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Strictly Geothermal and infloor radiant

Discussion in 'Heating or Cooling of your AP system.' started by magnusthescott, Aug 14, 2012.

  1. magnusthescott

    magnusthescott Member

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    I see a lot of topics heating the air in a greenhouse or specific parts of a a system. Why not tap that almost endless source of thermal energy under your system by combining geothermal with in floor radiant using a slab under your greenhouse or fishtanks. Where i live her in Oklahoma geothermal is very viable we have whole casinos heat and cooled by it due to its long-term payouts, we even have several Indian tribes using it for all their new construction projects for the same reason.

    If your going to go big why not go all the way. So we all know that at an ideal depth you can get the temperature that you want from the ground being x deg at x depth this will vary from location to location. We know that circulating tank water will cause bio-film so instead of using tank water use a reservoir as an air trap and install a re-purposed item a toilet tank fill valve to keep your water level up not that there should be much water loss. Likely you will have more oxygen gain depending on the type of plumbing you use below ground( some actually allow O2 migration inwards).

    An idea here if you bury your tanks with say 4 in. above ground(to keep any ground water runoff from going in the top) you get some thermal stability for the fish. Then if you use the bottom of your DWC beds at ground level sitting on a slab or just with coils in the bottom of them as a heat exchanger you can temper your water going back to the fishtank while keeping your geo-system a closed loop isolated from your tank water. This should help with any heat gain by your GB or you could use a manifold to isolate your water running through the slab to be off during your hotter months where it gains more heat and on in the winter where it is better served as a heat sync to be warmer where heat will rise and heat the whole greenhouse vs just the water.

    See the attached JPEG and give me your thoughts looking to build a system that will last long after its construction without having to worry will it last the winter(0 F) or survive the summer (110+ F) we have some extremes here in the midwest may not be those for too long but last year more than 70 days straight over 100 F and last winter with several weeks not above 5 F. This is based off of a small hoop house design and trying to maximize space and efficiency. I am not rich, money is definitely tight but i would rather invest in a healthy food source than a brand new 4x4 toy.
     

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  2. Walks-In-Storms

    Walks-In-Storms New Member

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    I have constructed something very close to this (photos are here elsewhere), with modest results. I finally had to install a window-type air conditioner, 5000 btus. When I dig (I've started, using water to penetrate otherwise impossible Texas clay) my CHOP sump and grow bed delivery pipes it will be buried as deeply as I can. I'd have put my entire system under the greenhouse as you have yours, but frankly didn't think of geothermal aspects to aquaponics at the time I started. The next one - I'm designing it now - will be very similar to your diagram here. As it is, I have both fish tank and grow beds in the greenhouse, but will have to (maybe - I'm working on that right now) put the latter outside (or add on to the greenhouse).

    However, my experience tells me that one must go deeper - at least six feet - to get the full benefit of geothermal dynamics. As it is, I have a heat sink buried five feet deep - in four inch pipe, one third of the water above ground (the fish tank on a concrete slab. I've learned that the entire water supply (the rest of the system, too), will eventually - dependent upon how much water is below ground, how deep, and how much is above ground, how high are ambient temperatures both above and below ground, etc. Eventually, as I said, the temperature will reach that close to the mean proportionate temperature between above and below ground. Here, the temperature where the buried pipes are is 72 degrees, so when the temperature above ground is 115 as it was last summer and has been this year, I have a temperature in the fish tank that is (at least: don't forget the proportion between water above and below ground) 93.5 - too hot for the fish.

    That's the reason I had to add the air conditioner, of course (I've also had to paint the roof of the greenhouse with silver reflective paint). If I could go down about eight feet, and circulate the system's water, I could get by on just geothermal cooling. Alas!

    Good to see you design, hope you have more ideas.
     
  3. magnusthescott

    magnusthescott Member

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    having an in at my local tribe who happends to be on the well drilling crew informed me that my idea was sound but i was going to kill myself with work for a low return on my time and money. The way they are accomplishing their huge energy gain on the cooling side is to sink a well shaft to below normal water table ex. water @150 FT well @200 ft sink coil and circulate water. At those depths the temperature can usually be found around here in the 50-60's F which would allow it to be a thermostat controlled system for the most part. I do agree WIS that depth will be the key facet of the whole system given my climate and long term cost requirements i just cant afford to run a heater in the winter or an air conditioner all summer finding a low cost renewable way to achieve both is my only long term option. Unless i make this a business and build an X000 ft greenhouse etc which at this time the economy will not support even if i catered specifically to the Asian restaurants and few Italian and Sicilian joints around here with gourmet produce. I have however peaked the interest of a few others who are interested in some backyard systems but they are having my same issues our summers are too hot and our winters too cold to make it work with out some careful planning
     
  4. Walks-In-Storms

    Walks-In-Storms New Member

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    Well, while I respect your opinion, I suggest that you do some more research. Our air conditioner in the green house runs only about four hours daily when the heat is worst. It costs sixteen dollars a month. With judicious effort like mine, that can be lowered even more (I'm sealing the gaps at the bottom of the greenhouse, painting the roof with reflective paint - the spray can cost $9.95, the expanding foam $4.95). I do all my digging with a spade, post hole digger, and muscle, use tools I already have (all purchased a sale for fifteen cents on the dollar).

    With all due respect, where there is a will, amigo, there is a way. Stay practical in what you want, and do - and be careful (study it, do research) to know what that is (I didn't even consider things like those you mention, for the very reasons you also mention, but I accomplished what you seem to want). Ask questions (ask me - I've not only made every mistake known to man, I've invented dozens). The only regrets I have about my independence - the food growing in my back yard, and the energy I've supplied both with my brain and my hands - is that I didn't do more, work harder.

    Best of luck, and remember: "What doesn't kill me (only) makes me stronger." :p
     
  5. Murray

    Murray Site Admin Staff Member

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    Geo thermal temp control is a really interesting idea and has been discussed many times in the past. It may well be the answer for most climates. The cost of setting it up is the drawback, particularly for home systems.

    I have not been able to discover what the average temp is at say 2mtrs here where I live but some claim it to be about 20 c. Which would be really good for our purposes.
    Guess I should dig a hole and drop a temp probe down, see what happens.

    The cost of running a suitable pump to move the water through the underground heat exchanger may be higher than anticipated.
     
  6. Walks-In-Storms

    Walks-In-Storms New Member

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    Murray, I just drove a two inch diameter pipe into the ground six feet, then dropped a thermometer down there and capped the pipe. A day later, I pulled up the thermometer and the read the temperature (78 degrees - 25.5 Celsius). The outside temperature that day was 45 degrees Celsius.

    I've left the pipe in the ground, the better to see if weather, atmospheric conditions otherwise, and the like make any difference. If I want to pull it up I'll use a come-along, a dead-man anchor and a pulley - the same method I'll use to dig my CHOP sump (I want it to be six to eight feet deep). I used the comealong-deadman method to straighten a fence with concrete anchors a while back and it worked great (or "a treat" as you Aussies are wont to say).

    Incidentally, the colleges here provide studies of sub-terranean temperatures everywhere. The same might be true where you are.

    Thought you might like to know....
     
  7. Rob's Green Thumb

    Rob's Green Thumb New Member

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    Well the cost of doing geo thermal depends if you relly want the cheapest side of it you want to dig no less then 10 feet digging will only cost you a shovel and some hard work.
    Then you use hose about 50 feet thats 10 feet down 10 feet up and 30 feet coiled at the bottom.

    Now you were trying to sepreate the water used for this instead of useing direct flow from your tanks because of bio film.
    What Ill be doing is useing a sheath i have giant rolls of this brown pipeing its large enouf to run a garden hose thru it so ill bury that with the hoseing inside this way if i need to pull out change replace or clean the hoseing its a simple matter of just pulling it out and threading it back in.
    Now i dont have to worry about bio film build up or haveing to re dig out old hose then i just connect one end to the sump pump other end goes to the fish tank

    The real trick is how far you dig deeper the better the size of the pipe or hoseing used to carry the water. Example thin copper pipe will do better at tempature tranference. Then the rate of flow the slower the rate of flow the more time the water has to change temp so you dont want it gushing out radpidly you want a slow steady stream just barly enouf to push water thru
    So strange enouf the cost of running the pump shouldnt be a deal breaker
    and if your sump only turns on when it fills what will happen is the water in the hose will have time to sit underground for 15 mins or so before more water is pumped thru again

    One thing to remeber geo thermal is not ment to be a stand alone heating / cooling system its main function is to give a buffer to rapid tempature changes like cold snaps to keep your temp well above frezzeing and as a heat sink of sorts.
    Note that people that use geo thermal in there homes only use it to reduce heating and cooling cost not as a sole source. It will lower the time your heating and cooling has to run and in extreme situations keep your fish alive if it goes down but you still need heating and cooling to run at peak tempatures.
     
    Last edited: Aug 16, 2012
  8. Walks-In-Storms

    Walks-In-Storms New Member

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    I've had to "shelve" the ideas which involve coils of hose and the like, together with anything requiring a pump (or pumps). My troubles with inferior merchandise imported from China (there seems nothing else available here) include - unbriaggo! - pumps. I therefore have had to rely upon passive systems, those reliant on temperature differential (I do a lot of mathematics like Fourier analysis). Of course, you are correct concerning the auxiliary nature pf geothermal systems. I've really intended to slow the time for my system to stabilize at a balance between the buried water and that in my fish tank, such that cooling at the surface won't need to be so much. So far (this murderously hot summer where temperatures outside my greenhouse on a fence reached 46.5 Celsius), I've been very successful, able to keep fish tank water temperature at a maximum of 36 Celsius.

    Thanks for the astute comment.
     
  9. redscotcheye

    redscotcheye New Member

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    I'll offer my .02 because of my backround in Energy Efficiency. The big negative to geothermal is the upfront cost. the payback on the initial investment is many years (10-15+)for a home system. the local utility is ending the rebates on these systems because the cost/benefits aren't there.
    the reason the casino is doing it is because of the scale of the project. the time to put a high cost long term payback system in is at start up. the Co. can add this to the mortgage/start up loans, and now its a small cost over time.
    I'd spend the money on the greenhouse. specificly twinwall polycarbonate.

    Cooling loads or cooling degree days in Ok of US is about twice that of my area , PA. As discussed, burying the pipes and tanks and solar coatings are all good ideas. I'd also Insulate the tank bottoms, sides and have a top cover for Fish Tank of rigid insulation board 2" min.
    I'd use an elastometric white solar roof coating like this:
    http://henry.com/roofing/coolroofcoatings/whiteroofcoatings/287solarflex
    which is better than the silver stuff, 85% reflective and I've used it on hundreds of roofs with good results.
    how about some shadecloth? radiant barriers can help cooling loads as well.
    window A/C's have come a long way. get an energy star rated unit or 11 EER.

    Heating loads or heating degree days in Ok is less than PA. if you build your greenhouse facing south and shield the North side in winter it'll help. a boiler with radiant floor heating would be an efficient way to heat. most green houses around here use a nat. gas ductless furnace to heat. not the best efficiency. but cheap to install.

    renewables, I'd take advantage of the wind . windmills will generate more kilowatts than solar for the money in your area. get it as high up as the code officials will let you.

    fyi, there is at least one US pump Co. around -Zoeller
    http://www.sumppumpsdirect.com/Zoeller-M98-Sump-Pump/p3752.html

    cheers. and good luck.
     
  10. koosjr

    koosjr New Member

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    From a technical point of view, a Greenhouse can be totally self sufficient in terms of temperature control between day and night.

    I have done calculations of both geothermal and water storage, but one does need huge storage volume to make it work without using heat pump systems. The greenhouse itself is not big enough to house the storage volume.

    My opinion is that is it a lot better and easier to rather work on a better insulated construction. The multi-wall polycarbonate is indeed an excellent candidate for this purpose. Light, strong, durable and good thermal resistance. I see one even get 5-wall plycarbonates with very low U-values.
     
  11. stonefox

    stonefox New Member

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    I was thinking of a plastic 750 gallon septic tank ($500-600) buried below the green house filled with water .With the garden hoses drop in circulating the system water and easily removed for cleaning purposes. I know I would not achieve a constant 55F but it would definitely be lower than the surface temp.I also like the idea of the partially buried FT.Along with good insulation around beds and plumbing FT.
    Come to think about it I wonder how those septic tanks would work for fish tanks ????
     
  12. koosjr

    koosjr New Member

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    Stonefox,

    The way that I worked it out, was for the winter condition because that is where one needs to heat up at night. To get rid of heat in summer, is easy.

    Working on a plain water storage tank, what I said was at day when it is easy to heat up the greenhouse air to 25⁰C, one simply has an air to water coil with a pump circulating to the storage tank, and a fan to circulate the greenhouse air through it for exchange. So what you do is keeping the greenhouse on 25⁰C and heating up the volume of water from the night.

    Right. Now lets say we manage to exchange whatever heat we can during the day and have the volume of water at 22⁰C at the end of the day. Night comes and once again, sets say we are generous and willing to drop the greenhouse air temperature to 10⁰C minimum and to achieve that, swing the volume of water down to 13⁰C.

    Lets for argument sake say we do it for 2 scenarios. Take a Greenhosue with 100m² total surface area and for a single wall construction, we assume a u-value of 5.8 W/m² ⁰C. For a double layer we will work on 3.5 W/m² ⁰C.

    From real weather data for my town, I would need 78 kWh of energy to get through a cold night. By swinging a volume of water through 9⁰C to manage that, I would need 7500 litres. That means in any case that the volume of water can be used for nothing else than thermal barrier. You cannot put fish through that swing twice a day and the growth beds would not like it either even if you do manage a way to store it there.

    For a double layer greenhouse, one would need only 47 kWh for that same night to stay on 10⁰C.

    Going geothermal, you would need an even larger volume of soil at least 1.8m down to manage that, so prepare to dig.

    I have included the PDF of the excell sheet that I use to calculate these things.

    That is why I for now, will concentrate to rather make a better greenhouse construction with decent thermal properties.
     

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  13. Tiboy

    Tiboy New Member

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    Am buying some rural land in southern US. Got a quote of about $1,200 from a contractor who will drill a hole about 60 meters deep (200 feet) big enough for a U-tube to circulate fluid (anti-freeze or water). They pour in an insulating grout to hold the U-tube in place and to isolate one line from the other. Then, it is ready to reject or supply heat. They claim that this U-tube system will be equivalent to 3.5 kW (1 ton). I'll have to spend other money to link it to an end-use. That seems reasonable for 3.5 kW/1 ton of heating/cooling for the price of running a pump.
     
  14. StarTrekTech

    StarTrekTech New Member

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    Hello Ms, Ga here, and am working on something similar. I also Know that WIS in TX is also working on a heat sink. I find some interesting facts just reading this post, and I am sure you will find even more info if you search this site. There is a search function top right of this site that should help you find that very information. I have just started a system here in my basement, as my learning curve, with the intention of going outdoors in the spring. To that end, I have been digging down about 3 feet to bury my IBC totes on top of buried pipes routed to an old dried up well. Don't know how well it will work, as it is still just an idea. But like I said, WIS, myself and others are working on this very idea, and I for one, welcome your input, your trials, and yes, your errors, so that we may all find success in this venture. Keep us posted, and PLEASE, provide Pics.
     
  15. Murray

    Murray Site Admin Staff Member

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    I have been very interested for a long time in Geo heating of my AP systems for winter.

    I have finally found a table of subsoil temps in my part of the world. A study done to determine the temps need to successfully decompose human bodies buried......nice..:oops:

    So, the plan is to bury a few hundred mtrs of black poly pipe, 25mm (1") at a suitable depth and move the water through the pipe during the night.
    Jade Perch (and Tilapia) do not do well below 15c so I want to keep the water temp above that. I do not know how well the ground will transfer heat over time, perhaps pumping cold water will eventually take all the heat out of the soil surrounding the pipe....maybe the efficiency will depend on having enough pipe underground and spread out over a wide enough area.

    Here is the table of soil temps at various depths in Brisbane Australia.

    The variation in temp is averaged over a year, not over a single night. The last column represents degrees C not 8C something happened in converting the PDF file to an image.

    Soil Temperature- 3.jpg
     

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  16. bobbyd

    bobbyd Member

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    The Melbourne Zoo wombat enclosure say 18 degrees at 2m down all year round.
     
  17. Murray

    Murray Site Admin Staff Member

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    Thanks for the info Bob. Should be a few degrees warmer here in southern QLD.
    I still haven't got my pipes installed as yet. Need a chunk of cash to do the earthworks etc.
     
  18. GrowTech

    GrowTech Member

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  19. Murray

    Murray Site Admin Staff Member

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    Here is the idea. I would love to build one of these or a variation of it, mostly for protection from the summer heat. Our winters here in Queensland are very short so I am sure it would be good for that. Thanks for the link Grow Tech.....There are many variations to this but the basic idea is the same.

    Greenhouse-walipini3.jpg.650x0_q85.jpg
     

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