Active thermal energy storage system and tank for use therein

Abstract

An active thermal energy storage system is disclosed which uses an energy storage material that is stable at atmospheric pressure and temperature and has a melting point higher than 32 degrees F. This energy storage material is held within a storage tank and used as an energy storage source, from which a heat transfer system (e.g., a heat pump) can draw to provide heating of residential or commercial buildings and associated hot water. The energy storage material may also accept waste heat from a conventional air conditioning loop, and may store such heat until needed. The system may be supplemented by a solar panel system that can be used to collect energy during daylight hours, storing the collected energy in the energy storage material. The stored energy may then be used during the evening hours to heat recirculation air for a building in which the system is installed.

1 . A tank for storing a thermal energy storage material, comprising:
 an outer shell and an inner surface, the inner surface defining a volume for accepting a quantity of thermal energy storage material;   heat exchange piping disposed within the volume for transferring heat between the thermal energy storage material and a fluid disposed within the heat exchange piping;   fill and drain connections;   wherein the fill and drain connections seal the volume from the outside atmosphere to prevent evaporation of the thermal energy storage material contained therein; and   wherein the inner surface of the tank and the outer surfaces of the heat exchange piping comprise a non-reactive material.   
     
     
         2 . The tank of  claim 1 , wherein the heat exchange piping comprises a polymer material or a metal material having an outer polymer layer. 
     
     
         3 . The tank of  claim 1 , wherein the inner surface of the tank comprises a material selected from the list consisting of polyethylene, glass polypropylene, fiberglass and Teflon. 
     
     
         4 . The tank of  claim 1 , wherein the heat exchange piping comprises copper or other high heat transfer material coated with an acrylic layer or other non-reactive coating material. 
     
     
         5 . The tank of  claim 1 , further comprising a level measurement system for providing an indication of a level of the thermal energy storage material disposed within the tank. 
     
     
         6 . The tank of  claim 1 , wherein the level measurement system comprises a visual indicator or an automated level detection system. 
     
     
         7 . The tank of  claim 6 , further comprising an automatic load leveling system that automatically adds a quantity of water in response to a predetermined low level reading from the level measurement system. 
     
     
         8 . The tank of  claim 1 , wherein the heat exchange piping is arranged within the tank in a configuration selected from the list consisting of U-shaped and coiled. 
     
     
         9 . The tank of  claim 1 , further comprising an electric resistance heater or other energy source for heating the thermal energy storage material. 
     
     
         10 . The tank of  claim 1 , further comprising a removable lid that provides access to the volume. 
     
     
         11 . A thermal energy storage system comprising:
 a water tank for holding a quantity of water;   a storage tank having a quantity of thermal energy storage material disposed therein, the thermal energy storage material comprising a substantially solid material having a melting point above 32 degrees Fahrenheit (F) and a latent heat of fusion approaching that of water;   a first circulation loop comprising a first loop section disposed within the second tank and a second loop section in thermal communication with a first coil of a heating, ventilating and air conditioning (HVAC) system, the first circulation loop further having a first pump for circulating water between the first and second loop sections;   a second circulation loop comprising a first connection to the water tank, a third loop section in thermal communication with a second coil of the HVAC system, a second connection to the water tank, and a second pump for circulating water between the water tank and the third loop section; and   third circulation loop piping connecting the water tank and the storage tank, the third circulation loop having first and second valves disposed therein, the first and second valves being operable to provide selective fluid communication between the third circulation loop and the first and second circulation loops.   
     
     
         12 . The system of  claim 11 , wherein the system has a first configuration in which the first and second valves are aligned so that the first pump circulates water between the third circulation loop piping and portions of the first and second circulation loop to transfer heat from the water in the water tank to the thermal energy storage material disposed within the storage tank. 
     
     
         13 . The system of  claim 11 , wherein the system has a second configuration in which the first and second valves are aligned so that the first pump circulates water within the first circulation loop to transfer heat from the first coil of the HVAC system to the thermal energy storage material in the storage tank. 
     
     
         14 . The system of  claim 1 , wherein the system has a third configuration in which the first and second valves are aligned so that the first pump circulates water within the first circulation loop to transfer heat from thermal energy storage material to the first coil of the HVAC system, and the second pump circulates water within the second circulation loop to transfer heat from the thermal energy storage material to the second coil of the HVAC system. 
     
     
         15 . The system of  claim 11 , wherein the HVAC system further comprises a compressor, first and second HVAC valves, an HVAC piping loop, and a third coil disposed in a ventilation duct for transferring energy between air in the ventilation duct and the third coil. 
     
     
         16 . The system of  claim 15 , wherein the first and second HVAC valves are selectively operable to form a first HVAC loop between the first coil and the third coil, and a second HVAC loop between the second coil and the third coil. 
     
     
         17 . The system of  claim 16 , wherein said compressor is a reversible compressor. 
     
     
         18 . The system of  claim 15 , further comprising a temperature sensor associated with the storage tank, wherein when the temperature sensor senses that the temperature of the TESM exceeds a predetermined temperature limit, the temperature sensor is operable to send a signal which causes the first pump to be turned off and the HVAC system to be turned on. 
     
     
         19 . The system of  claim 11 , wherein the first and second pumps are variable speed pumps. 
     
     
         20 . The system of  claim 11 , wherein the first and second valves are three-way solenoid valves. 
     
     
         21 . The system of  claim 10 , wherein the first coil and the second loop section of the first recirculation loop comprise a first heat exchanger, and the second coil and the third loop section of the second recirculation loop comprise a second heat exchanger. 
     
     
         22 . The system of  claim 10 , wherein the thermal energy storage material is selected from the list consisting of clathrate, imidazole, imidazolium chloride and a derivative of pyrrole.