Thermochemical Energy Storage System

Abstract

A system is described for the thermochemical capture of heat energy and the transfer of this energy to a point of use using a cycle decomposing SO 3 to SO 2 and O 2 and the subsequent oxidation of SO 2 and O 2 to SO 3 . This system can store this energy in the form of chemical energy by storing liquid SO 2 . Embodiments are described wherein oxygen is stored by a solid oxygen storage material or removed and added to the process by selective membranes or by electrochemical pumping. In addition, an alternative embodiment uses an electrochemical generator for the direct conversion of SO 2 to electrical energy.

1 . A thermochemical system that transports energy from a first location to a second location where the energy is used to generate steam for a steam turbine, comprising:
 a thermal source providing a first thermal energy;   a first reactor at the first location converting the first thermal energy to chemical energy by decomposing SO 3  into SO 2  and O 2 ;   a second reactor at the second location converting the chemical energy to a second thermal energy by oxidizing SO 2  with O 2  to produce SO 3 , the second reactor evaporating water into the steam for the steam turbine;   liquid SO 2  storage of; and   liquid SO 3  storage of;   wherein an output of the first reactor is coupled to both an input of the second reactor and the liquid SO 2  storage, and an output of the sec reactor is coupled to both an input of the first reactor and the liquid SO 3  storage;   wherein a flow split of SO 2  and O 2  from the first reactor to the second reactor and the liquid SO 2  storage is variable, and a flow split of SO 3  from the second reactor to the first reactor and the liquid SO 3  storage is variable.   
     
     
         2 . The system of  claim 1  wherein the thermal source is a solar concentrator that focuses sunlight on a receiver to produce a temperature high enough to decompose SO 3  into SO 2 . 
     
     
         3 . The system of  claim 1  wherein at least one of the first reactor and the second reactor comprises a catalyst for converting SO 3  into SO 2  and O 2  or SO 2  and O 2  to produce SO 3 . 
     
     
         4 . The system of  claim 1  wherein the first reactor converts SO 3  into SO 2  and O 2  at a temperature in the range of 600 to 1200° C. 
     
     
         5 . The system of  claim 1  wherein the second reactor converts SO 2  and O 2  to produce SO 3  at a temperature below about 800° C. 
     
     
         6 . The system of  claim 1  further comprising an oxygen storage material that chemically binds and stores a substantial portion of O 2  produced by the first reactor converting SO 3  into SO 2  and O 2 . 
     
     
         7 . The system of  claim 1  wherein pressures in the first reactor and the second reactor are maintained in the range of 1 bar to 100 bar. 
     
     
         8 . The system of  claim 7  wherein the pressures are maintained in the range of 5 to 15 bar. 
     
     
         9 . The system of  claim 6  wherein at least one of the oxygen storage material and a temperature of the oxygen storage material is chosen to adsorb and release O 2  at an O 2  partial pressure in the range of 0.01 to 3 bar. 
     
     
         10 . The system of  claim 1 , further comprising:
 a first electrochemical cell being located downstream of the first reactor, the first electrochemical cell being exposed on one side to a process stream and on the other side to the ambient air, the first electrochemical cell removing O 2  formed by the first reactor from the process stream and pumps it into the ambient air; and   a second electrochemical cell being located upstream of the second reactor, the second electrochemical cell begin exposed on one side to the process stream and on the other side to the ambient air, the second electrochemical cell pumping O 2  from the ambient air into the process stream to be used by the second reactor.   
     
     
         11 . The system of  claim 1 , further comprising:
 a first electrochemical cell being located downstream of the first reactor, the first electrochemical cell being exposed on one side to a process stream and on the other side to a vessel containing an oxygen storage material; and   a second electrochemical cell being located upstream of the second reactor, the second electrochemical cell being exposed on one side to the process stream and on the other side to an other vessel containing an other oxygen storage material wherein:
 the first electrochemical cell removes O 2  formed decomposing SO 3  into SO 2  and O 2  from the process stream and pumps it into the vessel containing the oxygen storage material; 
 the second electrochemical cell pumps O 2  from the other vessel containing the other oxygen storage material into the process stream to be used in oxidizing SO 2  and O 2  to produce SO 3 . 
   
     
     
         12 . The system of  claim 1  wherein the first reactor includes an electrochemical cell that removes oxygen from the first reactor to allow a higher conversion of SO 3  to SO 2 . 
     
     
         13 . The system of  claim 1 , wherein the second reactor includes an electrochemical cell that produces electrical power from the conversion of SO 2  and O 2  to produce SO 3 . 
     
     
         14 . A method of transporting energy from a first location to a second location where the energy is used to generate steam for a steam turbine, the method comprising:
 converting the thermal energy at the first location to chemical energy in a first reactor by decomposing SO 3  into SO 2  and O 2 ;   converting the chemical energy to one of thermal energy or electrical energy in a second reactor at the second location by oxidizing SO 2  with O 2  to produce SO 3 ;   using stored SO 3  liquid for the first reactor and storing a portion of SO 2  from the first reactor as a liquid when more energy is available at the first location then is required at the second location; and   using stored SO 2  liquid for the second reactor and storing SO 3  liquid from the second reactor when more energy is needed at the second location then is available at the first location;   wherein using stored SO 3 , storing a portion of the SO 2 , using stored SO 2  liquid, and sorting SO 3  liquid comprise:
 controlling a flow split of SO 2  and O 2  from the first reactor to the second reactor and a liquid SO 2  storage; and 
   controlling a flow split of SO 3  from the second reactor to the first reactor and a liquid SO 3  storage.   
     
     
         15 . The method of  claim 14 , further comprising using a solar concentrator to focus sunlight on a receiver to produce a temperature high enough to decompose SO 3  into SO 2 . 
     
     
         16 . The method of  claim 14  wherein at least one of the first reactor and the second reactor comprise a catalyst for converting SO 3  into SO 2  and O 2  or SO 2  and O 2  to produce SO 3 . 
     
     
         17 . The method of  claim 14 , further comprising operating first reactor at a temperature in the range of 600 to 1200° C. 
     
     
         18 . The method of  claim 14 , further comprising operating second reactor at a temperature below about 800° C. 
     
     
         19 . The method of  claim 14 , further comprising chemically binding at least a portion of O 2  produced in the first reactor by the decomposition of SO 3  into SO 2  and O 2  in an oxygen storage material. 
     
     
         20 . The method of  claim 14 , further comprising maintaining pressures in the first reactor and the second rector are in the range of 1 to 100 bar. 
     
     
         21 . The method of  claim 20  wherein the pressures are maintained in the range of 5 to 15 bar. 
     
     
         22 . The method of  claim 14 , further comprising:
 pumping, with a first electrochemical cell, O 2  produced in the first reactor by the decomposition of SO 3  into SO 2  and O 2  to one of ambient air and a vessel containing an oxygen storage material;   pumping, with a second electrochemical cell, O 2  from one of the ambient air and another vessel containing another oxygen storage material to react with SO 2  in the second reactor to produce SO 3 .