Methods and systems for rebalancing electrolytes for a redox flow battery system

Abstract

A rebalancing reactor for a redox flow battery system may include a first side through which hydrogen gas is flowed, a second side through which electrolyte from the redox flow battery system is flowed, and a porous layer separating and fluidly coupled to the first side and the second side, wherein, the hydrogen gas and the electrolyte are fluidly contacted at a surface of the porous layer, and a pressure drop across the second side is less than a pressure drop across the porous layer. In this way, rebalancing of electrolyte charges in a redox flow battery system may be performed with increased efficiency and cost effectiveness as compared to conventional rebalancing reactors.

1 . An electrolyte rebalancing reactor fluidly coupled to a redox flow battery, comprising:
 a first side through which a hydrogen gas is flowed without flowing an electrolyte from the redox flow battery,   a second side through which the electrolyte from the redox flow battery is flowed, and   a porous layer separating and fluidly coupled to the first side and the second side, wherein   the hydrogen gas and the electrolyte are fluidly contacted at a surface of the porous layer to facilitate an electrolyte rebalancing reaction at the surface of the porous layer, and   the porous layer is ionically conductive and electrically conductive, whereby an internal electric current is conducted through the porous layer to drive the electrolyte rebalancing reaction.   
     
     
         2 . The electrolyte rebalancing reactor of  claim 1 , wherein the electrolyte rebalancing reaction includes reduction of metal ions in the electrolyte and oxidation of the hydrogen gas at the surface of the porous layer. 
     
     
         3 . The electrolyte rebalancing reactor of  claim 2 , wherein the internal electric current is generated from the oxidation of the hydrogen gas at the surface of the porous layer. 
     
     
         4 . The electrolyte rebalancing reactor of  claim 1 , wherein the internal electric current includes current flowing through the porous layer to the second side. 
     
     
         5 . The electrolyte rebalancing reactor of  claim 3 , further comprising a negative electrode fluidly coupled to the first side and the porous layer, wherein an external current applied at the negative electrode and the internal electric current drive the electrolyte rebalancing reaction. 
     
     
         6 . The electrolyte rebalancing reactor of  claim 5 , wherein the porous layer includes the negative electrode integrated with the porous layer. 
     
     
         7 . The electrolyte rebalancing reactor of  claim 1 , further comprising an ejector fluidly coupled between an outlet of the first side and the redox flow battery, wherein the electrolyte exiting from the second side flows through the ejector thereby drawing the hydrogen gas exiting the first side through the ejector. 
     
     
         8 . A method of operating a rebalancing reactor fluidly coupled to a redox flow battery, including:
 flowing a hydrogen gas through a first side of the rebalancing reactor,   flowing an electrolyte from the redox flow battery through a second side of the rebalancing reactor without flowing the electrolyte from the redox flow battery through the first side of the rebalancing reactor,   interposing a porous layer between the first side and the second side, the porous layer separating and fluidly coupled to the first side and the second side, wherein the porous layer is ionically conductive and electrically conductive,   fluidly contacting the hydrogen gas and the electrolyte at a surface of the porous layer to facilitate an electrolyte rebalancing reaction at the surface of the porous layer, and   conducting an internal electric current through the porous layer to drive the electrolyte rebalancing reaction.   
     
     
         9 . The method of  claim 8 , wherein fluidly contacting the hydrogen gas and the electrolyte at the surface of the porous layer to facilitate the electrolyte rebalancing reaction includes, at the surface of the porous layer, reducing metal ions in the electrolyte and oxidizing the hydrogen gas. 
     
     
         10 . The method of  claim 9 , wherein the internal electric current is generated from the oxidizing of the hydrogen gas at the surface of the porous layer. 
     
     
         11 . The method of  claim 10 , wherein conducting the internal electric current includes conducting electrons from the first side through the porous layer to the second side. 
     
     
         12 . The method of  claim 11 , wherein the first side extends from a hydrogen inlet to a hydrogen outlet and the second side extends from an electrolyte inlet to an electrolyte outlet, the method further comprising maintaining a pressure difference between the hydrogen inlet and the hydrogen outlet greater than a pressure difference between the electrolyte inlet and the electrolyte outlet. 
     
     
         13 . The method of  claim 12 , further comprising, maintaining the pressure difference between the hydrogen inlet and the hydrogen outlet greater than the pressure difference between the electrolyte inlet and the electrolyte outlet. 
     
     
         14 . The method of  claim 12 , further comprising, maintaining a pressure difference across the porous layer greater than the pressure difference between the electrolyte inlet and the electrolyte outlet. 
     
     
         15 . The method of  claim 14 , further comprising, maintaining the pressure difference between the electrolyte inlet and the electrolyte outlet less than a bubble pressure of the porous layer. 
     
     
         16 . A redox flow battery system including,
 a plurality of redox flow battery cells, and   a first rebalancing reactor fluidly coupled to a second rebalancing reactor, each of the first and second rebalancing reactors including,   a first side through which a hydrogen gas is flowed without flowing an electrolyte from the plurality of redox flow battery cells,   a second side through which the electrolyte from the plurality of redox flow battery cells is flowed, and   a porous layer separating and fluidly coupled to the first side and the second side, wherein,   the hydrogen gas and the electrolyte are fluidly contacted at a surface of the porous layer to facilitate an electrolyte rebalancing reaction at the surface of the porous layer, and   the porous layer is ionically conductive and electrically conductive, whereby an internal electric current is conducted through the porous layer to drive the electrolyte rebalancing reaction.   
     
     
         17 . The redox flow battery system of  claim 16 , wherein the porous layer further comprises a positive electrode. 
     
     
         18 . The redox flow battery system of  claim 16 , wherein the surface of the porous layer includes a hydrophilic carbonaceous surface. 
     
     
         19 . The redox flow battery system of  claim 18 , further comprising a controller, with executable instructions stored in memory thereon to, maintain a pressure drop across the electrolyte inlet and the electrolyte outlet less than a pressure drop across the porous layer by more than a threshold pressure difference. 
     
     
         20 . The redox flow battery system of  claim 19 , wherein the controller further comprises executable instructions stored in memory thereon to, responsive to the pressure drop across the second side of the first rebalancing reactor being less than the pressure drop across the porous layer by less than the threshold pressure difference, redirect a portion of a flow of the electrolyte from the first rebalancing reactor to the second rebalancing reactor.