Sand & Clay Batteries - what I learned & what I should have done differently building the greenhouse 

This content is amazingly useful for cold weather locations. Also, good to see someone say, "I've built something cool, here's how to make it", then admire others improvements :) Love this, good job!

Good info Dean, clay has far more surface area than sand so it makes sense that it would store energy. The nice thing about sand is that it has 100 percent compaction from a building point of veiw. Its good to note that we both used what we had available, you can't let perfection get in the way of excellence.

I think your current concrete setup is already fairly good at capturing heat. What your friend in Alberta did was slow down heat loss by putting insulation under his sand and concrete. I think you could do the same, but rather than dig it up, think about where you are losing your heat. There is a community in Alberta, (might be Drake Landing, I don't remember) where they rely on the ground to be a thermal mass just like you (but with vertical pipes installed), but what they did was install insulation two feet underground outside, to keep the heat from escaping upwards. My theory is that you aren't losing heat straight down, as that is "charging the battery" and eventually the heat gradient will slow the heat loss downwards. Rather, you are losing heat sideways and up through the ground. Near the edge of your greenhouse the path for heat to travel involves let's say going down 2 feet, out 2 feet, and back up 2 feet, so travelling a distance of 6 feet total. Imagine putting insulation horizontally in the ground around your greenhouse - now the heat has to travel down 2 feet, out 10 feet, and back up 2 feet, so 14 feet total. I remember watching a youtube video of low-energy mobile homes being built this way where they didn't insulate the bottom of the mobile home, but insulated the ground around the mobile home and turned the ground beneath the home into the battery - with good results. Your greenhouse is likely already sitting on clay, just with perhaps a foot or two of non-clay near the surface. Just some food for thought. Regardless of if I'm right or wrong, thanks for posting the video and giving us something to think about! Keep it up!

Only use sand for this. Clay expands and contracts an insane amount with temperatures. Sand is little to no expansion. Your cement would heave and crack. Or lift

The massive advantage that sand has is how much easier it is to work with.

In your skittled rant, you actually made sence. I appreciate the insight of could have, would have thought. That is why we all seek whatever information we can to improve our plans. Bottom line, your ultimate greenhouse build will inspire even better builds. Awesomeness is contagious 🤠

Like the jacuzzi!❤️👏❤️ in the greenhouse! Really cool!😎🥰✅👏✅

Honestly the difference seems to be that Patrick has a basic understanding of science. What you have done is nice but the knowledge of why things work is the reason his system seem so much more effective. Good to see you pushing the boundaries and seeing what can work.

What you say about the heat moving down is 100% correct. If you have temperature sensors installed in and below the thermal mass at different depths its easy to see heat moves down in the summer and up in the winter. It takes a huge amount of heat to charge the deep ground, most of which you wont get back. If you have temperature sensors outside the greenhouse in virgin ground at the same depth, you can confirm the average temperature of the deep ground under the greenhouse steadily increases and eventually becomes stable at a new norm based on the in/out energy balance. In my case this took 5 seasons. Insulating below the sand will fix the amount of mass which isnt an issue with evacuated tubes, as they are able to charge the mass to higher temperatures. The downside is heat loss increases with temperature and you cant plant directly in the mass. The upside is the heat stored is 100% sensible. A sand bed without bottom insulation will have a higher moisture content which will increase its thermal capacity, conductivity and diffusivity compared to dry sand. Fwiw, you would increase the overall system efficiency by installing air tubes in the planting areas. The sand battery essentially only heats the air. You can transfer some of that heat ( oxygen and condensed water) directly to the root zone, resulting in increased productivity. The primary function of a greenhouse is to grow plants :)

New ways of thinking and applying new methods of heating large green houses! Clay vs sand! So interesting for our future homes and green houses! Really exciting, guys! I am an artist !I live in Maine and love these types of sharing with You Tube 👏❤️✅❤️👏🥰👏👏👏 Please keep up your great work to promote natural green houses in cold climates!!

Great thinking out loud man 👍🌴🤠

Wow. Good information. Thank you.👍🏼

Thanks again for sharing the info.

Great information; thanks for sharing!

I love this stuff so much.

I'm sure you've looked at the Drake Landing Project. It is practically a community heated with stored summer thermal energy.

FYI -40C is the same as -40F

Thanks for sharing the info.

Great video bro. Thanks.

Sand can be superheated to over 1000 degrees in a fully insulated container for long term storage of summer heat using parabolic mirrors. Then release it in the winter.

Valuable information. Thank you. I'm bookmarking this video for the time if and when I get my own property in the Pacific North West. I want to achieve "Tropical" (not sub-Tropical) green house with aquaponics Tilapia and Fresh water Prawns, and exotic Tropical fruit trees.

Thank you for the great video !!!

Great info Dean, saving this video for some future projects!

Awesome video

Love your insights!!! Thanks so much for sharing. It helps us all improve. I'm building a tropical 4 season dome greenhouse with solar heated radiant PEX along with radiator fans to heat the air. I'm on the plains and have almost exclusively clay so that will save the sand/gravel cost just using my local material. I also wanted to put the PEX below the entire greenhouse including the plant beds, with the intention of only heating the soil to 90F where tropical and other beneficial soil microbes max out. I plan to burry and insulate a 1000 gallon water tank, headed by thermal solar panels and use that for thermal storage, and supplement it on the cold cloudy days with a Liberator Pellet Stove in the greenhouse that I'll also use to heat water for the same radiant system.

Smart ! 👍

Great video mate I really liked the information you gave me and the idea of creating the heat sink for winter in a greenhouse. Have a ripper mate!

Well I am interested in that 'passive solar' barn you mentioned. 🙂

I think Dong Jianyi's chinese passive solar greenhouse in Alberta could give you perspective on using clay - I'm pretty sure he uses 1 meter wide wall on the north side, with a bunch of insulating materials. Dan bostan's passive greenhouse experiences in montreal/quebec is pretty genius too. He converted big barns into low-to no energy input for growing fruit trees. I hope these two folks can help you perfect your greenhouse! cheers.

Oh boy have you got my little brain thinking! I need to go back and see if I've missed any of your videos or if I've just forgotten some details (it happens a lot these days with everything else going on) because I'm suddenly full of questions and more to research. I've been so impressed with your greenhouse since the first video you put out about it and I dream of being able to replicate it as much as I can, but our leaders seem to want to drain our bank accounts more than any of their other goals.

Dude, what awesome content! All the best to you from B.C

I'm at the wild idea stage of planning my greenhouse: Wild idea #1: Use a ground source geothermal hvac system to transfer the heat between the pex in the clay battery and the greenhouse. This could still draw heat from the battery even when its below the ambient temp of the greenhouse, or charge it up during the day. Wild idea #2: Run insulated garage doors on the inside of the glazing as thermal shutters. Run them closed at night to minimize heat loss.

If you want to regulate the temperature of the in-ground pipes, have it as a separate system by heating the ground loop through a heat exchanger from the heat source that is at a higher temperature. When you need to use lots of pipe in the ground, the cost of a heat exchanger could easily be offset by saving on the pipe.

an issue that may arise is time delay i.e takes a while to warm up but more importantly takes time to cool down. I have electric storage heaters and the issue I have had is the temps outside can vary wildly so making storage inefficient.

Buddy you going to have to build greenhouse 2.0 !!! Great video and great ideas.

Have you thought about putting the electric heating elements directly into the sand or clay and deleting the water part of the system? From the chart it looks like sand and clay both transfer heat better then water. If you spaced the elements evenly through the medium you might be able to eliminate a chunk of the complication and cost. Just a thought. Really like what you've done.

I would say a huge no to the insulation under the slab due to lack of drainage. I'm sure this is why Patrick has problems keeping the humidity down. He mentioned some issues getting the watering dialed in. I suspect lack of drainage is contributing. I would be concerned about the long term effects, like mold and fungi growth.

The other thing is, i dont think we can get away with not heating our greenhouse without a Chinese style blanket . On those -40 days the amount of heat loss through the windows is to great to be overcome by the sand/clay battery alone.

To do this kind of thing without the complications of water, you can have underground tunnels full of 6-12" rock and blow hot air through it, including outdoor chambers pre-intake with glass underground roofs open to the sunlight to concentrate the solar heat before it is taken fully underground to heat the rocks. Minnesota DOT has used this to heat their highway rest stop buildings.

There are many different types of clay, and some get real wild as to expanding and contracting when wet vs. dry at a single given temperature. More variation over different temperatures. So before spending the money it is safest to check out your own local clay for its physical characteristics. A good thing to read up on is "mudjacking" or talking to a local mudjacker about what you can get away with using your local clay types. One way to protect yourself is to have an underground curtain of French drainage around the building, so soil moisture variability is kept in check.

Maybe instead of burying water pipes in the sand or the clay, you could bury an electrical resistance as it can heat above 100°C and so transfer more energy. If it is well calculated it could work directly on a solar panels array.

I think sand batteries are used in industrial situations because they can be heated to thousands of degrees and have no retained moisture. Clay would not compact well with zero moisture, and if you try to charge it with more than the boiling temperature of water, you would have issues.

The University of Minnesota has a deep winter greenhouse concept that applies this idea if you haven’t seen it, you should check it out.

I like the idea of warming up the ground instead of trying to store large amounts of hot water somewhere, seems a bit more realistic. Seems like there are lots of upsides to my soil being 95% sand.

I have done some calculations based on the water thermal capacity. The easiest way to store a huge amount of thermal energy, cheap, is to dig a big 1/4 swimming pool size whole, lay down poly and insulate it with straw bales from the bottom and all sides, add more poly and add water and cover it with straw bales. Run the energy from solar thermal panels through that water battery for the entire summer. 1 cubic yard, water can store 52KWh at around 55C temperature. A 30x15x1.5 yard pool will store about 35.5 MWh (and that is a lot of thermal energy - 127.6GJ) at 55C temperature. Clearly, increasing the size of the thermal pool increases the temperature proportionately. With a layer ( horizontally placed) straw bales the energy loss is around 3-6% per month! Clearly depending on the ground temperature as in the summer that loss is drastically lower.

Very interesting. Have you worked out the pay back period on the greenhouse? I'm curious about valuable grow space being used as mass, I've thought about solar water into 2X 300L HWC then use a DIY heat exchanger as a heater. Or run copper pipe around the base plate or option A and B

Dean, I was just wondering how easily you could add a role up blanket on the inside of your greenhouse to stop heat loss in the evenings. It seems to me that it would be very practical and functional to have a system like they use on the Chinese greenhouses. Just a thought I wanted to share. Keep up the good work.

Like it. Why not also add a thermal blanket that rolls out across the ceiling windows at night. That combo would be awesome

a Batch rocket mass heater would be awesome in this setup. A mass heater just makes sense for this kind of setup.

How about insulating the sand/clay bettery (also water proof) separate from the house or greenhouse and put a heat exchanger in between that and the house/greenhouse to keep the temp where you need it for in-cement PEX? Then you could store heat all summer and should be able to make it through the winter

One of the northern European country uses sand, as power plant. Saw it within the last 4 years.

One of the primary advantages of sand over clay is that it is easier to compact. Clay needs to be spread and packed in thinner layers. Even compaction is important to prevent settling and cracking in your concrete floor.

A few thoughts: Firstly, clay shrinks and expands with humidity - so be careful about having it support a layer of concrete if it is going to be seasonally heated. Secondly, I think your larger earthern battery could still out perform a smaller sand battery in the long run. The longer it takes to heat up the longer it will take to cool down and I think that a cooler heat source that can buffer tempertures seasonally is more usesful in your contex than a hotter heat source that can only buffer temperature for tens of weeks.

But reading the paper, they say that paraffin (or oil) is better than water in your pipes because water corrodes the system.

I am interested if this can be done in reverse in deserts and keep the greenhouses cool.

Love it Dean, Once I sell my house and build my own greenhouse - I’ll have you out too. Around Prince Albert National Park area… also, water is THE BEST heat sink of all per unit of volume vs. Other materials - with 1 caveat. That stops at 100 Degrees C. If one has a way of superheating the battery beyond boiling temp using solar mirrors or something crazy, then the best way to store heat beyond the 100C barrier is a sand battery. Still going to recommend like I did in the last video that you pick up Anna Edey’s book Green Light at the end of the tunnel and look closely at her solar passive heat designs, it’s possible to direct heat air up to about 80C using a combination of metal roofing and polycarbonate air chambers, and to also run water lines along the back side of the metal. I just see so much wasted opportunity to use the summer heat to provide heat in the winter, and to also use the power of the sun to pull cool air through the ground for passive a/c and then to use that heated air for heat storage. I plan to dig the biggest hole possible (way beyond 4’ down) and install channels of 3/4” washed rock just big enough for hot air infusion, with very large clay batteries between the layers of gravel protecting the gravel with landscape fabric. Water lines placed directly into the clay, and I’d even be curious to have a serviceable pv direct heating elements embedded into the middle of the clay batteries as a way to possible superheat certain areas… so many ideas flowing out of these videos! I’ve never thought of the pv direct to heating elements before watching your videos - I would like to run a lot of experiments too - but of course have to utilize cash as efficiently as possible, and I think the PV direct might be too expensive to start. Another technology I’m interested in trying out would be to order solar cooking (oven) vacuum tubes off of Alibaba wholesale, and run copper lines through them vs. The expense of the water heating specific vacuum tubes (would like to do a cost comparable on that idea). Thanks for the great videos!

Question... have you ever done some core samples or testing to see what the ground temp is, permafrost or such...? to see what your absorption gradient would be... maybe auger out some 30 cm holes a meter deep, put in a temp probe and backfill with various media - sand, clay, concrete etc. to collect some data for your particular area and geological conditions... the drawback to the sand or clay batteries is probably the extra cost and time to excavate, backfill and then make it firm enough to support the concrete and structures on top... but that is a one time capital cost... perhaps you can try these ideas in the animal barn floor...

my brother always has his bedroom window open because his computer puts out probably near 1000w of heat. i've wondered if it would be worth building a pc that has all water cooling tubes that then feed out of the case and into a sand battery built under the bed in the room, so that it heats up during the day while he's using the computer, his room doesn't get hot, he doesn't have to waste all the heat out of the open window, and then the heat comes out steadily during the night. though i have no idea how to balance such a design, how to know how thick to make the insulation, how large to make the mass. i picture spending ages building it and it just cooks him during the night :P i think its an interesting idea though.

I don't have sand or clay but I sure have a ton of rocks ... of course that's why they call it Rocky mountains where I live Thank you for the very informative video!!!

Heat rises, thermal loss down will be minimal. With the perimeter insulated your heat sink is very effective.

Yea sand battery's are pretty cool , watched sum videos on it on RU-vid. Thermal battery an copper coils. .

You could have a 40' container insulated & as a heat battery buried below the battery you describe as a secondary system.

Sounds like the back wall can have an integrated sand battery, that could be insulated to not allow the heat to dissipate in the summer. Then uncover the front wall to allow the heat to dissipate in the winter. Or buy a shipping container and create a sand battery, then have a heat exchanger integrated into the greenhouse/house.

I don't know much about greenhouses but as a physicist my guess is Patrick's idea will work fine, and for your greenhouses its a good experiment, but you'll probably need moisture in the soil to use the earth effectively.

5:06 ...Clay would be a very good material for a Thermal Battery (which is fully insulated from the outdoors), yet that Thermal conductivity makes it an heatsink when exposed to the rest of the ground. Your current setup is better, clay only makes the bill get higher.

First off as I recall that $100 of diesel figure is a bit misleading as he was also using wood heat. Even if it has no monetary cost it is still a required external energy input. Anyway thermodynamics estimation quickly gets into some overwhelming calculation problems. Even the big guys with a team of finite-element-analysis programmers still fall back on physical testing for complex systems. However there are still rules of thumb that can get in the ballpark if you have sufficient input information. Double the mass is double the heat capacity and conduction is proportioal to surface area. How deep is your mean annual temperature depth, how deep is your geothermal crossover point, and what is the temperature of each? What is the conductivity of your local ground, in the undisturbed subsoil and bedrock? The simplest way to go is to maximize mass÷surface area, dig down as deep as you can afford (if ground water allows) and insulate all sides and bottom, with thicker insulation as you get closer to the sides. Assuming a simple cuboid with a top the size of the building, you will make efficient gains at least to a depth of ¼ of the building width (eg 40 foot wide building 10feet deep) and still good gains through ½. This does not cover very long and skinny buildings, or very large buildings where the speed of conduction of the heat from the center of the mass becomes a substantial factor (ie it can hold a ton of heat but if it takes 3years to get into the growing space it may not be very useful for covering a cold snap or even a winter season. Not harmful, but a waste of investment.)

In Eastern Europe where temperature reach -40C they made the house floors more than hundreds years ago from few layers of clay mixed with dried straws and cow manure. The thickness of the floor was 50cm build pn top of packed river stones The walls were built with bricks made with same combination of materials. Are still parts of England where they still houses where they used same technique. The house needs an exterior coating to keep the moisture away. The ticker the walls or floor, you get better insulation. Was a very common way

Styrofoam floats and you have a pond, may make a great heat sink

Years ago I watched a video of an African village where the used salt heated by magnifying glass which’s used for cooking. I have a couple of magnifying glasses but lazy enough to run any experiment to beam it in water to creat a heating/boiling point. Can you experiment with salt water in a smaller or separate line to see if it’s any better or not?

Just a guess but with the total cost of all of your innovations to reduce heating bills I could build an old conventional greenhouse and propane heat for many years.

FAILURE OR SUCCESS? Water hold the most heat. Wet material sand/clay holds more heat then dry material sand/clay. Max temp 100°C or 212°F at sea level. What’s more cost-effective to build a well insulated water tank that holds 1 million BTUs, a wet clay/sand battery or a dry clay/sand battery. All three can be heated but evacuated tubes or PV. A high temperature dry sand battery can be heated in excess of 100°C or 212°F by your pv panels. You have a lot to consider.

Yet another great info video from Arkopia!! Thank you! Would you build your own water/solar panels? Could you not heat under your plants using a separate pump and water line circuit with a thermostat?

Hey, really appreciate the content. I am going to copy a ton of your designs and save myself a ton of time and money. I got an offgrid greenhouse youtube video coming out next week that you would like. All passive, no electrical, Zone 6. earth tubes. Uses Finches and frogs to control bugs

Both your project and Patrick's are very, very impressive. Sure, you could have done more to improve the performance of your greenhouse, but you're standing among tropicals while you point this out! I do like the idea of foamboard down deep, under the slab and a sand or clay bed. And I'd love to see some clever person do computer modeling on these ideas before we spend a lot of money on one of them. We have three evacuated-tube solar collectors on our home's roof to supply all our hot water needs. They work really well, but they do have some challenges, like the need to run glycol through a heat exchanger with an additional pump, which adds to the complexity. If I could do it over (and I might yet!) I'd have the collectors on a ground mount, because keeping them clear of snow is a bit of a chore. It means I need to use a very long-handled snow rake, followed by a brush. It's a daily ritual that could have been made simpler if the panels were closer to me. Keep up the good work! It's people like you, willing to take chances and spend hard-earned money on new ideas, who advance our knowledge of better building practices. Cheers from Williams Lake, B.C.

Biomeiler and biogas/bio digester are potentiel options.

Really appreciate the information on heat storage. How much does the hot tub affect the temperature and humidity in the greenhouse if it's on 24/7?

You mention several times about having a house on top of a thermal battery and how hot it would be in the summer, but if people are already putting foam insulation on the bottom and sides of the battery, why not put it on top too? In other words a fully enclosed totally insulated battery. Then when the concrete floor actually needs heat, just pull it out of the battery by moving some fluid between the concrete floor and the battery. But otherwise, let it stay in the battery. No need to always let it "just rise up and out" regardless of whether you need it or not.

4:14 its more than a walk in the park to walk any of the borders of the mentioned places!!! Its a hellaa trek!!

My concern would be when the heat dehydrates the clay it may shrink and form cracks that cause the plastic water line issues. Just something to think about. I would do a test of the clay in an oven before doing what you suggest.

"minus 40 or worse Celsius!" - you heard it here first folks

it seems to me that, the ideal combination would be a deep 6-sided insulated 'container' under the entire footprint of a building, with piping in it to transfer thermal energy into and out of it, then your "floor" above it, also with piping. you won't get the passive radiated effect, but you can then more accurately control the temperature of your "floor" layer, based on flow and intermix rates. you'd be way uprating the complexity of it though.

What size pot is that banana tree in (the first one on the concrete behind you)?

have you done any experiments with a gambion wall and a fan?

If your underground system goes bad, would the absorbed moisture clay freeze and buckle concrete? Or with heat and time cause clay ground below the concrete to become crumbly and unstable?

Next thing you might look into is food grade hydrogen peroxide in the hot tub instead of chemicals. 😊❤️

My $0.02 worth. Because heat rises, I would think that rather than multiple sets of pex layers you might use only two layers. Bottom layer for charging the battery and a top layer for extracting battery heat.

Great video. We have been thinking of a sand battery/earth battery and were especially impressed with the figures coming out of Finland for sand batteries' potential. The idea of using clay is quite appealing, as we too have it in abundance in Sweden. However, or headache is bedrock... We have it at varying levels under our structures. Can we use that as a heat battery or is it futile without insulation from below?

Good stuff, been following for decades, not as intensely as you. Understand the moisture content of either sand or clay can be an affect, drier holding the most heat. Can you comment?

Can you go back and put a heat sink around your greenhouse now?

if you used air lines and weeping pipe, the temperature difference would squeeze out the humidity from your greenhouse, wouldnt conduct heat as effectively tho. also it may smell bad after a while pumping air down a well could be better as you could have access to a 100ft deep hole worth of thermal mass, would be a more effective dehumidifier instead on inside a well, running air lines vertically through a deep drill hole is another possibility

Use a mixing valve for your concrete heat. A cold sink would be useful that could be heated, also more raised beds. Good to look at earthship growing area as a cold sink. Then a covering like a Chinese greenhouse to cut down on heatloss at nite probably on inside. Would cut down on cost with gravel walkways, concrete is expensive. Your friends evacuated tubes are straight up and down looks like glass in front of them, because they will collect ice and snow.

I think that you may improve your greenhouse by putting more ground insulation at the perimeter of the greenhouse; something like 1.5m or 2m deep. This way when you heat your soil it will be an efficient earth battery that does not leak much heat to the surrounding ground. If I remember correctly you already have 0.5m insulation which is surely a good thing and the earth under the greenhouse is already a reasonable heat battery. The question is, how good is it? Do you know how deep the perimeter insulation is at the new greenhouse of Patrick?

What's the frost line in Alberta, 7'? So if you wanted to take advantage of that like in other areas you'd have to go way down? I can see that being an asset in the summer for cooling though. I've been looking at building a greenhouse around a house like they do in Sweden. The biggest issue is actually the heat in the summer rather than the cold in winter.

❤it’s not a theory,the earth has taken the heat almost endlessly ❤

I think if you want to use the natural temperature of the ground you should not insulate. As long as the earth is above freezing and you have adequately insulated the glazed area the building will not freeze. If you insulate the earthwork inside the insulated space the ground will always be trying to move towards the ambient outdoor temperature regardless of how much insulation you have. This will necessitate heating the slab with some sort of active heat source. All of that thermal mass would keep the heat very well but I wouldn’t opt out of using the ground temperature unless you were in permafrost. To improve your system you could work on improving the air temperature. I would try some sort of heavy retractable blanket just under your glassed in sections. This would let the passive solar in, as you already have, plus reduce the heat loss over night. With your system the only way to heat the air is to burn fuel. Your system is close to perfect. Maybe try a huge roll, the width of your greenhouse,of bubble pack insulation on a pipe at the top of your glazing that rolls down to the south. Perhaps a pipe on the bottom for weight and a chain fall arrangement at the top to retract the sheet in the daylight hours. You could support the bubble pack on some kind of smooth pipe like chain link fence pipe.

Based on what you know now if you were to dig out the entire greenhouse down 4 feet would you put Styrofoam insulation across the entire greenhouse, including underneath the flowerbeds and garden beds?

How would you pack the clay? How much moisture would be in the clay? Thanks for all your videos!!

Between your videos and some others I've watched about ways to hear and cool green houses it's given me a question that maybe you've got some thoughts on. What if you did the sand or clay battery, with the PEX tubing as well as some air exchange tubes to help pull some heat out of the ground into the air? I know in the video you said the air tubes aren't as effective in the video. But what about the combination of both methods?

How much did the whole thing cost?

Yes, clay is best BUT any dry soil is an insulator! How would you keep your soil moist? Conversely, wet soil will drain heat away if the water can flow. So, will the adjacent planting areas keep the soil moist or will it cause water to actually run through the heat sink causing the water to move heat away?