Using Recycled Bulk Milk Tanks for Solar Heat Storage Tanks

 Tom Snyder has suggested another good option for solar heat storage tanks.  He uses used stainless steel bulk milk tanks.  

These tanks are available for about $1 per gallon used.  Sizes range from about 300 to 500 gallons.   They are probably easiest to find in areas with a lot of dairy farming activity.

Tom's company is Alternate Energy Systems -- their website has a lot of interesting content. 

Thanks very much to Tom for sending this in!

These are some pictures and description from Tom of one of his installations: 

stainless steel milk tank for heat storage  
The beginning of installing a 340 gallon Stainless Steel Tank for preheat of DHW and in floor radiant heat using 6 - 3X8 solar panels.

milk tank for solar heat storage
The plumbing for the solar pump, temperature and pressure gauges.

A closeup of the 3/4 inch copper coil for the solar loop (bottom)
and two 3/4 inch 60 foot copper coils in parallel for the DHW preheat.


The plumbing for the solar pump, temperature and pressure gauges

A closeup of the old style aquastat and
 temperature gauge for the in floor heat system.
The solar "manifold" for the solar loop from the collectors to the coils in the tank or outboard plate type exchanger. This solar  manifold consists of a cast iron pump, 2 fill valves, swing check valve, in line ball valve to help with filling the system, Schrader valve, relief valve and a P/T gauge.


The tanks include insulation on the sides and bottom.  I never have cut into the sides, but it is very effective for keeping milk cold and water hot.  In an article for Home Power I was flippant when I told one customer to "turn the tank over to put the insulation on top". On the top I usually put at least 2 inches of rigid foam and sometimes a fiberglass batt.  On two projects, an insulated room in the basement was built around the tank,  and on one we had the tank in an insulated box in an unheated attached garage with openings into the basement for heat into the box.  I also saw this method used on new homes in Omaha a few years ago.

On the photos of the tank, the wires to the sensors can be seen at the front, top.  A minor word of caution in using this method (a 1/2 inch of capped copper).  Over time the tube will get some moisture in it from condensation which could finally ruin the sensor.  Two ways to solve this is to silicon the top of the tube and the second is to make sure the sensor is not clear to the bottom of the tube.

Tom Snyder
Alternate Energy Systems
NABCEP ST certificate
Northeast Iowa Community College
Solar Thermal Licensing Instructor

Tom wrote an article for Home Power titled  "Solar Heating Basics Part Two Storage of Solar Energy", that has some additional material on using bulk milk tanks for heat storage and other cost effective heat storage methods.  The article appears in Home Power issue 42, August/September 1994.    How to get articles from Home Power ...

Another example of a bulk milk tank used for heat storage on Ken's solar space heating project...

Other methods for storing solar heat...

Comments and Questions

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