Backyard Aquaponics
A place to discuss aquaponics

The other issue with solar is everyones system is a different mass, so what works in one location may not work for another.

F&F my system in the hothouse has a total of 7000litres of water now. Air temp during the day was 22 deg C, I had all the doors open.
The water temp was 16 deg C. Because of the mass and part buried fish tank the water temp only drops by 1deg C overnight.
It takes two or three days of similar conditions to get a temp swing of 2 or more deg C. I don't run the pump at night.

With the biofuels process we often heat fuel to 55 deg C. Several people use solar heaters and thermosyphon to heat with. The same issues with copper exist with this process so we also avoid standard heat exchangers and often make our own.

In my system if I can increase the water temp in the day by solar, then using last winters data I stand to loose a max of 1 deg C overnight

As F&F suggested the amount of heating required to heat the water mass is the question, is it viable?

God bless, froggo.

Yesterday necessity drove me to some experiments, water got down to 8.5c. So I set-up an lpg heater and cycled batches of water. The burner heated the water directly which was then exchanged with the sump. Approximately 20 mega joules of gas raised the temp 4c to 12.5c. So the figures so far seem to stack up (my original post should have read mJ not kJ).

F&F the problem with heating the greenhouse is most of the heat leaves the greenhouse before it can enter the water. Heating the water directly ensures all the heat gets to the water. In my case I exchanged about 120L of water.

Cost is going to be a major consideration, strait gas is probably too high to warrant doing it, I am not sure how much I can off set the gas with the bio char. Solar might be able to contribute to the BB store therefore saving a bit of energy. Insulation is on my list to experiment with too.

Careful not to heat the water too much and kill bacteria...

Will a hot bath with a pex coil suffice to cycle water from the FT and exchange heat in the bath?

CB

Our bacteria are mainly surface dwelling the growbeds will never be above normal fish tank temps so no risk to bacteria.

Are you sure the bacteria is surface dwelling....I though the media, no matter the depth, provided the space needed for the bacteria to grow. If it is surface only, then my whole greenhouse plan has to be rethought as I am counting on depth to provided the needed volume.

The bacteria inhabit the thin film of water that clings to the millions of pits in the media... by surface tension... so it's fair to say they inhabit the surface area of the media to some extent...

But it's also equally true to say that the bacteria reside in ALL the system water.... indeed, some say up to 70% of the bacteria reside in the system water volume...

Rupert where have you seen this? 70% seems a bit high, if it were true, then why would we need such high surface area in bio filters? Why is water volume not enough on its own?

Also in your solar heating was your heating (70c?) in contact with the water? If so did you notice any impact on bio filtration?

It was reported from one of the UVI seminars... remember though, in the UVI operation, solids are removed... and nitrification is dependant on the floating rafts, raft surface etc...

With flood & drain... we're not only nitrifying... but capturing and converting solids...


Re : the solar heater...



My solar array is purpose built from stainless steel.... without the copper heat exchanger in the header tank that a normal hot water system would have...(which heats to 60c+).... and is triggered to exchange water to the fish tank whenever an 8 degree temperature differential occurs...

Typically.... the water never gets much above 30-40 degrees before exchanging....

And ... no... I've not seen any degradation in bio-filtration....


But I usually don't allow the tank to max out much above 30 degrees... covering the solar array with a blind in hot sunny, summer weather...

Ok thanks, looks like the blue barrel at 40c is reasonable so the s/s boiler will probably kill some bacteria but I will shut off the GB's over night, they are 50cm deep flood and drain 30cm leaving 20cm in bottom. I don't think there will be any bacteria problems but well see

I'd love to see the research that suggests that 70% of the bacteria are in the water. Perhaps it was a typo. I could almost accept 7% if someone actually did the research. 0.7% sounds more likely, but probably still a little high, perhaps 0.007%.

as far as heating the water goes, I hope it works for you. Personally, I prefer to live within the means of temperature variations, as I don't have the extra bucks to throw at trying to heat huge gobs of water found in outside ponds.