Fuel cell apparatus and method for downhole power systems

Abstract

A rechargeable power system comprising: a drill string configured to operate in a well bore, the drill string comprising: a fuel cell system; a generator in electrical communication with the fuel cell system; a turbine, configured to rotate due to an impingement of drilling mud on one or more turbine blades, the turbine in operable communication with the generator; and where the fuel cell system is configured to provide power at least when drilling mud is not circulating in the well bore, and further configured to be recharged by the generator when drilling mud is circulating in the well bore. A method for operating a rechargeable downhole fuel cell. The method comprises: monitoring a fluid supply pressure; determining whether the fluid supply pressure is below a threshold value; and stopping a fuel cell discharge if the fluid supply pressure is below the threshold value.

What is claimed is: 
     
         1 . A method for operating a rechargeable downhole fuel cell, the method comprising:
 monitoring a fluid supply pressure;   determining whether the fluid supply pressure is below a threshold value;   stopping a fuel cell discharge if the fluid supply pressure is below the threshold value.   
     
     
         2 . The method of  claim 1 , wherein the fluid is hydrogen, and the threshold value is a first threshold value. 
     
     
         3 . The method of  claim 1 , wherein the fluid is oxygen, and the threshold value is a second threshold value. 
     
     
         4 . The method of  claim 1 , further comprising:
 monitoring a second fluid supply pressure;   determining whether the first fluid supply pressure and the second fluid supply pressure are in proper proportion to each other;   issuing an improper pressure proportion warning if the first fluid supply pressure and the second fluid supply pressure are not in proper proportion to each other.   
     
     
         5 . The method of  claim 4 , wherein the first fluid is hydrogen and the second fluid is oxygen. 
     
     
         6 . A method for operating a rechargeable downhole fuel cell, the method comprising:
 monitoring a fluid supply pressure;   determining whether the fluid supply pressure is above a threshold value;   stopping a fuel cell recharge if the fluid supply pressure is above the threshold value.   
     
     
         7 . The method of  claim 6 , wherein the fluid is hydrogen, and the threshold value is a third threshold value. 
     
     
         8 . The method of  claim 6 , wherein the fluid is oxygen, and the threshold value is a fourth threshold value. 
     
     
         9 . The method of  claim 7 , further comprising:
 monitoring a second fluid supply pressure;   determining whether the first fluid supply pressure and the second fluid supply pressure are in proper proportion to each other;   issuing an improper pressure proportion warning if the first fluid supply pressure and the second fluid supply pressure are not in proper proportion to each other.   
     
     
         10 . The method of  claim 9 , wherein the first fluid is hydrogen and the second fluid is oxygen. 
     
     
         11 . A method for operating a rechargeable downhole fuel cell, the method comprising:
 (i) monitoring at least one of voltage or current at a fuel cell stack;   (ii) comparing the at least one of voltage or current to a threshold; and   (iii) stopping at least one operation of the fuel cell stack based on the comparison.   
     
     
         12 . The method of  claim 11 ,
 wherein process (i) comprises monitoring voltage at the fuel cell stack;   wherein process (ii) comprises determining whether the voltage is below a first voltage threshold for a given current; and   wherein process (iii) comprises stopping a fuel cell discharge if the voltage is below the first voltage threshold.   
     
     
         13 . The method of  claim 12 , wherein the first voltage threshold is a first voltage threshold for a given discharging current. 
     
     
         14 . The method of  claim 12 , wherein the first voltage threshold is a first voltage threshold for a given power discharge. 
     
     
         15 . The method of  claim 11 ,
 wherein process (i) comprises monitoring a supply voltage at a fuel cell stack;   wherein process (ii) comprises determining whether the voltage is above a second voltage threshold for a given charging current; and   wherein process (iii) comprises stopping a fuel cell recharge if the voltage is above the second voltage threshold for a given charging current.   
     
     
         16 . The method of  claim 11 ,
 wherein process (i) comprises monitoring a discharge current at a fuel cell stack;   wherein process (ii) comprises determining whether the discharge current is below a discharge current threshold for a fixed voltage; and   wherein process (iii) comprises stopping a fuel cell discharge if the current is below the current threshold for a fixed voltage.   
     
     
         17 . The method of  claim 11 ,
 wherein process (i) comprises monitoring a current at a fuel cell stack;   wherein process (ii) comprises determining whether the current is below a current threshold for a fixed voltage; and   wherein process (iii) comprises stopping a fuel cell recharge if the current is below the current threshold for a fixed voltage.   
     
     
         18 . The method of  claim 11 ,
 wherein process (i) comprises (a) monitoring a current at a fuel cell stack and (b) monitoring a voltage at a fuel cell stack;   wherein process (ii) comprises (a) determining whether the current is above a current threshold for a for a fixed power output and (b) determining whether the voltage is below a voltage threshold for a fixed power output; and   wherein process (iii) comprises (a) stopping a fuel cell discharge if the current is above the current threshold for a fixed power output and (b) stopping a fuel cell discharge if the voltage is below the voltage threshold for a fixed power output.   
     
     
         19 . The method of  claim 11 ,
 wherein process (i) comprises (a) monitoring a current at a fuel cell stack and (b) monitoring a voltage at a fuel cell stack;   wherein process (ii) comprises (a) determining whether the current is below a current threshold for a fixed recharge power and (b) determining whether the voltage is above a voltage threshold for a fixed recharge power; and   wherein process (iii) comprises (a) stopping a fuel cell recharge if the current is below the current threshold for a fixed recharge power and (b) stopping a fuel cell recharge if the voltage is above the voltage threshold for a fixed recharge power.