Solar hot water - Aquaponics - Thermal mass

One thing I'd like to do is to stabilise my grow house's climate.

Another is to make it warmer throughout winter.

It seems to be getting warmer, but the fish tank water temperature moves around a lot. So I seem to be making some solar hot water, but I am loosing too much heat overnight. Insulating my grow house is too much like hard work, but...

high tech water based heat sinks
I have a plan.

Actually I have two plans.

The first is to add thermal mass to the system. I'm going to move more water into the system. Water has the ability to store more heat than stuff like concrete, and a huge amount more heat than stuff like air. This increases the heat storage capacity of my hothouse and should allow me to "bank" some heat. Water is really cheap. Solar heat is even cheaper.

Heat radiates from where ever it is , to wherever it isn't. If I create less places where it isn't, there will be less places for it to radiate to. Creating less places where it isn't also means creating more places where it is.

That should work.

In other words...

If I add some stuff that holds a lot of heat, and add as much of it as I can I should be able to store some of the excess during the day when it is plentiful, and have that release into the system overnight.

Heat likes to share itself around evenly in a very generous manner, so all I have to do is put something in its way that holds a lot of it, and the storage bit should take care of itself. This is the kind of stuff you would learn if you were to study passive solar design, and renovate your house a bit, so lots of people have done lots of work on the subject.

This will mean the fish tank water should heat up more slowly, and cool down more slowly. That sounds like a definition of temperature stability.

There is only a finite amount of heat entering the system each day. This means that if I add a material that absorbs some heat, it must take that heat from somewhere else. What that means is that by storing some heat in my new thermal mass, I effectively cool my grow house a bit from its crazy afternoon temperatures. This means I will not only be storing some heat for the colder times, but I'll also be knocking off the sharp bits of my graph at the top as well, and cooling it a bit during the hottest part of the day. As the day cools down, my thermal mass will reverse it's attitude, and share its excess heat with the now cooler air within the grow house. It should also share its heat with the fish tank, and give my fishy friends a more stable environment.

Everybody wins.

Except the supermarket, and fish monger.

Does a fishmonger "mong" fish?

wiktionary seems to think so. It starts it's definition with "a mixture, a crowd"

So I'm saying yes. I'm defining "mong" as "to gather a stack of things for sale or for general craziness"

Anyway, I plan on doing this in three different ways.

First, I plan on adding water based heat sinks. I can add a stack of them around the base of my grow house where they wont get in the way, and wont take up any growing real estate. I should be able to add an additional 15L or so of water to my grow house. This should increase the total thermal mass of the system and allow it to store more heat.

Second, I plan on running a heat pump in the form of a solar heat conduction coil in the highest part of the grow house where it's hottest, and pump that heat down to the bottom where it's coldest, and where all my water based heat sinks will be.

The third will be for another post because I'm yet to know much about it.

My high tech water based heat sinks will be recycled, plastic, three litre milk bottles full of water.

My high tech solar heat conduction heat pump will be a 10 metre coil of 4mm black poly pipe stuck up high.

That should work.


  1. Thank you for posting the great content. I was looking for something like this. I found it quiet interesting, hopefully you will keep posting such blogs. Keep sharing.

    solar water heater systems


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