Backyard Aquaponics
A place to discuss aquaponics

Now where should I look to learn about solar water heating contraptions and heat exchange methods?

I want to set up a coil of black tubing on the roof right by the system and probably have it circulate or heat water in an insulated vessel through the day and then at night I would have a valve open that would circulate system water through a heat exchange coil in that vessel. When things start to get way too hot in summer, I think doing the opposite might be more appropriate, circulate water to the roof at night to chill and open the valve to the system water heat exchanger during the day.

It would be pretty easy to set the small pump for the roof coil on a little timer. just flip flop the on/off time when weather dictates chilling to be more important. (I suppose I could probably find all the stuff easily at a pool store that does solar pool heaters.) The trickier part for a DIY on this will be a temp controlled valve or pump that would start the water flowing through the heat exchanger in the insulated vessel.

I know there are already threads out there that cover some of this so I'll start searching and link to what is already related.

Hi TCLynx,

I've been reading/thinking about solar heating quite a bit lately.



IMO, the most difficult part is finding an appropriate heat exchanger. A SS coil of some sort would be ideal, but expensive.

It would be great if we could find a black poly pipe that didn't leach chemicals at high temperature, then a HE wouldn't be necessary at all.

So far in my quick research;

To thermosiphon or not to thermosihon? For heating this would require the insulated vessel to be above my solar coils. That would not be so great if the system is on the roof as it would require pumping system water up to it for the exchange to work.

If I give up some of the driveway slab near the system to a coil, it will be much easier to tinker with and placing an insulated container above it would be much easier and still in easy reach of the main system. IF I tinker in a temporary enough fashion, this might be ok.

One question I have. With the normal thermosihon water heaters, they work well to heat water without an extra pump. Would this design function at night as a water chiller? Somehow I doubt it. I probably need to have something that functions on a small pump if I want it to do double duty in the hottest part of summer.

refer my post

i think it would work as a chiller.

but as you want to use it as a heater as well then you may aswell just put a small pump on it.

problem is that you want a pump with a low GPH but a high head. will look into a pump for you.

PS, a normal thermosyphon heater uses the mains water pressure to then pump the heated water to your domestic outlet..........doesn't it?

just go a pumped setup


thinking thinking thinking

save on power and a new pump, use the system pump to pump water through the coil. use two cheap solenoids to bypass the coil when not required

Hay scottie,
I wasn't really all that worried about the poly pipe leaching so much. My reasoning for the heat exchanger is more along the lines of storing and using the heat/cool when it is needed most. Basically, using the solar gain in from the day at night to lessen the temp dif over night in the cooler seasons and chilling water overnight to use the cool in the day during the scorching hot summer. Using the solar heating coils for direct circulation of system water would cause stronger temp differences between day and night.

Thanks steve. I'm thinking for experiment puropses, I might test out a coil right on the drive way slab next to the system and abandon the thermo siphon method as it would want to work either one way or the other, depending on where one put the tank.

I was originally figuring on using the system pressure to pump the system water through the heat exchanger if I can figure out how best to control that. For the experimentation I can simply use manual valves.

Pumping the water around the solar collector/radiant chiller would require a small pump that can handle hot water. For experimentation purposes, I'll probably use one of my little tiny pond pumps and hopefully not kill the poor thing while trying out prototype ideas.

Heat exchange coils!

I can get a 5/8" tube dia coil (coil dimentions would be 5 1/2" by 8") Aluminum coil for $17 from Aquatic Ecosystems. I'm not sure about using aluminum though.

They also make Titanium and stainless heat exchangers but they are more a whole system (costing between $270 and $9,000) rather than just a coil I can put into my own vessel.

I suppose for may purposes, I could simply make a coil of pex tubing to stick into the vessel since I actually kinda want a slow transfer of heat rather than hot or cold water flowing back into the system. I have no idea where I would get a coil of stainless tubing.

Hi TCLynx,

I'm a bit confused ...



IMO, water heated in poly pipe should not come into contact with water in an AP system, due to leaching of chemicals from the poly pipe. It might be ok if using ornamental fish, but not with fish intended for human consumption.

Hence why I believe a HE is required to isolate the AP system from the solar heating system. (Either that, or find a cheap poly pipe that does not leach at high temperature.)

pex tubing?

Here is a more detailed answer to the question of PEX
http://www.ppfahome.org/pex/faqpex.html
PEX is the flexible tubing that is now becoming common in household plumbing systems here in the US. It usually comes in Red, Blue or Clear/whitish translucent and often that is an easy color code to know what lines they are, Red for hot, blue for cold. Anyway, it is good for potable water but requires special connectors. The handy thing about pex is that you can actually put conduit in a concrete slab and then later pull pex pipe through it to do your plumbing in new construction. If there is later a leak issue, the pex can be pulled out and replaced. I don't think pex tends to have leak issues though but the previous flexible tubing that existed (I think it was PB) did have many issues and is now being outlawed in many states.

So I have started a little experiment running (I tend to test things out even though I know something will theoretically work, I usually have to prove it to myself in practice.)

Anyway, I grabbed what was left of my roll of irrigation tubing (not sure how much but probably a couple hundred feet or so still in the bundle.)

Threw down a bit of black plastic sheeting on the driveway slab, plopped the coil on top (I didn't get fancy about trying to flatten out the bundle really.) and spread some clear plastic over it.
I loosely weighted down the edges of the plastic with some boards and hooked up the pump to one end of the coil and the other end of the coil just drains back into the container of water. I didn't want to pressurize the system in any way as the pipe fittings are only compression fittings.

Now the little pond pump does way too much volume to move the water slowly through the pipe so I decided to add a timer in. That way the water will sit in the tubing for a while to heat up and then the pump will run for a while to swap out the water. Unfortunately, the time I had to hand can only do 1/2 hour increments but it should at least give me some idea of what I can do very low tech. I suppose if I slung the coil up on the roof, the pump would not move nearly so much water and I could skip the timer but no climbing on the roof without anyone else at home (the ladder is really wobbly and not really tall enough.)

At the start the water temp was 84 F and the air temp 86 F(important as there is no insulation on the water container though it is in the shade)

At 2:50 pm water temp in tank at 93 F water coming from collector is warmer than that after the pump has been running for a while.
Air temp in 88 F

3:40 pm water temp in container at 100 F

Air temp 89 F

Looks to me like a simple system like this could be very effective for a little boost up in system water temp. Considering what I have just set up is definitely a quick throw together.

Now my biggest challenge will be figuring out the best method for doing the actual system water heat exchanger.

I'm probably going to get a good kicking for thjis ,, BUT I gotta say what I gotta say ,,
Why not run the pipes in cheap copper / normal water pipe ,, no need for heat exchanger ,, run straight into tank ,, just need to make sure water doesn't get TOO hot.

You will read that copper is bad for fish ,, this is very true ,, but the copper surfaces on pipes .VERY quickly turns to a copper oxide of some desxcription . OK think about this ,, some people say you can't use copper pipe ,, but I have filled my tank from the mains water supply ( hundreds of kilometres of copper pipe , without a problem. Another great example ,, we know Aluminium is not good for people ,, but people drink from aluminium cans everyday , more accurately Aluminium cans coated in Aluminium oxide. AHHH facts , statistics and Damned lies.

Copper pipe ,, and for that matter Aluminium pipe would be excedllent.

>>>> fire away here>

Well, I have the black irrigation tubing handy and a really easy place where I can get 1000 foot rolls right down the road for cheap. I have lots of experience and the tools/fittings to work with the irrigation tubing.

I am not so comfortable with the use of coper and I don't have the tools for it on hand.

I want to stick with the heat exchanger in an insulated box anyway for the intention of saving the heat or cool for several hours before using it anyway (I want to reduce my day/night temp differential rather than increase it by running direct with system water.)

You are right about the aluminum cans though. Perhaps I will just get the aluminum heat exchanger coil then as it is a good price. It says $17 for the 5/8" dia tube. The Aluminum coil is being sold by a aquaculture supply house. That would fit my bill I think. I've been doing some searching for stainless steel coils and so far the best price I've found is about $75 for a 50 foot coil of 5/16" tubing. They are sold as wort chillers for beer brewing.

I still feel the urge not to add more copper into a recirculating system.