Sand battery - thermal mass proto type.

Interesting experiment with sand battery.

Looks like this gent found a good way of using thermal mass in concrete to heat their home.

https://medium.com/@upnorthandoffgrid/6-heating-systems-5c5727c1607e

Combining heat pump + masonary heater I do find innovative.

Use of excess solar to store heat in sand.

Testing different types of sand.

The comparison of graphite verses the sand I found most interesting.

Sand Battery Comments Please!! July 2025

Before I put the blades on my baby windmill!!

Stove Top Element to 400 watt AC wild windmill:
*Cement Paver
*Canning Pot
*Antique mine cart forged wheel in the bottom
*Bricks with air holes
*Old HubCap
*Play Sand
More sand will be added if any heat generated.

I had information that a heating element creates a circuit so no neutral is in this Iteration #1.

#6 copper Wire 1 pc each end connected to a prong makes a kind of half hoop
#10 stranded wire wraps the ends of #6
*Ceramic Insulator pieces for electric wires
 Attached to 2 energy conducting wires from the windmill to keep the connection away from the side of the pot
*Three AC wild energy conducting wires attached to the #6 hoop to send energy to the heating element . see above
*Ground wire from a satDish we had once, attached to the Canning Pot, then goes through wall outside grounding to the soil

I do have refractory insulation
I do have a heat reading gun
I do have a multimeter
I also have some plaster of paris

Bever Branson wrote:Sand Battery Comments Please!! July 2025
Stove Top Element to 400 watt AC wild
*Cement Paver
*Canning Pot
*Antique mine cart forged wheel in the bottom
*Bricks with air holes
*Old HubCap
*Play Sand

Hi Bever,

Thanks for sharing your experiments with sand battery.


I have found that the elements will short out if they are placed in the sand,   I find it better to use them as they were designed with a pot over them and the elements not in the sand.      

That said,   thanks for sharing your experiment,  I look forward to see how you intend to use your sand battery.

Cheers.

July 2025 - sand battery stove top element

Are you saying put sand into a pot, then pot on top of the stove element?
Maybe in that scenario the stove element rests on the old hubcap, sand any sand...

Bever Branson wrote:July 2025 - sand battery stove top element

Are you saying put sand into a pot, then pot on top of the stove element?
Maybe in that scenario the stove element rests on the old hubcap, sand any sand...

Yes,  that is what I am suggesting.    

Mike on youtube has had success putting the coil in bout taking it apart and making a spiral  in the sand...    


https://www.youtube.com/@off-gridsurvivalmike8120/videos

Mike has several experiments going with sand batteries...    Some of them have been running for many months.

July 2025 Sand Battery with stove element:

I was pleased to find I could bend #6 copper wire, so the coil like Mike sounds very very feasible!!!

I will look for his topic

Thank you!
I'm tired of being afraid of electrical wires dernit

Bever Branson wrote:July 2025 Sand Battery with stove element:

I was pleased to find I could bend #6 copper wire, so the coil like Mike sounds very very feasible!!!

I will look for his topic

Thank you!
I'm tired of being afraid of electrical wires dernit

Yeah,  Mike has done great work, but he is not on permies as I am aware, but look at all his other videos, there is tons there.

2025 Sand Battery with Stove Element

Thank you Mart!!

It looks like a pretty cool project.  I often wonder how difficult it would be to do a DIY heat exchanger with a primitive boiler either wood or waste oil driven on the outside and utilize a pump with coolant filled lines to move the heat indoors.

Boiler, coolant filled lines heat to house sounds like a great project. Waste oil sounds like a longer boiler heat scenario than trudging out to refill wood fire.

My neighbor has a hot water trough attached to copper coils heating from a little woodstove for occasional soaking tired muscles and pain.  It's set up in an outhouse looking structure outside and makes an interesting rustic addition to the place

https://www.batsand.com

Commercial use of sand as thermal mass.

Sand Battery 2025 AC wild

July 2025. Thanks Mart Hale for the bat sand design link.
BatSand tech is familiar!  I've seen designs for large scale well over 45 KW too.
The fact there are blueprints included bode well for buyers who need credibility at the permits level. I think i sent the BatSand idea to a family member moving to Italy.

Bever Branson wrote:Sand Battery 2025 AC wild

July 2025. Thanks Mart Hale for the bat sand design link.
BatSand tech is familiar!  I've seen designs for large scale well over 45 KW too.
The fact there are blueprints included bode well for buyers who need credibility at the permits level. I think i sent the BatSand idea to a family member moving to Italy.

Yeah,   I think the next level is instead of resistive heating as they are doing is for them to combine in a heat pump as they do with modern heat pumps that cool the room and use the heat to heat hot water for showers.          I have posted several designs in thhis thread that are commercial I might have posted somebody that has already done that....

Indeed when you have commercial ventures doing this it does prove the tech is moving forward.

Interesting,    use of quartz tube heating....

Use of alum shavings mixed with sand looks promising....

I have seen a WWII immersion water heater that would be placed in a 55 gallon barrel. The base and burn chamber a donut shape that rested on the bottom of the drum and the chimney and feed pipe/air inlet up to the top of the barrel. At the top a vessel of a couple of gallons held diesel or waste oil that drips oil down the feed pipe to the burn chamber. No reason the heating medium couldn't be sand.

Robert Ray wrote:I'll try and pull up a picture today, I have seen a WWII immersion water heater that would be placed in a 55 gallon barrel. The base and burn chamber a donut shape that rested on the bottom of the drum and the chimney and feed stack up to the top of the barrel. At the top a vessel of a couple of gallon vessel held diesel or waste oil that  drips oil down the chimney to the burn chamber. No reason the heating medium couldn't be sand.

Thanks for sharing.        The problem I could see is that the dry sand would insulate the tube and create furnace like conditions like a rocket stove,   and a rocket stove you don't want metal in the hot part of the chamber as it will deteriorate  quickly...        

I would love to see the design,  I have been thinking ceramic on the inside of the chamber might be the way to go...

Never having built a RMH but seeing that some use pipe in their construction, maybe someone could offer their opinion in how long pipe lasts within an insulated construction. Temperatures within an oil drip stove would be nowhere near the temps achieved in a RMH. Duct hose and a bilge fan could be used to exhaust fumes from a structure.

Sent out a couple feelers and by noon had an immersion heater gifted to me. Will fit in a 30-gallon galvanized garbage can. Need to fab a drip can and will add a square of carbon felt in the drip chamber I don't have to drop paper in to start pan.

Robert Ray wrote:Sent out a couple feelers and by noon had an immersion heater gifted to me. Will fit in a 30-gallon galvanized garbage can. Need to fab a drip can and will add a square of carbon felt in the drip chamber I don't have to drop paper in to start pan.

Very nice...    

I was thinking that could come in handy to give frost protection in a green house.       that design looks simple enough that one could make one from pipe and a propane tank...


I was thinking about something like this for frost protection, move barrels next to plants cover,   then heat up the water in the barrels.

Robert Ray wrote:Sent out a couple feelers and by noon had an immersion heater gifted to me. Will fit in a 30-gallon galvanized garbage can. Need to fab a drip can and will add a square of carbon felt in the drip chamber I don't have to drop paper in to start pan.

I found them on ebay...  you got a real deal..

https://www.ebay.com/itm/287078011942?_skw=MILITARY+SURPLUS+IMMERSION+HEATER&itmmeta=01KFKYPH0D0DPXPTMY0ZS210ES&hash=item42d72ed426:g:GUUAAeSwxEBpaZ71&itmprp=enc%3AAQALAAABAO7PUuNWmJ%2B%2BUShgI9tQz%2FpZr08G91R5nGqFFSIiY7uiMgFLI3iWX7s%2FUCNHm4OxOxr7HrNbsJduObR6kfV8HZ2gURDrq%2BTaaV37xxPKQUyvh7CTfJfjJZ%2FUtVB%2Bkzas%2B330mo51zBkaG2m7BYvGGNOLD%2F4EvuZnG5IyOwUhykppPfIm0OVtCVxnsWFnWxGANvm19v3tr6PY5oESczOyu%2FqEUa%2BCk2T295DQnfreNgCihHL5HeUnPE%2F548P%2B4Ohde3oFBsmSR2dGvd1Pgf%2Frj5bnvgmRbQ69KsGN4wwoyoRtXJcKjr3ZcHQz580VIyPt5sibtVCLDYLFn6vFkR2nP6A%3D%7Ctkp%3ABk9SR7aQ2v78Zg

Sand battery  with ducting.....

I was looking at this and was thinking this would be cool to test with forced air from a rocket stove...

Storing heat chemically....

Mart Hale wrote: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.

That’s a really interesting experiment! It’s great that you’re testing and learning from the first attempt. The temperature difference between the bottom and top layers is pretty impressive, and the moisture buildup makes sense since the sand likely held a lot of water from being outside. It would be interesting to see how much better it performs after drying the sand completely and improving the insulation around the pot. I like the idea of using what you have on hand and refining the design through trial and error. Looking forward to seeing what improvements you come up with on the next version!

Open-Source Concept: Modular Off-Grid "All-Weather" Sand Battery for Home Heating
Hi everyone,
I want to share a low-tech, modular product concept I've been working on to tackle energy poverty and grid dependency. I'm putting this out here fully open-source for anyone in the maker and permaculture community to build, test, and improve upon like some of you already been doing.
The Core Concept:
It is a mobile, stacked off-grid thermal buffer designed for any home or apartment. The shell can be built using modular terracotta rings, concrete blocks, cast iron, or even an upcycled metal oil drum. Inside, it is filled with cheap, locally sourced construction sand.
The Hybrid "All-Weather" Energy Mix:
Instead of relying on the grid, the system uses a direct DC connection powered by whatever nature provides at that moment:
1. Plug-and-play balcony solar panels (Solar)
2. A micro wind turbine (Wind)
3. An inline micro-hydro turbine placed inside the rainwater downspout (Water power from heavy winter rains or rivers)
On dark, freezing winter days when solar is non-existent, the wind turbine and rainwater downspout turbine pick up the slack.
How it works & Benefits:
• The generated DC power goes straight into a heating element buried in the sand.
• The sand absorbs the high-temperature heat (up to +-300°C) completely pressure-free and leak-free.
• The outer shell slowly and safely radiates comfortable, steady heat into the room for hours. No inverter losses, no complex electronics, and zero grid load.
• In the summer, you can easily plug the solar/wind output directly into a DC-powered fridge or small AC for free cooling.
High-Temperature Wood Stove Synergy:
For those with a wood or pellet stove, the modular shell can be built around or right next to the stove's exhaust pipe. It acts as a thermal sponge, soaking up the intense 200°C+ waste heat that normally escapes through the chimney, preventing the room from overheating and creating a massive radiant night buffer.
I uploaded the 3D visualizations and the technical cross-section diagram here so you can see exactly how it's structured:
• Design Concept: https://ibb.co/DP7N6xqL
https://ibb.co/zhjtyvDW

Feel free to copy this, build a prototype in your workshop, or share it with local energy coaches and community workshops to help folks get through the winter safely without relying on dangerous candle heaters or expensive utilities.
I'd love to hear your thoughts on material choices (concrete vs. terracotta) and how to optimize the DC element setup or other input or ideas. And also want to show some appreciation for the info already shared.
Cheers from The Netherlands,

Cindy Mortera wrote:

Mart Hale wrote: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.

That’s a really interesting experiment! It’s great that you’re testing and learning from the first attempt. The temperature difference between the bottom and top layers is pretty impressive, and the moisture buildup makes sense since the sand likely held a lot of water from being outside. It would be interesting to see how much better it performs after drying the sand completely and improving the insulation around the pot. I like the idea of using what you have on hand and refining the design through trial and error. Looking forward to seeing what improvements you come up with on the next version!

Hi Cindy, sorry I have not replied sooner, but i just found your post.        Indeed  I did progress from wet sand to dry sand, and I found the need for insulation.        I did post further results later in this thread of using solar and a hot water heater element.      Others have also posted in this thread of their use of this tech to cook food.       There are many things one can do with thermal mass, some are already products that one can buy.

Cheers,

Danny Post wrote:Open-Source Concept: Modular Off-Grid "All-Weather" Sand Battery for Home Heating
Hi everyone,
I want to share a low-tech, modular product concept I've been working on to tackle energy poverty and grid dependency. I'm putting this out here fully open-source for anyone in the maker and permaculture community to build, test, and improve upon like some of you already been doing.
The Core Concept:
It is a mobile, stacked off-grid thermal buffer designed for any home or apartment. The shell can be built using modular terracotta rings, concrete blocks, cast iron, or even an upcycled metal oil drum. Inside, it is filled with cheap, locally sourced construction sand.
The Hybrid "All-Weather" Energy Mix:
Instead of relying on the grid, the system uses a direct DC connection powered by whatever nature provides at that moment:
1. Plug-and-play balcony solar panels (Solar)
2. A micro wind turbine (Wind)
3. An inline micro-hydro turbine placed inside the rainwater downspout (Water power from heavy winter rains or rivers)
On dark, freezing winter days when solar is non-existent, the wind turbine and rainwater downspout turbine pick up the slack.
How it works & Benefits:
• The generated DC power goes straight into a heating element buried in the sand.
• The sand absorbs the high-temperature heat (up to +-300°C) completely pressure-free and leak-free.
• The outer shell slowly and safely radiates comfortable, steady heat into the room for hours. No inverter losses, no complex electronics, and zero grid load.
• In the summer, you can easily plug the solar/wind output directly into a DC-powered fridge or small AC for free cooling.
High-Temperature Wood Stove Synergy:
For those with a wood or pellet stove, the modular shell can be built around or right next to the stove's exhaust pipe. It acts as a thermal sponge, soaking up the intense 200°C+ waste heat that normally escapes through the chimney, preventing the room from overheating and creating a massive radiant night buffer.
I uploaded the 3D visualizations and the technical cross-section diagram here so you can see exactly how it's structured:
• Design Concept: https://ibb.co/DP7N6xqL
https://ibb.co/zhjtyvDW

Feel free to copy this, build a prototype in your workshop, or share it with local energy coaches and community workshops to help folks get through the winter safely without relying on dangerous candle heaters or expensive utilities.
I'd love to hear your thoughts on material choices (concrete vs. terracotta) and how to optimize the DC element setup or other input or ideas. And also want to show some appreciation for the info already shared.
Cheers from The Netherlands,

Hi Danny,

I have found many people have experimented with using solar panels to store energy in a thermal mass...       I have posted several links in this thread, and my own experiments.        

So far the best I have done is to run the solar direct to my hot water heater.      After my batteries are charged a relay is tripped and a circuit is completed that goes direct from my solar panels to my hot water heater.      So the excess energy is stored as hot water.  

But your concept  has been pretty much so put into practice with Mike's work ->



For your Terra cotta idea I believe it should be in an insulated box then when you need the heat one could use a fan and remove the top cover...


Open source is the way to go.     I love seeing people take concepts and going out there and making it happen.

 
Peace.