Method and apparatus for installing geothermal heat exchanger

A method of installing a geothermal heat exchanger, the method comprising:

• at a site, after a borehole has been bored to a borehole target depth in the site, inserting a geothermal heat exchanger into the borehole to a desired heat exchanger depth;
• after inserting the heat exchanger into the borehole, permanently securing the heat exchanger in the borehole at the desired heat exchanger depth;
• wherein, when the heat exchanger has been permanently secured in the borehole:
• the heat exchanger has a closed distal end and an open proximal end;
• the heat exchanger has at least one fluid path between the closed distal end and the open proximal end;
• and
• installation fluid is disposed in the at least one fluid path of the heat exchanger;
• and
• after permanently securing the heat exchanger in the borehole, before cutting the heat exchanger and while the heat exchanger remains permanently secured in the borehole, and before excavation of a portion of the site immediately surrounding the borehole, temporarily sealing the heat exchanger between the closed distal end and the open proximal end by installing, through the open proximal end, at least one respective internal seal in each of the at least one fluid path, wherein for the at least one fluid path, the at least one internal seal is disposed below a respective notional subgrade depth.