Fuell cell system and operation method of fuel cells

Abstract

A fuel cell system of the invention includes: fuel cells that receive supplies of predetermined gases to generate electric power; and a humidifier that humidifies at least one of the predetermined gases supplied to the fuel cells with water content included in the exhaust gas discharged from the fuel cells. The fuel cell system further has: an exhaust water content detection module that detects an exhaust water content, which is included in the exhaust gas and is discharged downstream the humidifier; and a regulation module that, in response to detection of the exhaust water content of not lower than a preset level, restricts the exhaust water content discharged downstream the humidifier. This technique of the invention ensures adequate humidification control.

1 . A fuel cell system including fuel cells that receive supplies of predetermined gases to generate electric power, 
 said fuel cell system further comprising:    a humidifier that is provided in a flow path of an exhaust gas from the fuel cells and humidifies at least one of the predetermined gases supplied to the fuel cells with water content included in the exhaust gas discharged from the fuel cells;    an exhaust water content detection module that detects an exhaust water content, which is included in the exhaust gas and is discharged downstream the humidifier; and    a regulation module that, in response to detection of the exhaust water content of not lower than a preset level, restricts the exhaust water content discharged downstream the humidifier.    
     
     
         2 . A fuel cell system in accordance with  claim 1 , wherein the exhaust water content detection module detects the exhaust water content by measurement of a physical quantity affecting the exhaust water content.  
     
     
         3 . A fuel cell system in accordance with  claim 2 , wherein the exhaust water content detection module is a pressure sensor that measures atmospheric pressure as the physical quantity, and 
 the regulation module determines that the exhaust water content is not lower than the preset level, when the measured atmospheric pressure is not higher than a preset reference pressure.    
     
     
         4 . A fuel cell system in accordance with  claim 2 , wherein the exhaust water content detection module is a temperature sensor that measures temperature of the exhaust gas at an outlet of the fuel cells as the physical quantity, and 
 the regulation module determines that the exhaust water content is not lower than the preset level, when the measured temperature is not lower than a preset reference temperature.    
     
     
         5 . A fuel cell system in accordance with  claim 2 , wherein the exhaust water content detection module is a flow rate sensor that measures a flow rate of the exhaust gas from the fuel cells as the physical quantity, and 
 the regulation module determines that the exhaust water content is not lower than the preset level, when the measured flow rate is not lower than a preset reference value.    
     
     
         6 . A fuel cell system in accordance with  claim 2 , wherein the regulation module comprises: 
 a downstream pressure regulator that is located downstream the humidifier in the flow path of the exhaust gas to regulate pressure of the exhaust gas and accordingly regulate internal pressure of the supplied gas in the fuel cells, and    the regulation module activates the downstream pressure regulator to perform pressure regulation for restriction of the exhaust water content discharged downstream the humidifier.    
     
     
         7 . A fuel cell system in accordance with  claim 6 , wherein the regulation module further comprises: 
 an upstream pressure regulator that is located upstream the humidifier in the flow path of the exhaust gas to regulate the pressure of the exhaust gas and accordingly regulate the internal pressure of the supplied gas in the fuel cells, and    the regulation module activates the upstream pressure regulator to perform the pressure regulation, instead of the pressure regulation by the downstream pressure regulation, in response to detection of the exhaust water content of lower than the preset level.    
     
     
         8 . A fuel cell system in accordance with  claim 7 , said fuel cell system further comprising: 
 a humidification demand estimation module that estimates a humidification demand corresponding to a state of power generation by the fuel cells,    wherein when the estimated humidification demand is not higher than a specified level, the regulation module activates the upstream pressure regulator to perform the pressure regulation, irrespective of detection of the exhaust water content of lower than or not lower than the preset level.    
     
     
         9 . A fuel cell system including fuel cells that receive supplies of predetermined gases to generate electric power, 
 said fuel cell system further comprising:    a humidifier that is provided in a flow path of an exhaust gas from the fuel cells and humidifies at least one of the predetermined gases supplied to the fuel cells with water content included in the exhaust gas discharged from the fuel cells;    a decision module that identifies satisfaction or dissatisfaction of a condition for increasing an exhaust water content, which is included in the exhaust gas and is discharged downstream the humidifier, based on a state quantity of the exhaust gas; and    a pressure increase module that, upon satisfaction of the condition for increasing the exhaust water content, increases pressure of the exhaust gas in the humidifier to enhance a humidification efficiency of the humidifier.    
     
     
         10 . A fuel cell system in accordance with  claim 9 , wherein the decision module identifies satisfaction or dissatisfaction of the condition, based on any one of pressure, temperature, and flow rate of the exhaust gas in the humidifier.  
     
     
         11 . A fuel cell system in accordance with  claim 9 , wherein the pressure increase module has a pressure regulator located downstream the humidifier and controls the pressure regulator to increase the pressure.  
     
     
         12 . An operation method of fuel cells that receive supplies of predetermined gases to generate electric power, 
 said operation method comprising the steps of:    activating a humidifier that is provided in a flow path of an exhaust gas from the fuel cells to humidify at least one of the predetermined gases supplied to the fuel cells with water content included in the exhaust gas discharged from the fuel cells;    detecting an exhaust water content, which is included in the exhaust gas and is discharged downstream the humidifier; and    in response to detection of the exhaust water content, restricting the exhaust water content discharged downstream the humidifier to be not lower than a preset level.    
     
     
         13 . An operation method of fuel cells that receive supplies of predetermined gases to generate electric power, 
 said operation method comprising the steps of:    activating a humidifier that is provided in a flow path of an exhaust gas from the fuel cells to humidify at least one of the predetermined gases supplied to the fuel cells with water content included in the exhaust gas discharged from the fuel cells;    identifying satisfaction or dissatisfaction of a condition for increasing an exhaust water content, which is included in the exhaust gas and is discharged downstream the humidifier, based on a state quantity of the exhaust gas; and    upon satisfaction of the condition for increasing the exhaust water content, increasing pressure of the exhaust gas in the humidifier to enhance a humidification efficiency of the humidifier.    
     
     
         14 . A fuel cell system including fuel cells that receive a supply of hydrogen gas as a fuel gas and a supply of the air as an oxidizing gas to generate electric power, 
 said fuel cell system further comprising:    a humidifier that is provided in a flow path of an exhaust gas in an air system from the fuel cells and humidifies the air supplied to the fuel cells with water content included in the exhaust gas discharged from the fuel cells;    a sensor that detects at least one of atmospheric pressure, temperature of the exhaust gas, and flow rate of the exhaust gas as a physical quantity corresponding to a variation in exhaust water content, which is included in the exhaust gas and is discharged downstream the humidifier; and    a pressure regulator that is located downstream the humidifier and, in response to detection of the exhaust water content of not lower than a preset level by the sensor, restricts the flow path of the exhaust gas to increase pressure of the exhaust gas in the humidifier.