We have just started a new system in central Oklahoma that I would really like to use year round but I am stuck on the heating. I have read all of the post on the DIY element tank heaters and agree that they definitely work but it seems that it would be like running several hot water tanks. It could get pretty expensive on the electric bill. I have also looked into rocket mass heaters and I like the radiant heat concept but am not sure how warm it would keep the water. Does any one have any other ideas/experience/advice?
Idea 1: Grow trout which have no problem at all overwintering outdoors in Oklahoma. The green house can focus the warmth on the plants and roots as needed like greenhouses do best.
If you grow vertically you would only need to heat a fraction the space of a horizontal system. The other option is grow Koi and shut down the greenhouse Jan & Feb and only heat your tank and a bio filter too keep the fish and bacteria alive.
Some trout survive in SOME ponds and sreams in Oklahoma. Shading the pond and minimal chilling/aeration expenses along with proper thermal mass CAN be no more than that of heating for tilapia or other species.
Down here in north Texas, I built in heat exchange coils of 1/2" stainless steel, which I may have to expand with coils of Pex, into my 600 gal fish tank complex. I am building the solar water heating panel with small recirculating pump, solar powered, as we speak. That should handle the sunny cold days. The cloudy ones will probably be dealt with passively with thermal mass of the water and what heat actually gets generated by the "chinese style" greenhouse (see Tim Mann, Friendly Aquaponics, 592 sf version). Backup may have to be a small propane spa or pool heater or similar, recirculating through the heat exchanger coils. I tried a homebuilt submersible electric wand this spring during system startup, but didn't intuitively get that it would be practical $ wise. Currently, the 2000 gal. system is holding around 70 degrees with a roller furling 30% net over the greenhouse. But the 100+ degree days are coming.The geothermal cooling project starts this coming week. Remember that the water is 800 times more dense than air. Consider focusing on heating/cooling the thermal mass of the water. Jim
And while I'm thinking of it, does anyone have any thoughts on a practical roll downable thermal blanket for the winter nights. The greenhouse walls have R19 6" fiberglass insulation, which is about worthless, since it all goes skyward when the sun sets. By the way, the fish tank is insulated with Dow blue board and the grow troughs are inherently insulated by being on the ground with an air space around the sides. Jim
Hi Michael et. all,
This is the exact subject of a blog I've been writing for the past couple months. I've got a ton of posts about exactly this topic. You can also find them in the Cold Weather Aquaponics group here on the forum, along with some discussion.
The short answer is that if you design and use your system right you shouldn't have to heat much, if at all. Using converted freezers for fish tanks and insulated / air sealed grow beds reduces your heat needs by about 90% (depending on what you had before and how well you insulate/air seal your beds). My system (in Wisconsin) is heated by a 1000W electric heater, and it ran about 30% of the time in the coldest January of my life.
Regarding what fish to grow, there's an article in Aquaponics Survival Communities this month about that topic. The conclusion is that it makes the most sense economically to buy 7-8" trout in the fall and 7-8" tilapia in spring, switching them seasonally. You can also grow perch or catfish and keep them year-round.
As for the idea of a blanket over the greenhouse, there are number of options. The Chinese do exactly what you're suggesting to grow tomatoes. I've seen some in Beijing and they're amazing! I think they use straw in plastic sheeting, though insulation batts would be easier. You can also use a solar pool cover or bubble wrap over your greenhouse in winter, and you don't have to take that off at night.
This week I compared different system types for use in the cold. There are advantages to each, though I think the flood-and-drain with an indexing valve, possibly with DWC beds integrated in a hybrid system, makes the most sense in the cold.
I'd love to hear more ideas. I've still got so much to learn!
I just happen to have a solar pool cover which would be a perfect fit for my greenhouse! Haven't even thought about that. I also have some hybrid blue gill coming because i thought i might have a better chance of wintering them over!
I get the impression that there is no firewood in Oklahoma? Here in the mountains of NE TN we heat the air and the water with wood and on those clear days in the Winter I use a small pond pump to circ the sump water thru 100' of 3/4" pvc mounted on metal roof scrap 16' long, painted black and hung high up in the GH. (a closed loop requires just a very small circ pump) 20F below zero last Winter but the system water never dropped below 48F and with Winter crops there were no losses even when the GH temp fell to 16F twice due to just cut wood. The solar collector will bring the 2000+ gals of system water up 4F in a day and the woodstove's 1" x 7' ss loop another 2F per day. The woodstove mainly keeps the air around 60F and cuts down on the notorious Winter humidity in the GH.
Then there is the free heavy duty bubblewrap that the furniture stores throw out weekly that we use to make long tunnel GHs inside the GH and also to wrap the 5 FTs. I strongly urge you to stop in at a local furniture store and ask if they could save you some or if it is alright to raid their dumpster as we do. I also use it to wrap our bell siphons for shipping all over the world now. I will add some pics when I can get on the other computer.
yes sir, plenty of wood here. i probably have enough on my place to last several years. That's really why I thinking Rocket Mass Heater. Plenty of wood and it just looks like fun to build!
I've always wanted to see pictures of an aquaponic greenhouse with a rocket mass heater. Does anyone have one?
He has lots of Youtube videos on it too