Solar Boosted Geothermal Heating for a Greenhouse

This concept is the best design I know of for long term heating a solar greenhouse! Love to hear your thoughts!

My house has two windows on the south wall that are 6' high by 10' wide each. In the winter at -25 on a sunny day, it will be 25°C with no heat on. Building design is a huge part of efficiency.

I like this idea. I have been thinking about an even smaller version for my very small greenhouse. Homemade solar collector and a couple 55 gallon barrels buried under the 10 foot by 12 foot greenhouse. It would be for season extension by moderating night temps here in Colorado. I know it wouldn't get me through winter, but it ahould help extend the growing season some.

I have just discovered your videos and I am so glad I did! They are a treasure trove of ideas...I am sure I am going to have a LOT of questions going forward 🤣 Thank you so much for all of this!

I think it would be awesome if you went more into detail what every element involved is. This will help all of us beginners.

I love it. Planning on something similar later this year, great video.

Been looking at passive solar greenhouses, might also put this in with it for winter heating. Every little bit helps!

I appreciate you sharing your research and Ideas. We are just a bit south of you 2 miles off the coast of Lake Superior on the US side so loads of wind. I was a bit surprised to not see a water tank and an a wind mill as part of this video. Capturing the winter wind and turning it into heat is very appealing. Anyway thank you for anther interesting video.

I will be incorporating this into my greenhouse design, thank you!!

I like this system concept. A concern with keeping aircrete dry is realistic and similar to otner comments. Applying a coating to the aircrete might be considered. Another possibiltiy is making a small hill above the ground water line and placing the "heat battery" inside the hill.

Thanks, great info! I've started to look for sustainable greenhouse

Forget about the foamcrete or any crete for the "Ground Battery" dig your battery hole 8-10 feet deep put down perimeter of IFC blocks 2 high add to the floor 4-6inches of Expanded Polystyrene (EPS) foam board. Now it gets interesting with this part. We are going pack dirt into those ICF blocks use of rebar is optional. Line the inside of that battery with a pool/pond liner or some strong plastic maybe the fibered canvas stuff for greenhouses is like 10mil with fiber. This plastic does a few things for us 1 unlike when doing under slab insulation we are not worried about it filling with water later we would prefer to have it fill with water for better thermal exchange. But we dont want that EPS to float up so the plastic will hold it down as we add mass. Now lets add 1-2 feet of fill and tamp/pack it down this should be done in 6inch lifts but we dont want to hurt that foam so do a 1 foot lift then another foot. Next fill the walls up with the dirt packing to the frost line and fill the wall in lifts of 6 inches and tamping it the best you can. Now back to the battery at this point we are still at a depth of 5-7feet and we lay the entire floor with our hot line from solar the loop over loop method or concentric method using less total length of pipe is your choice. Those long metal staples for holding shade cloth can be your friends to help hold the pipe in place. Now we add another foot to the battery and also the outside of the wall up to the point the inside is filled again limit the range of lifts and compact the soil we dont want anything shifting the wall around to much. Now we lay our pump side line 1 foot above the hot line. At this point we can get our liner put down the outside of wall and do another foot lift. We will then continue until the battery is full to the frost line leaving outside of the wall 1 foot shorter and we will cap this battery with another layer of high quality plastic and down the outside of wall adding the last foot around the wall to trap plastic again. Dont worry about it being water tight as i said we need that water if it wants to come do work let it. Last we have to backfill the site with soil if you prefer source some top soil if your soil is of low quality and add 6 inches of top soil to finish. Now you have your "ground battery" it is time to design how you will use it. If it was me i would source not only solar pool heater panels but also like the content creator mentions a small PV array directly feeding 2 of those pumps. Solar DC to run the pumps and go not only under the soil or floor of green house but also to some 55gallon drums lining the north and east since i am in a northern climate. These barrels would be plumbed in the top of first one then out the first just 6 inches from the to top towards the second barrel in the chain into that barrel 6 inches from the top and a drop pipe to the bottom then repeat 6inches from the top out to third then 90 to the bottom rinse and repeat for all barrels. You can use a horse troth auto waterer or a toilet float valve or manually keep up with the water levels. The last barrel in the chain is return to the ground battery from the bottom of that barrel which will be your over head reservoir for your ground battery. I would temp control pumps coupled in all 3 ways barrel, floor, and radiator using the AC i would bring to the green house and contactor switches or set up deep cycle battery/ies and attempt using car relays and the available solar DC/DC. My one exception would be the fan on the radiator a common house fan is not appropriate for this use. I would rather source a squirrel cage unit from a furnace or other source forcing through the radiator using AC power from the grid and avoid the costs of batteries and hassles dealing with invertors and all that jazz. There are other option for the fan you could build a frame and use a fan with a shroud sucking through the radiator. Either way you suck or blow you need to pick the cold off the floor and blow it clear to the other end of green house preferably blowing from west to east or north to south depending on your orientation. No mater how you slice it the pump for the radiator and its fan are both needing more energy than im willing to pay for solar and battery to deal with. It is so much cheaper and more reliable to power them off the grid and displace the energy later with Solar grid tied with some micro invertors. One should have redundancies in the system so i dont think the AC power is optional if your looking at any issues for that radiator or solar to fail or just not produce a few days in a row. Those redundancies not only include the ability to increase solar heat, solar pv to a size to work but also a back up way to charge the battery, heat, and there comes the old school methods of yesteryear and that is to burn wood either inside the green house or outside of it to produce hot air from a controlled air space around the stove but to also be able to wrap that stove with copper and plumb it back to the heat line of the "ground battery"... You got 2 legs so everything you do should have 2 or more legs just the way nature intended it. Dont make your greenhouse hobble while you get to walk around freely. If you think displacing the AC grid power with solar it to expensive think about doing a ground mount but with a wooden pergola with rafters on 2 foot centers angled near 25-35degrees due south depending on where you live for me it is 34 degrees angle 10degrees off of south towards east. Then cover the pergola with uni-strut bolt panels to that with standard hardware from under side to the panel frame not through middle with fancy expensive hardware. Add some 350watt panels and enphase iq7a micro invertors per panel and enphase combiner. Dont cheap out on micros the ones that do 2-4 panels and cost 50dollars less are not your friend they are for solar fields and low wattage panels. You do need Qcables but, you can cheap out and use standard AC house with or THHN and standard boxes instead of there home run wires and expensive male/female adapters for your end of string run to the combiner box. You will save in many ways doing this you wont need the power for greenhouse except winter time, you got a new pergola to hang out under cheaper than any solar mount set up, you dont have to roof it, the enphase micros rarely die and if they do only that panel goes out. If you had a big honking invertor and it dies= no power and 3-8K gone. You dont need batteries saves enough for college right there. The system breaks even in 5 years since that is about when your big honking invertor would have broken and icing on the cake the micro invertors last easy 25years and since they make ac power you can run normal old AC wire back to the main panel you dont need all these little bits and bobs all the solar people try and sell and if you can build a greenhouse i put my money on it you can build a GREEN Pergola too. Mines 24x24 (actual 28x28feet counting angle and over hanging panels) from 16feet up my 2 story right to the ground looks like a A-frame house roof i got the bigger micros and bigger panels but that set up get you 900kwh/month easy under 20K for the entire pergola and solar if you do the work. Im now looking at my next move either mini split or point of use water heating its a close call since only 2 of us here im leaning towards the minsplit so i dont have to tote as much wood and she is leaning towards hot water thinking it will effect her shower in some meaning full way but it wont.. The windmill heat generator looks awesome but seem like a busy system to get right for me in the north here. Guess i will be stuck feeding the 700lb cast iron monster wood (ass-warmer 3000) stove in winter. Good luck to anyone that managed to read that far i hope your head is a full of ideas as mine is and your hands are capable to do at least one of those ideas.

Curtis Stone and a few others been talking about sand batteries. Theyre looking at concrete tank or large diameter pipe and insulate the outside of it fill with sand then run tubing in and out of it. This is another option if you dont want to dig up the yard (though smaller system though can get the sand up to hundreds of degrees). Curtis was looking at it as a dump load for his solar so he can heat his home once the sun goes down.

congratulations you are a very good analytic engineer and also very didactic and convincing

Good stuff sir! Thanks for sharing! Keep up the fine work!

Another great video. Makes me think more and more what I should do with my 'wallipini' green house build for 2022. What am I thinking? Straw bale walls. 3 to 4 feet dug into the ground. Air exchange thru a solar battery. Secondary solar battery using the principles in this video..... To assure that my average winter night time temps are maintained for citrus trees :) Look fwd to the next video! "Simple and cheap" solutions!!!

Ground-source heat pumps really are better for the climate here in Canada. Air-source heat pumps are great. But once they reach their limit, then their backup heating element has to kick in to provide the process heat for it to do its thing. The idea of having a solar thermal assist is even better. It pumps more heat into the ground. Solar thermal systems can be paired with ground-source heat pumps on the same circuit. Literally, all your home heating, hot water, and the heat for your greenhouse, or pool (if you have want) can come from zero-carbon solar and ground-source heat.

Really really cool, so how do I calculate the amount of ground space required per 100sqft of greenhouse or M2? I have multiple 800sqft hoops, we were looking into a boiler system, which would also regulate irrigation water temps as well. The quote was about 60K, crazy expensive. Propane unit heaters are about 15K plus propane lines and tanks and gas. This seems like the most efficient over long term as well. Thank you for the video, been loving your info you put out!

Just some things to consider and need further research as well as testing in my opinion. My most significant concern with an aircrete project has been the potential for it to become waterlogged. In my parts we have a 6-ft water table and a relative humidity constantly above 65%. As I understand it solid concrete has a insulation value similar to adobe. ( R values are simplistic way of measuring insulate value however keeping it in common reference values, about R1 per foot. I've seen home tests that show aircrete having a potential r-value as high as R6 per inch ) As the concrete begins to soak up the humidity and groundwater depending on where it's placed the r-value goes down. I acknowledge that aircrete by definition has has bubbles of air in it and that increases the r value but also makes the concrete more permeable and as such fluids move through it more easily. As a middle ground the consideration for me has been styocrete, basically taking trash styrofoam then breaking it down to beads and blending that into the concrete slurry so that the concrete is acting more as a binding agent, although this still has the potential issue of a significant portion of those beads not being closed cell.

I truly like this idea alot. The people who talk it down want money from you. Great video thank ya man.