Materials for a Geothermal Well

Approved grout = www.osti.gov/bridge/serlets/purl/757124-cUTd9a/native/757124.pdf

Tubing / pipe = www.flexicraft.com

About as quickly as you could pose this question, the answers could be found on Google. Search for Geothermal heat pump, or ground source heat pump. Here is what about 10 minutes of searching revealed: A mixture of Flintshot sand 4.0 with a .47 water. to cement ratio and a 2.0 sand cement ratio give a very respectable thermal conductivity of 1.346 BTU/hr.ft.Degree F. The piping type I leave for your personal research. -----------------HTRN-----------------------------------------------------------

Materials affordable? within your project budget or system cost effectiveness?

Somehow I think this project could get VERY expensive! What is the expected pay back period?

D.I.Y. average 8-10 years, contracted 25 years

Why don't you contact a contract driller in your area who is in the business of installing geothermal piping systems? I believe that it takes many more than one well and there is typically no casing, just a loop of polyethylene pipe grouted in a hole and connected to the network of other holes to the home system. It may be cased until the grout is placed, with the casing being withdrawn as the grout is pumped in to maintain complete 'coupling' with the earth/rock profile. In my area (New Mexico), a driller with whom I am acquainted uses a rotary drill and drilling mud to maintain the hole. Since the mud is less dense than the grout, it is displaced as the grout is pumped in from the bottom up and there is no need for a casing.

Along with a driller, you should consult with a professional who is experienced at designing geothermal systems or you will likely have an inadequate or too costly result, or both.

I am thinking that it all depends on the type of ground that you are drilling through. Here in Canada what is I think most commom is to drill through the soil to bedrock and install a steel casing to that depth and then the hole continues through the rock to target depth. Glycol is used as the medium and transfered through Kitec plastic tubing of 1" dia. with a closed loop at the bottom. Given the absense of bedrock at target depth the casing would need to extend to the bottom.