Carey, add thermo siphons to your list of handy things for heating. If you can place an insulated tank up high then a thermosiphon hot water heater doesn't use any pumping in the heating of water and is kinda self regulating since it won't thermosiphon when the array isn't being heated. Only pumping then would be with the heat exchanger. This would be handy for a hillside sunfacing application since you might put the solar array below the greenhouse even.
Biomass in the manner of pellet fuel. Compressed biomass by the means of a pelletmill is almost as efficient as wood pellets. You get a little more ash and a little less BTUs per ton, but it is better than cutting down all the trees to acquire it. Grasses, leaves, weeds, windfall branches, tree trimmings and etc.
Lonny Harper said:
Rick, by "biomass", do you mean compost?
Hi TC. Yes thermal siphons pump water without electricity which is good but I think it would be more applicably used in the hot water storage system during the day but still need electricity to run pumps during the night when the fish tanks need to be heated most.
Yes that is likely true Carey. But at least part of it would be off electricity.
Has anybody tried to run 1/2" black poly tube underground and then pumping water thru the pipe to maintain temperature? The average ground water temperature in Cocoa Fl. is @ 68-72*f year round. May be a little to cool for some fish, but with a deep tank, you should be able maintain an reasonable temp. I am guessing @ 100-150 ft of piping buried 18"-24" should provide a stable temperature.
Ed, it will all depend on what sort of system you have. See if you are doing flood and drain or NFT, then coils buried in the sand will likely have trouble keeping the system water warm on a hard freeze night but if you are running constant flood or raft or if you switch to constant flood for the cold spells, then perhaps buried ground loops would provide some benefit.
Keep in mind that our sand isn't the best heat exchange media of burying horizontal ground loops and the fact that you could grow bluegill or channel catfish without worrying about heating at all here in FL means it might be an expense not worth your while.
As to how much pipe you would need to bury, I have a feeling you will need to use far more than 150 feet to really be effective when it's needed most. I expect that amount of pipe is very effective for making water hot when set out in the sun, however when trying to use 70 F sand as your heat source, well you need more coil to get much out of it. And are you really wanting to dig up the entire property to bury the coils? You might be better off using a vertical well and ground water to help with the temperature.
I have some questions. The cost of electricity is going out of sight, heating water bumps the cost about 200.00 a month so lets find alternatives that work.
1. How often do you need to rebuild a Jean Pain style Biomuller (compost pile water heater)? If it is once a year that is worth it. Does it smell? It appears that it warms water 24 hr a day.
2. Has any one tried a thermo siphon located in the attic? I am tempted to move the solar blanket pool heater to the attic but the largest challenge is the head pressure on the pump. That calls for a air aqua zen lift pump.
3. The rocket stove idea works if you don't mind feeding it all night, that calls for a automatic pellet feeder. BTW I checked out pellet mills and they are cost prohibitive. The idea is to warm mass and let it release the heat all night.
There is a great 2 year study done by the Alchemy Institute on a compost heated greenhouse. It is possible but requires a great deal of compost (I think it was like 200 tons for a year,) 2 people a couple hours a day and 8 hours on the weekend, a dumptruck, and a properly constructed greenhouse. This could be adapted to an aquaponics system, but too labor intensive.
Biomass, or a biodigester producing methane are both good fuels. They require a significant investment to use either. You simply cant get something for nothing. You are looking at cash, labor, or a combination of both. Creativity and local resources may provide a localized and personal solution.
I am working on a system that will use the waste heat of my business, a micro-distillery, to heat a greenhouse that I am still working on the design for. It will use the waste heat from the 200 degree spent wash and a biodigester producing methane to provide the heat.
This will all require orchestration to get the heat to be consistent, and investment in the necessary equipment and plumbing. But the heat is a byproduct and would otherwise be wasted.
Last winter I built a "batch" (aka "breadbox") solar water heater for my small aquaponics system. By the time it was complete, the weather had warmed up enough that I didn't need to use it for very long, so I didn't get much data on how well it worked, but my preliminary sense is that it was able to raise the temperature in my fish tank by 5 or more degrees F. Materials cost was two or three hundred dollars if I recall correctly, while using as many free/scrounged parts as possible. I'll do a bit more work (and spend more money) improving it for this winter, primarily for PEX tubing - temperatures inside the solar collector get too high for PVC, and although it is a close-loop system, in case of leakage into the fish tank, I am staying away from any metal pipe. Fish tank & growbed insulation would be a good idea too, I know.
The system works like this: a used (free) household hot water tank, painted black, sits in an insulated box with a window (used double-paned patio door, $50) oriented toward the sun. Insulated pipe goes from the tank, underground into my greenhouse through a heat exchanger coil made of 5/8" poly irrigation pipe sitting in the fish tank, then back through another buried insulated line to the tank in the collector. I was not able to situate the collector lower than the fish tank, so could not use convection to move the water. Used an inline submersible water pump instead.
My goal is to keep the tank water warm enough so that my bluegill continue to eat through the two coldest months of the year. I think a 10 degree F increase in water temperature would be sufficient. FT is 100 gallons; total water volume for the AP system is a bit under 300 gallons; and the system is in a 120 square foot greenhouse.
As I make improvements and get more data, I'll post updates and pictures here.
Really interesting posts in this group - thanks to all for your contributions.