Backyard Aquaponics
A place to discuss aquaponics

Dan, i'm with ya concept has been brought up a couple of times.

I have split AC condenser ready to pipe a loop of stainless to for my trout, and a few "roomies" with the evaporators removed to play with too (yes BK and F&F, i'm holding one for each)

Would this be more or less efficient than a propane or NG tankless water heater? Or even a tanked water heater filled with a saline solution and a heat exchanger?

Locally electricity is at a much higher premium than gas.

energy wise it should be much more efficient, but as you say there is price disparity with gas.

I'd say NG would work out cheaper DOLLAR WISE, Propane in small bottles much more expensive...............


i cant for the life of me work out how electricity is cheaper when we use NG to fire the powerstations

No it isn't. That is a stubborn myth that just won't die.

http://backyardaquaponics.com/forum/vie ... sc&start=0

Here is a picture of a small heat exchanger.



The copper is the freon line and there is much more nylon tube because it does not transfer heat as well so it need more surface area. The pipe is filled with saltwater to conduct heat between the two tubes. This is one of four connected in series.

This worked for cooling hydroponic solutions. It should work ever better in the heat mode as long as enough heat is transfered. If the heat is not removed fast enough then the pressure goes way up and over heats the unit.

The best bet is to just buy some flexable stainless steel tubing and solder it in place of the hot coil and drop it in the tank.

That is a good question.. They say you save a third to half of water heating costs. HeapPumpWaterHeaters
They also say demand water heaters use 25 to 35% less energy. So taking the best case for both lets see. If you electric bill was $100 and you used 10% for water hear(8%-14%) then it would cost you $10 for hot water with a normal electric water heater. It would be $5 with heat pump water heater. and $6.67 for an electric demand water heater. The price of the heatpump water heaters makes it pointless to buy, so demand water heaters seem to be the more logical choice.

When you get it done let me know how it worked out.
When I made my heat pump water heater I quickly found out that using large pumps caused the heat and pressure to climb to fast causing problems. So, like the commercial units 5000 or 7500 BTU seems to be as big as you can go without over working the unit.

Thanks. Thats one of my first hydroponic carrots. As big as my arm ans sweet too! I can get 4 pounds of vegies from one 4' by 10' table every day year around. Enough for one person to live on! I really hope to do the same with aquaponics, only without having to buy mineral salts. Vegies come out to about 10 cents a pound, but if I can do it for free and get 400 pounds of fish to eat too.. Yea, thats a no brainer! I plan on growing duck weed to feed the fish. I just have to heat them in the winter.

Hi DdM,

Sorry for the continued hijack of the thread, but I need to ask what grow bed media you use for your carrots?

I have tried hydroponic carrots in perlite, but have never been able to get reasonable carrots. I had heard a (possible urban) myth that carrots needed a firm media around them ...

gg

Another heating option, is a heat exchanger around a fuel burning heat source, i.e., a wood stove, waste oil heater (bought or DIY) or a propane shop heater. My big reason for suggesting propane is that it's my main fuel source with electric being second. Oh, there's also spa heaters. You can get them used for a good price, sometime free. I have one, but need to change out the jets for propane.

I would prefer to use free fuel resources, such as wood or waste oil. But would also like to hook up the propane spa heater for emergency heat. I have a similar heat requirement, I'm raising redclaw crayfish and 50*F is fatal. Another suggestion that may seem obvious, an insulated cover or top to the fish tanks will help to hold in heat. Personally I'm not going to circulate through the gb's at night when it's cold. Just keep the fish tank circulating for aeration.

just my 2cents worth.

Out of curiosity, is your fish tank set in the ground or above ground? or the planned tank? If it's set in the ground, at a certain depth, the ground maintains a temperature. So that can both work with you and against you.

I use smooth pea gravel. $40 a yard (meter). It grows anything and does it well. I grew over 1000 carrots. I planted dense(1 inch apart) and as they grew I pulled out every other carrot to eat making room for more growth; a continuous harvest. These large carrots were what was left at the end of the season.

I did treat my gravel with trebel super phosphate to bind up the lime in the rock to prevent pH shift from the gravel.

I have lots of wood here. A wood gas stove would be super efficient and completely clean burning. If I have the time I want to use wood by destructive distillation (makes heat) run the gas through copper to make ethanol (another fuel for generator; piping the hot exhaust through heat exchanger) then take the carbon and burn some of it and then blowing steam through it to make hydrogen (more fuel for a generator). It all makes heat. Now I don't know that I will ever get the time to put something like this together, but talk about efficient use of wood!

My tank is above ground. I am going to raise tilapia. If I can borrow a hydro drill I plan to drill a 100 foot hole and put a pvc heat exchanger into the ground allowing me to warm the water to 65 to 70. I hope that enough for the fish to still be productive. My goal is 400 pounds of eatable fish per year. For this winter though its going to be heat pump heated water. I dont think a demand water heater could deal with the solids and algae in the water so Im not going that route. I only need to heat during nights and a few dark winter days. My solar heater collects more than enough heat. I plan on coating my tank with that yellow foam in a can.

Oh! I discovered that my refrigerator hot coil is make of steel. I think I am going to try to use that system. The coil should fit in my 8 foot tank just fine. Refrigerators only draw about 3 amps too. I will just place a fan in the cold coil and I may replace the cold coil for a much larger coil. I have to find some R12 for it first. When I get it done I will post pics.

One option for fuel style heaters is a rocket stove with a built in heat exchanger. For those of you not familiar with rocket stoves,

this is a link with some pictures . . . (its from another forum so you'll have to sift out the important aspects.) http://www.countryplans.com/cgi-bin/yab ... 1167119392


this is a link with more of a masonry/cob aspect.... the process is pictured in reverse chronological order (so start at the back)
http://s8.photobucket.com/albums/a34/sc ... /?start=20

This is the mother of all links. . . a great book detailing rocket stoves with a full description, diagrams and first hand experiences working with the stoves. . .
ftp://209.85.35.194/33618/Rocket_Mass_Heaters.pdf

***EDIT*** - The link above didn't work so I have the pdf file hosted at this link: http://www.mediafire.com/?acxggqslwzh





Rocket stoves appeal to me in all heating endeavors because They are relatively simple to construct, use cheap/free materials, burn efficiently, use small diameter wood so that branches and/or coppiced wood can be used.

I think retrofitting a rocket stove with stainless steel tubing wrapped around the 55 gallon drum (wrapped on the inside or outside?) and using convection to circulate through the tubing and sending that heat to the fish tank directly or by creating some sort of other heat exchanger between the rocket stove and the AP system. Plus the horizontal stove pipe of the rocket stove could be incorporated to run under the fish tank or be embedded inside the fish tank's foundation if it has one.

These are some general ideas and the details would have to be attended to but the idea of heating only through a combination of solar and rocket stove is very appealing. I envision planting trees around the AP setup that could be coppiced for fuel for the rocket stove plus possibly attracting bugs and or creating food for the fish. . . just some ideas, would love to hear people's opinions on the ideas.

Of course the drawback of this design is that it is not automated, somebody would have to tend the fire and watch the tank temperature. Perhaps housing the AP in a greenhouse and using the rocket heater to back up the solar heat for the greenhouse without a heat exchanger would be easiest/best? I guess it just depends on the circumstances of each person's AP set-up.

Low tech solutions always appeal to me and this stove is pretty low tech.

If the PDF file doesn't work just let me know and I'll try to find a way to put it up here.

It is asking for a password and user name. I can not open it.