Water management system in electrochemical cells with vapor return comprising air electrodes

Abstract

A system and methods for managing water content in one or more electrochemical cell is disclosed. The system includes a gas-phase conduit for receiving humid gas-phase associated with the electrochemical cell, a desiccator unit connected to each electrochemical cell and configured for extracting water from the humid gas-phase, a heater for selectively heating the desiccator unit, and a carbon dioxide (CO2) scrubber connected to the desiccator unit. The system may capture water vapor at the desiccator unit from a humid gas-phase exiting electrochemical cell, or release water vapor in desiccator unit, via actuation of heater, that is transported into the electrochemical cell depending on the mode of operation. The CO2 scrubber may also be used to capture water vapor, based on the mode of operation.

What is claimed: 
     
         1 . A system for managing water content in one or more electrochemical cells, each electrochemical cell comprising a plurality of electrodes, a gaseous oxidant inlet for receiving gaseous oxidant, and a liquid ionically conductive medium, the system comprising:
 a desiccator unit having an input connected to the one or more electrochemical cells, the desiccator unit being configured for extracting and capturing water from a humid gas-phase exiting from the one or more electrochemical cells;   a heater for selectively heating the desiccator unit to selectively release captured water from the desiccator unit to provide an output humid gas-phase through an output; and   a carbon dioxide scrubber configured to absorb carbon dioxide, the carbon dioxide scrubber being provided subsequent to the desiccator unit and in advance of each inlet of the one or more electrochemical cells,   wherein the desiccator unit and the carbon dioxide scrubber are configured to be selectively coupled in a scrubber humidification mode to deliver at least part of the output humid gas-phase from the desiccator unit to the carbon dioxide scrubber, and   wherein, during a cell discharge mode, the system is configured to transport ambient gaseous oxidant through the carbon dioxide scrubber to the gaseous oxidant inlet of the one or more electrochemical cells, thereby facilitating management of humidity and carbon dioxide concentration of the gaseous oxidant.   
     
     
         2 . The system of  claim 1 , wherein the plurality of electrodes of each electrochemical cell in the system comprises a fuel electrode and an oxidant reduction electrode, wherein each cell comprises a gaseous oxidant receiving space, wherein the oxidant reduction electrode of each cell has one surface facing the ionically conductive medium and an opposite surface facing the gaseous oxidant receiving space, and wherein each cell further comprises a gaseous oxidant outlet connecting through the gaseous oxidant receiving space with the gaseous oxidant inlet, thereby allowing transport of gas into and out of the gaseous oxidant receiving space. 
     
     
         3 . The system according to  claim 1 , wherein the carbon dioxide scrubber is connected in series with the desiccator unit. 
     
     
         4 . The system according to  claim 1 , wherein the ambient gaseous oxidant bypasses the desiccator unit in the cell discharge mode. 
     
     
         5 . The system according to  claim 1 , wherein, during a water capture mode, the system is configured to extract and capture water at the desiccator unit from the humid gas-phase exiting from the one or more electrochemical cells; and
 wherein, during a cell humidification mode, the system is configured to release at least a portion of the captured water in the desiccator unit, via actuation of the heater, to produce the output humid gas-phase that is transported into the one or more electrochemical cells.   
     
     
         6 . The system according to  claim 5 , wherein the water capture mode occurs simultaneously with the cell discharge mode, and/or wherein the cell humidification mode occurs simultaneously with a cell charge mode, a cell idle mode, the cell discharge mode or a combination thereof. 
     
     
         7 . The system according to  claim 1 , further comprising a level sensor associated with the one or more electrochemical cells, wherein the level sensor is coupled to the heater, and wherein the level sensor activates the heater to release the captured water from the desiccator unit. 
     
     
         8 . The system according to  claim 1 , further comprising a fan for transporting a flow of oxidant and/or the output humid-gas phase through the one or more electrochemical cells. 
     
     
         9 . The system according to  claim 2 , further comprising at least one fan associated with the one or more electrochemical cells for creating a flow of oxidant and/or the output humid-gas phase into the gaseous oxidant receiving space. 
     
     
         10 . The system according to  claim 2 , wherein the relative humidity of the humid gas-phase transported through the gaseous oxidant inlet into the gaseous oxidant receiving space is greater than 50%. 
     
     
         11 . The system according to  claim 1 , wherein during the scrubber humidification mode, the output humid gas-phase delivered to the carbon dioxide scrubber pre-wets the carbon dioxide scrubber. 
     
     
         12 . The system according to  claim 11 , wherein the output humid gas-phase is communicated from the desiccator unit to the carbon dioxide scrubber via an open conduit. 
     
     
         13 . The system according to  claim 11 , wherein the output humid gas-phase is communicated to the carbon dioxide scrubber via a liquid water reservoir, the liquid water reservoir configured to collect water exiting the desiccator unit for delivery to the carbon dioxide scrubber. 
     
     
         14 . The system according to  claim 11 , wherein the scrubber humidification mode occurs during a cell idle mode and/or when external grid power is available. 
     
     
         15 . The system according to  claim 1 , wherein the carbon dioxide scrubber comprises materials selected from the group of soda lime, sodium hydroxide, potassium hydroxide, and lithium hydroxide, lithium peroxide, calcium oxide, calcium carbonate, serpentinite, magnesium silicate, magnesium hydroxide, olivine, molecular sieves, amines, monoethanolamine, and combinations thereof. 
     
     
         16 . A method for managing water content in a system comprising one or more electrochemical cells, each electrochemical cell comprising a plurality of electrodes, a gaseous oxidant inlet for receiving gaseous oxidant, and a liquid ionically conductive medium, the system further comprising a desiccator unit and a carbon dioxide scrubber, the method comprising:
 (i) in a scrubber humidification mode:   selectively communicatively coupling the carbon dioxide scrubber to the desiccator unit;   absorbing carbon dioxide from humid air received from the desiccator unit using the carbon dioxide scrubber; and   directing the humid air from the carbon dioxide scrubber to the ionically conductive medium of the one or more electrochemical cells via the gaseous oxidant inlet; and   (ii) in a cell discharge mode:   absorbing carbon dioxide from an outside, atmospheric air using the carbon dioxide scrubber;   directing output air from the carbon dioxide scrubber to the ionically conductive medium via the gaseous oxidant inlet of the one or more electrochemical cells.   
     
     
         17 . The method according to  claim 16 , wherein the cell discharge mode further comprises inputting air from the outside, atmospheric source to the carbon dioxide scrubber. 
     
     
         18 . The method according to  claim 16 , wherein the one or more electrochemical cells have a fan associated therewith, and wherein the method further comprises:
 using the fan for transporting a flow of oxidant and/or the humid air through the one or more electrochemical cells.   
     
     
         19 . The method according to  claim 16 , further comprising:
 selectively collecting water exiting the desiccator unit using a liquid water reservoir, and   selectively delivering water to the carbon dioxide scrubber via the liquid water reservoir.   
     
     
         20 . The method according to  claim 16 , wherein the carbon dioxide scrubber is connected in series with the desiccator unit. 
     
     
         21 . The method according to  claim 16 , wherein, in the cell discharge mode, the atmospheric air bypasses the desiccator unit. 
     
     
         22 . The method according to  claim 16 , further comprising:
 a water capture mode, comprising receiving humid air from the one or more electrochemical cells in the desiccator unit and extracting and capturing water from the humid air exiting from the one or more electrochemical cells; and   a cell humidification mode, comprising releasing at least a portion of the captured water in the desiccator unit, via actuation of the heater, to produce output humid air that is transported into the one or more electrochemical cells.   
     
     
         23 . The method according to  claim 22 , wherein the water capture mode occurs simultaneously with the cell discharge mode, and/or wherein the cell humidification mode occurs simultaneously with a cell charge mode, a cell idle mode, the cell discharge mode or a combination thereof. 
     
     
         24 . The method according to  claim 22 , wherein the system further comprises a level sensor associated with the one or more electrochemical cells that senses a level of the ionically conductive medium, and wherein the method comprises:
 determining when the level of the ionically conductive medium is below a predetermined lower limit, and causing the one or more electrochemical cells to enter the cell humidification mod; and/or   determining that the level of the ionically conductive medium is greater than a predetermined upper limit, and causing the one or more electrochemical cells to enter the water capture mode; and/or   selectively activating the heater to release the captured water from the desiccator unit, the level sensor being coupled to the heater.   
     
     
         25 . The method according to  claim 16 , wherein the system further comprises at least one fan, and the method further comprising:
 transporting a flow of air through the one or more electrochemical cells using the at least one fan.