Liquid metal thermal storage system

Abstract

Embodiments of this invention relate generally to high temperature thermal energy storage, and more specifically, to the use of the latent heat of fusion of melting and solidifying metals to receive from and provide heat to a gaseous medium. Embodiments of this invention are also known as the Liquid Metal Thermal Storage system or LIMETS. Also described are methods of containing the storage material, heat transfer means, and choices of metals and alloys for thermal storage materials.

1 . A system for storing and retrieving thermal energy from gas heated by a high temperature source comprising:
 a chamber containing heat exchanger elements wherein the heated gas is passed through the chamber containing the heat exchanger elements which heat exchanger elements are in thermal communication with a non-alkali metal or metal alloy that melts at a specified temperature between 600° C. and 1400° C. to stores thermal energy; and   the same or a different chamber containing the same or different heat exchanger elements wherein a gas to be heated is passed through the same or the different chamber containing the same or different heat exchanger elements that are in thermal communication with the same metal or metal alloy that at least partially solidifies, giving up the thermal energy stored.   
     
     
         2 . The system of  claim 1  including the metal alloy composition for a latent heat thermal storage system that melts at a specified temperature by varying the fraction of each component. 
     
     
         3 . The system in  claim 1  wherein the heat exchanger elements are tubes which tubes are composed of a high temperature ceramic material. 
     
     
         4 . The system in  claim 1  wherein the heat exchanger elements are tubes and the tubes are composed of a high temperature metal alloy with a substantially higher operating temperature than the melting temperatures of the metal or metal alloy. 
     
     
         5 . The system in  claim 1  wherein the heat exchanger elements are tubes and the tubes are composed of graphite. 
     
     
         6 . The system in  claim 1  wherein the heat exchanger tubes are tubes and the tubes are composed of graphite that is clad in a metal or ceramic to prevent oxidation when using oxidizing gasses as the heat transfer medium. 
     
     
         7 . The system in  claim 1  wherein the heat exchanger elements are tubes and the tubes are solid metal or solid graphite with a cladding. 
     
     
         8 . The system in  claim 1  wherein the heat exchanging elements are tubes and the tubes are hollow and contain a element or compound with a boiling temperature above the metal or metal alloy to carry the heat from the solar source into the metal or metal alloy. 
     
     
         9 . The system in  claim 1  wherein the heat exchanging elements are tubes and the tubes are hollow and contain a element or compound with a boiling temperature below the metal or metal alloy to carry the heat from the metal or metal alloy to the gas stream to be heated. 
     
     
         10 . The system in  claim 1  wherein the heat exchanging elements are tubes and the tubes are arranged in such a fashion so as to maximize the heat transfer between the tubes and heat transfer gas. 
     
     
         11 . The system in  claim 1  wherein the heat exchanging elements are tubes and the tubes are one of hollow or solid rods have radial or axial fins to improve the heat transfer. 
     
     
         12 . The system in  claim 1  wherein the heat exchanging elements are tubes and the cross section of the tubes is designed so as to maximize the heat transfer between the tubes and the heat transfer gas. 
     
     
         13 . The system in  claim 1  that uses air, carbon dioxide, argon, helium, or nitrogen as the heat transfer gas. 
     
     
         14 . The system in  claim 7  wherein the source including a solar receiver to heat the gas to provide heat to melt the metal or metal alloy. 
     
     
         15 . The system in  claim 1  including a gas turbine that uses the stored heat to operate a gas turbine to provide mechanical power. 
     
     
         16 . The system in  claim 14  wherein the source including a windowed high temperature solar receiver that uses small particles to absorb concentrated sunlight and heat gases including at least one of air, carbon dioxide, helium or nitrogen in which they are entrained. 
     
     
         17 . The system in  claim 1  including a metal alloy that is made from two or more elements whose melting temperature is determined by the choice of the fraction of the two or more elements. 
     
     
         18 . The system in  claim 1  wherein the metal alloys including aluminum and silicon with a melting temperature from 600° C. to 1400° C. 
     
     
         19 . A method for storing and retrieving thermal energy from and to a gas heated by a high temperature source including the steps of:
 passing the heated gas through a chamber containing heat exchanger elements that are in thermal communication with a non-alkali metal or metal alloy that melts at a specified temperature between 600° C. and 1400° C. to store thermal energy in the form of the latent heat of fusion of the metal or metal alloy; and   passing the gas to be heated through the same or a different chamber containing the same or different heat exchanger elements that are in thermal communication with the same metal or metal alloy that at least partially solidifies, giving up the thermal energy stored in the form of the latent heat of fusion.   
     
     
         20 . The method of  claim 19  including choosing the metal alloy composition for a latent heat thermal storage system so that the metal alloy melts at a specified temperature by varying the fraction of each component of the metal alloy. 
     
     
         21 . A system for storing and retrieving thermal energy from a gas heated by a high temperature source comprising:
 a chamber containing heat exchanger elements; and   a non-alkali metal or metal alloy contained in the heat exchanger elements adapted for storing heat from the heated gases.   
     
     
         22 . The system of  claim 1  wherein the metal or metal alloy melts at a specified temperature of between about 600° C. and 1400° C. 
     
     
         23 . A system for storing and retrieving thermal energy from a gas heated by a high temperature source comprising:
 a first channel having first heat exchanger elements;   a second channel having second heat exchange elements;   a chamber containing a non-alkali metal or metal alloy that is adapted for storing heat from the heated gas; and   the first and the second heat exchanger elements in part extending into the chamber.   
     
     
         24 . The system of  claim 1  wherein the metal or metal alloy melts at a specified temperature of between about 600° C. and 1400° C. 
     
     
         25 . A method for storing and retrieving thermal energy from gas heated by a high temperature source including the steps of:
 passing the heated gas through a chamber containing heat exchanger elements that are in thermal communication with a non-alkali metal or metal alloy that melts to store thermal energy; and   passing the gas to be heated through the same or a different chamber containing the same or different heat exchanger elements that are in thermal communication with the same metal or metal allow that at least partially solidifies, giving up the thermal energy stored.