Fuel cell system

Abstract

The fuel cell system includes a humidifying unit for humidifying supply air to be supplied to the fuel cell, utilizing cooling water used for cooling the fuel cell. It also includes a pre-humidifying unit for humidifying the supply air beforehand with air discharged from the fuel cell, the pre-humidifying unit being positioned in the upstream of the humidifying unit within a supply air path. The cooling water, which recovered heat generated when the fuel cell generated electricity, releases heat in a cooling water heat radiator. The heat is then utilized for heating water which circulates in a hot water path and the hot water is stored in a hot water reserve tank.

What is claimed is:  
     
         1 . A fuel cell system comprising a fuel cell for generating electricity by use of fuel gas and oxidizing gas, a first humidifying portion and second humidifying portion which sequentially humidify at least one of supply fuel gas and supply oxidizing gas, said supply fuel gas being fuel gas to be supplied to the fuel cell, said supply oxidizing gas being oxidizing gas to be supplied to the fuel cell, 
 wherein the first humidifying portion performs said humidification by use of moisture contained in at least one of exhaust fuel gas and exhaust oxidizing gas, said exhaust fuel gas being fuel gas discharged from the fuel cell, said exhaust oxidizing gas being oxidizing gas discharged from the fuel cell, and the second humidifying portion performs said humidification by use of hot water.    
     
     
         2 . The fuel cell system according to  claim 1  further comprising a cooling system for allowing cooling water to flow in the fuel cell, 
 wherein said hot water is the flowing cooling water.  
 
     
     
         3 . The fuel cell system according to  claim 1  further comprising a heat-storage portion for storing at least one part of the heat which has been recovered from the fuel cell by the cooling water.  
     
     
         4 . The fuel cell system according to  claim 3 , wherein said heat-storage portion has a hot water tank in which hot water heated by a heat exchange with said cooling water is stored.  
     
     
         5 . The fuel cell system according to  claim 3 , wherein the first humidifying portion has flow paths for at least one of the supply fuel gas and the supply oxidizing gas and flow paths for at least one of the exhaust fuel gas and the exhaust oxidizing gas, each of the supply gas flow paths and each of the exhaust gas flow paths being in contact with each other with a moisture transmitting film for selectively transmitting moisture being interposed therebetween.  
     
     
         6 . The fuel cell system according to  claim 5 , wherein the first humidifying portion is formed by laminating a plurality of flow path plates, 
 each of said flow path plates having the flow path for at least one of the supply fuel gas and the supply oxidizing gas on a first main surface and the flow path for at least one of the exhaust fuel gas and the exhaust oxidizing gas on a second main surface,    the plural flow path plates being laminated such that each supply gas flow path is in contact with each exhaust gas flow path with the moisture transmitting film interposed therebetween.    
     
     
         7 . The fuel cell system according to  claim 5 , wherein the second humidifying portion is formed such that each of the flow paths for at least one of the supply fuel gas and the supply oxidizing gas is in contact with each of paths for the cooling water with a moisture transmitting film for selectively transmitting moisture interposed therebetween.  
     
     
         8 . The fuel cell system according to  claim 7 , wherein the second humidifying portion is formed by laminating a plurality of flow path plates, 
 each of said flow path plates having the flow path for at least one of the supply fuel gas and the supply oxidizing gas on a first main surface and the flow path for the cooling water on a second main surface,    the plural flow path plates being laminated such that each supply gas flow path is in contact with each cooling water flow path with the moisture transmitting film interposed therebetween.    
     
     
         9 . The fuel cell system according to  claim 7  having a humidifying unit wherein the first humidifying portion is adjacent to and integral with the second humidifying portion.  
     
     
         10 . The fuel cell system according to  claim 9 , wherein the humidifying unit is formed by laminating the plural flow path plates with the moisture transmitting film for selectively transmitting moisture being interposed between every two plates, 
 each flow path plate having, on a first main surface, the flow path for at least one of the exhaust fuel gas and the exhaust oxidizing gas in the region of the first humidifying portion and the flow path for the cooling water in the region of the second humidifying portion and having, on a second main surface, the flow path for at least one of the supply fuel gas and the supply oxidizing gas which continuously extends throughout the first and second humidifying portions.    
     
     
         11 . The fuel cell system according to  claim 9 , 
 wherein the first humidifying portion of the humidifying unit is formed by laminating a plurality of first flow path plates with the moisture transmitting film for selectively transmitting moisture interposed between every two plates, 
 each first flow path plate having the flow path for at least one of the exhaust fuel gas and the exhaust oxidizing gas on a first main surface and the flow path for at least one of the supply fuel gas and the supply oxidizing gas on a second main surface,  
   wherein the second humidifying portion of the humidifying unit is formed by laminating a plurality of second flow path plates with the moisture transmitting film for selectively transmitting moisture interposed between every two plates, 
 each second flow path plate having the flow path for the cooling water on a first main surface and the flow path for at least one of the supply fuel gas and the supply oxidizing gas on a second main surface, and  
   wherein the first and second humidifying portions are laminated to constitute the humidifying unit.    
     
     
         12 . The fuel cell system according to  claim 9 , wherein the humidifying unit is adjacent to and integral with the fuel cell.  
     
     
         13 . The fuel cell system according to  claim 7 , wherein the second humidifying portion is adjacent to and integral with the fuel cell.  
     
     
         14 . The fuel cell system according to  claim 7  further comprising a humidity detector for detecting the humidity of at least one of the supply fuel gas and the supply oxidizing gas to be supplied from the second humidifying portion to the fuel cell and a control unit for controlling the humidity of the supply gas based on the humidity of the supply gas which has been detected by the humidity detector.  
     
     
         15 . The fuel cell system according to  claim 14 , wherein the control unit controls the humidity of the supply gas by controlling the temperature or flow rate of the cooling water to be supplied to the second humidifying portion.  
     
     
         16 . The fuel cell system according to  claim 14 , wherein the cooling system has a cooling water path for allowing the cooling water to flow to the second humidifying portion and a cooling water bypass path connected to the cooling water path for bypassing the second humidifying portion, and wherein the control unit controls the humidity of the supply gas by controlling the flow rate of the cooling water to be supplied to the second humidifying portion through the cooling water path and the flow rate of the cooling water to be supplied to the cooling water bypass path.  
     
     
         17 . The fuel cell system according to  claim 7  further comprising a cooling water temperature detector for detecting the temperature of the cooling water to be supplied to the second humidifying portion and a control unit for controlling the humidity of at least one of the supply fuel gas and the supply oxidizing gas based on the temperature of the cooling water which has been detected by the cooling water temperature detector.  
     
     
         18 . The fuel cell system according to  claim 17 , wherein the control unit controls the humidity of the supply gas by controlling the temperature or flow rate of the cooling water to be supplied to the second humidifying portion.  
     
     
         19 . The fuel cell system according to  claim 17 , wherein the cooling system has a cooling water path for allowing the cooling water to flow to the second humidifying portion and a cooling water bypass path connected to the cooling water path for bypassing the second humidifying portion, and wherein the control unit controls the humidity of the supply gas by controlling the flow rate of the cooling water to be supplied to the second humidifying portion through the cooling water path and the flow rate of the cooling water to be supplied to the cooling water bypass path.  
     
     
         20 . The fuel cell system according to  claim 7  further comprising a gas flow rate detector for detecting the flow rate of at least one of the supply fuel gas and the supply oxidizing gas to be supplied to the fuel cell, and a control unit for controlling the humidity of the supply gas based on the flow rate of the supply gas which has been detected by the gas flow rate detector.  
     
     
         21 . The fuel cell system according to  claim 20 , wherein the control unit controls the humidity of the supply gas by controlling the temperature or flow rate of the cooling water to be supplied to the second humidifying portion.  
     
     
         22 . The fuel cell system according to  claim 20 , wherein the cooling system has a cooling water path for allowing the cooling water to flow to the second humidifying portion and a cooling water bypass path connected to the cooling water path for bypassing the second humidifying portion, and wherein the control unit controls the humidity of the supply gas by controlling the flow rate of the cooling water to be supplied to the second humidifying portion through the cooling water path and the flow rate of the cooling water to be supplied to the cooling water bypass path.  
     
     
         23 . The fuel cell system according to  claim 7  further comprising an electricity generation detector for detecting the amount of electricity generated by the fuel cell, and a control unit for controlling the humidity of at least one of the supply fuel gas and the supply oxidizing gas based on the amount of generated electricity which has been detected by the electricity generation detector.  
     
     
         24 . The fuel cell system according to  claim 23 , wherein the control unit controls the humidity of the supply gas by controlling the temperature or flow rate of the cooling water to be supplied to the second humidifying portion.  
     
     
         25 . The fuel cell system according to  claim 23 , wherein the cooling system has a cooling water path for allowing the cooling water to flow to the second humidifying portion and a cooling water bypass path connected to the cooling water path for bypassing the second humidifying portion, and wherein the control unit controls the humidity of the supply gas by controlling the flow rate of the cooling water to be supplied to the second humidifying portion through the cooling water path and the flow rate of the cooling water to be supplied to the cooling water bypass path.