Backyard Aquaponics
A place to discuss aquaponics

its going to be a function of the surface area that the keg presents and you would HAVE to have water flow around it to make it even worth while. sitting the bubblers under it might create enough flow.

can do the calculations for you, just bump me every few nights, brain is fried at the moment, shouldn't have done the calcs on the air heater thing, i was bored.

Here`s a twist to consider
In a AP greenhouse the relative humidity could be as much as 80%+ due to the tank/growbeds, it will make a big difference to any calculations.

For example,in old money, 90F air at 80% RH (a typical AP greenhouse perhaps) would hold about 2lbs of water per 1000 cubic feet, routed through pipes surrounded by cool water it might sustain dewpoint down to 65F and if the exit air is 65F at 40% RH it will have released around 1lb of water (1000 btu) per 1000 cubic feet.

In a direct litre to litre comparison, 1 litre of air using a 25F temperature differential (90F-65F) with the phase change would warm 1 litre water by 0.2C versus the 0.125C gained from dry air with a 122F temperature differential. I`m old so i can mix units

Your greenhouse might benefit more from the air conditioning effects than the actual water heating

interesting Hex - thanks for that

Hi C1
My brain has been fried a bit lately too so don`t take the figures as absolutely accurate..everything involved is dynamic so its constantly changing.

It`d be easier to catch an eel with a spoon

very true.

I'm using a pretty simple way to heat water for a system.


If my barrel were black, it would probably work even better. I'm using a sump placed where the water will heat up more instead of heating the water with electric heaters. This is a quick pic from my breeding wall thread.

It might not be as effective as a more traditional solar heater set up but I haven't worked out all the details with finding safe piping or heat exchanger materials or the right kind of high head, low flow pump. This seems pretty effective for now. At least I should say it has brought up the daytime temps in the system by over 5 degrees F.

The simplest way to heat water using solar, is to pump it through a 50 metre roll of the black pvc tube used for garden sprinklers. Just break open the roll and spread it out a bit, either on the roof or on the driveway, you don't need to lay it out straight, just lay it in curls over itself to maximise sun contact.
You can increase its effectivness by laying clear plastic over the coils to stop wind chill.
But you do need to be careful you dont cook the fish prematurely, A friend of mine used 3-4 rolls to heat a large swimming pool!

Biggest question has been, is the black tubing safe for potable water? what does it leach out when it heats up? It might be dandy for a swimming pool which you don't generally drink or eat from but for a recirculating food system we need to think things through more carefully.

the black tubing is either HDPE (high density polyethylene) or PP (polypropylene)
both are even safer than PVC
intensely used in water distribution grids
PP is better for hot water
for cold water even the thin walled versions (1 to 1.5 mm) of both resist up to 10 bar
frequently used in air pressure systems
you can get much better prices for 100 m coils of say 10 x 1 mm with compressor appendages wholesellers

I would use thin walled PP for hot water max. 70°C to max. 3 bar, not more


what specifications are you looking for?

frank

But even with one bubbler or fish ,water is always moving in a ft

I'm not sure on this one as lots of the black irrigation pipe is Polyethylene Tubing and there has been talk that at high temperatures, it leaches. I'm not sure on this one as I've not had much time to investigate it on my own yet.




Not really sure as I've not had much time to really work on the solar hot water thing lately.

no aggression intended,
but you do realize that by your reaction, you are only adding to "talk"?

apart from (maybe?) stainless steel, we don't have to much options:
lead has been a long way out, copper is out, aluminum probably also (maybe not if it is anodized)
of all plastics PP and HDPE are (or should I say appear to be) the least harmful
PP is more resistant to high temperatures than HDPE
my choice would (and will) be PP for solar heating

Now it might be that in the future PP and HDPE will be out,
but for now we have those to work with as "best of worst options"
as far as I have found, the amount of possible leaching in a year would (to today's available knowledge) probably be less harmful than smoking a pack of cigarettes or than taking a half hour walk along a highway
but I am not a scientist

Frank

I must admit that most of my experience with black tubing is the irrigation tubing that is labled, "NOT FOR DRINKING WATER" I suppose that is the main thing that has made me cautious about using it extensively in my system. I must admit that there are some bits of it here and there.

I was doing some looking and some of the HDPE I did find listed by the NSF as safe for drinking water, also says to keep it out of the sun. Would make it hard to use as a solar collector if it breaks down in UV.

I have found references about PP and PB being better for Hot water and as yet, no reference about their UV stability.

So, looking for 1/2" black tubing that is listed safe for drinking water, appropriate for hot water, and UV stable (don't want it busting in the sun in less than a year.) If I can find those things, I need not worry about getting a stainless steel heat exchanger.

If you're worried, try some 3/4" food grade tube, poked up the centre of 1" black poly pipe to act as a heat gathering sleeve, this will protect the good tube from the UV and if the black stuff deteriorates, it wont drain your tank.

It is definitely an idea there D!cko but I'm not sure how easy it would be to thread 500-1000 feet of tubing within other tubing. I only mention those lengths cause that is what the irrigation tubing comes in from the supply place (not gonna pay retail for 50-100 foot chunks of the stuff.)