Methods and system for redox flow battery idle state

Abstract

Methods and systems are provided for a redox flow battery system. In one example, a method of operating a redox flow battery system includes, responsive to switching the redox flow battery system to an idle mode, initiating a first timer monitoring a first threshold period of time. An electrolyte pump may be activated when the first threshold period of time elapses, the electrolyte pump driving circulation of electrolytes through one or more electrode compartments.

1 . A method of operating a redox flow battery system, the method comprising:
 responsive to switching the redox flow battery system to an idle mode, wherein the idle mode includes operation of the redox flow battery system outside of a charging mode and outside of a discharging mode,
 initiating an off cycle timer monitoring an off cycle threshold period of time; 
 activating an electrolyte pump in response to elapsing of the off cycle threshold period of time to circulate electrolytes through one or more electrode compartments. 
   
     
     
         2 . The method of  claim 1 , wherein a drain timer is initiated concurrent with the off cycle timer and an on cycle timer is initiated after the off cycle threshold period of time elapses, and wherein the on cycle timer measures an on cycle threshold period of time for circulating the electrolytes and the drain timer monitors a drain threshold period of time. 
     
     
         3 . The method of  claim 2 , wherein the drain threshold period of time is longer than the off cycle threshold period of time. 
     
     
         4 . The method of  claim 2 , further comprising completely draining electrolytes from one or more electrode compartments of the redox flow battery system, purging the one or more electrode compartments with a gas, and refilling the one or more electrode compartments with fresh electrolytes when the drain threshold period of time elapses. 
     
     
         5 . The method of  claim 4 , wherein a vacuum is generated in the one or more electrode compartments when the one or more electrode compartments are drained, and wherein the vacuum draws the gas into the one or more electrode compartments to purge the one or more electrode compartments. 
     
     
         6 . The method of  claim 4 , wherein when elapsing of the off cycle threshold period of time is concurrent with elapsing of the drain threshold period of time, the draining of the electrolytes from the one or more electrode compartments is prioritized over activation of the electrolyte pump. 
     
     
         7 . The method of  claim 4 , further comprising, in response to maintaining the redox flow battery system in the idle mode after the drain threshold period of time has elapsed and the one or more electrode compartments are refilled with the fresh electrolytes, initiating the off cycle timer again. 
     
     
         8 . The method of  claim 4 , wherein the electrolytes are drained from the one or more electrode compartments by opening a drain valve of the one or more electrode compartments. 
     
     
         9 . The method of  claim 8 , wherein the drain valve is closed when the one or more electrode compartments are purged with the gas, and wherein the gas is hydrogen or argon. 
     
     
         10 . A method for a redox flow battery system, comprising:
 responsive to operation of the redox flow battery system in an idle mode,   cycling an electrolyte pump between an off interval and an on interval, the off interval having a duration corresponding to an off threshold period of time and the on interval having a duration corresponding to an on threshold period of time, wherein electrolytes are circulated through one or more electrode compartments during the on interval.   
     
     
         11 . The method of  claim 10 , wherein the off threshold period of time is longer than the on threshold period of time. 
     
     
         12 . The method of  claim 10 , wherein the off threshold period of time is adjusted based on a power module voltage of the redox flow battery system, and wherein the off threshold period of time is increased when the power module voltage is increased and decreased when the power module voltage is decreased. 
     
     
         13 . The method of  claim 10 , wherein the electrolytes are circulated through the one or more electrode compartments during the on interval at an idle threshold flow rate, and wherein the idle threshold flow rate is lower than a charge or discharge threshold flow rate. 
     
     
         14 . The method of  claim 10 , wherein the duration of the off threshold period of time is decreased when anticipated power demands are increased and the duration of the off threshold period of time is increased when the anticipated power demands are decreased. 
     
     
         15 . The method of  claim 10 , further comprising monitoring a drain threshold period of time, the drain threshold period of time initiated concurrently with initiation of the off threshold period of time, and wherein when the drain threshold period of time elapses, the one or more electrode compartments are drained, purged, and refilled. 
     
     
         16 . The method of  claim 15 , wherein the drain threshold period of time is longer than the off threshold period of time. 
     
     
         17 . The method of  claim 15 , wherein the drain threshold period of time is longer than the off threshold period of time and the on threshold period of time combined. 
     
     
         18 . The method of  claim 15 , wherein the drain threshold period of time is a duration of time before a pH of the electrolytes in the one or more electrode compartments rises and causes formation of iron hydroxide. 
     
     
         19 . The method of  claim 15 , wherein the drain threshold period of time is a duration of time where a likelihood of reduced battery performance is increased due to accumulation of iron hydroxide. 
     
     
         20 . The method of  claim 15 , wherein the one or more electrode compartments are refilled with the electrolytes from an electrolyte storage tank or at least one rebalancing reactor.