COAXIAL BOREHOLE ENERGY EXCHANGE SYSTEM FOR STORING AND EXTRACTING UNDERGROUND COLD

摘要

An energy transfer system is provided for commercial and industrial refrigeration and air conditioning applications. Cold is extracted from underground using a boreho le drilled into overburden materials and bedrock, typically 150 to 180 m in depth, as a coaxial energy exchanger. Water is conveyed to the bottom of the borehole by pumping through a concentric middle tube, with return to the top via the spacing between the inner tube and the borehole. Heat is lost and cold is gained by the circulating fluid along the length of the heat exchanger. The major innovation in this system is the ability to transfer and store cold energy in the temperature range from 0 to 8 C for a prescribed period of time, without the use of refrigerants, due to the low borehole thermal resistance of the coaxial design. Other improvements include lower drilling costs and easier installation.