Backyard Aquaponics
A place to discuss aquaponics

i have been thinking about using solar energy to heat my aquaponics system when it gets big enough.

The idea i had was to use black poly pipe in the sun to add heat in the morning. I have seen people use this idea to heat swimming pools and spas. it can be used to heat to quite high temperatures without the need for pumps. it uses concentric loops of the black poly pipe attached at the top and bottom of the tub/pond/pool and the thermal currents move the cold water into the pipe and as it heats it moves to the top of the pool.

The problems for aquaponics is that the temperature like this would swing to a large degree which would greatly stress the fish.

My ideas were to use a pump to circulate the water through the pipe and to only do it for a number of hours during the morning. This would mean it would not be chilling the water at night and would not cook the fish too much as it continued to heat up the water through out the day. The other way to figure it out would be to use some kind of thermostat like those in reptile enclosures, but the down side of this would be that the water returning to the pond/tub following sitting in the pipe would be very close to boiling, similar to a hose sitting in the sun on a hot day. These are the reasons to only run it in the morning to get them up to temp to eat.

well any other ideas or comments would be appreciated.

I'm looking at doing something similar. My pump will be on a timer so that it only operates during the day, and will probably also be cycled during that time (eg on 15 minutes then off 15 minutes). The pump will also be connected to a thermostat which will switch the pump off if the temperature in the fish tank reaches 30 degrees.

I will not actually be pumping the water in and out of the fish tank, instead I will be pumping water from a seperate container (say a blue drum), through the poly on roof and then through piping that is in the fish tank (hopefully stainless) to transfer the heat to the fish tank. This avoids the issue of hot water going directly into the fish tank and more importantly (from my arguably paranoid perspective) water which has leached chemicals from the heated plastic going into my tank. For a while I was considerring trying to have this seperate container get the water very hot during the day and then have a solenoid close at night so that the water continued to cycle through the fish tank, but only from the heated container (not through the pipework on roof, which would just cool water at night). It would operate a bit like a hot water system. I have decided this may be a bit complicated and unnecessary. It would be more costly due to extra components needed and also the need for the pumps to handle much hotter water.

Anyway this is still in development mode at present. There are a number of things I need to source before it can come to fruition.

Sounds great guys.

VB, i hear ya on the heat exchanger theory and the reason why too!

IMO you won't have to worry about the water coming out boiling hot, even in summer. Yes it does come out very hot from a hose that has been sitting there in the sun, but the water has not moved, just been heated up. If you had 1000Lt tank circulating water though the pipe you'd find that the temp difference between the inlet and out let might be 10 degrees or so.

I have a thermostat concept for you. If any one can get hold of a cheap temperature controller (they are around, i imported 30 odd from taiwan a few years ago at $20 each, spewing i sold them all) then you can do a really cool thing. As long as the input is a thermocouple type.

Wire two thermocouples in series, but opposite polarity. Put one in your tank and one just before the outlet of your solar poly pipe. With this configuration the temperature displayed on the controller will be the DIFFERENTIAL of the tank and heated water. So you can set the control to 5C and it will operate as long as the water in the solar poly pipe is atleast 5C warmer than the tank temp. Using a bypass solenoid the main pump can be used to do the pumping, and if the solar heater is cooler than the tank water then the solenoid simply bypasses it. So it will operate by itself whenever there is a temperature gain to be had.

If anyone gets a solar heating setup and would like to go down this track then i can help with the specifics then.

Also if you are going to use stainless in the tank you could still use copper in the solar collector frame. It has much better heat transfer characteristics ans comes coveniently rolled in a coil

Did i mention my first trade was in process control?

I have my system set up with black poly coils on the roof. My water is pumped from the drain tank back into the fish tank, and I installed a valve and some extra fittings so that I can switch the water flow so that it is pushed through the coils on the roof before being returned to the fish tank.

At this time of year I switch the one valve when I get up in the morning, water is then pumped through the coils all day long as the water is being returned to the fish tank, then in the evening I turn it off. Although this does raise the temperature in the system a little bit, it only makes a real difference of about 2-3 degrees in a 1500L tank on a sunny day by late afternoon. In fact lately I have been wandering about the logistics of using it because I can hear my return pump labouring having to push the water through all of that extra pipe, and I've had to replace the return pump a few times....

I think some of the most important thing in keeping a system warm is location, orientation and keeping the heat in the whole area of the system, creating a buffer of air around your whole system.....

just a side not: all the literature u read about green houses facing south are from the states. i'm fairly sure its opposite here becasue we're in the souther hemisphere? Ie you want it facing north to catch the most sun due it being more in the northern sky during winter

Yep, north facing...... Something stopped me dead in my tracks the other day.... I was walking to the shops, it was late afternoon and had begun to get cold and windy. As I stepped up from the carpark to the shopping centre the heat radiating out from the shopping centre wall hit me. It was hot......! It was a north facing brick wall that had been heating up during the day and now at dusk, as the temperature was dropping, it gave off a very, very noticable amount of heat.... Certainly enough for me to take notice and make a big mental note about thermal mass...

Steve - the only reason I thought hot water could be a problem is because of cycling the system, but to be honest, the bigger issue for me is the leaching. Not sure how viable it is going to be to use stainless steel piping in tank, might be too costly. I hear what u say about using copper pipe as the collector. Would copper also be a safe alternative for the transfer of heat into the fish tank, instead of stainless. I know from reading here that it is toxic to yabbies, but if I went for fish only then I wonder if it would present any other problems regarding the toxicity to those eating the plants and fish???

The thermostat thing sounds good - though my electronics and electical skills are nil so I could not do such a thing without very detailed instruction. I purchased the thermostat a while back. Only problem is the people I bought it off misled me regarding its function, so I will need to add a relay to get it to work the way I need it. It is designed to turn on when temp gets high and off when low, so it is the opposite of what I need. I will speak to my next door neighbour (a sparky) to see how I can best use the thermostat. I am not convinced that it couldn't be used without a relay - but that is too complicated to explain here.

Joel - theoretically you should get better temperature increases than you are getting. Solar pool heaters achieve multiple degree temp increases for much larger quanitities of water. Maybe the use of normal poly pipe and the amount used just doesn't function to the level needed for this application. I intend to do it a bit differently, which I hope will result in major temperature gains. Will explain fully when I finish the design - it is very simple though (of course it may not work).

Regardless of any of this, as Joel has said, the proper siting of the setup and use of greenhouse of some kind would seem to be essential.

VB, this is what I was eluding too, Part of the reason that the solar heating doesn't work as well in an aquaponic system is because it's so much of a heat radiator. An above ground tank that has cold air passing over it and around it. The water is constantly being pumped through thin pipes, then into raised growbeds that have air flowing past them, both under and over, plants transpiring and evaporation happening all the time. When your heating up some water in black pipes and pumping it into your system, this heat and more, is being lost through the cooling aspects inherent in the rest of the system.

Where as a swimming pool being heated by the same method generally has a much larger thermal mass than an aquaponic system. It will take a lot longer to heat up, but then it will also hold the heat better because of it's greater mass. Plus this is usually buried below ground as well, also helping to retain the heat.

If your fish tank was buried, and your growbeds buried, with underground piping this would help, and I've seen some systems like this..

I guess that after keeping barra alive over winter in my open system, using every means possible, 1 300W heater, tank wrapped in bubble wrap, foam on water surface, switching system off every night, topping up with hot water every morning and running the water through the black coils during the day. I came to realise that in a Perth type climate it was near impossible to keep tropical species outside without a hell of a lot more thought and action than what I was doing... It was beyond a joke, and that is when I swore that I would never grow a warm water fish in that system again, because the effort was just way too much, and not only did the fish not really grow, but they were sickly.... This also meant very little nutrient for the plants to grow.

I came to realise that it was too difficult to close in my pergola area where the system was situated, so for me, from now on in this system, it's cold water species only.... But even they aren't liking it much when the water temp dips to around 8 degrees in the mornings at the moment...

VB,

Did some research a few weeks back on copper.

It only really seems to go into solution when the water is low PH, but toxicity for fyabbies and the like is only a few PPB parts per billion (0.001 mg/L) Fish can tolerate more, but its still in the parts per billion range. Not worth the hassles me thinks

I'm under the impression that its fairly ok for us. (as humans, not for our setups )

Steve

Re Copper....some folks wear a copper bracelet or the like believing that it helps with arthritis.
Stainless tube is not that much more expensive than copper but is a pig to bend and join etc.
I am personally not too worried about all the stuff that might get into me out of the pipes etc.

I will worry about that when I find a way to avoid all the fumes from cars, trucks and the like, also give up eating and drinking almost everything from the supermarket with all the added colourings, flavourings, preservatives, thickeners and the like, then all the trans fats that are added to the bread together with the bread extenders, preservative and all the stuff they add to the white bread to try and make it taste like bread.........and all the stuff we don’t know about that they dip the vegies and fruit in to preserve them, colour them and to kill the bugs.......... .....ahhhhhhh ...hang on a minute, that is why I am doing this Aquaponic thing !!!!!!!!!

Quick, down to the fish tank to see if my little Jades are ok ! They have some vegies to grow !!! Back to work you little mongrel Jades, you are not crapping enough!!!

To be honest I wanted this to get kids interested in aquaculture - and then as a possible way to breed large amounts of tropical fish for myself... and now, well, I have a burning desire to get the entire school interested in this - a way to grow food in a manner which hugely limits the ammounts of pollutants in our food (as Murray pointed out above) There is more than enough stuff out there which can make us sick , and if I can get the kids to start eating healthier food, then my job is done!
My goal is now to supply food to the canteen - that way our efforts have the greatest effect.

I will be installing polly pipe along a fence to heat the water in my system during winter... just so that they stay warm enough to eat properly - but I will also be using a timer so it will only go from about 9am till about 3pm...

Yes Murray there certainly is a lot of hazardous crap that we are exposed to on a daily basis. I am not really full on about avoiding these things, but I do grow my vegies without chemical fertilisers or pesticides. I like the fact that by doing this, at least to the extent that we eat our homegrown stuff then we are avoiding the shit that the commercial producers put on the stuff.

When it comes to us of plastics in my aquaponics situation, maybe I am making it difficult for myself unnecessarilly. When it comes to poly, I am not really concerned about poly tanks. In fact I will shortly purchase 2 poly tanks for rainwater use. What concerns me more is the use of the cheap, thin poly pipe. Not coming from a postion of knowledge, it seems to me that maybe that poly in this application (not being food grade and being very thin and possibly not pure) may not be as safe as the tanks etc. The stuff smells chemically and couple with the high heats it would reach being used in a solar application, it just makes me think that it might not be safe. I am probably wrong and if somebody can give me info about its safety, then I would happilly use it and make things cheaper and easier for myself.

Frosty - good to see you back here. Do you know anything about this thin blakc poly hose, the type used for basic sprinkling type use. Would you use it. Not that I would restrict myself to only using things that you use. I know that because of past exposure you are hypersensitive.

Murray,

I'm not worried about the copper at all as far as human consumption goes.

Its the fish that have trouble with it



We are talking about orders of 10 parts per billion. Thats why i recommended vb use stainless only for the heat echanger that was in contact with his tank water. I have worked with 1/4 inch stainless before, and it is a Pr!@k to bend. the same diameter copper you could almost bend with your mind

I think that if people make a little effort they can be amazed at what rubbish the can cut out of their diet. I'm not preaching. I went through an eye opening couple of month of research a few years ago and have changed my consumtion of "crap" quite dramatically. The only thing left for me is the ciggies. Thats not to say that i never eat a blue M&M, its just being smart about it. I went on a crusade to save all my friends from themselves when i did all this reading, the answers i got were "somethings gonna kill you anyway" (which is funny, 'cause i used to say that) and also "Ha! see you just ate XYZ". The answer i give to "somehtings gonna kill you, is "yes, and crossing the road might get you run over, but you're 10X more likely to get run over if you cross the road 10X back and forth.

I just wanted to make them informed about what things were in certain products and food. But very few people actually want to know. I've been told many times "i dont want to know, because then i won't be able to eat xyz or use xyz product" ??????!@#$%^?????? how does that work? . I'll never quite undersand that mentality. I don't expect people to go live in the country completely chemically free (sorry frosty ) But i would expect people to want to make INFORMED decisions. Just ranting again, this wasn't aimed at anyone

VB i know what you mean about the black poly pipe. It may seem distinctly different becasue it is LDPE (low density) compared to the high density in the "blue line". But still where can we find info. most of the pages i get from google is just product marketing / sales

Steve

Did some googling of my own and found a couple of references to it not being food grade and that it shouldn't be used as water pipe for drinking purposes.

I now must think how I can best organise a stainless steel heat transfer device. Will make some calls when I finish exams.

VB can you post me some links if you still have them?