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Thermal sand battery prototype.
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Thermal sand battery prototype.
Idea..
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This discussion was modified 2 years ago by
MartHale7.
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This discussion was modified 2 years ago by
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19 Replies
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Today I decided to test out making a sand battery. I had this old pot with a hole in the bottom, I then took two cans cut out the bottom on those and put inside the pot over the hole then filled the pot with sand fir the first layer. Second layer I cut down the can a bit so it would fit in the pot and I laid in another layer of sand. For this first go around I had temps at the bottom at 325 degrees and at the top at 165 degrees…. After this I brought is inside put a welding blanket inside the cooler and put the pot inside…. I noticed a large amount of moisture building up inside the cooler, which figures as the sand I used was from outside. I am formulating how I could improve the heating of the sand was a fun experiment.
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Interesting way of moving heat around, I’ve done similar with rocks. If you want to get more heat in the sand you might consider using MANY smaller tubes over the single large chimney. That way it heats the sand more evenly and faster. With a fan blowing through it will also transfer heat to the wanted area faster.
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Yes, I have been thinking that metal bolts might be a better option, something that would allow more airflow, perhaps fist sized rocks might work better….
As I looked closer at this I do believe either an auger, or putting the sand into pans, then dumping the hot sand into a container afterword.
I am thinking putting the sand into my rocket oven heating it up then dump into an insulated box might do better…
I have a few ideas going in my mind but just will have to test to see what works….
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How about a rocket stove made mostly from ammo cans a small one inside a large one with sand in between. With an easily removable chimney. Take it outside burn it to get it hot after it’s done simply dump the ashes and carry it in leave the feed chute open for air to pass in and out the the chimney access.
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Interesting idea… make the stove itself the thermal mass….. Might work…. The idea I am working on in my mind is to have the stove outside, and the sand inside but transfer the heat to the sand via a pump and water heated by the rocket stove. Like a boiler.
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So, basically, a thermal mass. It may look a bit different, but a technique used for centuries variously known as “thermal mass fireplace”, “Russian Fireplace”, or the more recent “rocket mass heaters”. essentially the same idea. Heat up a mass, then let the mass radiate the heat over time. Even “Passive solar” buildings use a version of this, substituting the sun as the heating source onto thermal masses inside the house during winter.
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Yes, I run a rocket stove group on MeWe, and I have been looking at all kinds of rocket stoves, gasifier stoves, and TLUD stoves.
My attention got caught on thermal mass when I visited a man who built a cob oven. From one firing he runs the oven 2 – 3 days and cooks over 6 turkeys at a time in it. It is a huge oven, but he did not use much wood to heat the oven…… Since that time I have been collecting data and trying different methods of using thermal mass. My idea is to have the thermal mass right outside my window, and then with thermostat pipe that heat into my home as needed.
I have also worked with heat retention, thermal cookers, hay box cookers and I want to learn how to use the thermal mass of sand to hold heat and use it to my advantage. Thus using old junk steel cans give me a starting point to see how to get started…
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Yes, Earth Ships are famous for this….
I also do solar cooking… I know one guy who heated up steel rods to over 800 deg, he would then use the rods to cook on at night…. I want to harvest solar energy and use the rocket stove / oven to capture energy for cloudy days…. So testing what works and what does not.
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I have dried several 5 gal buckets of sand in my rocket oven wet sand is not very good at storing heat.
I now have built a solar hot water heater able to take 5 gal of water at 80 deg to 132 deg in 5 hours.
Now I have put 100 foot of pex into a black container, connected to the solar hot water heater and pump I am now re circulating the solar heated water thru the sand. I hope to use the sand as a battery ( like a hot water heater ) to capture the heat for later use. I have covered the sand with a bag of loose styrofoam, and put some insulation underneath. Finally I can get some data on what this sand battery can do.
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Today I really improved the insulation, more than before with the sand battery. I am glad to see that the sand is starting to hold energy. I believe with more tuning I should have some decent heat stored with the sand. The chart below tells me I am on the right track. I have about 3 gal of water in the system temp hit 180 degrees yesterday.
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Looking back at the data I collected that last couple of days.
I have a sand battery with 4 – 5 five gal buckets worth of sand in the battery.
The temps range from 107 deg to 132 degrees. This impresses me for the amount of sand that is in the battery, and the length of hours it takes for it to cool down.
I believe this could be made into a solar powered thermal cooker by removing 1/2 of the sand from the battery I would be in the range of cooking food..
If I use this setup as it is, I could use this to create ideal temps for making methane, or make alcohol just by adding or removing sand. Or perhaps a germination chamber for getting seeds started by adding a few more buckets of sand…..
I plan on adding more insulation to the pex lines, and check for where I am getting heat loss in this setup. A bit more tweaking and i should have a sand battery hot water heater that I can take a hot shower in the morning from the heat stored from the previous day. The temp ranges I am seeing is encouraging me that I am on the right path.
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Well.. I switched from having hot water heat the sand to just using a hot water heater element in the sand to heat about 5 five gal buckets of sand…..
Well the temp is now staying between 140 to 153 deg F I have not had a clear sunny day yet it has been mostly cloudy days and it is keeping this temp with two used 260 Watt panels in series. ( they normally give 220 watts of power each )
I am amazed that I have that much mass at that heat level with two panels on cloudy days, when I get a sunny day I will then test extracting heat with the pex pipe I have in the sand….. But for it to keep above 140 degree temps for over 24 hours is very very impressive to me on cloudy days…
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Yesterday my sand battery with the dutch oven, insulated with fiberglass hit over 600 F! This morning the next day the lowest temp it was at was 234 F!
The temp is going up again, looks like I will have this well over 200 F for over 24 hours!
This is with 3 solar panels 220 watts each… I have about 1 5 gal bucket of sand in the mix.
I am now thinking about what if I used an aluminum puck in the dutch oven so that I could pull it out and cook on it……
These temps are with partially cloudy days, next week they are calling for clear sunny days….
Now I am thinking of moving forward with building a sand battery the size of a IBC container 250 gal…….
I would then use the power I am not using after my batteries are charged to dump into that to store heat…..
The present setup should give me a good idea of how to scale up….
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I think what you’ve done so far and are doing is great. Once you get comfortable with the process look in to converting some of that heat back in to usable electricity!
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I have a pelter fan that could be useful…
Now I am looking into storing heat chemically..
If you put these hand warmers into boiling hot water they re-charge. They would store heat for years….
I have ordered some quicklime to do some experimenting with.
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I found this interesting, I did not remove the 2 1/2 gal pot from last night but covered it over still sitting on the sand / steel base. I removed the water when it started to boil, but I found that the temp of the thermocoupler was surprisingly high… I have also noticed that i was loosing a good deal of heat from the top so I added a bit more fiberglass insulation on top, after removing the boiling water. Plan to recharge this and try again with 1/2 of the amount of water…
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My progress on my sand battery.
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Overview of the sand battery:
1752 A DIY Sand Battery – The Theory, Practice And Use
https://www.youtube.com/watch?v=Icai6OOIh2M
Using the waste heat of a Diesel heater:
DIY Vevor Diesel Stove with Free Energy Sand Battery
Sand heat storage fireplaceㅣCleaning the fireplace
Isec solar cooker build:
https://www.youtube.com/watch?v=YX1SGK7gTg8
Someone who is doing a similar build as mine:
https://youtube.com/shorts/I5CHVMwNlys
My permies thread on my progress on sand battery:
https://permies.com/t/206700/Sand-battery-thermal-mass-proto
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This being a proto type I am breaking new ground here. I can use a fan with it to blow heat to me, or I can use it as a hay box cooker or thermal cooker I am thinking, but since this is the first time I have made this I am exploring. I like sand better than water for heat storage as i can go to higher temps without worry of steam problem like water.
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