Methods and systems for determining and controlling fuel concentrations in fuel cells

• US 8,617,767 B2
• Filed: 04/24/2009
• Issued: 12/31/2013
• Est. Priority Date: 04/24/2008
• Status: Expired due to Fees

• Current Assignee: IRD Fuel Cells A/S (Den Selvejende Institution Tre-For)
• Original Assignee: IRD Fuel Cells A/S (Den Selvejende Institution Tre-For)
• Inventors: Odgaard, Madeleine, Yde-Andersen, Steen, Lundsgaard, Joergen Sehjerning
• Primary Examiner(s): APICELLA, KARIE O
• Application Number:
  US12/429,363
• Publication Number:
  US 20090269625A1
• Time in Patent Office: 1,712 Days
• Field of Search: 429/400, 429428-432, 429/502
• US Class Current: 429/502
• CPC Class Codes: H01M 8/04194 Concentration measuring cells
• CPC Class Codes: H01M 8/04447 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04649 of fuel cell stacks
• CPC Class Codes: H01M 8/04798 of fuel cell reactants
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Methods and systems for electrical determination and adjustment of the fuel concentration in direct methanol fuel cells (DMFC) are provided.

Claims

1. A system for measuring and adjusting fuel concentration of a fuel cell stack comprising a fuel cell stack with a plurality of fuel cells and fuel solution reservoir, a mean for applying a direct current to one or more fuel cells of the fuel cell stack, a means for applying an alternating voltage directly to one or more fuel cells of a fuel cell stack, a means for measuring alternating current impedance of one or more fuel cells of the fuel cells stack following application of the alternating voltage, a means for measuring direct current of one or more fuel cells of the fuel cell stack following brief periodical load interruptions, and a means for adjusting methanol or water content of the fuel cell stack by adding either pure methanol or water to the fuel solution reservoir based upon the AC impedance and DC measurements, wherein lower AC impedance as compared to AC impedance at an optimal concentration of 1M methanol is indicative of a lower methanol concentration in the fuel cell stack and a need for addition of methanol to the fuel solution reservoir, while a higher AC impedance as compared to AC impedance at optimal concentration of 1M methanol is indicative of the methanol concentration in the fuel cell stack exceeding an optimal concentration of 1M and a need for water to be added to the fuel solution reservoir, and wherein lower voltage transient as measured by DC as compared to an initial open cell voltage is indicative of lower methanol concentration in the fuel cell stack and a need for methanol to be added to the fuel solution reservoir while higher voltage transient as measured by DC as compared to an initial open cell voltage is indicative of methanol concentration in the fuel cell stack exceeding the optimal concentration of 1M and a need for water to be added to the fuel solution reservoir.