Controlling a fuel cell system based on fuel cell impedance characteristic

• US 8,652,697 B2
• Filed: 02/25/2009
• Issued: 02/18/2014
• Est. Priority Date: 02/25/2009
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Gottmann, Matthias, Muhl, Patrick, Pearson, Chad, Smith, James Daniel
• Primary Examiner(s): Rizkallah, Kimberly
• Assistant Examiner(s): HENRY, CALEB E
• Application Number:
  US12/379,618
• Publication Number:
  US 20100216043A1
• Time in Patent Office: 1,819 Days
• Field of Search: 429/432, 702/22, 324/428
• US Class Current: 429/432
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• CPC Class Codes: H01M 8/04641 of the individual fuel cell
• CPC Class Codes: H01M 8/04686 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04701 Temperature
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method of controlling a fuel cell system includes applying alternating current (AC) signals to an individual fuel cell. The AC signals have a plurality of different frequencies. A voltage across the individual fuel cell is determined at each of the plurality of different frequencies. An impedance characteristic of the individual fuel cell is determined based at least in part on the voltage across the individual fuel cell at each of the plurality of different frequencies. The individual fuel cell is controlled based at least in part on the impedance characteristic.

Claims

1. A method of controlling a fuel cell system comprising:

determining an impedance characteristic of at least one fuel cell, wherein the impedance characteristic is determined while the at least one fuel cell is providing power to a load; and

controlling the at least one fuel cell based at least in part on the impedance characteristic to optimize at least one operational parameter of the at least one fuel cell while the at least one fuel cell continues providing the power to the load;

wherein controlling the at least one fuel cell comprises optimizing a fuel flow rate for the at least one fuel cell.

2. The method of claim 1, wherein the impedance characteristic of the at least one fuel cell is determined using electrochemical impedance spectroscopy.

3. The method of claim 1, further comprising determining a second impedance characteristic of a second fuel cell, wherein the second impedance characteristic is based at least in part on extrapolation of the impedance characteristic of the at least one fuel cell.

4. The method of claim 1, further comprising generating a Nyquist plot for the at least one fuel cell, wherein the impedance characteristic is based at least in part on the Nyquist plot.

5. The method of claim 1, wherein the impedance characteristic of the at least one fuel cell includes at least one of an ohmic resistance or a polarization resistance.

6. The method of claim 1, wherein determining an impedance characteristic of at least one fuel cell comprises:

applying alternating current (AC) signals to the at least one fuel cell, wherein the AC signals have a plurality of different frequencies;

determining a voltage across the at least one fuel cell at each of the plurality of different frequencies using a monitoring circuit, wherein the monitoring circuit includes a power source configured to apply the AC signals to the at least one fuel cell; and

determining based at least in part on the voltage across the at least one fuel cell at each of the plurality of different frequencies an impedance characteristic of the at least one fuel cell.

7. A method of controlling a fuel cell system comprising:

loading and unloading at least one fuel cell at a plurality of different frequencies;

determining a voltage across the at least one fuel cell at each of the plurality of different frequencies using a monitoring circuit, wherein the voltage is determined while the at least one fuel cell is providing power to a load;

determining, based at least in part on the voltage across the at least one fuel cell at each of the plurality of different frequencies, an impedance characteristic of the at least one fuel cell; and

controlling the at least one fuel cell based at least in part on the impedance characteristic to optimize at least one operational parameter of the at least one fuel cell while the at least one fuel cell continues providing the power to the load;

wherein controlling the at least one fuel cell comprises optimizing a fuel flow rate for the at least one fuel cell.

8. The method of claim 7, wherein the impedance characteristic of the at least one fuel cell is determined using electrochemical impedance spectroscopy.

9. The method of claim 7, further comprising determining a second impedance characteristic of a second fuel cell, wherein the second impedance characteristic is based at least in part on extrapolation of the impedance characteristic of the at least one fuel cell.

10. The method of claim 7, further comprising generating a Nyquist plot for the at least one fuel cell, wherein the impedance characteristic is based at least in part on the Nyquist plot.

11. The method of claim 7, wherein the impedance characteristic of the at least one fuel cell includes at least one of an ohmic resistance or a polarization resistance.

12. A method of controlling a fuel cell system comprising:

determining an impedance characteristic of at least one fuel cell, wherein the impedance characteristic is determined while the at least one fuel cell is providing power to a load; and

controlling the at least one fuel cell based at least in part on the impedance characteristic to optimize at least one operational parameter of the at least one fuel cell while the at least one fuel cell continues providing the power to the load;

wherein determining an impedance characteristic of at least one fuel cell comprises;

applying alternating current (AC) signals to the at least one fuel cell, wherein the AC signals have a plurality of different frequencies;

determining a voltage across the at least one fuel cell at each of the plurality of different frequencies using a monitoring circuit, wherein the monitoring circuit includes a power source configured to apply the AC signals to the at least one fuel cell; and

determining based at least in part on the voltage across the at least one fuel cell at each of the plurality of different frequencies an impedance characteristic of the at least one fuel cell.

13. The method of claim 12, wherein the at least one operational parameter is selected from the group consisting of efficiency, power level, temperature, fuel flow rate, fuel utilization, ripple current, and water flow rate.