Earth-embedded, temperature-stabilized heat exchanger

In a system for heating and air conditioning a structure in which thermal energy is exchanged between the structure and the earth, the system having a first closed circuit in thermal contact with a second closed circuit in a heat exchange zone;

• the heat exchange zone embodying a fluid-to-refrigerant charge heat exchanger;
• the first closed circuit having a compressor for circulating a refrigerant charge through the heat exchanger and through an air conditioning coil;
• a means including said coil and a fan for distributing heated or cooled air to a conditioned space within the structure;
• the first closed circuit further including a 4-way valve in series with the compressor, the heat exchanger and the coil whereby in one mode of the valve the heat exchanger functions as an evaporator and the coil functions as a condenser;
• and in the other mode the functions are reversed;
• the second closed circuit including a passageway of the heat exchanger, an underground pipe having a heat conductive portion, and a pump for circulating a heat transfer fluid through the passageway and the underground pipe;
• wherein the improvement comprises:
• a temperature-stabilized heat exchanger which is embedded in the earth, the heat exchanger having a hermetically-sealed enclosure which jackets a section of the heat conductive portion;
• the thickness of the walls of the enclosure being at least as great as that of the wall of said section;
• a composition which upon crystallization releases latent heat in the amount of approximately 100 BTUs per pound and which is contained within the enclosure, the transition temperature of the composition being approximately 10.degree. F. below the average winter temperature of the undisturbed soil at the depth at which the temperature stabilized heat exchanger is embedded, so that a large amount of thermal energy can be stored in close proximity to said heat transfer fluid, thereby protecting the environment in the vicinity of said section against the effects of extremely low temperatures when heating of the structure is required;
• the enclosure having a large surface-to-volume ratio and having its outer walls in thermal contact with the soil, so that the composition can be restored to its liquid state by thermal energy transfer from the earth to the composition when the heating requirements are low.