a large differential (300C fire and 50C water in pot).  For example: http://www.customthermoelectric.com/powergen.html

There are a couple folks that make USB charging kettles and small camp stoves with seebeck modules for 10W 5V output in the kettle setup. 

The danger if this over a fire is that running the pot dry will burn up the module.  Some of these are good to 320 C, but not much higher without paying extreme prices.
 

Offline gardner

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #28 on: September 23, 2014, 02:26:56 pm »
I'm still struggling to come up with an application

These things have been around for yonks.  The most practical application I know of.
http://www.caframo.com/hearth/hearth_products_woodstove.php

These are recent and a bit gimmicky.  The recovered energy is used to run a fan to boost combustion.
http://www.biolitestove.com/products/campstove/

These are also fairly new and, IMO, gimmicky
http://www.leevalley.com/en/garden/page.aspx?p=68887&cat=2,40731
--- Gardner
 

Offline steves

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #29 on: September 23, 2014, 04:06:27 pm »
...
How much power would be available if a temperature difference of 70C or 80C could be maintained? Thanks.

Like Dave explained so marvellously in his video, stating a mere temperature difference doesn't tell you squat about the power you can expect.
Depending on your system you will have a certain thermal resistance from the medium providing the heat, through the Peltier device, into the medium dissipating the heat. That thermal resistance will determine how much heat (as in watts) will flow through the Peltier device at a given temperature difference. And if we assume an efficiency of 5%, then 5% of that heat flow will be converted into electrical power.

The datasheet shows the temperature difference between the hot junction and the cold as being dependent on the electrical power being input when used in peltier mode, so does the reverse applies in seebek mode?

Perhaps I should rephrase my question:

Under ideal conditions, including a heat source of zero impedance, what is the maximum electrical power that this device can deliver?
and how about under optimal real-world conditions? What would the hot and cold temperatures be?

Thanks.
 

Offline bitwelder

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #30 on: September 23, 2014, 05:09:51 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 .
Just wondering... how are Peltier modules working with the cold side under 0C? Does that affect their efficiency?
 

Offline Tuoppi

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #31 on: September 23, 2014, 09:45:14 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.

Not really. If you use the TEG module you will effectively cool down your room, so in order to keep your room at the same temperature as originally you have to crank your heaters slightly up. The electricity you generate with your Peltier will show up (even if you don't notice it due to the magnitude) in your kaukolämpö bill. Laws of Physics cannot be cheated.

 

Online NANDBlog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #32 on: September 23, 2014, 10:41:43 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.
I really wonder, how much time it takes to generate the amount of energy the manufacturing of one module takes. If it will break even (under what condition) during the lifetime of these TEGs.
 

Offline EEVblog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #33 on: September 23, 2014, 10:46:38 pm »
I really wonder, how much time it takes to generate the amount of energy the manufacturing of one module takes. If it will break even (under what condition) during the lifetime of these TEGs.

These are not commercial solar panels that must have payback to be viable. They are for niche applications that are otherwise impossible without them. Payback is of no relevance.
 

Offline coppice

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #34 on: September 23, 2014, 11:53:38 pm »
I really wonder, how much time it takes to generate the amount of energy the manufacturing of one module takes. If it will break even (under what condition) during the lifetime of these TEGs.
These are not commercial solar panels that must have payback to be viable. They are for niche applications that are otherwise impossible without them. Payback is of no relevance.
Right. You really need to compare the cost of these solutions with the kind of batteries which might be able to do the job. Harvesting is interesting where the battery solution looks nasty for cost or lifetime reasons.
 

Offline Excavatoree

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #35 on: September 24, 2014, 12:47:35 am »
My water heater uses a Seebeck generator for the electronic controls.  No battery to worry with, no connection to the mains, (after all, older, non-electronic controlled gas water heaters had no electrical connection) it just works.    I suppose changing a battery wouldn't be a deal breaker, but you know no one would do it until that first cold shower - then one would have to wait. 
 

Offline fchk

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #36 on: September 24, 2014, 08:58:02 pm »
You shall call Wuerth by name "Wurt", not by value "worth".

We do not have a th.

fchk
 

Offline German_EE

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #37 on: September 24, 2014, 09:07:19 pm »
Think of it as German with an Australian accent :)
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Online NANDBlog

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #38 on: September 24, 2014, 10:26:10 pm »
I really wonder, how much time it takes to generate the amount of energy the manufacturing of one module takes. If it will break even (under what condition) during the lifetime of these TEGs.

These are not commercial solar panels that must have payback to be viable. They are for niche applications that are otherwise impossible without them. Payback is of no relevance.
I'm thinking more about the effectiveness of the application. If you take a lithium primary battery, or a zn-air battery, the same size as the peltier-heatsink construction, would it provide more power over 20-30 years than the TEG generators?
AFAIK these are used on satellites with radioactive materials and maybe F1 cars are using this in their ERS this year, so it must be somewhat viable.
Are you thinking about a smartwatch with peltier?
 

Offline ckambiselis

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #39 on: September 25, 2014, 04:39:23 am »
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.

Not really. If you use the TEG module you will effectively cool down your room, so in order to keep your room at the same temperature as originally you have to crank your heaters slightly up. The electricity you generate with your Peltier will show up (even if you don't notice it due to the magnitude) in your kaukolämpö bill. Laws of Physics cannot be cheated.

Well the initial idea was to connect it to the fireplace chimney, so I'm not using the heat of the room but the heat of the smoke.
 

Offline ziggyfish

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #40 on: September 26, 2014, 01:35:33 pm »
They sound good in theory (even then its not that great). But if you take into account you only get 5% efficiency and that a solar cell can most definitely produce more power at lower costs. These things don't seem that viable as a solution to anything.

In remote sensing applications, you still have the problem of either cooling one side or heating the other which requires power. So although its cool, I just don't see a use for it.
 

Offline Hypernova

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #41 on: September 26, 2014, 03:26:08 pm »
They sound good in theory (even then its not that great). But if you take into account you only get 5% efficiency and that a solar cell can most definitely produce more power at lower costs. These things don't seem that viable as a solution to anything.

In remote sensing applications, you still have the problem of either cooling one side or heating the other which requires power. So although its cool, I just don't see a use for it.

Then use the heat nature provides and sink to the ground or sea, environmental corrosion aside unlike solar panels under the sun these things will last indefinitely.
 

Offline hamdi.tn

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #42 on: September 26, 2014, 07:21:28 pm »
Interesting video, i was thinking about getting this energy harvesting kit from wurth to play with , i think i don't have to now i saw how it work,i will just get this peltier device, thanks dave  ;D
It's unthinkable to use it as a main power source for any sort of application even for remote sensing, as all energy harvesting solution they only useful to charge battery or a super cap while system is in a low consumption mode, sleep or whatever. used that way i can think about thousand of application where solar energy is not really the right solution. Really interesting stuff
 

Offline VK3DRB

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #43 on: September 27, 2014, 04:43:07 pm »
I use Peltiers to keep 3 watt CW laser SHG crystals at a specific temperature (typically around 45 deg +/- 0.2 deg C). The thermal mass is low but change in temperature over time is large at laser firing time. If the temperature varies by more than 1 degree, the crystal can be damaged and the laser can be destroyed. Hence recovery time to the temperature set point must be fast but we cannot overshoot. A difficult task.

By far the most the most difficult challenge with Peltiers (and power resistors at fast heaters) was to keep a silicon wafer and 528 probe tips at a constant temperature whilst slicing though the each wafer's plastic carrier support sheet to contact the silicon substrate to test the chips. The other side of the wafer was a large gold plated disc with a large thermal mass which would contact all 528 devices. Too hot and the silicon could be damaged by the impact of the 20 micron probe tip. Too cold, the plastic could not be reliably penetrated to make contact. The temperature was critical. Designing the heater/cooler and the airflow mechanisms was difficult enough, but the real killer was getting the PID algorithm right because the thermal lag was very long.
« Last Edit: September 28, 2014, 01:32:26 pm by VK3DRB »
 

Offline VK3DRB

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #44 on: September 27, 2014, 04:50:06 pm »
Dave's video was quite good and highlights the amount of time that can be spent understanding a circuit or device.

One criticism of Linear Tech's board. Look at 09:26 in the video. What was the PCB layout guy smoking when he put in the designator for C01?
« Last Edit: September 27, 2014, 06:05:03 pm by VK3DRB »
 

Offline dshay

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #45 on: September 30, 2014, 10:01:35 am »
Real TEGs are expensive, $35 to 40 a pop at single piece prices, but they're worth it if you've got expendable income. Charge a cell phone with your camp stove kind of power outputs.

As has been mentioned they're great for when you have an application you can't get to to run power lines, like a old factory retrofit, buried sensors you cant get a field repair tech to replace, geothermal heat and mining applications, spacecraft that have a long term radioactive heat source. Russia used them in remote locations to power radio communication devices in the 50s and 60s.

Mosquito traps use them because they burn fuel to produce the CO2 and heat signature they're attracted to and the nail in the coffin is the electric powered fan they get sucked in with.

They're also commonly used as off grid back ups for wind/solar, just have an ignited fuel source kick in.

for $40 you can buy a lot of spare LiPos. At this point rich kid hikers would be the biggest market.

To check to see if it's a real TEG check the max temp conditions, 300C (400C in bursts), they also have high temp silicone insulation on the leads.

In idea conditions on a good mudule you can get anywhere from 10W, but you'd need conditions like I have, northwestern Minnesota winter. A outdoor stove is a perfect application for these, you could power thermostats/dampers or a fuel feed auger.

It's all about the delta T, eventually your cold side is going to heat up, in less than ideal conditions without a good cold source you're going to see 5W out of that same module if your trying to use ambient temp/heat sinks to cool. Best to find a water source/radiator.

Bismuth Telluride is a byproduct of lead mining, a finite resource unless people start recycling metals for their bismuth, a commonly used alloy.

There are two main manufacturers of real TEGs Marlow Industries and Tellurex. I know Tellurex has an online store based out of the US you can purchase directly

Scroll down to the bottom for their Thermal Power Generators.

Click here for tellurex.com



 

Offline fubar.gr

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #46 on: October 24, 2016, 10:22:01 am »
I have some questions about TECs/TEGs.

1) All these PN junctions in series should result in a massive forward voltage drop requiring several tens of volts to make them work. But in reality a TEC behaves like a small value resistor.

Why is that? Is it due to the semiconducting material (Bismuth Telluride) used?

2) I don't get where the cooling effect comes from. Obviously, whatever process is taking place on the cool side is endothermic, but what is this process?

3) Does a single silicon diode also exhibit this cooling/effect?

Offline peltierseebeck

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #47 on: October 03, 2018, 03:11:17 am »
I have some questions about TECs/TEGs.

1) All these PN junctions in series should result in a massive forward voltage drop requiring several tens of volts to make them work. But in reality a TEC behaves like a small value resistor.

Why is that? Is it due to the semiconducting material (Bismuth Telluride) used?

2) I don't get where the cooling effect comes from. Obviously, whatever process is taking place on the cool side is endothermic, but what is this process?

3) Does a single silicon diode also exhibit this cooling/effect?


1) Per 3) below, the semiconductor arrange in a diode is different than a Peltier module arrangement and thus the behavior is different. In the absence of a temperature difference across the Peltier module, it behaves like a resistor. Once a temperature difference is applied, a Seebeck voltage is generated and the true resistance will be difficult to obtain. One thing to note is that the electrical resistance of a Peltier module should be measured with an AC ohmmeter. Using a DC ohmmeter will create the Peltier effect, one side will get cold, one side hot and a Seebeck voltage will appear. This will change the resistance reading. Additionally, the resistance changes depending on the average temperature of the semiconductors. 

2) Usually the term endothermic is related to chemical reaction but the Peltier works a bit different. We know heat transfers from hot to cold. This is not the case for Peltier/Thermoelectric modules. Heat transfers from cold to hot. Just like a heat pump and these modules are heat pumps.

When a voltage is applied, charges carriers move inside the Peltier module p and n semiconductors. Charge carriers are electrons and "holes'. Charge carriers pick up heat at the connections (junctions) between the n and p semiconductors and copper strips connecting them. When the charge carriers reach the opposing semiconductor junction in the p-n couple, the heat is released. Peltier cooling (heat absorbed) happens at one side and Peltier heating (heat released) at the other. And of course by reversing the current flow direction, the charge carriers reverse direction and the direction of heat transfer changes.

Check out this link for more details: How do thermoelectrics transfer heat?

3) Diodes have a different arrangement of the p and n semiconductors and thus different physics. The p and n semiconductors in a diode are not connected by the metal strip, they are joined directly together. See this: How a junction diode works

 

Offline Kleinstein

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #48 on: October 03, 2018, 05:39:08 am »
The main difference in the setup is that the materials are joint with ohmic contacts  like metal  n-semiconductor - metal - p-semiconductor - metall ..... So there is no forward voltage drop like in a diode.

The heat pumping action comes from the electrons not only carrying the electric charge, but also some thermal energy - how much depends on the material. When going from one material to another, the electrons have to adjust there thermal energy and the difference appears as heat or cooling effect.

The question of heat sources inside a normal silicon diode is interesting.  A similar and even rather strong peltier effect also happens there, at both contacts. When operated in forward direction, the contacts itself are cooled from this, and there is a significant heat source where the recombination happens. As silicon is a rather good thermal conductor and the regions are rather close not very much of this is visible from the outside.
 

Offline goolong

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Re: EEVblog #664 - Peltier TEG Energy Harvesting Experiments
« Reply #49 on: November 14, 2018, 08:28:59 pm »
Anyone have a clue about these TEC from https://phononic.com/ ?   They claim their efficiency is close to a regular refrigerator at 30 percent efficient.

Also, can someone let me know if this setup improves efficiency/ energy requirements for cooling  or am I screwing with the heat dissipation of the TEC too much

ie      pump heat ---> cold side (TEC) Hot side --(touching) -> Hot side (TEG)  coolED side  with large heat exchanger ( 2 to 3 times the surface area of TEC cold side)   

battery power input into the TEC,     recover some of the heat using a TEG   into a cap to recharge the battery.  I hope this is kinda clear.

 By the way im working on a Fontus clone and will be posting in the forums for help soon.
 


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