Heat Transfer Trench, Storage Tank, and Heat Exchanger Details


This page covers the details for the tank used to store the solar collector heated water,  the trench and pipeline used to transfer heat from the tank/shed area to the house,  and the heat exchanger used to preheat Domestic Hot Water for the house.


The trench carries solar heated water from the partly buried tank on left (which will be covered by
the shed and collectors) to the house.  The pipe is buried below the frost line and insulated to
reduce heat loss.


Heat Transfer Trench

I ran four inch Pex Pipes to the house, two for DHW, and two for space heating. I buried the pipes 6 feet down to get below frost line and used 2 inch rigid pink foam insulation around them.  I used three-2x2 pieces of insulation between a bottom and top piece insulation, glued together with gorilla glue and wrapped with packing stretch wrap.


Click on pictures for full size

PEX pipe with insulation being applied.

Insulated pipe going into the trench.



Heat Storage Tank

For the heat storage tank I used a 750 gallon stainless steel milk bulk tank with 4 inch insulation added to the outside.

I buried it in the ground with a heat exchange fit though the man hole cover.  At the end of the tank. I built a pump pit for the pump.


The dairy milk bulk tanks can be found in dairy farm auctions. I went to a dairy supply store that works with dairy farmers They get the tanks trade in when the cooling system fails and like your refrigerator new ones are more efficient. The tanks are food quality when removed from the farms so there in good shape and clean. I paid 50 cents a gallon for the tank. For a tank that wont rust and should last a vary long time I thought it was worth it.



Click on pictures for full size

750 gallon stainless steel bulk
milk tank used for heat storage.

Placing insulation around the partially
buried tank.  Placing tank below
collectors allows a simple drain back
system for freeze protection.
Note large access hatch.

Pump chamber on end of tank. 


Heat Exchanger

Click on pictures for full size

This heat exchanger is placed in the storage
tank via the hatch.  It is used to preheat
domestic hot water.

It is a good idea to place the heat exchanger
near the top of the tank to take advantage of
any stratification in the tank.

I used the water from the tank for space heating using under-floor radiant heating (stapled up inch PEX pipe). I have found out that I can run the radiant space heating pump then use my off peak electric baseboard heaters to control the temperature in the house. My tank temperature rarely exceeds 90 degrees so Im using all heat I produce But I have quite a lot of cloudy days except when it is very cold (-10F) then the sun is out and and the tank really heats up!! .

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On to the homemade pipe Tee Extractor tool...




Gary March 22, 2010