Backyard Aquaponics
A place to discuss aquaponics

Last night before things really started to cool off, I shut off/unhooked the black tubing from the experiment and closed both coolers.

This morning the coltrol cooler was at about 78 F and the cooler that had the hot water in it was at 90 F. The low air temp last night was probably around 75 F.

Today I'll try and hook up the food grade tubing to the aquarium system sump barrel. And I'll have to keep a close eye on things to make sure I don't cook any fish.

Interesting stuff TCL!

might need to incorp. an auto air bleed valve for longtime use?

Well it's about 11 am here. I've had to to up the barrel (sump) from the hose so the temp is about 70 F in the water in the barrel right now. Air temp in shade is 83.8 F and rising.
I've got the pump off while I was setting this up and I won't turn it back on until the water is up to at least 78 F-which is about what the water is in the aquarium right now. (don't want to be shocking them with cool water and then making it hot.)

Will have to see if I was successfull in getting a good siphon going on this larger tubing. I installed one of the duckbill check valves for sucking out the air since this tubing is stiffer than the irrigation stuff and the tank situation is a little less open. I can't be laying it down stopping it with a finger and the quickly lifting it back up into the tank water.

Ok, it seems that the one thermometer has slipped and is no longer accurate.

I did think 70 F was too cool for what our well water usually is this time of year.

Hum,......

Ok, I don't seem to be able to keep a good thing going here.

In the ice chest experiment, I lifted the chest up onto a bin and I'm starting to think that between the elevation, the smaller pipe, and the constant level in the chest, may have been the only reasons that it worked.

With the sump, I have some bubblers in it so can't leave the siphon outlet pointing down or it gets bubbles. I also probably don't have enough elevation on the barrel to make it work. Hum.

The ice chest set up must have simulated a closed or sealed system just enough that it worked.

I didn't want to mess with a pump for this.

Ok, if I try this another way it will no longer be a thermosiphon but.......

I don't want to impede the draining from the beds but, if I let that fall into a small bucket that has a drain on it which I can divert to feed the black tubing which I can have drain back into the barrel by gravity. .......

Let me think, if I have the parts to test this out. gotta make sure I don't set myself up for air locks.........

Ok, so I've got a little something hooked up and working now. It isn't a thermosiphon. But, it isn't costing me extra electricity to run another pump either.

I took a couple pics but they really don't show what is going on very well. So I'll just try to explain it instead.

Where the water comes out the window to fall into the sump, I added a T on the 1 1/2" pipe. Out the bottom of that T I hooked up the fittings to get to the 3/4" black pipe and ran it out the top bung hole that I removed the bung from. The side of that T is left open to allow the free draining of the water when the 3/4" black tubing is full or when I shut off the valve for the 3/4" tubing because it is either too hot or for overnight. Now the black tubing runs out and is in a bit of a coil then comes back to the bottom bung on the barrel where I have hooked up fittings through the bung threads and installed a ball valve so I can shut the flow off from the black pipe.

Ok, so I didn't get the thermosiphon heater working.

What I did get working, and seems to have worked very well, I guess I'll call the drain into sump heater. Or should we call it a drain heater?

Anyway, it is a bypass from the direct drain that I can control with a valve. When conditions are right and appropriate for heating, I open the valve and a portion of the water that is draining into the sump gets diverted for a gravity ride through the black tubing in the sun. This seems to have worked amazingly well. It only took a few hours before I decided things were warm enough and closed the valve.

This is all manual at the moment and doesn't do anything special to retain heat overnight.

I think I'll create a separate thread to describe this again since what I created here isn't a thermosiphon and therefore people looking for other passive ways of heating could miss this.

As to the Thermosiphon idea. It does work if your situation is correct for it. I think I could probably make a useful Thermosiphon heater for use with a heat exchange coil. Will have to tinker more with that another time.

I'm quoting some things over from the passive drain heater thread so we can discuss this within the Thermosiphon experiment since I still believe this idea has plenty of merit but just not for the aquarium at the moment.

I agree that the ice chest experiment was pretty down and dirty but even though, it did work!

boy did it work.

Using only a short bit of irrigation tubing laying mostly flat and hooked up to a small wide container, it still only too a few hours for the water to get over 100 F even while open to evaporation. Noting that such an ineffective method still produced such results, I have no doubt that with some better engineering, it would be really great.

So, How can we manage a thermosiphon set up on small scale, that can be used to either;
1) passively heat fish water directly (but do it without too much worry of cooking the fish)
2)passively heat fish water running through an exchanger
(when I say passive here, I mean not using any sort of controllers or additional pumping other than what is already pumping the fish water around. The control for such things is manually opening or closing a valve at the appropriate times of day if needed.)
or
3) using small pump on timer or other regulator (say temp controlled) to run fish water through an exchanger in the thermosiphon tank. This option (for my purposes at least) must use an inexpensive but energy efficient pump and easily available and inexpensive control.

I don't want to spend more money trying to use solar heating than it would cost to just use the electricity to heat. I have no intention of spending much money on these things cause I can't afford it right now.

As far as good taller tanks (though I've seen many a design that uses not so tall tanks but manages the vertical height with the incline of the solar collector and making sure the heights of the inlet, outlet and such are arranged properly,) A barrel placed vertically would be pretty easy to deal with. As might an old hot water heater tank.

Trying to figure out how to place such things so I could still use thermosiphon principals to heat the water is a bit trickier.

I'm sure it must be possible to scrounge a second hand boiler.
that would already be a big step:
it will be insulated too
fit for drinking water, so fit for AP
if it is one that was used in a heating system it will probably have an incorporated heat exchanger, but that might be copper
there are some double sided stainless steel ones too where the outer mantle is the heat exchanger
those would be the ones to look for

... but there is a better way, which will eliminate the risk of cooking your fish:
a heat exchanger is not necessary if you would connect the solar heater to a deviation on your system pump

let me tell you why:
the basic turn of thought is one I made about 10 years ago
My specialty is cleaning systems for the food industry
Mostly cleaning is done at the end of the day
while cleaning a big volume of warm water is required during say two to four hours
so that means a heating system with a high on the spot output capacity.
Expensive.
all of these companies also had huge cooling systems of which the energy was blown straight into the air day and night. Inefficient cooling fluid (mostly ammonia) to air heat exchangers especially on hot days.
I thought that a waste and wanted to do something about it
but the problem was that while the cooling systems were huge, they were not nearly enough to cope with the on the spot warm water demand during the two hours of cleaning. the systems were just not compatible

I have designed a simple solution for this:
start with an empty tank
during the night and the day fill this up slowly with hot water from an ammonia to water heat exchanger. Cooling with water is much more efficient than with air.
at the end of the day you dispose of enough water for your cleaning, heated for free.
and if it is a cold day in winter, when much less cooling is needed and less warm water produced, a small heating system switched on a few hours in advance can also fill the tank.
a very simple system that needs only a thermostat and a solenoid valve to function perfectly.

why this story?
because the situation is similar: heating the fish water during the day is less important than keeping it from cooling at night.
while during the day the sun might even be too hot and the solar system too performing to mix the water directly in the fish tank with the risk of cooking the fish,
it would be very convenient to have at your disposal a tank of hot water to add during the night

so that is what I propose to do:
put a boiler on top of your fish tank (or at this height)
deviate part of your pump output to the solar heater
put an electrovalve at the exit of the coil
command this with a thermostat: each time the coil outputs warm enough water, send that to the boiler, slowly filling it up.
have a second electrovalve on the drain of the boiler
command that with a second thermostat: while the water cools, some hot water is added by gravity

simple and reliable

frank

the system described cannot be thermosiphon
but it would not require extra pumping
only will take away a very small bit of your pump's output
I would call it a solar batch heater

of course it can be improved by i.e. adding an extra circulation pump and a differential thermostat (which is what I did on the industrial systems) and a PLC (programmable logic controller, a very common and inexpensive device nowadays which allows you to program a series of switches subject to conditions you yourself determine)
but that is all optional

a differential thermostat is a thermostat that compares two temperatures before switching the solenoid valve.

frank