Aquaponic Gardening

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Has anyone utilized solar hot water systems to heat or ground source heat pumps to cool aquaponics systems? I considering alternatives to lighten electricity/ natural gas load as much as possible in a system I am planning. Not too much info out there except for folks who want to heat a swimming pool or put in a radiant floor in their home....

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I have tried it.  The solar water heating that is.

It can sort of work to an extent however it does have some challenges.

1-metal tubing and fish water should never touch.

2-small tubing and fish water probably means major clogging issues.

3-heat exchangers mean less efficiency.

4-sun is out during the day and heating is normally needed at night.

5-Aquaponics systems have a large amount of water so it usually takes a large amount of heated water to make much difference to it meaning rather large insulated heat storage tanks.

 

I had two swimming pool panels on my roof and a freezer chest as my hot water tank.  That was really not enough heated water to make more than a 1/2 degree F difference in my Big AP system which was about 900 gallons of fish tank and 1400 gallons of flood and drain gravel under a greenhouse film cover.  I would heat the water from the freezer chest during the day when the sun was able to hit the roof and then in the evening I would cycle system water through a coil in the freezer chest to warm the system water but the water in the freezer chest would be chilled down to the system water temp in only a few hours.  And Flood and drain gravel is a very efficient heat exchanger with the air so the air temp in the greenhouse at night would have a far greater impact on the water temp than a few hours of cycling water through the hot tank.  I finally gave up trying to keep my inland central Florida system in a greenhouse warm enough to keep tilapia alive through winter (two winters in a row I had to run water from the hot water heater in during freeze nights to keep the water from dropping below 50 F and keeping the greenhouse closed to regain heat during the day was making it real hot for the plants and I was suffering all sorts of pest problems because the plants were struggling.)  So now I'm growing fish that don't require me to heat the system here in central FL and the plants are doing much better with no greenhouse at all and I haven't bothered with heating either.

 

Now in a cold climate, a geo exchange heat pump for hydronic heating or cooling might be useful and if you can set up a real solar domestic type hot water heater with a fish safe heat exchanger you might get enough heat stored into a hot water tank to be of some real use but I wouldn't depend on a swimming pool heater being much use for a large aquaponics system.  Or perhaps I should say for a solar pool heater to be of much use to a large aquaponic system, you would need a heat storage tank almost as big as your fish tank.



TCLynx said:

So now I'm growing fish that don't require me to heat the system here in central FL and the plants are doing much better with no greenhouse at all and I haven't bothered with heating either.

 

TCLynx - What fish are you growing now? Is there a disadvantage over Tilapia? I'm in Southern California, the air temps here can get down to the 40-50s. I'm planning to add a heater to my AP, once I get it built.

I'm growing Channel Catfish (which I've been growing from the beginning and we actually like them best so far.)  And just this spring I got Bluegill for the first time for something new.

 

Advantages of tilapia, well they are pretty tough and can handle poor water quality during cycle up and low DO is not as quickly fatal to them as most other fish and they will breed for you but that is both a pro and a con since breeding tilapia are not eating or growing tilapia.  Tilapia may survive water down to around 55 F but they stop eating and growing usually when the water gets below 70 F.

 

Channel Catfish need a bigger tank than Tilapia (I wouldn't grow them in less than 300 gallons of water  and I like the water depth to be at least 2 feet deep for them, not a 2 foot deep tank.  Channel catfish can grow fast in warm water and they can get big too but they do need slightly better water quality and dissolved oxygen levels than tilapia but the catfish will keep eating at cooler temperatures than the tilapia will.  I reduce feeding when the water gets below 70 F but I don't think they completely stop eating till the water is down to about 55 and they can survive water down below freezing (I've had water down to 32 F in central FL.)  Drawback, of channel catfish is that breeding them in a home aquaponics system is highly unlikely since they are not mature till about 3 or more years and by that time they are quite large and normally bread in large ponds.  However, Channel Catfish are usually fairly easy to get from fish farms so this hasn't been a problem for us.

 

Bluegill don't grow super fast or all that large but they are still good eating.  I haven't had mine that long so I can't speak from much experience other than eating them after fishing trips up in Michigan.  I know people who have had them in swimming pool aquaponic systems where they did breed. 

 

I believe the Bluegill temp range is probably similar to channel catfish and all three types of fish do well with the same commercial feed (though the bluegill and tilapia prefer the smaller pellets.)

I'm in the planning stages for a commercial system with around 30,000 gallons, so with volumes this big, I don't expect a large temperature swing between the day and night you'd get with a small backyard system. I am hoping to insulate as well as I can and since Tilapia are not legal in Santa Barbara, will be trying Koi which can handle a broader temperature range. The solar heat is meant to keep the water temp as close to the low 70's as possible to maximize plant growth during the off-peak seasons. I know seasonally, I'll have some weeks where I can't keep it as warm as I like it but have heard the evacuated tubes work well in cloudy and foggy conditions which is when you need some extra heat the most.

 

I'm much less certain of what a ground source heat pump and system can do. Since temperatures underground are a near constant 55-60 F, they may help keep summer temps down and provide some crucial heat during the coldest of seasons here. For the cost, they may not be all that effective here but I haven't yet run the numbers of what is possible and what it would cost.

 

My plan is for a Friendly style raft system so I shouldn't have the heat loss flood and drain systems have but really, it is all just guesswork at this point. Thanks for the input TCLynx.

 a ground source heat pump uses the ground for heat absorbtion or removal,  You can get 100 degree heat with 55-60 degree ground temp or great cooling when the cycles reversed. Basically its a closed loop heat pump. So if you want to install an elaborate setup costing about 10k to condition your water it'll work fine, but you;ll also have about the same size utlity bill as you will for heating/ cooling of your house.

Now I agree with TC if you use a solar heating setup it would probably suffice as long as you use mixing valves from your  cool tanks to prevent overheating or to high of temps in the heat exchanger part of it. It really comes down to what you really want to spend, and being your building such a big setup a solar water heater should work well because of what you mentioned....not having the swing because of the size.
Randy Turner said:

I'm in the planning stages for a commercial system with around 30,000 gallons, so with volumes this big, I don't expect a large temperature swing between the day and night you'd get with a small backyard system. I am hoping to insulate as well as I can and since Tilapia are not legal in Santa Barbara, will be trying Koi which can handle a broader temperature range. The solar heat is meant to keep the water temp as close to the low 70's as possible to maximize plant growth during the off-peak seasons. I know seasonally, I'll have some weeks where I can't keep it as warm as I like it but have heard the evacuated tubes work well in cloudy and foggy conditions which is when you need some extra heat the most.

 

I'm much less certain of what a ground source heat pump and system can do. Since temperatures underground are a near constant 55-60 F, they may help keep summer temps down and provide some crucial heat during the coldest of seasons here. For the cost, they may not be all that effective here but I haven't yet run the numbers of what is possible and what it would cost.

 

My plan is for a Friendly style raft system so I shouldn't have the heat loss flood and drain systems have but really, it is all just guesswork at this point. Thanks for the input TCLynx.

What about heating water with hot-compost.

http://www.youtube.com/watch?v=PCXSoV4jNAA

Heating with compost can be done but it tends to be sort of short lived or takes a log of work rebuilding the compost around the tubing all the time.  How effective it would be will depend on the size of system and amount of heat needed as well as the space for a big compost pile.

I have seen a promising system here on top of a very cold mountain for heating a greenhouse.  Now the system in question does not heat the green house enough for what we are talking about, but might work for heating water.  Basically it is this:

Large water reservoir burying and insulated in the ground.  It is hooked up to 4 solar pool heaters, and the pump is activated on a thermostat to build tank heat during the day.  The gentleman shows water temps in the system reaching as high as 120 degrees.  At night the pump relocates the water to radiators in the greenhouse.  It has reduced his propane bill by 75% on average.

This might work well for a tilapia tank system, with warm water storage for when temps start to drop.  A lot of engineering would be required, and its going to cost a bunch.

Biomass is an inexpensive fuel to heat your water with. And if you are in a greenhouse it will of course heat the air.  Here in the PNW you need both. Biomass is also renewable and sustainable, and carbon neutral.

 

Rick, by "biomass", do you mean compost?

The following are a couple of things I've tried and would like to introduce to you folks.

First off I have to say that even though these systems do work, the capitol and/ or labor outlay is probably prohibitive for most folks.

As a home automation guy (my former profession before coming to China), taught me to zone and layer everything for efficiency, so the first concept I would like to introduce/ reintroduce, is to control the root-zone temperature instead of heating/ cooling the massive volume of air inside a greenhouse. This works for open sky growing as well.

My biggest challenge to date is how to pump large volumes of water (especially vertically) without using electricity.  Solve that and we would truly have a solution to world hunger. Of course there are the old wind powered, foot/ hand powered or even solar powered (P.V.) eletrical pumps but that is not what I am/ have been after. I'm thinking more along the line of capillary pumps or simple solar pumping system maybe using ammonia absorption cycle? Where physics and nature are incorporated to accomplish certain tasks. I'm not talking perpetual machines.

One example I can use, is say; supplemental cooling a greenhouse with geothermal exchange: where a solar chimney on the roof of a greenhouse draws air underground (6 feet) and through pipes filled with rocks. Warm air is cooled by the rocks and enters the greenhouse at or close to the surface of the soil, cooling the soil. Heated air rises and as it rises, collects more heat to rise even quicker until it reaches near the top of the greenhouse where it is wicked away by the even hotter air inside the solar chimney. The negative pressure draws more air through the underground tube and the cycle repeats.

In winter the solar chimney can be relocated to the bottom of the south side of the greenhouse to supplement heating by a few degrees. Of course by adding systems like this we can almost eliminate active heating but the ROI would be longer. However, in the long run, it should be much more ecologically sustainable and the eventual cost of services and maintenance over the lifetime of the building would be much less.

So, so far I have talked about three technologies that can be implemented: root-zone heating and cooling, solar chimnies and geothermal exchange. Within these technologies, we can find different ways to apply them for even more benefits. All without using electricity.

I'd love to write more (much more) but unfortunately I simply don't have time so consider this as some food for thought.

Cheers

Heating and cooling aren't actually problems, it's just a matter of money one has to lay out first, that keeps us from going crazy and use the variety of technologies we should. We should try to use what nature provides in our specific location.

Lets take biomass. We can compost it and get some heat or we can make pellets for high efficiency burners/ stoves. Both work but which is more doable for you? I deliberately let my yard go after harvest so I can make pellets for my stove and rabbits winter feed. Rabbit poop becomes worm food which I use in spring in my growbeds (after the worm poop thaws). 

Now lets talk about solar. Most people only think of the traditional black hose in a black box type of solar heaters but by adding a concentrater, one can increase efficiency tremendously. I wish I had pics but we use to have an eight food portable array that generated steam to sterilize soil in fields. With this kind of heat, it's just a matter of storing it till you need it. A back wall full of water cans painted black can keep a greenhouse nice and warm all through a winter night. No reason why you can run a heat exchange to pond/ tank esp if it were well insulated which is something neither commercial nor hobbyist do well enough in my opinion. Everything should be insulated for better thermal control.

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