Backyard Aquaponics
A place to discuss aquaponics

jrl91rs/Yavimaya/helomech: I think that is a really great idea! In fact, I think the hot water barrel idea could be simplified even more by placing the "radiator" pipes in the deep water grow bed instead. What do you think of that? A greenhouse-sized grow bed with a raft system would hold the temperature very well in my opinion (since it would be the largest body of water that wasn't a fish tank), as long as the pipes didn't interfere with plant growth.

A good question to answer would be whether a system like this, (a radiator from the hot spring to the grow bed/water barrels), coupled with a pump that was rigged to a temperature operated electrical outlet and thermometer, could accurately keep the large amount of water within a very narrow temperature range.

I am now considering testing this idea out at my friend's place. Perhaps I will use a big above-ground pool, or even a wooden "trough" with some pond liner to simulate a big grow bed.

Gosh, now I am wondering if the pipes, if placed at the bottom of a raft grow bed, could disturb the roots of the plants. Does anyone have an opinion on that?

Yea 100, this is pretty much what i said, but i said fishtank, if you have a GB to put it in, even better, that way the water temp going back to the FT is more even, instead of maybe getting warm/cool spots in the tank.

Definitely heating the tank is best, the tank will then heat the rest of the greenhouse alot easier than the air heating the water.
The less steps in the process the less you will need to have your pump turned on, spending less money for the same result.

If you did want the air kept at a certain temp, then you can also have a barrel that you could keep at a higher temperature, using another controller and a solenoid, could use 90% same pipe work and same pump.


As far as the last questions, keeping temp stable will be up to 2 things, is the thermal spring stable? ( it should be), if so, then it just comes down to how robust your system/ programming is.

The pipes wont disturb anything as you wont be moving them anyway, as far as too hot for the roots, for it to be efficient, you will want water moving past the pipes fast enough to not allow them to heat enough for them to hurt plant roots, you dont want a kettle effect, moving water will transfer heat the best.

The ideas discussed here are fine as long as you get all the factors right which will take some time by experiment or calculation. Even with doing the energy transfer calcs you will find that they will just get you in the ball park not spot on. An engineered solution would be based on being able to transfer the maximum amount of heat wanted and the control to stop transfering heat when you had "enough".

A coiled loop of pipe can be a heat exchanger. It may be a very simple one but it is a heat exchanger. The question of whether it is good enough comes down to a whole stack of factors.

Answers to these questions will make a good start:

How big is the spring?
Is it a closed pool or does it over flow?
How hot is it?
How big is your GH?
How well is it insulated?
How much heat are you going to be losing when you need to be heating?

A potential problem with any plastic pipe is that plastic is not a very good conductor so that means that the length of pipe that you need to get a reasonable exchange of energy has to be longer. In commercial GH they sometimes have a challenge getting enough heat out of steel pipes to heat the GH.

Many people have tried to control their system water temperatures and this forum has many examples that have failed to achieve any significant heating or cooling and those that have got measurable results have been disappointed by how small they have been. This is largely due to people not understanding the shear quantities of energy that needs to be added to a GH to keep it warm or removed to keep it cool.

What you are trying to do can be done after all commercial GH operations do it all the time but it is going to take more than just another pump and a few extra pipes. To put things in perspective a heating system for a commercial GH is a significant percentage of the capital cost of the GH (10 to 60% for examples I am aware of but can be higher or less depending on how you figure it) and is coupled with expenditure on other climate control components like thermal screens and computer controlled ventilation.

If you are spending $2000 on a system for GBs FT pump and a simple GH for arguments sake are you prepared to spend another $500-1000 to get the heating system installed and working well? More money for manually controlled thermal screens that could be closed every night you want to keep heat in and spending the extra time and effort to seal the greenhouse so you are not losing heat to drafts but then balance that with extra work of adjusting the ventailation so that the GH is not depleted of O2 during the night or CO2 during the day?

A lot of BYAPers have spent a few extra dollars on a simple HVAC systems (thermal solar panel, water chillers made from a residential fridge or the like) and have been disappointed when they haven't seen any benefit.

The advantage you have is that the heat is free you just have to spend enough money on the equipment to get it from the spring to your house.

I think you overthink things sometimes stu.

after all that you have written there, if he could find a programmable controller cheap, then all it would take is one temp. probe and roughly 10 lines of code, thats if it isnt simply a matter of setting numbers in an interface.

With all of that opening and closing of windows etc, why would you need to do that when you simply pump more spring water through the tank?
with enough water flow, it would be impossible for him to lose temp. hell, he has a hotspring, if he wanted the water at that temp at all times he could do it with a coil of pipes and a decent pump.
obviously if you under engineer anything it wont work, but in a case like this i would always assume everyone would over engineer, it would be needed to guarantee the thing works.

Sometimes I do but...

Lets say you throw a basic system together and it can be seen to work but not much. One of the ways to make it work better would be to go around the house and seal all the drafts and lets say that works to the extent that while it would be nicer to have it warmer its helping and its decided that its "good enough"

Now I have no idea what the climate is like in Idaho but if it is cold but sunny then there is the chance that during the day the plants could get starved of CO2.

I can't remember if we have been told any dimensions of the GH or spring. A coil of pipe in a barrel may be enough for a GH 2m x 4m but if we are talking about something that is 7m x 20m (the size of my first GH) it is just not going to cut it.

The two mistakes that we commonly seen made with system discussed on the forum when it comes to heating and cooling are that 1. people do not realise it is the climate of their GH they need to control as well as the water temp of the system and 2. the amount of heat a GH can lose or gain is massive.

When you have components like NFT or GBs that very effectively transfer heat into or out of the system water you need to control the loss of energy from your GH air or dramatically increase the amount of heat you add or remove depending on whether you are trying to heat or chill.

To think about it another way how expensive was the heater for your house? The one you live in. How much energy do you need to keep your house warm? How much better sealed and insulated is your house compared to your green house?

Some of the american GHs I've looked at could not get enough heat into the house by using hydronic heating in the floor of the house and even extra steel pipes between bays did not keep the house warm enough so extra heat was added with gas burners. Also take note that this was in a house with thermal screens and pretty good air seals.

Your approach of over engineering the system is one that is often used in commercial design certainly more often than many engineers would like to admit but some times it doesn't work because without a proper understanding of what is involved you actually can get a system that is under engineered.

I'm currently working on some designs using ground source heat pumps. The heat exchangers for them in ground are just coils of poly pipe but they have to be massive because of the low rate of heat exchange through the walls of the poly pipe. The obvious solution to this is to use a pipe that is more conductive but the rate of heat transfer through the soil becomes limiting and so the extra expense of copper or steel pipe is not justifiable. In the greenhouse a metal heat exchanger may be more viable because of the greater conductivity of water and the ability to move the system water past/through the GH heat exchanger. Options are still being considered. There is an article on the use of ground source heat pumps that is either just out or is just about to be in Practical Hydroponics.

I am not thinking of heating a barrel of water to heat a GH to heat a system, that is someone elses idea and i think a silly one.

I am talking of heating the system directly. This is easy to do and easy to over engineer, although i do understand the likelyhood that not doing alot of math can lead to mistakes. It is one reason why i put alot of thought into the method used rather than the fine details of a specific method.

Sorry to suggest that you suggested the barrel Yav.

My point is that in extreme climates (to us anyway) it may be hard to over engineer.

Even professionals get this stuff wrong. I was talking to a guy last week about a cooling system dumping heat into the Rhine (i think). The resulting warming of the river/estuary was such that the algae growth was fouling the props of ocean going ships.

In this situation it may be the reverse. If the spring is not big enough or the GH large enough then extracting the heat form the spring may seriously lower the temperature of the spring. Particularly if it is a pool that does not over flow.

Also bare in mind that this thread is in the commercial system discussion area.

Here is a video where a guy is using barrels to heat a dirt greenhouse and only heats the barrels with sunlight. He has a 20 degree difference in temps versus outside temps and by the looks of the greenhouse it is obviously not a very well sealed one. If these barrels were heated constantly with a hot spring like 100 has it would be signifigantly more efficient, especially in a well built house. Also, by running pex tubing through these barrels from the AP tank it would heat the AP tank as well. Depending on the size of the AP system and greenhouse, this could be very effective at heating the system.http://www.youtube.com/watch?v=I_gLSscWLfA

100, can you give us the size of the system and greenhouse to help eliminate some of the variables? The spring is obviously of signifigant size if a water bottling company was using it at one point.

This is a very interesting discussion.

Spring information: The hot spring in question is not huge. It is housed in a building that is maybe 30'x30' (9mx9m). What is lacks in diameter it makes up in depth and consistency. It is not measurable, but is predicted to be hundreds of feet deep. Surface temp is a consistent 180F/82C (if I remember correctly), and the water temp gets hotter and hotter as you go down. It overflows into a small stream.

There is an existing nearby building I would use to house the FT, but I am still unsure on what greenhouse size would be best (I am still in the "business planning" stage), but for estimation purposes, I think I can say it could be around 72'x24' (21mx7m). Something like this http://www.greenhousemegastore.com/product/24-foot-cold-frame-sidewalls

@Stuart Chignell: I would definitely be willing to spend a good amount of money in order to guarantee stable water temps and a well-heated greenhouse. The average monthly temps here are 19F-67F (-7C to 19C), and I don't think my business idea would be cost-effective without harnessing the spring's energy in some way. I am loving the discussion and learning a lot!

i never even considered that. very nice forethought.

For some reason i just assumed that it was a free flowing spring.

Heck my greenhouse last winter with just a few hundred feet of tubing laying on the ground for heat, and it never got close to freezing. Most nights I had 20F more temp inside than outside by morning. If I had a hot spring and 300 feet of pex pipe I could easily keep my fish water warm.

On some really cold nights I had a gas burner that I would turn on, but I had very little flame on it. I used it the whole winter and never emptied the 5 gallon bottle I was using for the fuel tank.

@100

Do you know what the rate of over flow is?

Even though it was bottled it still may have minerals that could clog pipes. The spring water on my Mum's place tastes way better than rain water and when filtered doesn't taste as good. If you leave it sitting in bottles for a long time then a whole stack of minerals precipitate out leaving a brown sludge on the bottom.

@jrl91s The Utube video shows a system using buffer tanks. What is going on is that the barrels are being heated during the day and releasing that heat over night. This system works great as long as they are heated during the day. Such a system will even out the temperature peaks and troughs but they don't actually heat the greenhouse as such.

In mild climates espeacially during Spring and Autumn such a system can remove most of even all the need for heating and cooling but in harsher climates you need to go to greater lengths.

However the heat is delivered to the house it needs to be able to match the heat lost from the house. There is a very real possibility that plastic pipe would not be up for this job within the greenhouse.

Since the spring pool is very deep and gets hotter as you go down a couple of rolls of poly pipe could be connected to insulated pipes (so heat is not lost in the relatively cool water at the top) to collect the heat and if it is delivered to the house hot you may get away with running pipes through the GBs, raft tanks or sump. If it enters the GH only warm then plastic pipe may not be enough. Certainly I wouldn't recommend heating barrels because the surface area of the barrels is relatively small and would not transfer heat very quickly.

What works in a mild winter just won't cut it when there is two feet of snow lying on the ground outside. Similarly I can grow trout all year round at my place when just half an hour down the road they cant because my summer is so much milder than FnFs, Jims or espeacially Journeymans.

@Helomech What is the climate like in Texas vs. Idaho?

What temperature increase would you expect to get with out the pipe on the ground? A 20F shift might be close to what you would get from just the greenhouse.

Also we are talking a commercial system. If the outside temperature is 40F a 20 degree shift to 60F would be really useful. If the outside temperature is only 20F then shifting to 40F is going to do stuff all.

The 20F difference was after a full night of cold weather with no additional heat. So yes it is simply the green house working. The rise in temp with the pipe on the ground varies with each day, but a few days ago the water in my tank was 50F and the water coming out of the pipe on the ground was 70F. That was not long after the sun came up. Of course as the sun gets higher the effect is greater. I have seen it come out well over 90F.


They get colder, but we get into the low teens. 40F over night would not cause any harm to the plants. That temp is only for a short period of time. Heck my tomato plants a few nights ago got down in the 40's and they are still looking great. They actually made all last winter. We get lots of sun, so my greenhouse during the day even when it is below freezing outside gets up to the high 70's. Which gives me lots of warm water.

Keeping the plants above freezing over night is really all that is required to keep them going. The day time temps get high enough for them to flourish.

On this I would disagree. For a BYAP system sure but for commercial they need better control.

Multiple ha system in Qld (hot) went bankrupt and the new owners (who were actually most of the old owners)under instruction of their new GH manager installed a heating system and turned the operation around within the first year.

I dont know a comparable geography in the States (florida maybe) but Qld is in the North of Australia and much warmer than the southern states like NSW, Victoria, SA or Tasmania.