Thermoelectric Power

[Neb]

Okay so that is a regular toggle with 4 separate junctions inside making 4 complete but separate circuits with one switch? Or am I reading that wrong?

What you are saying is to use three one for 12V one for 24V and 48V with each voltage wired with the same modules in different combinations for each switch? Sounds like a plate of spaghetti ! Are both positive and negative going through each switch? Leaving each one an open circuit until the switch is closed?

Good point!

Yes you will will need to switch voth the positive and negative side of the cells. The simplified wiring would look like this for 2 sets of cell to switch from serial to parallel.

But if you have 4 sets of cells you will need 8 poles. 8 pole single throw (8pst) are hard to come by. You could use a pair of 4pst for each option. That is one approach if you care to fo that route.

The next option that comes to mind is a selector switch.

They USED TO BE stackable so you could add as many poles as you want. I couldn't quickly find stackable versions. DigiKey would be a good place to look. That would let use a single selector switch to select which configuration tou want. Drawback is those contacts are not rated for high current.

High current versions may not be in production anymore because there are cheaper ways to do it now using semiconductors or relays. The selector could control contractors....

That can handle the current but they require a voltage source to actuate them and more cost in the contactor and the voltage to activate them.

There are rail-mount relay contacts ...

https://www.digikey.com/en/products/detail/finder-relays-inc/20-21-9-024-0000/10055777
While they are sweet and wire up easily and neatly they would set you back $500 or more and still need a control voltage.

So the double switch for each selection may run about $50. There is another cheap option.

Battery terminals...

Combined with alligator clips you can configure any circuit you want.

Ben

 

[Biggkidd]

Thanks Ben this will be a fairly low amp / low wattage unit I'm thinking around 100 (50-150) watts so in hindsight it's probably not worth the extra expense to wire it multiple ways. But if it does turn out to be worthwhile I like the selector switch idea the best. I've done the post deal a few times. lol

Thank you for taking the time to explain this so I could understand it, much appreciated!

 

[Biggkidd]

Alright the IR temp gun came in and testing of the stove's heat output has begun. Problem is it's not cold enough to burn it very hard. I have a pretty good base line for now but I need to test it when it's rolling and that would run us out of the house right now. lol It's 39 out and 73 f in and the stove top is 84c and the steel plate is 60c. The steel plate seems to change temperature much slower and seems to stay about 20-25c cooler than the stove top. Which is what I was hoping for but I still have to see where the top end temperatures get before I know which way to go setting up.

 

[UrbanHunter]

So I was looking at the 4PDT-3-MTD-CDD switch 4PDT-3-MTD - Gama Electronics and it appears to be the equivalent of 2 double pole double throw switches connected together 4PDT-3-MTD - Gama Electronics , it looks like you could easily wire 2 modules (or equal groups of modules) lets call them A and B, switching it one way would give you A+B voltage wise, the other way would give you A parallel to B. That would give you 2 variations, its a 30 AMP switch so you could cover the 100 to 300 watt range. $16 isn't too expensive for the ability to switch between 2 voltages on 1 system.

 

[Biggkidd]

Thanks I'll check it out.

Ended up getting the stove a little hotter than I meant to tonight but it gave me some good test numbers. Stove top got nearly to 200c the 1 inch thick steel got to 110c. The stove is headed back down it's at 165c now but the steel is still holding better at 107c. Looks like the steel plate is doing exactly what I need it to do. But that doesn't mean that's the route I'm going to go. I have another idea or three to try, that was just the first shot in the dark.

 

[Biggkidd]

The new stove fan came in today I got another one from Amazon but this one oscillates and the fan blade appears to turn a lot faster than the other one. Curiosity made look to see if had a larger power module and it does. I am robbing the other one to put on the radiator going in Savannah's room.

https://www.amazon.com/dp/B09KN2QXJH?psc=1&ref=ppx_yo2ov_dt_b_product_details
I think these things are to cool producing their own power from heat! Seeing as a larger module makes them turn faster and since I have a couple spare 40x40mm modules for my project the old one may get a larger module before I mount it upstairs.

 

[Biggkidd]

Got the old fan modified to be powered via hot water last night. I put a 40x40mm water cooling block over a thin piece of insulation foam on top of the fans base piece then put a TEC1-12706 with thermal paste on both sides on top of the block and used longer screws to mount the fans top half back over it. The hot water will go through the fan first then go through the radiator. Hopefully that will allow the fan to come on anytime it has hot water going through the system. The fan will be positioned to blow air through the radiator cooling it while heating the room.

The TEC1-12706 is also a lower temperature module then the one that came on the fan so it should work better with the fan now being in a much colder area.

 

[Biggkidd]

Hopefully the rest of my project parts will arrive this week. I think I just about have a solution to the heating / overheating of the modules but I need to run a bunch of tests and to do that I need the parts I'm still waiting on.

All this fooling with heat and power made me dust off some older ideas I had for a horizontal burn rocket mass heater. I got that all worked out on paper last night. Who knows if I'll actually build it. But just to let y'all in on the details this would be a relatively small footprint for a mass type heater being 12 to 18 inches wide and 52 inches long and tall. Which I know doesn't sound small at all but believe me for a mass type heater it's practically tiny!

 

[Biggkidd]

Yet another shift in plans. Now I'm glad I had to wait on parts. lol Going to go ahead and finish routing heat through a couple rooms from the woodstove but now I'm NOT going to put the modules on that stove in the house. I came up with a safer way to do it without chancing burning the modules out by overheating them. Also going to kill two birds with one stone if things workout like they should. Going to require a couple days fabricating things BUT this will work out MUCH better in the long run! Plus it will put some heat and power in one of the out buildings. Oh and for those who like repurposing things this entire project NOT counting the electrical parts is coming from the junk pile!

Did you know 200 gallons of water heated to 190f with a mean temperature of 70f holds around 60kwh of energy. If I can remove just 10% of that for electrical power I will call that a HUGE win!

 

[Biggkidd]

Getting lined up to run a simple test to see which of these three modules make the most power at the same relative temperatures. This test is between a TEC1-12706 a SP1848-27145 and a Kyocera #12016896A. Anybody got odds on which one will perform the best?

 

[Biggkidd]

my post went poof

Test was a fail. Between a leaking hose and it not being cold enough to crank the stove. I did learn one thing and that's the fact with the stove top at 250f and the modules on an inch or so tall finned heat sink with the pump cooling them on top isn't enough to get any usable power.

 

[Neb]

my post went poof

Test was a fail. Between a leaking hose and it not being cold enough to crank the stove. I did learn one thing and that's the fact with the stove top at 250f and the modules on an inch or so tall finned heat sink with the pump cooling them on top isn't enough to get any usable power.

Any chance of getting some pictures to help us follow along.

Ben

 

[Biggkidd]

Any chance of getting some pictures to help us follow along.

Ben

Once I make some actual progress I'll get some pics for ya. Sometimes ya just gotta love failing on account of what it can teach ya! I may have had a failure of yesterdays tests but it was WELL WORTH IT on account of what I learned! There's no doubt in my mind I can use the 1 inch thick steel plates as a damper on the woodstove for the modules to ride on and make it work that way. But that doesn't mean it's the best option for me. It would be if I only wanted to make power during cold weather but what about the other 8 or 9 months of the year? Besides I kinda like the look of my woodstove just as it is. lol Which is laughable coming from me since I have always been a function over form kinda guy!

The really important part here is the mass it's more critical than everything else from what I have learned so far.

 

[Biggkidd]

I think I am ready for a mini proof of concept build to actually see if what I think and what I've learned mesh with reality. lol In all honesty I'd like to just jump in and build a full size unit but that just doesn't make much sense until I can prove my theory...

 

[Biggkidd]

Any of you guys who know about electronics is there any type of switch or solenoid that can turn on and off at set voltages? Take my water heater for instance if I could put a switch inline to turn it on when the battery bank is above 56 volts and turn it back off when it drops back to 52 volts.

 

[UrbanHunter]

Any of you guys who know about electronics is there any type of switch or solenoid that can turn on and off at set voltages? Take my water heater for instance if I could put a switch inline to turn it on when the battery bank is above 56 volts and turn it back off when it drops back to 52 volts.

Most of the ones I have seen were either 12, 24, or 48 volts (12 volts are the most common); that said they are hard to find...

 

[UrbanHunter]

I have seen 12 Volt circuits that cut on or off at a range of about 2 volts.
I am wondering if that kind of circuit combined with a resister can trick the control circuit to "think" that it is seeing a 12V supply and control a 12V DC relay. Normally the control voltage source and the switch voltage supply can be isolated. The ones I have used have dip switch controlled cut off and turn on voltages.

When I looked back at them: I see they have a 48 volt version that can take voltages up to 60V. https://www.amazon.com/dp/B07WDLFTY9?ref=ppx_yo2ov_dt_b_product_details&th=1

It has 4 disconnect settings between 40 and 48V and reconnect voltages between between 42 and 52Volts...

It appears to be about 4 volts below your targets....

 

[Biggkidd]

I have seen 12 Volt circuits that cut on or off at a range of about 2 volts.
I am wondering if that kind of circuit combined with a resister can trick the control circuit to "think" that it is seeing a 12V supply and control a 12V DC relay. Normally the control voltage source and the switch voltage supply can be isolated. The ones I have used have dip switch controlled cut off and turn on voltages.

When I looked back at them: I see they have a 48 volt version that can take voltages up to 60V. https://www.amazon.com/dp/B07WDLFTY9?ref=ppx_yo2ov_dt_b_product_details&th=1

It has 4 disconnect settings between 40 and 48V and reconnect voltages between between 42 and 52Volts...

It appears to be about 4 volts below your targets....

That is exactly what I need but with a slightly higher set of parameters. Okay so what resistors would I need to trick it into thinking the voltage is lower than it is?

 

[Biggkidd]

Do you think this one would work. Says it's good to 60 volts and up to 30 amps.

https://www.walmart.com/ip/10V-60V-...OuzUNj3daroomt52voBkmDu1q2H9vuQ4aAqyZEALw_wcB
Click robot or human no idea why it says that but the link goes to walmart.

 

[Neb]

That is exactly what I need but with a slightly higher set of parameters. Okay so what resistors would I need to trick it into thinking the voltage is lower than it is?

A voltage divider

https://www.google.com/search?q=vol...ENC4xMZgBAKABAbABDw&sclient=mobile-gws-wiz-hp
But without knowing the input impedance of the sensing circuit we don't have all the numbers.

A potentiometer of 100k ohms may do the trick.

https://www.allaboutcircuits.com/te...ge dividers,will suffice for this experiment.

Ben

 

[Biggkidd]

Do you think this one would work. Says it's good to 60 volts and up to 30 amps.

https://www.walmart.com/ip/10V-60V-...OuzUNj3daroomt52voBkmDu1q2H9vuQ4aAqyZEALw_wcB
Click robot or human no idea why it says that but the link goes to walmart.

Less than $20 I'm going to try it.

 

[Biggkidd]

If this works it will make my solar hot water heater totally automated which would be AWESOME! I forgot it again the other day and it ran WAY to long and ran the batteries down. It has a thermostat but it hadn't reached that level yet. Even better it'll turn on and off on these days that are partial clouds and sun and best it won't be able to run when the panels aren't keeping up with the loads.

 

[Biggkidd]

Okay guys I'm currently working on a way to lift the modules up when the stove gets to hot. What I'd like to create is something that will let the modules start lifting about 275f and to keep the lift height close enough to the stove top to maintain 250 or 260f on the module mounting plate. So a real thermal balancing act!

If anyone has any ideas I'm all ears! Please try and keep in mind I am striving to make a design most anyone can copy cheaply with basic tools.

 

[Neb]

Okay guys I'm currently working on a way to lift the modules up when the stove gets to hot. What I'd like to create is something that will let the modules start lifting about 275f and to keep the lift height close enough to the stove top to maintain 250 or 260f on the module mounting plate. So a real thermal balancing act!

If anyone has any ideas I'm all ears! Please try and keep in mind I am striving to make a design most anyone can copy cheaply with basic tools.

Could you help us help you by posting some pictures?

Thoughts

If the hot side was a water bath the temp would automatically top off at 212 degrees F. Well below the upper limit.

Aluminum has twice the thermal expansion factor as cast iron.

If you had two strips of aluminum the same thickness as the plates they could lift the cells off the plates as they expand.

Ben

 

[Biggkidd]

Could you help us help you by posting some pictures?

Thoughts

If the hot side was a water bath the temp would automatically top off at 212 degrees F. Well below the upper limit.

Aluminum has twice the thermal expansion factor as cast iron.

If you had two strips of aluminum the same thickness as the plates they could lift the cells off the plates as they expand.

Ben

Now that's a slick thought using the different thermal properties of the metals. How are steel and copper compared to aluminum when it comes to heat expansion ?

 

[Neb]

Now that's a slick thought using the different thermal properties of the metals. How are steel and copper compared to aluminum when it comes to heat expansion ?

https://www.google.com/search?q=the...MTcuMTaYAQCgAQGwAQ8&sclient=mobile-gws-wiz-hp
Ben

 

[Biggkidd]

https://www.google.com/search?q=the...MTcuMTaYAQCgAQGwAQ8&sclient=mobile-gws-wiz-hp
Ben

Very cool Thanks! I had to save that. lol

 

[Biggkidd]

After messing with thermal paste or grease a few times I have to wonder if it isn't the same compound as anti-seize, feels the same looks the same and seems to move the same does anyone know if they are the same or interchangeable? Anti-seize is cheap in comparison to thermal paste...

I'm getting close to having a way of lifting the modules off the heat at the desired temperature. I ran several tests yesterday and I THINK I have it lifting around 260 which would suite me just fine. I will be happy anywhere between 250 and 280 f, I would like to be as close to 275f as I can get. Still trying to find the proper fill for the cavity to keep the thermostat in some sort of full contact heat transfer, although I probably need to try it dry again too.

 

[Biggkidd]

This time I tried filling the cavity with thermal paste. Maybe I should say I'm still filling, every couple hours I have to add a little, that crap moves slow!. What I have here is a 205f thermostat pressed in a 3/4 in copper pipe about an inch and a half long. I also crimped a pex ring on the end that sets on the stove top to give it more heat transfer. No matter how this test works out doesn't mean having it press fit in a 1/4 in aluminum plate will be the same, but it should give me a starting place. I'm figuring I'll mount all the modules on a 12x12x1/4 plate and put the thermostat on one end. Once the two surfaces break contact the thermal transfer slows to a minimum. But if I set it up right maybe I can still keep it close enough to make decent power while contact is broken. I will stop short of the end opposite the T-stat since it will be closest to the stove top.

 

[Biggkidd]

Pretty sure I've now got a viable thermostat controlled way of lifting the module plate. Not sure exactly when it lifted as I got busy eating dinner and the last time I checked before it lifted the temp was at 260ish when I checked just now it was lifted about 1/32 to 1/16 at 325ish. So it either lifted inside my target range or just over it. If it was over it that can be easily handled with a little insulation. The key point is it's now lifting somewhere north of 260 and that's freaking super cool! I think I've done about all I can do for now except cap it and test it again then wait until the aluminum plate gets here. I expect it will lift a little sooner once it's in the plate due to more surface area transferring heat to it faster. I just hope it's only a little sooner. I'd still like to see it start lifting at 275f. But I'll take anywhere between 250 and 280f. If it lifts to soon I can adjust the lift point a tiny bit by raising or lowering it in the 1/4 thick aluminum plate but the most play I'll have there is about 1/8 inch. If it lifts to late I can insulate the top of it to make it lift sooner.