Author Topic: Peltier units and Wood heaters  (Read 1561 times)

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Offline Pete

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Peltier units and Wood heaters
« on: July 17, 2018, 05:25:20 pm »
Hi Folks well it is winter here where I live. Lots of clouds so the solar is struggling a bit.
I was wondering if any of the members have had any experience with using Peltier units on their wood stoves as backup battery chargers?
It seems that it would be fairly easy to make one, but there are problems with keeping one side cool etc.
Any advice from those who have used them would be great
Pete

Offline DJ

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Re: Peltier units and Wood heaters
« Reply #1 on: July 18, 2018, 05:07:38 am »

I have looked at peltiers as generators and my conclusion was waste of time unless you want to spend $100 on a setup to charge a phone ( slowly) from a camp-fire. 

They produce decent heat or cool  from electrical input but the power they generate from heat is useless.  You'd need a wood stove the size of a small shipping container to stick enough of the things on to put any worthwhile charge in a battery bank.

If you want a backup battery charger, what I was looking at this morning might do you well.  Chinese Vertical Cylinder Diesel engine coupled to a decent output 24V alternator with a controller to take it to 48V if you need.
You could run the thing off Veg or engine oil as I have so fuel would be no cost other than the collection.

There are other things you could do like run an induction motor as a generator driving a small welder as a charger and other ideas.

Unless you want to charge a phone or some AA batteries, peltiers will be no help to you at all and you'd get far more out of a used panel even in winter than what peltiers could practically give you.

Yeah, I was bummed too. Seemed like a great idea till I looked into it a little bit.   :-[

Offline hiker1

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just do it

Offline Pete

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Re: Peltier units and Wood heaters
« Reply #3 on: July 18, 2018, 05:23:53 pm »
Thanks Hiker, I do have a generator and my inverter is also an 80 amp charger, I was just looking for ways to get around using fuel. I don't like to have noisy engines running unless it is absolutely necessary. Like to run the welder etc.
I did see those units, they seem pretty pricey to me, and the video said that if you put too much load on them the fan will fail and they will die.
Not much use really
Thanks again
Pete

Offline hiker1

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Re: Peltier units and Wood heaters
« Reply #4 on: July 18, 2018, 11:19:48 pm »
The fans don't fail...to big of a load ...robs the power from them...that's why they have the load sensor for the power output...if you don't use that .then yes you could harm the unit with to big of a load causing the fans to stop...overheating the unit...45 watts isn't bad at all .for something that compact.....pricy yes...over time perhaps the price will go down...
just do it

Offline DJ

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Re: Peltier units and Wood heaters
« Reply #5 on: July 19, 2018, 02:31:38 am »

Am I missing something or is there some abstract reason or situation where Spending over $500 on a devise that generates 45W under ideal circumstances is justified for home use? 

Just buy a couple of used panels and You'd make loads more power even on overcast days.

Reading the info, stove has to be over 500F, 260 C for the thing to work.  I wonder how long that's going to take to heat the house, especially if it's a small off grid place, till the joint is so hot you have to open the windows or doors. From there on you are constantly keeping the fire hot and wasting wood in the process.  Probably spending more on fuel for the chainsaw and splitter than just going and buying fuel for a small generator that you can do a lot more with  and would be far more practical.

I have one of those cheap little 2 stroke generators that do 800W.  Thing runs all day on bugger all fuel, is quiet as a mouse and cost bugger all.  Rather get one of those and pay for the fuel if I was off grid and needed power than throw money away on one of those things.
I can use the genny in summer too.  Not about to go lighting hot wood fires and in a lot of places, may not be allowed anyway.

Things like this just make me shake my head.
Last thing I saw aimed at the same twits whom would buy something like this was a little Hydro Generator.  It was aimed at people who liked the outdoors to give them a source of power. You put this little propeller in a stream or creek and secure the other end and the thing makes power you can charge things with it like phones and flashlights etc. at .... a massive 4-5W.
This idiot thing won awards and and was featured in all sorts of magazines and articles like it was bred that sliced and toasted itself.

Do people never think about using these ridiculous things?  First, you have to find water, water running at the correct speed of course that you can get to easily. second, even when you do find the right water, You'd have to sit there all dam day for the thing to make enough power to charge the average phone.
I think that one was about $2-300 from memory.  As they say, one born every minute.  For way under $100 you can get foldable panel arrays that you can drape over a back pack as you walk along and they are rated up to 60W.  Again, even on a bad day or walking in bush are going to give you the same sort of power as the hydro thing and cost at least half the price.  In clear sunshine, no contest.

I do not understand how they even bother to offer things like this.  I'm sure some people buy them though which is even more a worry.

Offline hiker1

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Re: Peltier units and Wood heaters
« Reply #6 on: July 19, 2018, 11:55:49 am »
Yes just a interesting gizmo...just another in a world of gizmos......like the iPhone Im using for this..who would have thought what a phone would change into back in the 70s....
just do it

Offline MadScientist267

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Re: Peltier units and Wood heaters
« Reply #7 on: July 19, 2018, 04:20:00 pm »
Radio shack sold a tiny cheesy solar cell and a little motor that was just strong enough to get out of its own way... in the 70s. It was 15 bucks as I recall, and served absolutely no "practical" purpose... Outrageously expensive in terms of per-watt, and I remember thinking (in addition to being told) that it would never be useful beyond a toy.

Or would it...

I for one was forever intrigued by the magic... and if I had to attribute any single "thing like this" to my interest in solar, that would be it. Many years later I put what it started (along with a whole bunch of other concepts) to the test with a Uhaul truck... and lived in it for over 2 years, full time. So much for useless.

So, I told you that to tell you this...

This isn't even to mention the *absolutely* practical value of things related to peltier and it's cousins... Without people looking into how these mysterious forces work, many an adventure wouldn't have been possible, say, in space. Big-G "RTG" for information on this not-exact but closely related "useless" technology...

Guess where it starts...

I'm not saying that the seebeck effect (what you're actually describing) is incredibly efficient; it's not. But neither is peltier as a cooling device, and yet I've proven for myself that they are indeed viable under the right circumstances, for more than trivial purposes.  Horses for courses type thing.

Is everything always practical? No. But this is how we learn how to do new things... "Playing" with principles and refining them into something actually useful. That said, I don't advocate building some massive seebeck device out of a bazillion peltier modules running "backwards"... in an attempt to run your house from a mega bonfire... But shooting things completely out of the air just because at present they're not "quite there" in terms of practicality, that's equally as bad.

... end rant lol

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline DJ

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Re: Peltier units and Wood heaters
« Reply #8 on: July 20, 2018, 09:46:49 am »

But shooting things completely out of the air just because at present they're not "quite there" in terms of practicality, that's equally as bad.

I do get what you are saying Steve but in this particular example I think it's different to the value of inspiration and thought to what you describe.

To me, this specific devise and the hydro one are nothing short of con jobs in that they purport to have a practical functionally they charge a premium price for but cannot deliver. they are taking advantage of that intreauge in the magic you had many years back and lies within a lot of us. I see a detrimental effect with these things in them being far more likely to turn people off creatively thinking about them than being inspired.

You buy the Hydro thing and then realise the thing is useless because the water you put it in is not flowing at the unusually high speed required.  You pay over 500 bux for something that you have to near cook yourself with and work at wasting firewood just to charge a small battery.
The end result is the though you wasted money and these things, Hydro/ peltiers don't work the way they are made out and are dismissed and leave a sense of disappoint as well.

The creators of these Priced to kill products know their shortcomings and their very narrow and impractical window of living up to the created hype. To me that makes them con men.
The fact the hydro thing won so many awards is just a bloody sad indication of how Gaa gaa the world has become about anything touted to be " Green" and how so many will turn a blind eye to the shortcomings of such products because they feel obligated to gush over and never criticise the green religion.
Again, to me this is detrimental rather than helpful.

What would be much better in my mind would be to be honest, admit the shortcomings and work on solutions so they did live up to the expectations created and be able to be used in a practical, everyday way.

There is still this ridiculous and often dishonest/ self serving attitude or excuse that things that are lacking need to be built so they can be learned from even if they do fail spectacularly. I have seen this applied to things like electric cars and many other things.
It's a complete crock of ship.
You don't need to build anything thse days to know what it's going to do, it can all be computer modelled.  If they can design things like aircraft from passenger airliners to cutting edge Fighter jets and the things take off and fly round without problem and go into production with virtually no modification, there isn't much else you need to build a bunch of to see how they will perform.

There is a big difference between something that's sold as a Toy which will inspire creative minds and some priced to kill gimmick who's one and only function is to remove money from peoples wallets under largely false pretences.

I too had one of those little solar cells driving a little motor you could put a fan on or a swirling coloured disk in one of the tandy ( radio Shack)  100 in one electronic kits.   :D


Offline hiker1

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Re: Peltier units and Wood heaters
« Reply #9 on: July 20, 2018, 12:40:40 pm »
Electric bike..solar powered..small solar motor powers it....bought that I belive back in the 70s. ?  Love to bike so I've had that all these years.....😜
just do it

Offline DJ

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Re: Peltier units and Wood heaters
« Reply #10 on: July 20, 2018, 09:50:57 pm »

These days you could order about $10 worth of solar cells, Hook them up and the now not so young man would peddle that bike faster than any Olympic or professional rider on earth!  :0)

Offline Wolvenar

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Re: Peltier units and Wood heaters
« Reply #11 on: July 31, 2018, 02:24:06 am »
Seemed relevant to the seebeck effect discussion. http://people.clarkson.edu/~bhelenbr/Research_Pages/Students_files/m.s.pdf
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline Pete

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Re: Peltier units and Wood heaters
« Reply #12 on: July 31, 2018, 05:08:47 pm »
Thanks for that article Wolv. I did see a system many years ago that was apparently designed by the British for their polar stations. It was a thermocouple power unit that supplied around 60 watts ( from memory) when put on top of a gas or fuel stove.
I have never seen another one of those.
I have since purchased another 1kw of solar panels and added them to my system. We have fairly minimal power consumption here but live in the clouds on many days. So with 2.2kw of panels we don't need much sunshine to bring our batteries back up.
It has gone quiet on the site, I miss reading everyones stories
Thanks
Pete

Offline noneyabussiness

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Re: Peltier units and Wood heaters
« Reply #13 on: August 02, 2018, 04:30:37 pm »
Im with you Pete, it is very quiet. .. still check in regularly though

Offline Wolvenar

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Re: Peltier units and Wood heaters
« Reply #14 on: October 08, 2018, 03:39:55 pm »
Yeah, its gotten a bit dull. Oztules tends to spice it up here and there.
One summer I hope to be rebuilding my setup. I have so many projects going though I can't ever tell which summer.
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)