my pizza oven / pool heater build

[tomds]

Hi all,

After setting up a swimming pool in the garden, and finding out that there's not much fun in keeping a cold pool tidy that nobody's swimming in, I started playing with the idea to build a wood burning pool heater. Much and most examples on the internet, youtube diy versions as well as commercial ones, seemed to be rather smokey contraptions, not to mention dangerous ones, and often plain ugly. 
Then I stumbled upon the rocket stove technology, and spent quite some time reading up, and thinking about how to use it in an aesthetically pleasing way.

I decided I was going to build a rocket powered pool heater, but given the fact that it would be a time consuming and rather bulky, not to mention costly project, I wanted to have a safety net, in case the pool heater didn't perform as desired. This made me come up with the idea to integrate a pizza oven with a swimming pool heater. When pool performance would be laughable, I could always continue enjoying the pizzaoven part.

In the end, this resulted in the build I would like to show you all in this thread. It's proven to be capable of heating my 16000L pool from 20 to 30 °C in 24 hours of wood burning. I did the math, and this would mean that on average, the heater is giving off 10 kW to the pool, which pleases me a great deal. During the building process, it has already served many a pizza, and a few roasted chickens as well. 

Given the fact that my wife accepted it, I think it is fairly pleasing to the eye as well, but I will leave that judgement up to you.  

If anyone would like to attempt the same, I hope they will find inspiration in the following pictures.

[tomds]

Step one, foundations


 

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[tomds]

step two, insulating the base with portland cement / vermiculite mix.

[tomds]

step three, buying a second hand stainless steel boiler and cutting 32 mm thick refractory bricks into a riser and a batch box.

[tomds]

step four, assembly of the batch box rocket on the foundation, using refractory mortar, and after curing, lighting it. => first success

[tomds]

step five bricklaying and making compartments with a stainless steel plate


 

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[tomds]

step six, insulating the rocket stove with vermiculite and creating an oven floor with t-bars and 4 cm thick concrete slabs. (T bars were given expansion room) (All in all, maybe not the best technical option, but wanted to keep footprint as small as possible) The black soot on the backplate is because I had played with fire on that in the past already.

  

[tomds]

step seven, insulating the concrete slabs with vermiculite /portland cement mix, and laying refractory tiles

Not much space between the walls and the start of the dome, I know. (small footprint remember) I "insulated" that with 5 layers of aluminum foil, which in the end proved sort of satisfactory. The wall heats up to the point you can't keep your hand to it for more than a few seconds, but the good thing is that sitting beside the wall in the evening is rather cosy and comfortable.

[tomds]

step eight, creating a mould for the dome, and building the dome


 

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[tomds]

step nine, taking away the mould, and cutting and installing refractory sidewalls

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[tomds]

step ten, bricklaying on a second mould, restarting over and over, until in the end, I had an arch at the front, and a closable window in the back, of the same surface area as the riser, which has 150 mm diameter. The top of the window is flush with the oven ceiling, to minimize flue gas obstruction.


 

[tomds]

step eleven, making a lid for the rear window with a brick and testing the oven. (beer in the butt chicken)
The oven stood in this stage for quite some time, until I could figure out how I would insulate the walls of the boiler compartment at a reasonable cost, and with good efficiency.

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[tomds]

step twelve, bought a roll of superwool, and created a skeleton I could tie the insulation to and put around the boiler.

I also created a condensed water collecting tray from the bottom of the outer shell of the boiler, that I cut off. The outer shell was no stainless steel, so I hesitated to use it for this purpose, but the metalworker who welded the piping to it assured me that I would not see it rust to shreds any time soon. (of course stainless would have been the better option anyway... time will tell)

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[tomds]

step thirteen, installing the boiler onto sort of a pedestal, so I can later clean out the ashes collecting in the tray. 

 

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[tomds]

Step fourteen, filling up the edges of the compartment, to avoid shortcutting of hot flue gas to the exhaust. I used cutouts from the outer shell of the boiler for this, and plugged it at the top with superwool.