Heating options for fish tanks

[daniel]

I have been fiddling around with different methods of heating my 2300 ltr tank trying to find a low cost way of heating.

Firstly I made up a coil of copper pipe and fitted it into a 25 ltr drum filled with water.
Set up a gas burner under that. It worked fine, raised the water temp by 4 deg in a 12 hour period. The down side is that it burnt $20.00 worth of LPG.

I made up a grid of sorts out of 1” black poly pipe and put it up on the shed roof. I managed to raise the temp from 15 deg to 18 deg over the day (3 deg C), but at night the temp dropped back to 15 again.
Last winter I only had a 600 ltr tank so it was easy to cover every night. Making a lid for the big tank is what I will have to do, that is obvious.
I think if I go and get a 100 mtr coil of 3.4” thin walled low pressure irrigation hose and run the water through that up on the shed roof, it should improve. More distance for the water to travel and therefore heat up.

The good part about living in S.E.Qld is that our winters usually have nice sunny warm days around 22 to 25 deg, the bad part is that it hardly ever rains !!!
So the solar hose thing together with a lid on the tank should do the job.

Muzza

I am all for sustainable water heating. Water takes sooo much energy to heat that it can ends up getting prohibitively expensive for projects like this, AND will produce large amounts of CO2.

Living in Australia allows us the luxury of sunny weather a lot of the time, so I am a keen fan of solar heating of water.

Here are a few projects i have noted from around the net that could be adapted to heating of water.
http://hacknmod.com/displayMOD.php?hack=309
http://www.thesietch.org/projects/so...nel2/index.htm

The size of any medium to large size setup should, i believe, be looked at in the same manner as swimming pools when it comes to heating. There is a range of solar pool heating methods around. That in mind, most roofs, if orientated correctly, would make perfect mounting surfaces for a solar water heating setup.

Sorry if this sounds like a rant

[Murray]

Daniel, that is not a rant.....I am with you all the way.
Thanks for the links....later tonight I will go in and have a good read.
Murray

[njh]

I've just published an article in the latest renew (100) about how to heat an aquaponics tank using solar power - I've getting more than 5kW and 75% of heat from $100 in parts. Would easily scale to very large systems.

Those designs posted by daniel look a bit fiddly for the amount they will collect. I would look at trickling water down a piece of old, unpainted corrugated gal roofing iron first. Rust is good. Cover with thin polyethylene film, then polycarbonate roofing to form a double glazing with the ideal plastic for each job. I got about 20% conversion efficiency from this some years back, and it's very simple to make. You can put it on top of an existing roof.

[Jonty]

njh,
You hit the nail on the head with the mention of double glazing. I used a solar heater to melt beeswax years ago and it was really efficient with double glazing.

[njh]

njh,
You hit the nail on the head with the mention of double glazing. I used a solar heater to melt beeswax years ago and it was really efficient with double glazing.

Yeah, that little bit air really makes a difference. I melted polystyrene foam using a single layer of polycarbonate and some shadecloth. That's over 100C!

[GaryD]

Hi njh,

I like your solar water heater idea. It's much simpler to put together than all of the other suggestions that I've seen previously.

Since you wouldn't need it during the night (in fact, it would have the reverse effect), would you suggest having the pump on a timer?

Gary

[Frank]

Gary. I've been trying to find the link to the article so I can have a look.

Where did you find it?

Frank

[njh]

Hi njh,

I like your solar water heater idea. It's much simpler to put together than all of the other suggestions that I've seen previously.

Since you wouldn't need it during the night (in fact, it would have the reverse effect), would you suggest having the pump on a timer?

Gary

Actually, what you want is a differential thermostat. These are easy to make if you do electronics (I use 1-wire bus for my temperature measurement - cheap and easily extensible). You turn the pump on only when the temperature difference between the gal metal and the tank is suitably far in the right direction.

A timer would be a cheap starting point (but would require changing as the day length changes). Remember that it won't heat up instantly, especially from a cold night - give it a few hours of daylight to warm up first.

You might be able to salvage something using a 'pair of thermocouples' salvaged from a central heating unit (not sure of the volts / temperature difference). These are designed to switch on when the temperature difference is high enough. However, the difference may not be high enough, they probably will need a diode added (use a schottky hot carrier diode for minimum drop) to make them work in just one temperature direction and they won't have much length (perhaps 50cm from hot to cold).

I can think of all sorts of simple analog circuits to try using basic thermisters, but to be honest, I bought a USB to 1-wire transceiver for $80AU and I can buy as many thermometer chips as I like for $4 each. Then you just need a way to turn on a relay using a computer and you're done. (There are a billion such circuits on the web using the parallel port)

If people are interested in building a computer to monitor their greenhouse, I've found a good low power embedded computer that comes with linux preloaded and all the ports you need to talk to 1-wire, turn on and off relays, connect to my water level sensor(http://njhurst.com/electronics/watersensor/) and log all the data on the web(http://njhurst.com/GHT.svg). I'm happy to help people set one up.

[Macca]

I've just published an article in the latest renew (100) about how to heat an aquaponics tank using solar power - I've getting more than 5kW and 75% of heat from $100 in parts. Would easily scale to very large systems.

I've not heard of that publication. Is it available on the net? How would we best get a look at the full text of your article - sounds interesting.

[njh]

I've not heard of that publication. Is it available on the net? How would we best get a look at the full text of your article - sounds interesting.

The best way would be to buy the magazine:
http://www.ata.org.au/publications?page_id=15

I hear that being their 100th's edition, it's going to be a bumper-crop too.

They are not-for-profit and can only produce their magazine if people buy it. (I was not paid for writing my article, but support their cause)

Gary was talking about my trickle collector suggestion. It's not the same, but it's easy to make. I made my prototype in an afternoon. The trickle collector is well suited to putting over an existing garage, carport or shed roof. It is not as efficient, cheap or flexible in use as the system in renew. You might try the idea out using an existing piece of corrugated iron and some plastic film first to see whether it is practical for you or not. Jonty is absolutely right in pointing out the advantage of the double glazing: if you use a single layer glazing you will get condensation on the glazing which will transfer a lot of your heat away. Per square meter this is still a very attractive approach, and much cheaper than the swimming pool heating stuff (I was quoted about $100/m^2 for the swimming pool stuff, this is more like $30/m^2 new and free corry iron is very easy to get, the system in renew could cost as little as $2/m^2 new).

(Admin: Perhaps this discussion should move out of Murray's system?)