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Solar vacuum tube Mod.... Testing heating with soldering iron

 
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Running my first test,   I had an idea this morning that instead of the silicon heater which i have used before which emits a smell when it get warm,   I would instead try out a prototype of just using a soldering iron and a 1 foot long copper pipe.      I have put in 1/2 cup of water and I will check temp as this progresses.   Soldering iron pulls 30 watts of power, but one end of the pipe was 200 deg the other was 120 degrees.    I am thinking this would run off my solar system off battery with ease.     Initial tests look very good to me, no smell of the silicon heater and only copper heating the inside.

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Mart Hale
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I was able to hit 145 degrees inside the tube heating 1 cup of water with the soldering iron     good for a cup of tea :-)    I have better insulated the entrance to the tube and i am going to give this another try to get over 160 degrees.

20190910_142457.jpg
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what is the end goal?
 
Mart Hale
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David Baillie wrote:what is the end goal?



I want to see what the lowest amount of energy I can use to cook with.   If I can hit 190  degree I will be happy to cook on cloudy days with my solar via batteries...

So far  the instant pot blows this away with the energy / time / hassle factor.


But you don't know till you try.
 
David Baillie
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Interesting. A 12 volt immersion heater works great. Usually about 10 amps at 12 volts. I have one for the car its great for tea reheating. the problem with the low wattage of something like a soldering iron is you have to overcome the "resistance" and losses to the vessel for longer so its overall efficiency goes down. Yes its instantaneous draw is higher but it wins in the end.   Something like this:  https://www.amazon.com/Zerodis-Immersion-Electric-Heaters-Camping/dp/B07DNZWBM7/ref=sr_1_4?crid=37UXC409FQ2JX&keywords=12+volt+immersion+heater+for+water&qid=1568205308&s=gateway&sprefix=12+volt+imm%2Caps%2C181&sr=8-4

Cheers,  David
 
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I would be astonished if anything with so much conversion loss could beat out a properly designed solar cooker. Granted, you might, in higher latitudes, need to use solar power stored over a much longer period of time, when it would perhaps be difficult to get a solar cooker up to temperature.

If the 12v immersion heater didn't work out, I would look to the immersion heaters being touted for home sous-vide cooking. Granted, those usually include some kind of circulation impeller to make sure you don't get cold or hot spots in the water, but there you have a method of cooking that is designed for low temperatures. Perhaps that would tilt the scales.

Not to discourage, but is this practical? I mean, if the sun is strong enough where you are, you should be able to use a solar cooker, or generate enough electricity through solar that an induction hotplate would be easy to operate. If the sun isn't strong enough, doesn't that mean that you're cold, and that added heat is a boon?

What's wrong with a tiny, efficient, flame? The barrel of the smallest diameter rocketstove that you could design and construct would make an excellent hotplate, and if it's built to burn efficiently enough, there would be no waste, and little to no exhaust, a definite step-up from situations around the world where an open pit flame is the normal method of cooking.

-CK
 
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David Baillie wrote:Interesting. A 12 volt immersion heater works great. Usually about 10 amps at 12 volts. I have one for the car its great for tea reheating. the problem with the low wattage of something like a soldering iron is you have to overcome the "resistance" and losses to the vessel for longer so its overall efficiency goes down. Yes its instantaneous draw is higher but it wins in the end.   Something like this:  https://www.amazon.com/Zerodis-Immersion-Electric-Heaters-Camping/dp/B07DNZWBM7/ref=sr_1_4?crid=37UXC409FQ2JX&keywords=12+volt+immersion+heater+for+water&qid=1568205308&s=gateway&sprefix=12+volt+imm%2Caps%2C181&sr=8-4

Cheers,  David



Thanks David...

That is a good suggestion.    It is a balancing act as you do want to get the job done and an immersion heater works fast.     On the other hand,   the place I am putting it is inside a glass vacuum tube...  ( I don't want to create a sudden temp change and destroy the glass)..     But I could put the immersion inside copper tube so it would diffuse the heat...    

I was able with time to raise the temp up of the 1/2 cup of water to 144 degrees.   with 29 Watts of input.      If I get another $5.00 (shipped )   soldering iron that would push the temp up over 160 degrees and I would be cooking....    at the cost of total 60 watts of energy.

I am considering getting two sodering irons, and taking them apart and fitting them deep inside the tube with silicon wire which can take the high temps..




 
Mart Hale
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Chris Kott wrote:I would be astonished if anything with so much conversion loss could beat out a properly designed solar cooker. Granted, you might, in higher latitudes, need to use solar power stored over a much longer period of time, when it would perhaps be difficult to get a solar cooker up to temperature.

If the 12v immersion heater didn't work out, I would look to the immersion heaters being touted for home sous-vide cooking. Granted, those usually include some kind of circulation impeller to make sure you don't get cold or hot spots in the water, but there you have a method of cooking that is designed for low temperatures. Perhaps that would tilt the scales.

Not to discourage, but is this practical? I mean, if the sun is strong enough where you are, you should be able to use a solar cooker, or generate enough electricity through solar that an induction hotplate would be easy to operate. If the sun isn't strong enough, doesn't that mean that you're cold, and that added heat is a boon?

What's wrong with a tiny, efficient, flame? The barrel of the smallest diameter rocketstove that you could design and construct would make an excellent hotplate, and if it's built to burn efficiently enough, there would be no waste, and little to no exhaust, a definite step-up from situations around the world where an open pit flame is the normal method of cooking.

-CK



This beats a solar cooker hands down on a day with no sun :-)


A day with sun  also beats this because I can use solar panels to run the cooker and I stay cool inside instead of going out into the heat.


I have obtained over 400 degree temps with this solar tube when I had it extra well insulated with sun.     So the vacuum insulation on this baby works awesome.      I am just trying to get it to work inside and let the solar panels I have outside allow me to stay inside.   Also here in
Florida we often get mid day rains so running out to grab the solar cooker is not always fun,  I prefer set, and forget methods when I can find them.


Mart




 
David Baillie
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Mart Hale wrote:

David Baillie wrote:Interesting. A 12 volt immersion heater works great. Usually about 10 amps at 12 volts. I have one for the car its great for tea reheating. the problem with the low wattage of something like a soldering iron is you have to overcome the "resistance" and losses to the vessel for longer so its overall efficiency goes down. Yes its instantaneous draw is higher but it wins in the end.   Something like this:  https://www.amazon.com/Zerodis-Immersion-Electric-Heaters-Camping/dp/B07DNZWBM7/ref=sr_1_4?crid=37UXC409FQ2JX&keywords=12+volt+immersion+heater+for+water&qid=1568205308&s=gateway&sprefix=12+volt+imm%2Caps%2C181&sr=8-4

Cheers,  David



Thanks David...

That is a good suggestion.    It is a balancing act as you do want to get the job done and an immersion heater works fast.     On the other hand,   the place I am putting it is inside a glass vacuum tube...  ( I don't want to create a sudden temp change and destroy the glass)..     But I could put the immersion inside copper tube so it would diffuse the heat...    

I was able with time to raise the temp up of the 1/2 cup of water to 144 degrees.   with 29 Watts of input.      If I get another $5.00 (shipped )   soldering iron that would push the temp up over 160 degrees and I would be cooking....    at the cost of total 60 watts of energy.

I am considering getting two sodering irons, and taking them apart and fitting them deep inside the tube with silicon wire which can take the high temps..




OK, Why not make a separate heating container for cloudy days? You can find a double walled thermos bottle at any thrift store for pennies; Usually stainless but maybe the old school glass ones (for extra coolness points it would have to have that rocking 70's plaid pattern). You know the double walled stainless could take the heat. I fully respect a person's desire to tinker of course.
David
 
Mart Hale
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OK, Why not make a separate heating container for cloudy days? You can find a double walled thermos bottle at any thrift store for pennies; Usually stainless but maybe the old school glass ones (for extra coolness points it would have to have that rocking 70's plaid pattern). You know the double walled stainless could take the heat. I fully respect a person's desire to tinker of course.
David

I do have a stainless thermos that I could experiment with thanks for the idea.      




 
David Baillie
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Here is a good calculator spreadsheet to let you know what a 100 percent efficient heater would consume... Lets you guesstimate how well you are doing.
https://bloglocation.com/art/water-heating-calculator-for-time-energy-power
 
Mart Hale
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These two videos are what have motivated me...


2 60 watt light bulbs   cook a chicken in 90 minutes->




 
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very interesting - cooking with insulation and 120 watts.  implies that most heat used for cooking is basically wasted out the oven door or wood stove top. so you could presumably easily run an insulated oven with a 300W solar panel (direct DC heat resistance) for several hours, given a few hours of sun.

separate question, has anyone run a parabolic solar heater on to some kind of vacuum insulated container like this below?  you would have to paint it black of course.  I believe radiation heating goes through a vacuum, which is what allows the GoSun solar cookers to be so effective.

https://www.webstaurantstore.com/thunder-group-sej73000-60-cup-wood-grain-insulated-sushi-rice-pot/407SEJ73000.html
 
Mart Hale
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Josh Garbo wrote:very interesting - cooking with insulation and 120 watts.  implies that most heat used for cooking is basically wasted out the oven door or wood stove top. so you could presumably easily run an insulated oven with a 300W solar panel (direct DC heat resistance) for several hours, given a few hours of sun.

separate question, has anyone run a parabolic solar heater on to some kind of vacuum insulated container like this below?  you would have to paint it black of course.  I believe radiation heating goes through a vacuum, which is what allows the GoSun solar cookers to be so effective.

https://www.webstaurantstore.com/thunder-group-sej73000-60-cup-wood-grain-insulated-sushi-rice-pot/407SEJ73000.html




What I did was put a silicon heating pad used for 3d printers inside of something like this ( a heat retention pot )   but the pad emitted an odor and was not a good thing.       I have since tried a bread machine coil but it did not get warm enough with my 220 watt panel.


I have found it is very very hard to beat an insta pot for energy in and then all computer controlled cooking under pressure.
 
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I was thinking more about running a relatively large DC water heater (200 -300W) element inside a fairly large wooden oven (lined with tinfoil big enough for a big roasting pan, maybe 3 cubic ft) and line that whole assembly with 2-4 inches of poly-iso foam with a lid.  The goal would be to get it to baking temps for breads, etc, but could also be used as a slow cooker for meats/veggies if the temps did not make it that high.  You could also let it sit for a while to cook longer.  

 
Mart Hale
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Josh Garbo wrote:I was thinking more about running a relatively large DC water heater (200 -300W) element inside a fairly large wooden oven (lined with tinfoil big enough for a big roasting pan, maybe 3 cubic ft) and line that whole assembly with 2-4 inches of poly-iso foam with a lid.  The goal would be to get it to baking temps for breads, etc, but could also be used as a slow cooker for meats/veggies if the temps did not make it that high.  You could also let it sit for a while to cook longer.  



Yep for that size element you need a very large amount of power but yep could be done.

I like playing with this but very hard for me to beat my bread machine.
 
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