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Radiant heat for fish tanks
http://byap.backyardmagazines.com/forum/viewtopic.php?f=1&t=6709		 Page 1 of 2
Author:  mjmckinney [ Dec 16th, '09, 00:44 ]
Post subject:  Radiant heat for fish tanks
We live in east central Illinois. We do have winter night time temps in the 10 - 20 degrees F at times in January and February.

I would like to avoid the expense of building a solar greenhouse with the insulated wall etc etc.

Instead I would like to build a double wall poly greenhouse.

But I would like to add a system of pex tubing that would be used to keep the fish tank at warm temperatures and for that matter it could be used in the grow beds as well. The pex tubing would either be installed in the tank or surround the outside . It would be heated by a standard home water heater.

So my question is this - has anyone tried this and if so with what results? My goal here would be to heat the fish water and the grow beds rather than heat the entire cubic footage of air in the greenhouse.

Thanks,

Mike
Author:  TCLynx [ Dec 16th, '09, 03:10 ]
Post subject:  Re: Radiant heat for fish tanks
I'm sure it can be done. I don't know if anyone on the forum has actually done such an install though. I expect you will have some major condensation/humidity issues inside such a greenhouse. Also, if doing flood and drain, every time the cold air sucks down into the wet media, a fair amount of heat exchange happens. If the air is really cold, flood and drain will serve to chill the water. I expect you will use lots of electricity to keep the water warm if you are not doing much to keep the air in the greenhouse warm. Insulating the heck out of the fish tank and the grow beds might help a little but the air moving in and out of the tops of the grow beds is where the chilling happens. Perhaps leaving the beds flooded constantly with a continuous flow of water might help a bit in winter but you then need to make sure there is plenty of additional aeration to the system.
Author:  DéjàVoodoo [ Dec 16th, '09, 04:54 ]
Post subject:  Re: Radiant heat for fish tanks
I was actually thinking the same thing...radient heat mesh in FT ST and GB all made of concrete. In Texas though I do not have the extremes as those up north. I'm thinking I can probably keep it at a toasty 70 year round.

Mark
Author:  TCLynx [ Dec 16th, '09, 05:12 ]
Post subject:  Re: Radiant heat for fish tanks
It does not take long for water going through a flood and drain situation to drop much of it's heat. You want the greenhouse to provide a fair amount of insulation over night if you are going to keep water above 40-50 F without spending huge amounts of electricity on heating.

Here in Central Florida (in the sub-tropics) where the water comes out of my well above 70 F. My system under single layer poly last winter could easily have gotten down to below 40 F if I had not taken measures to keep the water warmer than that. I think 54 F was my low before I started running water into the system. (and that was shutting down the grow beds overnight and keeping the plastic sealed up during the day to try and re-gain some heat and using a solar water heater during the day.) It only took one chilly week with a couple of freeze nights in a row and I was struggling to keep the tilapia alive. I have made improvements to the greenhouse this winter but I've also decided not to bother much with tilapia in the future so I won't be keeping it all sealed up during the day to re-gain all the heat (plants did kinda poorly with the extremes of hot and cold last winter.)

Definitely put a little extra effort into improving the greenhouse design a bit if you can and it will save you big time on the heating bills.

Now if you are going to heat, I do think the hydronic radiant heating is a good choice. But I also believe that adding easily solar heated thermal mass and as much insulation as possible and perhaps even protecting the greenhouse from radiant losses over night if possible would be worth the extra effort.
Author:  aLostHippy [ Dec 16th, '09, 12:37 ]
Post subject:  Re: Radiant heat for fish tanks
there was a guy on youtube who built a large compost heap and through the middle he coiled some black poly pipe.. the heat from the compost breaking down acted like a water heater.. infact he used it as a hot water service for a shower.


if space is an issue, there is a few designs around for home made solar hot water units that might help.. or paint the tank or sump black and position it to get some sun..


i think i have copied this right...
http://www.youtube.com/watch?v=ILzxOH6n7-c
Author:  Chappo [ Dec 16th, '09, 20:52 ]
Post subject:  Re: Radiant heat for fish tanks
The compost heat idea is an old one ,, problem is that to get any reasonable amount of heat you need several hundred cubic metres of the stuff. I wish it was possible in small usuable amounts , but it just isn't:(
Author:  TCLynx [ Dec 16th, '09, 22:01 ]
Post subject:  Re: Radiant heat for fish tanks
I actually recall a member on here trying to heat water with coils in a compost pile. He did manage to heat some water with the compost but it required a huge amount of work for only a small heat gain and before the winter was out, I think he ran out of materials for the hot composting.

I know there are greenhouses out there that gain some heat by having the compost piles in the greenhouse but it is a rather small heat gain for the amount of space used by the compost. However, if the greenhouse is good at retaining heat over night, it could be enough gain to make a difference in a cold climate.
Author:  RupertofOZ [ Dec 16th, '09, 23:56 ]
Post subject:  Re: Radiant heat for fish tanks
It CAN be done Chappo...

Daryl (from Windsor) rigged up a simple otto wheelie bin packed tight with grass clippings... to heat his Barra tank... initially he coiled 20mm tubing through the clippings... and pumped water through it... but found the water cooled the clippings down...

So now he runs 4mm air hose... and pumps the air from his air pump through instead... :wink:

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Read from here... http://www.aquaponics.net.au/hq/viewtop ... 3473#p3473

Set up one myself... but never used it ... due to broken thermometer and broken mower... luckily I haven't needed to get heat into my Barra tank...

The clippings were getting up to 50 degrees... and Daryl was getting 4-5 degrees into his tank...
Author:  Chappo [ Dec 17th, '09, 00:29 ]
Post subject:  Re: Radiant heat for fish tanks
Read it Rupe ,, and i see NIL quantifiable data.
I do see , he needed to change from water to air as the compost was unable to heat the water.
ANYWAY , i recon it don't gonna work ,, 1,000 litres of water need some 20,000 BTU to raise its temp 5C , thats a LOT of grass. Once again i hope I'm wrong , but unfortunately i doubt I am.
But the heated air may be a valiable, although minor, addition to any heating plan
Author:  Food&Fish [ Dec 17th, '09, 04:34 ]
Post subject:  Re: Radiant heat for fish tanks
Chappo heated air makes a diff my air line to the trout tank is buried and one sunny day i couldn't reason why the tank temp kept climbing till i measured the air temp 38 deg turned it off and ran a small remote pump and it slowed down considerably
Author:  TCLynx [ Dec 17th, '09, 06:29 ]
Post subject:  Re: Radiant heat for fish tanks
Size is gonna make a difference. Small fish tank being heated by wheelie bin of hot compost could be effective. That same wheelie bin of grass clippings may have a negligible effect on a swimming pool.

So, it can work, question becomes, is it worth it. Now if you are trying to just nudge a small tank temp up a little for a few weeks it might be reasonable. If are you trying to maintain a 40 + degree F differential on thousands of gallons for 4 months? Big difference.
Author:  DéjàVoodoo [ Dec 17th, '09, 07:20 ]
Post subject:  Re: Radiant heat for fish tanks
I think I am in a good climate to give it a try, the average temperature in houston is above 50F/10C in Dec, Jan, Feb the rest of the year it is above 60. Those are averages though and we can drop as low as freezing for a few hours in the night when the daytime temps will be 35/40F 1/4C. That cold is always short lived, and we will rocket back up. I'm looking at electric radiant heat mesh in the concrete to more keep the tank temps stable. GBs, ST, and FT (about 4000L) will all be concrete and block. Keeping Tanks at a toasty 70 is probably unrealistic, 50 - 60 should certainly be doable. I would add radient to GB as well as FT. The sump will also be burried quite deep and should benifit from geothermal protection (could add radiant here too and probably will). I guess my target temperature in FT and GB should be what the geothermal temp is a 4-5 feet. This should give me pretty stable temps through the cold months.

Mark

PS pulled some radishes out of the regular garden today. All but one had split from the excessive rain we have had.
Author:  Web4Deb [ Dec 17th, '09, 21:17 ]
Post subject:  Re: Radiant heat for fish tanks
Replying back to the original question on heating the water....

I'm in a fairly cold zone also, Last year I put a heater in the water, hoping it would heat the greenhouse. With the warm water and the cold air, you will have a large amount of evaporative heat loss from the water and will drive the humidity of the greenhouse up to near 100%. The condensate will then freeze to the polycarb and anything else that is cold.

It was so bad, that the doors to my GH froze shut and I couldn't get into it....finally had to remove a section of polycarb to get in!

Here's a before and after photo of what the condensation looked like:
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Author:  DéjàVoodoo [ Dec 17th, '09, 22:01 ]
Post subject:  Re: Radiant heat for fish tanks
Web4Deb wrote:
With the warm water and the cold air, you will have a large amount of evaporative heat loss from the water and will drive the humidity of the greenhouse up to near 100%. The condensate will then freeze to the polycarb and anything else that is cold.


Crap - never thought about that. Did the plants survive or did they all freeze also? What are your temps like and did you abandon the idea all together?

Thanks
Mark
Author:  Web4Deb [ Dec 17th, '09, 22:20 ]
Post subject:  Re: Radiant heat for fish tanks
Last year, everything died. Heating the water couldn't keep up with the falling air temps. This year I put in a couple of cheap space heaters from Harbor Freight and made a custom thermostat to keep the temp at 40. It costs about $0.50/hour to run, even at that low temp.

I posted my "scientific" data here: http://www.backyardaquaponics.com/forum/viewtopic.php?f=18&t=5098&st=0&sk=t&sd=a&start=45

If you come up with a more cost effective solution, keep me posted!!!

Also, check out the my video tour so you can see how my setup works.....
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