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Author Topic: Thermoelectric generator - candle and cold water  (Read 60505 times)

Offline conradelektro

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Thermoelectric generator - candle and cold water
« on: August 16, 2012, 01:23:38 PM »
It is a very old idea, electricity from a temperature difference. The effect is called "thermoelectric effec" or "Seebeck effect", see for instance http://en.wikipedia.org/wiki/Seebeck_effect#Seebeck_effect .

I used two Peltier elements in series with a size of 30 mm x 30 mm x 3.6 mm each http://uk.farnell.com/multicomp/mcpe-127-10-13/peltier-cooler-38-1w/dp/1639751

Each Peltier element is held between two flat aluminium bars, one hot and the other cold. Heat is provided by a candle and coldness by cold water (in a container).

See the attached photos showing a crude contraption. The output is up to 2,8 Volt (no load, 10 Mega Ohm digital volt meter, two Peltier elements in series) and up to 80 mA (short circuit current).

When running a Joule Thief driving a gutted CFL or a 220V 1W LED lamp, the Voltage holds at about 1,25 Volt and the current is about 68 mA (about 80 mW). Of course neither the gutted CFL nor the 220V 1W LED lamp have full brightness.

An output of 80 mW is not much, but with a better design and more powerful Peltier elements an output of 1 Watt seems to be feasible.

I found very good Peltier elements for electricity generation at http://thermalforce.de/de/product/thermogenerator/index.php?uid=f06c1126a7b53e606196e78a328e41e9&ref= but one probably can also find some in the US or elsewhere.

A design I will try next is depicted in the attached drawing.

The difference between cooling elements and generator elements is in the temperature resistance. There are generating elements which can be run at several hundred degrees (centigrades) of temperature difference. The cooling elements are designed for a temperature difference of about 70° (centigrades).

The basic idea:

During winter (where I live) one just has to put a bucket of water outside to cool it to freezing temperatures. In the house one then uses a candle as heat source (and cold water) to drive a thermoelectric generator which could power a small reading or novelty lamp.

I like to light a tiled stove during winter, which could also provide heat for a thermoelectric generator (again coldness from cold water).

The cold water is of course heated up over time and has to be exchanged every hour or so (depending on the volume of the cold water container).

Greetings, Conrad
 
« Last Edit: August 16, 2012, 11:46:12 PM by conradelektro »

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Offline Pirate88179

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Re: Thermoelectric generator - candle and cold water
« Reply #1 on: August 17, 2012, 04:53:54 AM »
Conrad:

I was thinking of exploring this area myself after reading a 1951 Physics book explaining thermocouples.  They said it was just 2 dissimilar metals, they used copper and iron, and one coil at one end cold and another coil at the other end hotter than the other coil...and....electricity!!!!  No degradation of materials and you could use a whole bunch of them I am guessing and add up the power or volts.  I also am rethinking the Stubblefield coil in that...it used copper and iron wire and a coil was in the ground.  Well, here in KY where he lived, the ground temp is 54 degrees year around as that is the average temperature.  Well, it gets well over 100 degrees here in the summer so, that is a pretty good differential.  So maybe that is part of how he did all of that?  Who knows.  I will follow your experiments here with much interest.

Bill

Offline Magluvin

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Re: Thermoelectric generator - candle and cold water
« Reply #2 on: August 17, 2012, 06:36:02 AM »
I havnt tried using them as a gen yet but with 2 modern cpu heasinks and cpu blower fans(squirrel cage) and a peltier chip, with 12v at 1 amp per fan and around 4 amps for the chip, it is a small solid state A/C unit.

Sitting on the bench, blowing the cold side on me and the warm side elsewhere, I had to tun it off after a while as I was a bit chilled. ;]

A guy has a candle powred deal on YT where he actually runs a fan to cool a PC cpu heatsink, for the 'cold side' , with a candle on the hot side.
The cooling fan runs off of the output of the chip.  :o ;)   Candle powered fan.

I have that on my list. ;]

They have campfire chargers also. Charge and run devices on a camping trip with the camp fire. Survival outlets have them.

If ya think about it, per square area, these might give out more in a solar application that solar cells. The cooling side will have to be dealt with. The hot side is easier.

Now, there was the woman who was a biologist, that invented a sun powered micro refrigerator, using what she learned in biology about how our bodies get rid of heat.

2 aluminum containers, same height, 1 is smaller in diameter to have some space between the container walls if we insert the smaller one into the larger one.

The outer container has many small holes or larger holes with a screen wrapped around it.  In the space between the container walls, you put sand, dirt, sponge, what ever that might absorb water.

Put an insulated lid on it and put it in the sun. The evaporation through the screen/holes brings down the inner container to 42 deg F.   :o :o

Now, if those efforts were combined, the sun can be used to 'power' the hot side of the chips, and the 'cold' side. And if we consider the amount of heat on the hot side of the chip from the sun, then the solar refrigerator would be better than just running a lot of water for the cold side. ;]

Very neat devices. And ebay has them in bulk for great prices. And many sizes to choose from.  I think they come in 6in x 6in.   :o :o ;)

MaGs

Offline Pirate88179

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Re: Thermoelectric generator - candle and cold water
« Reply #3 on: August 17, 2012, 06:43:52 AM »
Mags, I like the solar aspect to this...never thought about it.  What about a bunch of peltier junctions floating on a lake or pond, with the cold side in the water, and the hot side facing the sun?  I believe that there is a lot more that can be done with these than is being done at the moment.  Or, perhaps mounted in the back of our freezers with the cold side...and the hot linked to the cooling coils that are very hot.....we pay for this cooling anyway so....sort of "free" electricity?

Bill

Offline Magluvin

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Re: Thermoelectric generator - candle and cold water
« Reply #4 on: August 17, 2012, 07:49:51 AM »
Hey Pirate

Well, we could use the heat of the fridge to power the hot side. If you look around for info, the ratio for hot side and cold side to get decent power out is 'hot' and 'cold'. So heat from the fridge for the hot, where do we get the cold? If we get our cold side from A/C in the home, then the A/C has to work harder to keep the fridge coils cooler, through the peltier gen, So maybe the energy from the peltier is free? And all from heat just passing from the fridge to the home A/C unit? ;]  Being that the fridge is heating the house anyway, that the A/C cools, that loss is inherent. So the peltier gen output is a gain. The heat from the fridge through the gen, then into the open air, wont make the house any hotter.  ;] It is what it is.  ;]

So put 50 of these chips on the back of the fridge, mount aluminum heat sinks to the cold side of the chips, lol, then power and inverter to run the fridge, with inherent losses that exist in the house already.  lol  im nuts.  ;) Maybe not. :o


There is a lot of vids on YT that are inspiring with these chips. Their efficiency is not great.
That when I decided that the candle power, if it could charge a phone, that would make me forget about the efficiency fast. The outcome would be worth it in power outages, or other things like disasters like hurricanes. 

Thinking about it further, then I came up with the sun powered hot and cold side. ;]

I want to get like 10 of these and try to make a small solid state A/C unit. Just to see what a larger scale of what I did with 1 works like.

The single is about 70 watts fans and all at 12v. Times 10, 700 watts. Like a smaller wall shaker unit, maybe less.  And 20 fans included in that estimate would create a lot of wind. These are not the simple bladed pc fans.

I find that it is best to use more fan and fins for the hot side. The faster you get rid of the hot side heat, the better the cooling on the cold side.  Like in your car, if you put the ac blower on low, the air coming out is colder.

So maybe the 20 fans could be divided to have more of them on the hot side, and less on the cold. Then if you want the solid state ac to be a heater, just reverse the chips input polarity.  ;]  They supposedly run best at near 16v input. As a gen, the voltages are more like less than 10v, closer to 5v, depending on the heating and cooling design. As a gen, the candle will get the hot side hot, so in the gens case, we also want to get rid of the heat from the opposite side of the chip as fast as possible for best results.

You can series and parallel them for greater outputs.  And series the chips physically also, so 10 chips for the SS A/C unit, 5 stacks of 2 chips would do close to the same job as all 10 laid out on heat sinks.

Computer shops will sometimes have boxes of these heat sinks and fans that you can get from them dirt cheap, from the right guy. Comp usa has good prices on new also.

The chip is only as good as the design of the application. ;]



MaGs

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Re: Thermoelectric generator - candle and cold water
« Reply #4 on: August 17, 2012, 07:49:51 AM »
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Offline TinselKoala

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Re: Thermoelectric generator - candle and cold water
« Reply #5 on: August 17, 2012, 10:02:32 AM »
TK likes this.
Two thumbs up!
 :)

Offline conradelektro

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Re: Thermoelectric generator - candle and cold water
« Reply #6 on: August 17, 2012, 11:08:02 AM »
TinselKoala & Pirate88179: thank you for the encouragement.

Magluvin: thank you for the good information (camp fire charges, aluminium boxes). I hoped to get feedback by creating a thread, and in come the great ideas. There are so many things out there which one can learn.

Efficiency: I read that NASA achieves about 7% efficiency in the latest Mars rover (2000 Watt of heat from the plutonium, about 150 Watt electricity out from the thermocouples) http://solarsystem.nasa.gov/rps/rtg.cfm . The easily available elements reach about 4%.
 
From this web site http://thermalforce.de/de/download/index.php?uid=f06c1126a7b53e606196e78a328e41e9&ref= (sorry, most of it in German) I learned a lot.

For electricity generation one wants a high temperature difference (100° or 200° centigrades difference), that really boosts the output (to near 4% efficiency). One also has to assure a good heat transfer from the Peltier element to the cooler/heater and they sell a lot of glues and pastes for that http://thermalforce.de/de/product/waermeleitmittel_zubehoer/index.php?uid=f06c1126a7b53e606196e78a328e41e9&ref= (again in German). I am not a sales person for this German firm but I am so happy to have found a source that sells one or two items to me.

May be some one knows US sources and info in English.

All winter from September to May I often light two tiled stoves in my house (kitchen and living room) because it creates a very comfortable atmosphere. And I want to combine this habit with a battery charger (during the day) or a lamp (in the evening) based on Peltier elements. Nothing new, but I want to come up with a simple and practical set up.

See the attached drawing for a principal lay out. The cold water container should be mounted on the outside of the house (the stove is on the inside of the wall) and two pipes lead to the heat exchanger at the Peltier elements (which are basically glued to the stove). One pipe feeds the cold water and the other returns the slightly warmer water (after it went through the heat exchanger) back to the cold water reservoir. If set up in the right way convection should start by itself.

In the sixties all water heating systems (with radiators in each room and a burner in the basement) were build to self convect. Nowadays one uses an electric pump to move the water through the pipes and the radiators because that allows for more freedom when installing the pipes and the radiators around the house.

All this is of course not new and probably not OU (but will be patented to make me rich, all rights reserved). My wish is to come up with a system that is easy to install and with commonly found (and hopefully low cost) components (besides the Peltier elements which cost about 50.-- Euros a piece). I also do not want to destroy my house or to install a really awful looking contraption. But sacrifices have to be made in order to advance science.

Greetings, Conrad

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Re: Thermoelectric generator - candle and cold water
« Reply #6 on: August 17, 2012, 11:08:02 AM »
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Offline conradelektro

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Re: Thermoelectric generator - candle and cold water
« Reply #7 on: August 17, 2012, 01:00:08 PM »
Here the camp fire charger mentioned by Magluvin (I like it):

http://www.youtube.com/watch?v=J2rA9XK_6wI (unboxing video)

http://biolitestove.com/campstove/camp-overview/features/ (2 Watt at 5 Volt)

http://biolitestove.com/homestove/overview/


Here a rather complicated description of a cooling system with two flower pots, sand, water and a paper kitchen towel:

http://www.ehow.com/how_7504579_diy-water-cooling-system.html


Greetings, Conrad

Offline TinselKoala

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Re: Thermoelectric generator - candle and cold water
« Reply #8 on: August 17, 2012, 06:06:29 PM »
Can these Peltier elements be completely submerged in oil? If so that would really help with the heat transfer, going in either direction. A non-pumped, convective flow of oil submerges the element and a high-efficiency heat exchanger interfaces with the environment or outside heat source/sink.
One side of the Peltier module is contacting (submerged in) one sealed oil chamber and ditto the other side of the module, one side hot, the other side cold.

Offline conradelektro

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Re: Thermoelectric generator - candle and cold water
« Reply #9 on: August 17, 2012, 07:45:07 PM »
Can these Peltier elements be completely submerged in oil? If so that would really help with the heat transfer, going in either direction. A non-pumped, convective flow of oil submerges the element and a high-efficiency heat exchanger interfaces with the environment or outside heat source/sink.
One side of the Peltier module is contacting (submerged in) one sealed oil chamber and ditto the other side of the module, one side hot, the other side cold.

The Peltier elements I have consist of two thin ceramic plates (non conducting) and the thermo coupled metals are sandwiched in between. Additionally there are two wires leading out from in between the ceramic plates. (See the Peltier element in the attached photo montage.)

The ceramic plates could each be a wall of a container, one container with hot liquid and the other with cold liquid. One needs a good glue (heat resisting glue for the hot side) and a suitable design / geometry of the containers.

I kind of go half there with may next design. I use a 110 mm diameter evacuation tube (PVC) with an end cap at the bottom as a cold water container. The end cap carries an aluminium plate with holes. And the cold ceramic plates of two Peltier elements will be glued over the holes. The cold water will be able to reach the aluminium plate but also the ceramic plates through the holes.

One wants the cold ceramic plate at the bottom of a cold liquid container, because the liquid which becomes a little warmer will rise being replace by the coldest liquid in the container by natural convection.

One wants the hot ceramic plate at the top of a hot liquid container, because the liquid which becomes a little colder will sink being replaced by the hottest liquid in the container by natural convection.

But in my next build I will only use the cold water container (with two cold ceramic plates at the bottom) and a candle to heat the two hot ceramic plates (two Peltier elements next to each other). In order to distribute the heat from the candle flame more evenly I will use an aluminium plate glued to the hot ceramic plates. (See the photos and the drawing in the attached photo montage.)

Greetings, Conrad

(I will travel for a week, therefore no more progress for at least a week.)

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Re: Thermoelectric generator - candle and cold water
« Reply #9 on: August 17, 2012, 07:45:07 PM »
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Offline Magluvin

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Re: Thermoelectric generator - candle and cold water
« Reply #10 on: August 18, 2012, 02:55:46 AM »
Hey Conrad and TK

I havnt seen oil used with these yet.  I think a nice slug of aluminum with many thin fins, and a glob of heat sink compound does very well. These things ar not very thick from hot side to cold side. The edges are filled with silicone it looks like, white, maybe high temp, and looks just to keep the weather out from the matrix inside.

Literally if you put power to a naked chip, do not have your fingers on either side, because things happen fast. Ive only done it in short bursts and you can feel it happen, one side cold, and one hot. Its a strange experience, as it is not a common one.

I saw a vid where with a naked chip, frost develops on the cold side fairly quick.

Conrad

Maybe you could get 2 PC cpu heat sinks to help get rid of the heat in the water.

Use a dremel, or a jigsaw with a fin laminate blade and cut a square hole in the side of your  plastic water tube. Use on cpu heat sink with fins inside the tube with the water, with the flat mounting side of the heat sink facing out and seal it into the tube with silicone well to avoid leaks. So the tighter the heat sink fits in the cut out of the tube, the better mounting adn sealing will be. Then apply some heat sink compound to the flat surfaces of the mounted heat sink  and figure a way to mount the outer heat sink to that surface. 

Or use an aluminum water container. Preferably square with flat sides that cpu heat sinks can be mounted.

Or, you can just use the heat sink alone on the cold side of the chip. it is the end result in the end. ;] Heat into the air.

Any fan will make a difference in getting rid of the heat from the sink fins. More is better.

I used an aluminum block, 2.5x2.5x3/4 in between the hot side and its heat sink for the SS A/C unit, as a buffer of sorts, to give a larger volume of aluminum to absorb heat from the hot side. Ill post some pics tomorrow.

So my setup, as an AC unit, is running backwards compared to your gen. And the water is your aluminum block. ;]   It might be best to put a small heat sink on the side of the chip thats in the water, giving more surface area 'to the water'. ;]  Chip surface area < heat sink fin surface area.

MaGs




Offline Tito L. Oracion

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Re: Thermoelectric generator - candle and cold water
« Reply #11 on: August 18, 2012, 03:58:00 AM »
 ;D


This is interesting though old but really interesting.  ;D


i will try putting the cold side in a cooler so that cold will last longer.  ;)


and i will try the iron that heats very long. and since heat is transferable then we can make it more stronger device. hmmmmm  8)
  :D


This is more efficient if we add some transistors and diode. hmmmmm  :o


I salute you contrad   :-* 


I think it much more better if we add some salt in the cooler to add extra cool.  8)   8)   8)   8)   8) 
I think liquid nitrogen can be also but  :o  lol

Do you know that to make heat, we only need two dissimilar metal  :o , why?, it acts like a battery then put some resistor. ok to prove it , try shorting the two hands of a battery wright? ;)


 ;D

Offline Magluvin

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Re: Thermoelectric generator - candle and cold water
« Reply #12 on: August 18, 2012, 08:21:59 AM »
;D


This is interesting though old but really interesting.  ;D


i will try putting the cold side in a cooler so that cold will last longer.  ;)


and i will try the iron that heats very long. and since heat is transferable then we can make it more stronger device. hmmmmm  8)
  :D


This is more efficient if we add some transistors and diode. hmmmmm  :o


I salute you contrad   :-* 


I think it much more better if we add some salt in the cooler to add extra cool.  8)   8)   8)   8)   8) 
I think liquid nitrogen can be also but  :o  lol

Do you know that to make heat, we only need two dissimilar metal  :o , why?, it acts like a battery then put some resistor. ok to prove it , try shorting the two hands of a battery wright? ;)


 ;D

From what I understand, the chips/module cant be driven too hard with higher voltages than around 16v. Im reading about them more as i found them also being discussed in one of my power supply builder books, Regulated Power Supplies  by Gottlieb.  They can be used to help keep PS transistors cool. They use them in microprocessor cooling also.

great book. Even discusses magnet biased cores. ;]  If you pulse the primary of a magnet biased core in one polarity and measure the input/output, then reverse the pulse polarity and remeasure, one way causes more input and more output, and the other causes less input and less output. ;] or instead of reversing the pulse polarity, you can reverse the bias magnet polarity. The difference in in/out depending on polarities is caused by saturation effects, affected by the magnet in the core. ;]



MaGs

Offline TinselKoala

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Re: Thermoelectric generator - candle and cold water
« Reply #13 on: August 18, 2012, 08:48:45 AM »
Yep. I used that latter effect to improve the output of my early Steorn Orbo replication, Orbette. The only toroids I could find at the time were long cylinders instead of rings, and when I used biasing magnets of the right polarity, the thing really sang, without any increase in applied power. Well, it was a pulse motor of type 3, a core effect motor, so biasing the core makes great sense in that design.
It's also very interesting to play with a strong NdB around the toroid of a Joule Thief.

Offline Tito L. Oracion

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Re: Thermoelectric generator - candle and cold water
« Reply #14 on: August 18, 2012, 08:52:23 AM »
i think 30v is permissible for other chips and that is enough for us.  ;)

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Re: Thermoelectric generator - candle and cold water
« Reply #14 on: August 18, 2012, 08:52:23 AM »

 

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