Experimental climate battery using water instead of air.

I am designing a 10ft x 15ft greenhouse for a property on the border of 7a and 7b. I have been considering a climate battery, a water wall, and an aquaponics setup for my greenhouse.
I had the realization of using water instead of air as the medium for the climate battery. Climate batteries depend on transferring their thermal energy to the water stored in the soil, so by using water as the baseline medium I think in theory it would be at least as efficient if not more. In addition if I plan on incorporating aquaculture and general irrigation into the greenhouse, so I am pumping water around the structure anyway.
The conceptual idea is could liquid water be substituted for gaseous air in a climate battery setup.
The practical idea is integrating the conceptual idea with a aquaculture setup.
The goal is a single system that redistributes both nutrients and thermal energy simultaneously.
The only disadvantage I can think of is that water is heavier than air and thus more energy intensive to move around.
I am curious if anyone has heard of such a system and if anyone can think of any inherent obstacles in this design.

I am new to the forum and apologize if this is not the best place to post this question.

Hi Alexander, welcome to permies!

So you'd be pumping water through pipes underground?  Is the goal to store heat down there in the summer and retrieve it in the winter?  Or pump it down there at daytime and retrieve it at night?  Or not really pump any heat down but draw up warmth as needed from the warmth of the earth?

How sunny is it where you are, especially in winter?

Thanks Mike,

The idea is to have a system of pipes that moves warm summer water underground and transfer that heat to the surrounding soil (insulated at the foundation as a climate battery should be). Then during the winter the same system could be used to bring the heat back. Or is that even necessary since heat naturally rises?

We have only been here a few months and also just had a number of trees removed. So I'm not tot sure how much sun the spot for the greenhouse I was considering will receive in the winter. My best guess is some but not full winter sun. I've heard enough cautionary accounts that overheating is typically the greater challenge.

Heat does rise.  It also technically sinks and moves in every direction.  Hot air rises though.

There's a geothermal climate battery system in a big greenhouse in northern Canada that pumps heat underground (with air) all summer and they calculated the floor and some insulation in the floor so that it delayed the return of the heat up into the greenhouse until winter.  Much more science and math in their building than you or I are ever going to undertake.  They might also have insulation below their climate battery as well.

I think one key question is how hot you need the returning water.  Does it need to be at "fish temperature"?  If so, that might be a challenge.  You may have deeper earth temps in the mid 50s.  If you heat that up all summer it might get into the 60s or 70s.  The earth will be sapping away that heat (down or in any direction) and trying to get it back to the mid 50s.  But it's within the realm of reason to bump it up quite a bit and have enough heat down there to use in the winter.  Especially if you can pump more down there on sunny January days.

Air systems rely on a lot of surface area between the pipes and the ground and a lot of cubic feet per minute.  I'm not sure if you need the same amount of surface area given you would be using water.  Certainly you would have much less volume of flow.  In my head, I'm thinking that if they're blowing hot air down there and it heats up the drain tile and then the earth, you may need a similar amount of surface area to transfer your heat to the earth.  Which would be a crazy amount of piping.  But my brain may be thinking about it all wrong....

Yeah so that gets at the literal "deeper" question. I'm a big DIYer as I'm sure many on here are. I was envisioning just getting a lot of garden hosing and snaking it around the flooring of the structure around 2ft down. I know that there's a diminishing returns with traditional climate batteries in terms of the length of tubes. But it would seem to me that after a section of earth reaches temperature equilibrium with the water in the hose then the water will simply continue farther down the hose and transfer the heat farther down in the system until the full 150 sqft of soil has reached equilibrium, if it ever reaches that point.

The primary goal is cooling the greenhouse during the summer. The secondary goal is warming the greenhouse during the winter. The tertiary goal is creating a win-win that contributes to both the primary and secondary goals.

Hi,  welcome to permies!

From my understanding it takes 180 BTUs to bring a gallon of water from 32°to 212°.
970 additional  BTUs to turn that gallon of 212° water into water vapor.

Blowing air through the buried pipes condenses water vapor from the air, depositing BTUs in the process.

So a climate battery that uses water,  would it deposit solar heated  into a network of underground pipes?
[edit]
I see,  a loop of garden hose.
I think I would use PEX or poly pipe instead, more durable  , more heat resistant.

Thanks William,

It gets quite hot in the summer here during the summer, so the system I'm envisioning would bring cooled water from an underground storage tank to a high point in the structure and then snake it around relying on gravity, kinda like a backwards radiator. So as the water makes it's way back to ground level it is has as much air contact as possible and absorbing as much heat from the air as possible. From there it would redistribute that warmth underground until returning to the underground storage tank.

Per William's reply, I think one advantage of the air climate batteries is if the dew point is reached underground, condensation causes a large transfer of heat to the ground.

I would think that you'll need much much more piping than 150 feet of garden hose and that it would want to be 4-8 feet underground.  But that's just a hunch...

So yeah that's the crux of the idea. Air climate batteries rely on the dew point to transfer the heat to the ground, using... Water. By using water as the base medium, shouldn't this system circumvent that threshold entirely?

Yeah the greenhouse is 15ft x 10ft (per local building codes, grumble grumble) so it is 150sqft. So the amount of hose I'll need I'm sure will be quite a lot, potentially an unreasonably amount.

I see what your saying now.
I think a "radiator" and fan will be needed to  effectively transfer the heat into the water and cool the interior.
You could capture the heat from sun falling on the interior of the greenhouse,  but I don't think that would help cooling so much.
Better to make those surfaces white and leave it at that.

Alexander Fraley wrote:So yeah that's the crux of the idea. Air climate batteries rely on the dew point to transfer the heat to the ground, using... Water. By using water as the base medium, shouldn't this system circumvent that threshold entirely?

 Possibly, or likely?  I guess if your humid greenhouse air is condensing on the water pipes before it goes into the ground, then you are getting the heat transfer of the phase change at that point.  Unless by having it happen up in the greenhouse it isn't as effective as if it happened underground...

So the pipe/hose component would only be below grade. Above ground I would use a gutter system as it moves down so that there would be direct contact between the moving water and the hot air. Sorry about the missing details, it's a little hard to come up with a concise description.

No problem, we're getting it figured out  So the aquaponics water and the climate battery water are different or the same?

And the climate battery water is pumped through pipes underground and back up to the greenhouse where it cascades through gutters or other exposed methods to pick up or give off heat before ending up in a sump tank where it is again pumped underground.  Did I get that anywhere close to correct?

Would you be insulating under the climate battery or just on the sides?  Where in the world do you live?  It would work better in Colorado than it would in Seattle...

I was thinking the aquaculture and the battery system would be the same.

So the flow would be: underground tank > pump to ceiling if green house > elevated rain barrel > barrel overflow to "radiator" cascading gutters (pick up heat) > aquaponics bed (deposit nutrients) > pond/IBC tank with fish (pick up nutrients) > underground pipes in floor (deposit heat) > underground tank and repeat.

As I write that out I'm realizing that the nutrient material could clog the underground pipes, but I bet if the pipes are sufficiently large enough in diameter I would think that would get around that problem.

I'm in Virginia on the the border of zones 7a and 7b, coldest I've ever seen winter get here is probably around -15 F, hottest is probably 115 F. But this past winter we were barely hitting freezing and this summer didn't reach 100 more than twice.

I planned on insulating the sides of the foundation to a depth of two feet, our frost line is at 18 inches. I had not considered insulating beneath the floor itself.

My personal bias against aquaponics is that it seems to be very hard to get the fish and the plants to work well together.  Balancing the system and not killing one or the other seems to be a constant struggle.  Adding in another variable of heat transfer would likely make that even trickier.  How big a temperature range can the fish handle?  When it's collecting heat from the greenhouse, how hot will their water get?  When it's collecting heat from the ground, how cold will their water get?

Why not install roof vents  and even whitewash the glass roof to reduce the heat in the hot house.
Even shade cloth drawn across like a curtain may be a lot easier and effective.

Yeah I've never actually tried aquaponics before so I have those concerns as well. A friend of mine has done it so I can ask him.

A better reframe might be to have the pump and be able to switch out the hoses easily so I can use the same piece of equipment for both temperature regulation and aquaponics, just not at the same time.

I just found two articles describing what I'm thinking of:

https://www.theguardian.com/notesandqueries/query/0,5753,-24934,00.html

The main critiques I saw here seemed to focus on maintaining 76 degrees year round for an entire house. My structure will be much smaller than a typical house and mostly just seeking to take the edge off the temperature extremes so the plants don't die.

https://www.instructables.com/id/Free-Air-Conditioning/

This one is extra exciting because my home actually is full of decommissioned baseboard heaters that I've been wanting to get rid of anyway. So these would replace the gutter/radiator system I outlined earlier as a system to collect excess heat from inside the greenhouse.

Could I also then use some of heat exchangers underground as well to facilitate transferring the heat to the soil?

But yeah I kinda should have started the discussion with pointing out that water exchanges heat far more efficiently than air does. That's why it's used to cool everything from computers to nuclear plants to wort when making beer. But in these systems once the water has absorbed the excess heat it is discarded, which is where the climate battery idea comes in.
The other thing I wanted to point out is that typical climate batteries have to expend energy to push warm air down as well as to bring cold air up, fighting physics in both directions. While water is heavier to bring up, it will follow gravity regardless of it's temperature.

Thanks John,

Yeah I plan on taking advantage of as many of the numerous cooling techniques out there as I can.

This is a "two birds with one stone" idea with the aquaponics.

Also I like experimenting and trying new things. I'm mostly looking for a "there's no way that will remotely work. You failed to consider X." Which I'm not really hearing or reading in the literature. I think in principle this could address some the issues that come up with climate batteries, while simultaneously being a flexible component that could be incorporated into other designs in a variety of ways.