Aleksandar
It’s been a tough couple of months on the Martian homestead as we survived winter, but now it’s time for summer projects and boy do we have a bunch. In this video series we will be going over our major design projects for the year and will be soliciting your help, designs, ideas, and physical labor as we tackle:
1. Heating,
2. Insulation,
3. Microgreen processing,
4. redesign of the microgreen lanes,
5. Rewiring of the building to get as many amps as possible out of it.
6. Custom lighting
7. Pumping solution
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It seems to me, if I understand you, that your high inlet could be an oversized pipe run across the peak to avoid a second round of trenching.
Actually, passive geothermal is what most people call earth banks. Digging down like a walipini to get closer to earth temperatures.
Listen. I want to do this soon, like really soon on a project but theres a serious problem on all the videos. Its just what he is saying around 17:00 about condensation. All the geothermal projects might have an issue with molds with such long tubes in the ground collecting water if they aren't perforated… however if they are perforated, they might back up with water completely if a bad rain or a lot of snow melts off, no? Its one thing to have molds in the non-perforated pipe but its another thing for the entire system not to work if it got clogged from excess water seeping back in?!
I have been trying to find a video of someone that has done horizontal passive air earth tubes to cool a greenhouse in hot climates over 90 degrees (N. Florida) but seem to only find how to heat a greenhouse. Have you came across someone that has successively done this for cooling, I also don't want to hire a drilling rig when I think horizontal should work if you calculate the depth and total footage correctly.
From fallowing this idea from any sources and discussing it on permies.com I think the more you can store heat under the floor and in the building the better for radiant heating in the winter. So optimise drawing heat from the ceiling and through the center lane way floor during the summer. You also talked about having algae tanks to feed the digester; filling the center lane way with water tanks for algae and or warm water fish would also be a huge heat sink.
Would like to mention that 'if' you decide to do this, and rent an excavator, it would also be an idea to excavate around the greenhouse extending the small slope you have around part of it, most if not all the way around. Cold air 'sinks', so if the greenhouse is on an actual 'hill' all the way around it will be a tad warmer than the lower ground around it.
It would also somewhat prevent groundwater moving through the soil below the greenhouse, as the soil directly below it isn't connected to the soil all around. Nor will run-off be able to reach the greenhouse.
The easiest way to make a system like this work is work with the principle of cold air going down and hot air going up. When it comes to warming in the winter this is easiest, as the air in the ground-pipes will be warmer, thus as long as you build the inlets at the lowest point in the ground, and the outlets higher than the inlet, the cold air will want to flow into the piping (as it is lower) and push the hotter air out… When it comes to cooling the system would stop working though, as all the air inside the greenhouse is warmer than the air in the ground, and thus it won't work… but, you could still force the air with a blower, and if i am not mistaken the dehumidifier has a blower in it? … so i would construct the system as such:
I wouldn't insulate the lanes entirely, but leave the bottom 3 inches or so open (for say 6ft furthest from 'the pit'), then i would make the current double barrel heating hole (referred to as 'the pit' ) have inlets, this will make it so that there is a 'lower than the ground' place for the coolest air to go to. There i would start to dig the trench out from 6ft to 10~12ft, all the way back and forth; then i would place the dehumidifier in the hole as well, so that it 'sucks air in' from the ground, dehumidifies it, and blows it out, then from there i would just use 4 pipes (2 of which are already in place) to move that air to the lanes, and have them come up just above the highest grow bed.
Now in winter the cool air will naturally flow towards the 'pit' through the 3inches that are open, the warmer air will be pushed out of the geothermal, as well as sucked up through the dehumidifier, and brought in at the top, dehumidified… Now i know this is counter intuitive, because you bring more heat to the top, where it should already be warmest. YET, this causes the air below it to no longer go up, so cold air leaves near the bottom, and warmer air fills up the insulated area, now because warm air continues to be added near the top, the just a little less warmer air below can't raise, and as such the whole will fill up with warm air (this works, it is how the ventilation and heating is set up in my house, all the doors have a gap at the bottom only letting the coldest air out, hot air fills the room, until the coldest, yet still warm air is forced out. Also, because you didn't put it near the entire top there is still a place for heated air from other sources to go, and only cold air will be able to escape near the opening at the bottom, move to the central pit, through the tubes, through … well you get it…
In the summer the system can operate the same way, but now it relies heavily on the dehumidifier to pump air through (could place a blower near the inlets though to force air in). The coldest air would be forced into the pit, through the geothermal, sucked up by the dehumidifier and pushed in near the top of the growbeds, cooling where it is hottest and flow down through the lane and sucked out the other end. This creates a circulation where the air near the top/end is constantly cooled, and while the coolest air is being sucked out constantly it will still cool the entire area.
Notes:
1. I did not add another pipe for the processing area, this because as you explained it will be open to the area of the grow lanes, and thus benefit from it already. The fridge will be there heating that room, the room will be insulated itself, the operator will be active and clothed appropriate for the season, if needed it's fairly easy to have a small electric heater specifically for that area set up, or a fan during the heat of summer. This sounds a lot cheaper than running a pipe all the way from the back end to that specific area.
2. You could still feed in the water from the fish tanks and digester, you just wouldn't have to dig a big trench in the middle, just entrenching them on a slope towards the pit would be enough to feed them in there. And this saves you a bunch of big piping just for those water lines.
Wouldn't you be able to lay the 250' level and back fill to be level? If you're going down that far it seems like you could just set what you wanted and even mound higher at ground level.
Also, this video helped me learn that even on an active system you must time delay it to not pump cold/hot air down when you don't want it.
https://www.youtube.com/watch?v=exopLq6krto
with limited energy for heating you need to keep it all in so id say sealing the air gaps would be the first priority i found this expanding ruber foam that might work as it would flex with the cover material and expand to seal the gaps
https://www.smooth-on.com/product-line/flexfoam-it/
Have you considered an exterior wood boiler to heat with that way you only run a small circulation pump and the heat can be run in tubes around the grow lanes or into a heat exchanger with you forced air dehumidifier and or a combination of both. Then you could also just run the cool water through the system in the summer for passive cooling.
Here in the northeast, our town considered geothermal heating / cooling for a new public library. But analysis proved that it was impractical. So they opted for furnaces that could use either natural gas or oil, whichever happens to be cheaper.
Build a giant compost pile inside the hab to generate heat? You already have manure you can't get into the digester. Just need some carbon to mix. (hint: plant it now)
Geothermal: dig vertical, not horizontal with a water/glycol hydronic heating/cooling system. Air based geothermal system are great but requires some maintenance, especially to deal with mildew and/or other fungus.
Insulation: this will not be funny. To be efficient, you'll need a double wall insulation, with an heated air gap to minimize the inner heat loss.
At this point, I'm not sure if a tarp barn is really an option for a yearly operation. Best scenario will be a 8-10 months operation per year.
Keep up your good work.
My suggestion: one loop of tubing in the ground with H2O as heat transfer fluid together with one pump, or one extra for redundancy. Then on the inside you can connect how many loops you want, with fish-water or humid air via heat exchangers (hex). Just remember to put some kinda of condensation outlet to the humid air to liquid hex. For the hex I'll guess the best solution is to weld something together by yourself since they tend to be quite expensive. If you dimensioned things wrong, then you can always upgrade and change out the hex with heat pumps, but then you might need to put some coolant in the outside loop to keep it from freezing. Of course, no system is complete without going crazy with temperature logging all over with the help of Arduinos that also can be used for fan/pump speed controllers.
Best of luck!
hi, good luck with the geothermal. i like the sound of passive air exchange, very cheap to run fans to move the air in and out and i like the idea of the humidifier manifold to minimize the condensation. i might use the smooth walled pipe, to reduce friction and have it pitched so that condensed water can towards some weep holes to drain excess condensation. how do you come up with the calculations for the 250', 4 in pipe?
https://youtu.be/zyiDXU60EqY
You need to check out LDS Prepper YouTube videos on his geothermal greenhouse. He is in Idaho so the temperatures are similar to yours.
I'm far from convinced that these geo-systems are viable for you not least because of the trench sizes and underground systems you already have in place. I think that you must seriously consider a wet heating system heated by a significant specifically designed outdoor wood burning boiler(s) to cope with the worst weather conditions you experience plus some worse! (eg spare capacity to thaw snow on your solar panels and second proposed building).
It seems to me that you are in an area where there is a vast amount of timber grown and waste product available that could be delivered but this will require drying out (seasoning) to release maximum heat when burnt. Whether this boiler is fuelled with big pieces of timber handled mechanically or an automatically stoked model using wood chips I'm unsure.
What are the dimensions of the French drain as it relates to the build structure?
How about instead of digging trenches for expensive and large air pipes, you dig and bury pex tubing (maybe multiple circuits), and circulate water to collect the heat, and do heat exchangers inside you fish lanes so the fish are always warm 54f and you take the heat from the fish and put it into the air where ever ever you need it using water/air "calufairs" .
is there anyone in your area that does feild tile?
Thumbs up Marian!
I will try to contact you by email. I have been researching these same technologies for building a home in Wyoming. I think the Earth Tubes are a great idea for cooling and could be done on a smaller scale for the fish. I think you are overlooking a few problems you have with your current site set-up. I do believe the 2" rigid foam would be a great benefit for your frost/moisture problem around the exterior. It is also necessary to have this same thermal break on the inside…. the deeper the better. I think the proper solution for your heating would be a Solar Evacuated tubes as deep as you can get on the interior with the foam being a thermal break and 3/4" pex tubes with an antifreeze/water solution. The dirt put on top will form a heat bank for overcast days. If needed the wood stove can be used on the coldest of days or multiple overcast days. The system is not very expensive and the only power needed is about 0.7 amps for the pump and little more for a few valves/control zones. I have a few youtube videos and companies you should check out.
https://www.youtube.com/watch?v=rtm1dnUR0wo
Isn't this supposed to mock a system on Mars? Would geothermal even work there? The digester is your best bet once it gets going. however my suggestion is to look into outdoor wood stoves. That would solve the problem of the creosote and allow you to burn larger pieces of wood. usually fill up once a day or twice on the extremely cold days. My other suggestion would be a large compost pile with the pipes running through it to heat them. I'll look for a video of what i'm thinking of and link it in a reply.
Don't over engineer this, it's easier than your making it. With the right heating solution enclosing the lanes won't be required. I do really like the idea of moving the frost line with the foam and plastic. Do that for sure.
you should do an out building greenhouse as a power/heat station. it used fresnel lenses to heat pipes with oil. they did a project in Tamera Portugal. they also used a Stirling engine to do water pumping and electric generating with the heat differential. or have banks of evacuated solar tubes. either way you need to scale the system to handle capture heat in the winter and remove it in the summer.
I found the company that makes the tech http://www.sun-orbit.de/ you really could integrate a system like theirs into a Mars habitat