Recovering the compression energy in gaseous hydrogen and oxygen generated from high-pressure water electrolysis

Abstract

Exemplary embodiments include an apparatus, and method associated therewith, for recovering the compression energy stored in hydrogen gas and oxygen gas generated by the electrolysis of water in a high-pressure water electrolyzer. The restored compression energy may be recovered and converted to a useable form to provide power to the high-pressure water electrolyzer, or alternatively to provide usable power to a coupled system that uses high-pressure hydrogen gas or oxygen gas such as a fuel cell for an electric vehicle, or both for use in providing power to the electrolyzer and to the fuel cell electric vehicle.

1 . A system comprising:
 a water electrolyzer including a water inlet and an oxygen gas outlet;   an oxygen gas expansion engine fluidically coupled to said oxygen gas outlet; and   an electrical generator coupled to said oxygen gas expansion engine and electrically coupled to said water electrolyzer.   
     
     
         2 . The system of  claim 1 , wherein high-pressure oxygen gas produced in said water electrolyzer is expanded within said oxygen gas expansion engine to drive said electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer. 
     
     
         3 . The system of  claim 1  further comprising an oxygen gas storage tank fluidically coupled to and between said oxygen gas outlet and said oxygen gas expansion engine. 
     
     
         4 . The system of  claim 1  further comprising a hydrogen gas expansion engine fluidically coupled to a hydrogen gas outlet on said high-pressure water electrolyzer, said hydrogen gas expansion engine also being coupled to said electrical generator. 
     
     
         5 . The system of  claim 4 , wherein high-pressure hydrogen gas produced in said water electrolyzer is expanded within said hydrogen gas expansion engine to drive said electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer. 
     
     
         6 . The system of  claim 1  further comprising:
 a hydrogen gas expansion engine fluidically coupled to said hydrogen gas outlet; and
 a second electrical generator coupled to said hydrogen gas expansion engine and electrically coupled to said water electrolyzer. 
   
     
     
         7 . The system of  claim 6 , wherein high-pressure hydrogen gas produced in said water electrolyzer is expanded within said hydrogen gas expansion engine to drive said second electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer. 
     
     
         8 . The system of  claim 1  further comprising a hydrogen gas storage tank fluidically coupled to and between said hydrogen gas outlet and said hydrogen gas expansion engine. 
     
     
         9 . The system of  claim 8  further comprising:
 a fuel cell electric vehicle fluidically coupled to said hydrogen gas storage tank.   
     
     
         10 . A system comprising:
 a water electrolyzer including a water inlet and a hydrogen gas outlet;   a hydrogen gas expansion engine fluidically coupled to said hydrogen gas outlet; and   an electrical generator coupled to said hydrogen gas expansion engine and electrically coupled to said water electrolyzer.   
     
     
         11 . The system of  claim 10 , wherein high-pressure hydrogen gas produced in said water electrolyzer is expanded within said hydrogen gas expansion engine to drive said electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer. 
     
     
         12 . The system of  claim 10  further comprising a hydrogen gas storage tank fluidically coupled to and between said hydrogen gas outlet and said hydrogen gas expansion engine. 
     
     
         13 . The system of  claim 10  further comprising:
 a fuel cell electric vehicle fluidically coupled to said hydrogen gas storage tank.   
     
     
         14 . A system comprising:
 a water electrolyzer for converting water to a high-pressure gas;   a gas storage tank coupled to said water electrolyzer;   a gas expansion engine fluidically coupled to said gas storage tank; and   an electrical generator coupled to said gas expansion engine and electrically coupled to said water electrolyzer, wherein said high-pressure gas produced in said water electrolyzer is expanded within said gas expansion engine to drive said electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer.   
     
     
         15 . The system of  claim 14 , wherein said high-pressure gas comprises high-pressure hydrogen gas and high-pressure oxygen gas. 
     
     
         16 . The system of  claim 15 , wherein said high-pressure hydrogen gas exits said water electrolyzer through a hydrogen gas outlet to a hydrogen gas storage tank, said hydrogen gas storage tank being coupled to a hydrogen gas expansion engine that is electrically coupled to said electrical generator, wherein said high-pressure hydrogen gas is expanded within said hydrogen gas expansion engine to drive said electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer. 
     
     
         17 . The system of  claim 15 , wherein said high-pressure oxygen gas exits said water electrolyzer through an oxygen gas outlet to an oxygen gas storage tank, said oxygen gas storage tank being coupled to an oxygen gas expansion engine that is electrically coupled to said electrical generator, wherein said high-pressure oxygen gas is expanded within said oxygen gas expansion engine to drive said electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said water electrolyzer. 
     
     
         18 . The system of  claim 16  further comprising:
 a fuel cell electric vehicle coupled to said hydrogen gas storage tank, said fuel cell electric vehicle including a fuel cell hydrogen gas storage tank, a fuel cell hydrogen gas expansion engine and a fuel cell;   wherein high-pressure hydrogen gas contained within said hydrogen gas storage tank may be delivered to said fuel cell hydrogen gas storage tank and expanded with said hydrogen gas expansion engine to provide a quantity of hydrogen gas to said fuel cell.   
     
     
         19 . The system of  claim 18 , wherein said fuel cell electric vehicle further comprises an electrical generator coupled to said fuel cell hydrogen gas expansion engine, wherein said high-pressure hydrogen gas is expanded within said fuel cell hydrogen gas expansion engine to drive said fuel cell electrical generator to produce electricity, said produced electricity thereafter used to aid in powering said fuel cell electric vehicle. 
     
     
         20 . The system of  claim 19  further comprising:
 an electric traction motor coupled to said fuel cell, said electric traction motor aiding in propelling said fuel cell electric vehicle.   
     
     
         21 . The system of  claim 20  further comprising a fuel cell electrical generator electrically coupled to said electric traction motor, wherein a portion of said electricity is used to aid in driving said electric traction motor. 
     
     
         22 . The system of  claim 18 , wherein a portion of the mechanical energy produced by expanding said high-pressure hydrogen gas within said fuel cell hydrogen gas expansion engine is used to propel said fuel cell electric vehicle. 
     
     
         23 . A method for partially powering a high-pressure water electrolyzer, the method comprising:
 providing a high-pressure water electrolyzer having a water inlet and a gas outlet;   coupling said gas outlet to a gas expansion engine;   coupling said gas expansion engine to an electrical generator;   electrically coupling said electrical generator to said high-pressure water electrolyzer;   introducing a quantity of water within said high-pressure water electrolyzer;   generating a quantity of high-pressure gas from said quantity of water within said high-pressure water electrolyzer;   introducing a portion of said high-pressure gas to said gas expansion engine; and   expanding said portion of high-pressure gas within said gas expansion engine, wherein the expansion of said high-pressure gas drives said electrical generator to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water.   
     
     
         24 . The method of  claim 23 , wherein generating a quantity of high-pressure gas, introducing a portion of high-pressure gas, and expanding said portion of high-pressure gas comprises:
 generating a quantity of high-pressure hydrogen gas from said quantity of water within said high-pressure water electrolyzer; introducing a portion of said high-pressure hydrogen gas to a hydrogen gas expansion engine through a hydrogen gas outlet; and expanding said portion of said high hydrogen pressure gas within said hydrogen gas expansion engine, wherein the expansion of said high-pressure hydrogen gas drives said electrical generator to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water.   
     
     
         25 . The method of  claim 24 , wherein generating a quantity of high-pressure gas, introducing a portion of high-pressure gas, and expanding said portion of high-pressure gas further comprises: generating a quantity of high-pressure oxygen gas from said quantity of water within said high-pressure water electrolyzer; introducing a portion of said high-pressure oxygen gas to an oxygen gas expansion engine through an oxygen gas outlet; and
 expanding said portion of high-pressure oxygen gas within said oxygen gas expansion engine, wherein the expansion of said high-pressure oxygen gas drives said electrical generator to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water.   
     
     
         26 . The method of  claim 25 , wherein said electrical generator comprises a pair of electrical generators, one of said pair of electrical generators being coupled to said hydrogen gas expansion engine and the other of said pair of electrical generators being coupled to said oxygen gas expansion engine;
 wherein the expansion of said high-pressure hydrogen gas drives said one of said pair of electrical generators to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water; and   wherein the expansion of said high-pressure oxygen gas drives said other of said pair of electrical generators to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water.   
     
     
         27 . The method of  claim 24 , wherein generating a quantity of high-pressure gas, introducing a portion of high-pressure gas, and expanding said portion of high-pressure gas comprises:
 generating a quantity of high-pressure oxygen gas from said quantity of water within said high-pressure water electrolyzer;   introducing a portion of said high-pressure oxygen gas to said oxygen gas expansion engine through an oxygen gas outlet; and   expanding said portion of high-pressure oxygen gas within said oxygen gas expansion engine, wherein the expansion of said high-pressure oxygen gas drives said electrical generator to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water.   
     
     
         28 . The method of  claim 24  further comprising:
 coupling a high-pressure hydrogen storage tank between said hydrogen gas outlet and said hydrogen gas expansion engine.   
     
     
         29 . The method of  claim 28  further comprising:
 coupling said hydrogen gas expansion engine to a fuel cell hydrogen gas storage tank on a fuel cell electric vehicle having a fuel cell;
 introducing a quantity of said high-pressure hydrogen gas from said high-pressure hydrogen gas storage tank through said hydrogen gas expansion engine to said fuel cell hydrogen gas storage tank to achieve a first hydrogen gas pressure within said fuel cell hydrogen gas storage tank; 
 wherein the introduction of said quantity of high-pressure hydrogen gas to said fuel cell hydrogen gas storage tank is accomplished by first expanding said quantity of high-pressure hydrogen gas within said hydrogen gas expansion engine, therein driving said electrical generator to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water. 
   
     
     
         30 . The method of  claim 29 , further comprising:
 releasing a first portion of said quantity of hydrogen gas from said fuel cell hydrogen gas storage tank to said fuel cell; and   substantially simultaneously introducing a corresponding portion of said high-pressure hydrogen gas from said high-pressure hydrogen gas storage tank through said hydrogen gas expansion engine to said fuel cell hydrogen gas storage tank to maintain said first hydrogen gas pressure within said fuel cell hydrogen gas storage tank;   wherein the introduction of said corresponding portion of said high-pressure hydrogen gas to said fuel cell hydrogen gas storage tank is accomplished by first expanding said corresponding portion of high-pressure hydrogen gas within said hydrogen gas expansion engine, therein driving said electrical generator to produce electricity, wherein said electricity is introduced to said high-pressure water electrolyzer to partially drive said generation of high-pressure gas from said quantity of water.   
     
     
         31 . The method of  claim 30 , wherein releasing a first portion of said quantity of hydrogen gas from said fuel cell hydrogen gas storage tank to said fuel cell further comprises:
 expanding said first portion of said quantity of hydrogen gas within a fuel cell hydrogen gas expansion engine; and   introducing at least a portion of said first portion of said quantity of hydrogen gas with a hydrogen gas inlet on said fuel cell.   
     
     
         32 . The method of  claim 31 , wherein the expansion of said first portion of said hydrogen gas within said fuel cell hydrogen gas expansion engines drives a fuel cell electrical generator to produce electricity, wherein said electricity is used to power said fuel cell electric vehicle. 
     
     
         33 . The method of  claim 32 , wherein said electricity may also be used to power one or more vehicle components on said fuel cell electric vehicle. 
     
     
         34 . The method of  claim 31 , wherein the expansion of said first portion of said hydrogen gas within said fuel cell hydrogen gas expansion engines is converted to mechanical energy to propel said fuel cell electric vehicle.