Backyard Aquaponics
A place to discuss aquaponics

Even though using a heat exchanger seperates the heated water from the fish water , I would not use anything in the heated water that was toxic. I mean a little copper or water from plastic pipes that got into the fish water if a hose leaked etc no real worry , but PG would be an unecessary risk in my opinion.

Hamish , I like the ebay pics of the staino heat exchangers ,, but I'm a little suspect of their total surface area to obtain efficient exchange ( i.e the 'fins" do not look very deep")
I must say the stainless wine heater coil ( 50 ft) looked better and all connections could be above tank water level. Hook this up to any off-peak hot-water system , have a solonoid hooked to the tank supply so water only used when cheap off-peak electricity is available .
By George I think we are onto a winner.

Hi Hamish,



Too difficult, IMO.

In such a scenario, we'd need to find suitable piping that was UV-proof & didn't leach chemicals - even at high temperatures which are likely to occur on sunny days. Also, the solar collector needs to be of a suitable material also.

And, it needs to be relatively inexpensive.



That's my plan.

I've procured a SS wort chiller which I intend to use as a heat-exchanger. I'll probably use poly-pipe for the piping (as it's an isolated sytem & the poly-pipe won't come into contact with the fish-tank water, I won't have to worry about leaching of chemicals), which is great cos it's cheap & easy to work with.

I'm not sure what I'll use for a solar collector - ideally I'd like to find a second-hand one like KEXIV, but if not I'll probably just plagurise this idea:

http://www.thesietch.org/projects/solar ... /index.htm

Regarding the solar heating being off-peak demand-wise...

Easily solved by increased the thermal mass of the water (since it has pretty much the highest specific heat of commonly available materials). Even pumping water into growbeds, a 1 kL system will not show much temperature variation.

The "downside" is that your stocking density will probably be low compared to water volume.

I don't see how drilling underneath your driveway would be easier/cheaper than getting a really big tank

KEXIV,

Have you worked out a solution to release excess pressure & prevent outgassing of the liquid from building up & stopping the syphon effect?

I was just going to do something like a car radiator overflow. I would need a radiator cap where the pipe exits the top of the panel, and run an overflow pipe down to a bottle hanging within reach under the eaves so that I could top it up if necessary.
I haven't worked out how I can insert a radiator cap into the pipework though. (but I'm not getting alot of time to think about it either)

get a radiator place to solder some threads into a radiator cap spout, add 't' piece, instant goodness.

On the little bit of mucking around i have done with solar heating using the ss wort chiller with a solar heater you may as well pee in it that will ad warmth and amonia to

dont tease Whats the results?

Hi F&F,



Tell us more! Have you got a link? pictures?

How did you solve over-pressure & outgassing problems?

What sort of performance did you get?

Tried playing with a solar panel [now at steves ] and a length of ss pipe dident work steve has panel and ss pipe in shed [somewhere] to make it successful you need 2 temp sencers a dedicated pump ect ect thermo syphen for what you get you would need a large setup [big bucks] ie over night you have say 20 cubic meters grow bed cooling it down and during the day you have5 cubic meters heating it up so unless you make it super efficiant it wont work

thats what I was starting to think

My heat exchanger:


Copper from the solar hot water panel and LDPE for the fish tank side. Salt water is placed in the large outer tube to conduct heat between the two. It requires a much longer length of plastic tube because of the lower thermal conduction.

When doing test using a refrigerator iron coil in the fish tank I found that all heat was removed from the line within a 3 foot length.

I'm not trying to discourage anyone , but hooking straight up tothe"off-peak" power at only 7 cents per kilowatt hour is starting to look very cheap.
I actually bid in ebay on some solar panels ( didn't win) so I certainly haven't given up.

Youd think I would know this...is a kilowatt hour a 333.3 watt heater running continuously for 3 hours? or what

Yep, that would work. Watts*hours/1000 = kWh