Thermal energy storage system with input liquid kept above 650°c

Abstract

A thermal energy storage system has an insulated storage container filled with a particulate earth material. A heat input conduit circuit is buried in the earth material and transfers heat from an input liquid flowing in the heat input conduit circuit to the earth material. A heat output system is operative to transfer heat from the earth material in the storage container to an external heat consumer. During operation the input liquid enters the inlet port of the heat input conduit circuit at an input operating temperature and leaves the outlet port at an output operating temperature, and the output operating temperature is above about 650° C. The input liquid remains liquid at the input and output operating temperatures under atmospheric pressure. Energy is stored at a relatively high temperature compared to the prior art, and provides increased efficiency for heat consuming processes.

1 . A thermal energy storage system comprising:
 an insulated storage container substantially filled with a particulate earth material;   a heat input conduit circuit buried in the earth material and configured to transfer heat from an input liquid flowing in the heat input conduit circuit to the earth material, the heat input conduit circuit having an inlet port and an outlet port, each port defined in one of a top, bottom, and side wall of the storage container;   a heat output system operative to transfer heat from the earth material in the storage container to an external heat consumer;   wherein during operation the input liquid enters the inlet port of the heat input conduit circuit at an input operating temperature and leaves the outlet port at an output operating temperature;   wherein the output operating temperature is above about 650° C.; and   wherein the input liquid remains liquid at the input and output operating temperatures under atmospheric pressure.   
     
     
         2 . The system of  claim 1  wherein the earth material comprises one of sand and crushed lava rock. 
     
     
         3 . The system of  claim 1  wherein the storage container is sealed and contains a substantially inert gas atmosphere with the earth material, and wherein a purge and makeup regulation system is operative to selectively release inert gas from the storage container and add inert gas to the storage container to maintain atmospheric equilibrium therein during thermal expansion and contraction of the inert gas atmosphere as temperature changes. 
     
     
         4 . The system of  claim 3  wherein the storage container is formed by an inner wall and an outer wall with an insulation space between the inner and outer walls, and wherein the insulation space contains the same substantially inert gas atmosphere, and wherein a purge and makeup regulation system is operative to selectively release inert gas from the insulation space and add inert gas to the insulation space to maintain atmospheric equilibrium therein during thermal expansion and contraction of the inert gas atmosphere as temperature changes. 
     
     
         5 . The system of  claim 3  wherein the substantially inert gas atmosphere comprises at least one of nitrogen, carbon dioxide, helium, and argon. 
     
     
         6 . The system of  claim 1  wherein walls of the storage container comprise stainless steel. 
     
     
         7 . The system of  claim 1  wherein the storage container is buried in the ground such that the ground supports walls of the storage container. 
     
     
         8 . The system of  claim 1  wherein the heat input conduit circuit is divided into at least first and second input zones and is configured such that the flow of input liquid can be directed through one of the first input zone, the second input zone, and both input zones to transfer heat to earth material in one or both corresponding first and second earth material zones. 
     
     
         9 . The system of  claim 8  wherein the heat output system is operative to transfer heat from the earth material in one of the first earth material zone, the second earth material zone, and both earth material zones to the external heat consumer. 
     
     
         10 . The system of  claim 1  wherein at least one conduit of the heat input conduit circuit comprises a main conduit and at least one auxiliary conduit arranged in proximity to the main conduit, wherein the input liquid flows in the main conduit, and wherein an auxiliary liquid flows in the at least one auxiliary conduit such that heat transfers from the auxiliary liquid to the input liquid, and wherein a melting temperature of the auxiliary liquid is less than a melting temperature of the input liquid. 
     
     
         11 . The system of  claim 10  wherein the auxiliary conduit is inside the main conduit. 
     
     
         12 . The system of  claim 10  comprising first and second auxiliary conduits, wherein the first auxiliary conduit is arranged in proximity to the main conduit such that heat is transferred from a first auxiliary liquid flowing in the first auxiliary conduit to the input liquid, and wherein the second auxiliary conduit is arranged in proximity to the first auxiliary conduit such that heat is transferred from a second auxiliary liquid flowing in the second auxiliary conduit to the first auxiliary liquid, and wherein a melting temperature of the first auxiliary liquid is less than a melting temperature of the input liquid and wherein a melting temperature of the second auxiliary liquid is less than a melting temperature of the first auxiliary liquid. 
     
     
         13 . The system of  claim 12  wherein the first and second auxiliary conduits are inside the main conduit. 
     
     
         14 . The system of  claim 13  wherein the second auxiliary conduit is inside the first auxiliary conduit. 
     
     
         15 . The system of  claim 10  wherein a boiling temperature of the auxiliary liquid at atmospheric pressure is greater than the input operating temperature. 
     
     
         16 . The system of  claim 12  wherein a boiling temperature of the first auxiliary liquid at atmospheric pressure is greater than the input operating temperature. 
     
     
         17 . The system of  claim 12  wherein the second auxiliary liquid has a melting point lower than ambient temperature at a location of the system. 
     
     
         18 . The system of  claim 17  wherein the second auxiliary liquid is water, and the first auxiliary liquid is a metal alloy. 
     
     
         19 . The system of  claim 18  wherein the melting temperature of the metal alloy is below a boiling temperature of the water in the second auxiliary conduit. 
     
     
         20 . The system of  claim 19  wherein pressure is maintained in the second auxiliary conduit to increase the boiling temperature of the water in the second auxiliary conduit. 
     
     
         21 . The system of  claim 18  comprising a valve operative to selectively release pressure from the second auxiliary conduit such that the water in the second auxiliary conduit boils out of the secondary auxiliary conduit. 
     
     
         22 . The system of  claim 1  wherein the heat output system comprises a heat output conduit circuit buried in the earth material and configured to transfer heat from the earth material in the storage container to an output liquid flowing in the heat output conduit circuit. 
     
     
         23 . The system of  claim 22  wherein a temperature of the output liquid delivered to the external heat consumer is controlled by adjusting one of a bypass mixing valve and a variable output pump circulating the output liquid through the heat output conduit circuit. 
     
     
         24 . The system of  claim 22  wherein the heat output conduit circuit is connected to circulate through an input loop of a heat exchanger and wherein an output loop of the heat exchanger is connected to a boiler, and wherein the output liquid in the heat output conduit circuit and the input loop of a heat exchanger is sodium, and wherein a boiler liquid in the output loop of the heat exchanger is not sodium. 
     
     
         25 . The system of  claim 1  wherein the input liquid is one of aluminum, sodium, and tin.