Homemade sand battery

I have been looking for one, I took it up to 1400 degrees and shut it off as I did not need that much heat. I lifted the hood and felt the volcano of heat coming out so it does work great.

Now I am thinking about all of the things I wanted to try before but could not, this can melt glass, and I am thinking I want to make quickcrete from limestone with this…

Even thought how fast this would make pizza LOL

Now I need to find some fire extinguishers so I can cut them up for crucibles, and get some gloves / tools for high heat…

And sadly… read the manual.


Is it programmable to go up to a certain temperature in steps like a pottery kiln?

It might be good for burning out wax from molds as well.

I used a tin can for my crucible, but the aluminum eats through the steel after a couple of rounds. I think in the thread ‘all about metal casting’ there is a video or two on how to make graphite/clay crucibles.

Whatever you do with it, make sure you have stuff on at least the bottom to protect from spills and splatters.


Yes it has multi stages has been used for pottery… I may burn out a tuna can and put some alum in for a test pour…

Love that I can power this with solar … sunny days that is.


In testing the sand battery I put 2 1/2 gal of water in a pot on the heated steel / sand. this was the results from the thermo coupler, and the pot heating up.

I was a bit disappointed it only went up to 180 degrees but the water started at 60 deg.

I noted that much heat was leaking out the top and I have added more fiberglass in that area.


I left the pot of 1/2 gal of water on the sand / steel battery. I took the water off as it was putting steam into my insulation.


For maximum transfer of power, the source impedance of the panels must match the impedance of the load. David Poz explains that in his solar panel direct to water heater element discussion. See https://www.davidpoz.com/


I’ve noticed that people melting Aluminum in Propane furnaces use a piece of cardboard under the crucible to keep it from sticking to the firebrick. I have recycled hundreds of three-ring notebooks, taking the steel to the scrapyard, the plastic to the landfill, and keeping the 1/8th inch thick paper board. The Kiln that you (Mart Hale) bought is FANTASTIC!


Thank you for that link, I have downloaded his spread sheet months ago and I have found it most useful both for hot water and stove top burners.

David sure helped me to understand better matching my solar panels to the heating element.


Yeah, I am just now finding out that I can melt glass in it… hmmm I wonder how glass compares to Aluminum for heat retention…

I am thinking I want to melt down some aluminum and make a large puck to go into my sand battery under my pots. or … fill the gap between two pots with melted aluminum that are large enough for me to set my pot with water in, which would be inside the sand /metal battery /…

I am now thinking about putting aircrete on the outside of the kiln to hold in the heat. I don’t want to cook the electronics so I may make a custom shape.

I have been thinking about making “lego” aircrete I would like insulation in circles or blocks that would stack on on another so that you could build a square or cirlce of them that could be moved… sorta imagine milk crates with no bottom. that stack inside one another…

I was thinking that with the kiln I could make a ceramic chimney / burn tunnel for rocket stoves…


Glass retains heat a lot better then aluminum and has a higher thermal capacity. Aluminum conducts heat significantly better then glass but it has a low thermal capacity.

You could probably make char in your kiln. :slight_smile:


Re: char…

Yeah I was thinking high grade char, first burn the charcoal to get rid of the volatiles, then seal from air to put out the flame, then put the char in the kiln to make it high grade.

I want to make quicklime by putting limestone in…

I will have to get some pans for this kiln as an 8 oz can does not stand up straight in it…

Going to have to visit some Garage sales…


I looked at my Sand battery, and I notice for over 10 hours it is above 500 degrees.

This has got me to thinking that I could use this to distill methanol from wood… Put a paint can above this filled with wood, and I could make either syngas or distill methonol…

I am also considering distilling plastic.


It’s unfortunate that I just scrapped a very large electric resistance furnace. A gas heat treat oven is going soon.

I’ve got a pallet of used crucibles that possibly I could share with someone. A shelf full of new ones in the barn. I’m trying to not give up on the foundry but age and the likely sale of my shop is really changing life plans.

Absolutely work safe in a foundry. We had asbestos spats that we wore just in case of a splash. Not only can metal splash - it can also squirt out from between the mold flasks if there is a gap between the mold flasks. If the pour is large enough - the density of the liquid metal can lift the upper half of the mold and lead to a leak. We have iron and steel weights to put on top of the mold to help prevent this from occurring. The volume of metal in the mold, gate, sprue, and riser can be rather significant and once it starts ejecting - it can continue to squirt out even as the operators are trying to stop the pour and vacate to safety. Spats don’t protect the backs of your legs and feet when you are trying to run away.

High top leather work boots are definitely preferred. I see video’s of folks in India working in foundries wearing simple sandals and it gives me the willies.

When I was a patient in the burn unit, there was a gent who came in that had liquid iron splash and some ran down into his boot. The iron burned his leg and the top of his foot as it ran down and solidified as a ring around one of his toes. I wasn’t impressed that it was the hospital maintenance guy who ran the disk grinder to cut the ring of iron off. I don’t think he had all that much experience using a grinder. His skill at operating a grinder close to a terribly burned foot and toe was suspect. They also didn’t think about the fact that the offending metal would get hot during the cutting operation.

You don’t need nichrome wire for hot wire cutting styrofoam. It’s common in composite work to simply use stainless steel safety wire. Harbor Freight sells spools of it fairly reasonable.

I made foam filler blocks for ailerons using a hot wire. In order to work alone, I made a simple “bow” using 1/2" electrical conduit. It more resembled a 10ft long hacksaw frame when I was done. A spring on one end allowed maintaining tension on the wire as it changed length due to heating. A simple variable resistor and battery charger provided adjustable current. My variable resistor was the open coiled nichrome heating element from an electric clothes dryer. An alligator clip allowed connecting to the exposed coils as needed. A variable speed motor controller can also be used to adjust the input voltage to a battery charger for an adjustable power supply for a hot wire.

If you have a helper, you can use the handles used for electric fence gates for each operator to hold on to to stretch the hot wire and perform a cut. Hardboard, salvaged aluminum siding or aluminum flashing can be cut for templates. Numbers along the periphery can help each operator keep track of where the partner is at to maintain accuracy.

Glad to hear Martin Payne is still around.



Thanks for your advice Ron.

When I was working in a factory I heard of a guy who was welding and the hot melting metal he was working on fell down into his boot… I can’t imagine making a liquid metal pour and having that spout back at you, or going into your boot that would make for a very bad day.

Your right about the stainless wire, I have seen people take stainless dish washing scrubies and take a wire off of that and use it to light fires with.

I have been using nichrome wire with solar panels, if I need to adjust I just cover more of the solar panels or change the position of the alligator cllip on the wire. I made a zig zag pattern to chop up lots of styrofoam so that I would just set the blocks on top and they would melt thru the grid, then I would put them in the electric lawn mower to chop them up…


For the last 5 days temps have been 250 degrees + 24 hours a day.

I guess I want to add more steel to my thermal mass to see what it does to the graph, I would hope it would lower the top temp and make it bring up the lower temp… But I am not sure …


I don’t remember exactly how your sand battery is constructed, so correct me if I’m off. Thermal conductivity is where steel will help flatten your curve. Iron, or mild steel, has maybe 200 times the conductivity of sand, which has about 5 times the conductivity of rock wool. Sand is more of an insulator than conductor. Steel bar, maybe rebar, could help conduct the heat from your heating element much faster, lowering the temperature peaks and heating more of the sand. Leaving plain sand on the outside should act as a first layer of insulation, and can take the heat, obviously. Rock wool on the outside would help reduce the heat loss and bring up the lower temperature. Fiberglass, according to the table (Solids, Liquids and Gases - Thermal Conductivities), is a little better than rockwool, and could probably take the sort of temperatures you would have on the outside of the sand.

Remind me, where is your thermocouple?


Hi Kent,

I have made many changes since I first started, it has been requested on other boards that I do a video of my setup and I am planning to do just that.

I have a trash can in which I I have lined the inner layer with fiber glass. on the bottom of the can I have put a pot filled with sand about 2 gal. On top of that I have a stop top burner in the metal shrowd you normally put on the top of the stove before you put the burner in. On top of that I have a dutch oven filled about 1/2 with sand and now a 12 inch long railroad rail. This I cover with fiber glass, then on the outside of this I have a 55 gal barrel with padded foam around the outside.

The thermo couple is at the top of the dutch oven, so I doubt I am getting any idea of how much heat is stored in the sand below… right now considering swapping out the sand in the first container on the bottom with steel bolts.

At this point I am getting consistent results, so I believe it is time for me to document everything with a video before making any changes.

I am glad I am not destroying heating elements I I have done before :wink:

It does seem to be Thermal Conductive of the element, and the specific heat capacity of them that seem to be the way to think of how to change the curve of the heat…

I have been reading a book written in 1975 telling how they stored heat back then, they used Iron, and some other chemicals I am not familar with.

I agree with your advice about rockwool, I have been searching for it on craigslist, I normally wait till I find it for 1/2 off the price on craigslist.

I think before I make this bigger I will try different mixtures of metal, sand, rock etc to see how it affects the heat curve. If I moved the hot plate to the bottom of the barrel instead of in the middle I believe the sand would absorb more heat… So many things I want to change, but first will document where I am so i can return to this point if I want to…


I now have this book. Interested he worked on the Manhatten project…

He also worked on storing heat in metal and composite setups… If nothing else it has given me new search terms to look for for looking this stuff up.

It can handle higher temperatures, but if the fiberglass hasn’t melted, it probably isn’t necessary.

Sand holds heat. the Iron is more heat conductive. So for storage the sand is better, for recovering it, the iron is better. I wouldn’t put the burner at the bottom, maybe near the bottom as heat rises. but your biggest issue is always going to be the size of the system. The ratio of surface area to volume is too large to efficiently hold heat.

You also might try glass since that is silicon dioxide, the main component of sand that holds the heat value. Then pack sand around it in the air gaps to drive the air out.

The best insulation is actually a vacuum. So if you can seal the inside from the outside and suck most of the air out. the insulation value will go up. It is very similar to what they do with double and triple pane windows, except they fill them with like argon, but I believe they are still under a slight vacuum. Less is more in this case. But I haven’t a clue as to how to build it. :slight_smile:

Crossing material boundaries typically slows down heat transfer as well.

I would probably look at a kiln refractory coating. Aluminum oxide and magnesium oxide are used as a refractory a lot.

Just some ideas, but you also have your own so don’t let me distract you. :slight_smile:

No distraction, good ideas.

I thought of a vacuum, I had an idea of building a vacuum chamber about 4 foot cubed… Then inside the vacuum chamber a chunk of iron or steel dangling from the top of the vacuum chamber with say fiberglass rope a poor conductor. Then use either a laser or inductive cooker to heat the metal. In theory, the metal should hold the heat for a very very long time…

There is a new tech where they use two panes of glass and they leave a tiny gap between the two panes and pull a vacuum between those two panes… I was consdiering doing this as well as a test.

Glass is on the list, I now have a kiln where I can melt glass… so I should be able to form it as I want it to be…

Yeah, next on the agenda is to make a video of what I have done, so that I can share it, I have found when I share my ideas on multiple boards I get tons of great input.

Thanks again for you insights.

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