Combined ground-based heat exchange and thermal storage

Abstract

An integrated underground heat storage and heat transfer system is provided for CO2-based heating and cooling installations. The invention enables both energy storage and heat exchange in a single Underground Thermal Energy Storage (UTES) system. Excess heat produced during warm weather heats the ground to relatively high temperatures, which in cool weather serves as an artificial geothermal source. A geothermal heat pump (GHP) system reclaims this heat during cool weather. When the GHP is reversed in warm weather, the rejected heat is sent to a separate loop installed in cold earth.

I claim: 
     
         1 . A system for simultaneous heat exchange and seasonal heat storage for a carbon dioxide-based heating and cooling system for a facility, comprising:
 (a) an underground CO2 network containing circulating liquid carbon dioxide;   (b) a first underground water network containing circulating water, in thermal contact with the underground CO2 network;   (c) a second underground water network containing circulating water, not in thermal contact with the underground CO2 network; and   (d) a geothermal heat pump switchable between a cool weather state and a warm weather state; wherein
 (i) when in the cool weather state, the geothermal heat pump is configured to recover heat from the first underground water network and deliver the recovered heat to the facility, and 
 (ii) when in the warm weather state, the geothermal heat pump is configured to remove heat from the facility and deliver the removed heat to the second underground water network; 
   
       wherein
 (e) the carbon dioxide is compressed and heated by a compressor system into a non-gaseous fluid state; 
 (f) the fluid carbon dioxide is passed through a heat exchanger, where heat is transferred to a hot water system of the facility; 
 (g) the fluid carbon dioxide exiting the heat exchanger is directed into the underground CO2 network, where heat is transferred to the surrounding soil; 
 (h) the fluid carbon dioxide exiting the buried loop is directed to an evaporator, where the fluid CO2 is cooled by conversion to the gaseous state and absorbs heat collected by a chilled water system of the facility; and 
 (i) the gaseous carbon dioxide exiting the evaporator is supplied to the compressor system at step (e). 
 
     
     
         2 . The system according to  claim 1 , wherein the compressor system is a three-stage mechanical compression system. 
     
     
         3 . The system according to  claim 1 , wherein the compressor system is a thermal compression system. 
     
     
         4 . The system according to  claim 1 , wherein the second underground water network is in thermal contact with an underground aquifer. 
     
     
         5 . The system according to  claim 2 , wherein the second underground water network is in thermal contact with an underground aquifer. 
     
     
         6 . The system according to  claim 3 , wherein the second underground water network is in thermal contact with an underground aquifer.