A heat exchanger having a helix coil incorporated into a stainless steel elongated variable diameter cylindrical housing and a radial direct-firing burner and a blower-driven hot flue gas to heat water. A buffer tank is incorporated within the lumen of the helix coil. At least one rope seal is disposed between adjacent coil loops of a portion of the helix coil for enhancing heat transfer to the helix coil. In one embodiment, the heat exchanger further comprises a Stirling engine comprised of a free piston having hot and cold ends that is disposed within the cavity taken up the buffer tank, wherein the hot end receives heat from the burner and the cold end is cooled by the incoming cold water line to form an electric power generator.

A geothermal system exchanges heat between a target and ground which receives geogenic heat from below. Heat exchange tubing in a continuous loop within the ground receives a circulated heat exchange fluid. An insulating layer spans over the ground with a greater footprint than the continuous loop in the ground below. The insulating layer may cover an area of land of at least 400 square metres and may be formed of a synthetic heat insulating material such as recycled plastic materials so that the insulting layer has a total R factor of 30 or greater. A heat pump is operable to transfer heat from the heat exchange tubing to the target for extracting the geogenic heat from the ground for heating the target in cold seasons, and transfer heat from the target to the heat exchange tubing for storing excess heat from the target to the ground in warmer seasons.