I just purchased an EKO-40 and have limited space for thermal storage. I am looking at the possibility of installing a used 500 gallon propane tank for a pressurized system. I found an old study (1979-80) for NASA where sand was used for heat retention. In this case they used 1 ½ inch metal pipe surrounded by 6 inches of sand. The study is extremely detailed and way beyond my grasp but after reading some of this my thought was to pressurize the tank and check for leaks etc. and when everything checked out satisfactorily, build a frame around the tank and insulate the frame (maybe 6-8 inches of the hard foam insulation) and leave at least a 12 inch space between the tank and insulation for sand. The sand will absorb and retain the heat better than the insulation and some of that heat from the sand should transfer back to the tank when the water is circulated back through the tank. Someone told me that this method was used in Alaska but I haven’t been able to find any information. Has anyone seen anything like this? Any thoughts?
If anyone is interested, this is the address for the study:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800021359_1980021359.pdf
If anyone is interested, this is the address for the study:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800021359_1980021359.pdf
