Homemade sand battery

Today hit the highest temp ever, over 803 deg F…

It was a bright sunny day, I had replaced the wire with silicon covered wire…

Also I removed some of the sand and I put a 12 inch long rail road rail in the dutch oven with some sand inside.

I believe if I opened this up and put a pot on the top with water it would instantly boil…

I am most curious how long this will take to cool off…


I, too, have the Sun Oven, which seems to be a bit “low powered” compared to my large oven which uses 54 bathroom mirror squares (12" X 12") all focused down to a 4" spot (+ or -). Supposed to be 3000 peak watts and 950 C. I believe there is a photo somewhere on this site. I TIG welded spiders to force each mirror into a very slight parabolic shape, and mounted six rows of 9 mirrors on a boat trailer with a dolly at the front. The mirrors focus on the oven (if you pay attention) and the trailer dolly needs to be moved every ten minutes or so, wearing a pair of welding goggles.
We roasted chicken, made angel food cake, pizzas, and breads. It will light a 2 X 4 on fire if you stick it in the beam. (My wife’s favorite thing.) If unattended, it could melt plastic car bumpers, etc.
I have also experimented with AirCrete as an insulator, and used plenty of charcoal fines, and even some broken glass powder. I have been saving Styrofoam pieces, but have yet to make a grinder. (One guy uses an electric lawnmower to chop it up and blow it into bags.) I did experiment with chopped cardboard and printer paper sliced very small.
This year I installed a solar powered Mini-split that runs off of 8 used 250 watt solar panels. We just leave it on, and in the winter, it provides heat when the sun is shining, and the rest of the year it is in the cooling mode. (Only when the sun shines, of course.)
Most of my recent effort has been with the installation of over 80 used solar panels that feed into the grid, and power our house and barn, and keep two EVs charged. The panels are available for about $50 each from Santansolar.
I recycled all my solar water heating hoses and schemes for heating water directly with the sun and pumping it to a large tank in favor of heating the water with the 3 used solar panels, and sending the electricity to the heating element in the water tank. I have a valve to turn off the water so it does not thermally moved up and down the pipes. Also, heavy insulation all around the tank, so it will store the hot water for many days.


Search on “Helios” on this site for a photo of my concentrator.


Ray, how many bags of charcoal do you have now in your barn?


Have you been reading my diary?

LOL I have 30 Santan solar panels and with them I run 2 window mini splits with solar, using EV batteries. I am off the electrical grid with this system.

I have been saving mirrors and watching youtube videos on how to cut glass so I could make a solar mirror. Now that you mention it, I like your idea of leaving them whole and then focus them all onto a spot…

I was thinking with the boat trailer that one could create a “path” for the front of the trailer to move in an arc with winches moving the front of the boat.

I made the lawnmower setup to chop up the styrofoam… But I am now starting to think that using nichrome wire to cut the styrofoam into shape might be even better.

I was thinking another option we could try is to re-mold the styrofoam into blocks using steam… not sure if it would work… Also thought about pressing the styrofoam into a mold shape.

Heavy insulation does look to be the next stage in my expirments… I am thinking putting this trash can that is in this 55 gal barrel into an IBC and filling that IBC with the styrofoam that I made or chop up some cardboard…

I am now looking at buying a used Kiln… I would really love to melt aluminum and use my 3d printer to make moulds.

I am curious what insulation you use on your hot water tank…
Thanks for your sharing your adventures, I will look up your solar heating beast :wink:


Link to Hellos Mirrors…


Bags everywhere! Some of those white plastic horse feed bags have been decomposing, which makes a mess. Several months ago, I gave Martin Payne a load of charcoal, and I have been adding it to my 5 compost piles. (Mix it into the pile with a front-end loader.) I moved some of the charcoal to other outbuildings.
I was going “great guns” on melting aluminum cans with a Gingery charcoal furnace which has air blowing in at the bottom via a pipe L. A stainless steel can I was using as a crucible melted and dumped a liter of melted Aluminum down the air hole. I went online and bought a VEVOR propane furnace and some real crucibles, but I like doing it with the charcoal.
I’ve been cleaning some fence lines, and making even more charcoal, which I have been leaving in piles outdoors. Also make a small stainless steel kettle of it inside my woodstove, which is really high-grade stuff. I am saving that in old sealed coffee cans, with labels (Bamboo, Willow, Oak, Red Cedar, Mesquite, Huisache, etc.) Charcoal is so easy to make. I have had very little success convincing neighbors NOT to burn slash piles to a white ash. I have been attempting to organize and clean out the barn, but its something I’ll be doing until my clock runs out.


My water tanks use a Home Depot water tank insulator, covered with wall type fiberglass, which is all covered with a cover blanket from a double bed. There are two tanks, side by side, because the best one is 45 years old, and came with a heat pump water heating system I bought in the eighties. It takes many aluminum cans to make a muffin tin full of aluminum. The cans have paint and a plastic liner which burns off and leaves lots of slag. Old pistons, aluminum motor windings, old ladders, and computer heat sinks are easier. I label the ingots as “cans” or “Cast”.


The process they go through in the stove video is pretty much what I have to do with my wood stove heater three times a year. Because it’s all designed around capturing heat in thermal mass with a convoluted smoke path it absorbs enough heat burning hot fires that the 30 foot long flue only gets to around 200-220F. Creates a crusty type of creosote that comes out easily with a regular chimney brush but will clog the flue if i don’t clean it, usually some time in December, then February and April. Looks real similar to what they were pulling out of that stove.

The heat riser in the Rocket mass heater in my greenhouse is a piece of 8 in black stove pipe lined with one inch of ceramic fiber blanket. https://www.homedepot.com/p/UniTherm-Ceramic-Fiber-Insulation-Blanket-Roll-8-Density-2300-F-1in-x24in-x25ft-for-Kilns-Ovens-Furnaces-Forges-Stoves-CF8-1-24X25/305950070 This stuff from Home Depot was cheaper than I could get it off Amazon. I’ve been running it for three years now with no problems. I’ll pull the barrel this spring to see if it needs to be replaced. I wish I would have back filled the bed with sand because it would have been so much easier but mine is mixed cob. It took a year of running the system to get it dry enough that water wasn’t leaking out between the gaps in the stone retaining wall. Cob was supposed to have superior heat storage capacity but I never saw any data comparing it to just sand. Way back when, glaubers salts was used for heat storage for passive solar systems. Haven’t heard that mentioned for a while but I don’t really research it much anymore. To anyone building a Rocket mass heater system I recommend upsizing your ducting if you are doing any length of bed. My bed is 18 foot long with a 16 foot run of 6 inch duct out and back. For that amount of length it should have been an 8 inch ducted system. With an 8 foot exit stack I have to run a duct fan to get the system drawing well enough to not smoke back from the fuel port. Lengthing the stack would help but I don’t want something 12 foot in the air. ,


I have built the 5 min riser with this method… I tried to use sodium silicate to bind in the ceramic fibers from the insulation, as you don’t want to be breathing in those fibers…

Those who build kilns use this stuff and use a coating of something called “satanite”… to protect the fibers.

I have had the fibers break down, and was one of the reasons I moved over to solo stoves…

With the insulation in it does make the 8 inch riser into a 6 inch one…

I do prefer people use the Morgan Superwool instead of ceramic fiber if they can…

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I also run a group for rocket stoves on Gab…


You -might- be able to repurpose the hoses to cool the backs of the solar panels. It bumps up their efficiency if they are cooler, and maybe pre-heat the water. It is like a 10-15% gain so the additional expense isn’t usually worth it, but in your case you may have the materials already. And it still might not be worth it. :slight_smile:

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you might want to check out an old beek Farrington (SP?) Daniels, Direct Use of Solar Energy. He discusses using various salts and heating them and capturing the heat of fusion. I read it over four decades ago so my memory may be a little fuzzy.




Using direct from solar panels to motors / heating elements led me down this trail…


Thanks for that link.

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It is similar to something 100 refractory wash/coating except I think it is cheaper but not cheap. :slight_smile:

The Superwool, is still a potential class 2 carcinagin according to their documentation for Europe. I wouldn’t leave it uncoated or breathe it anymore then any other wool material. It may not break down as fast though.

what do you use solo stoves for? I was just looking at making one out a 55 gallon drum to essentially boil water. :slight_smile:


I figured out that if you put a tray on top of the solo stove a try of sand in an insulated 55 gal barrel you can cook pizza in about 15 min. I put a cast iron pan sheet ment to go on charcoal grills on top of the sand, and the heat in that barrel cooks pizza FAST. but with the sand and cast iron it is even heat so no burnt spots unless you are slow. :slight_smile:

The best part of this is you get smoked pizza, the smoke of the burning oak is in the crust…


Definitely use some Sodium Silicate to keep it from shedding. Just handling superwool releases the crud. It’s fiberglass wool on steroids. Gloves, Goggles, and Mask are a must.


That is the book. Like I said it was a long time ago I read it. Some is dated info but other info is still useful. I checked my library and it is still there. Should have checked before I responded to you and I would have had the title correct.