CHARACTERIZATION OF AUTOMOTIVE FUEL CELLS

Transcription

1 CHARACTERIZATION OF AUTOMOTIVE FUEL CELLS Dietmar Gerteisen, Ulf Groos, Stefan Keller, Nada Zamel Fraunhofer-Institut für Solare Energiesysteme ISE October 7th, 2014 F-Cell 2014, Stuttgart

2 AGENDA Who we are Why do we need spatially resolved characterization? Characterisation of Fuel Cell Stacks Outlook 2

3 PEM fuel cells are our profession. Characterization and modeling of PEMFC from cell to system level (micro to automotive fuel cells) LT- & HT-PEMFC stacks operated with H 2 or reformate from 0.01 to 1 kw el System technology for membrane fuel cells from 100 mw el to 20 kw el 3

4 Scientific publications 4

5 5 Our research enables fuel cells.

6 We are co-operating intensively with industry. 6

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8 8 We help to bring down costs. First, we have to understand the phenomena.

9 Do you know the current or voltage distribution? air pressure hydrogen cooling cooling 9 hydrogen air

10 Stack and system characterization at Fraunhofer ISE 20 kw el test stand Single cell monitoring with electrochemical impedance spectroscopy of 50 cells in parallel. 10

11 We are testing a 20 cell short stack from Daimler/AFCC. Stack is a 4th generation Automotive Design from 2009 Normal operation conditions: Stoich: anode: , cathode: , according to stack current Cooling: 68 C inlet temperature Humidification: dewpoint temperature anode: 64.6 C, cathode 61.1 C Pressurized operation: 1 to 3 bara according to current Dry operation conditions: Same as NORMAL, except dewpoint temperature for cathode 57.1 C 11

12 The stack reaches automotive performance targets. NORMAL conditions 12

13 The cell voltage difference is below 20 mv at the maximum operation point. NORMAL conditions 13

14 There is no obvious performance difference between normal and dry conditions. 14

15 The impedance spectra are very homogeneous also at different current densities. DRY conditions Very low 1 khz Average (bold) as well as minimum and maximum impedance spectra at different current densities EIS measurement with frequency range from 1 khz to 0.1 Hz with 5 points per decade in galvanostatic mode with 4 A AC perturbation amplitude. 15

16 The spectra of inlet and outlet look similar. DRY conditions Average cell spectra at 1.5 Acm -2 EIS measurement with frequency range from 1 khz to 0.1 Hz with 5 points per decade in galvanostatic mode with 4 A AC perturbation amplitude. 16

17 At maximum power point the low frequency impedance differs from cell to cell (for dry conditions). DRY conditions Single cell spectra at 1.5 Acm -2 EIS measurement with frequency range from 1 khz to 0.1 Hz with 5 points per decade in galvanostatic mode with 4 A AC perturbation amplitude. 17

18 The cooling temperature influences the high frequency impedance DRY conditions Average (bold) as well as minimum and maximum HFR and cooling temperature at inlet and outlet 18

19 SUMMARY Simultaneous single cell EIS gives detailed insights, regarding Stack design Material properties Operation strategies Outlook: performing measurements at extreme climate conditions 19

20 Outlook: Understanding local effects within a single cell rh c T hydrogen 20

21 21 We look at local effects and inhomogenities.

22 Cell design evaluation with respect to materials and operation conditions. Inhomogenieties are inevitable due to heat production, varying species concentration along the channel, and water generation. Spatially resolved investigation and modelling is needed. current density [Acm 2 ] O 2 conc in CL [mol cm -3 ] saturation [-] Modelling of local phenoma within a fuel cell. The simulation is compared with experiments in a segmented fuel cell by using a multi channel characterization system. Fraúnhofer ISE. 22

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25 Characterization of automotive fuel cells Segmentation of automotive cells (50 segments with up to +/- 5 A, 18 segments with up to +/- 30 A altogether up to 790 A) Cell dimensions max. 650 x 300 mm² (L x W) Test stand for spatially resolved characterization of automotive fuel cells with 68 potentiostats and frequency response analyzers (left), gas supply (middle, background) and portal with test cell (right). Max. portal pressure 120 kn Heating / cooling of test cell Spatially resolved characterization of U, I, EIS Evaluation of cell design, material (combination), operation strategy 25

26 First you have to understand the system. 26

27 First you have to understand the system. 27

28 Then you reduce complexity. And so, you reduce costs. 28

29 Fraunhofer ISE started an industry network regarding mass production technologies for stack assembly. GDL + MPL bipolar half plate anode screws, etc. membrane CCM MEA + gasket cell 250x stack cathode GDL + MPL end plate, current collector, etc. 2x 29 bipolar half plate MEA: Membrane Electrode Assembly GDL: Gas Diffusion Layer MPL: Microporous Layer

30 Announcement for the ModVal 12 when March 26 th 27 th, 2015 where Schloss Reinach, Freiburg-Munzingen, Germany organizer More information on 30 Save the date & Join us in beautiful Freiburg in Spring 2015

31 Additional Workshops to come: International Workshop»Medium Temperature PEMFC Materials, Stacks, and Systems«2 nd & 3 rd December 2014, Fraunhofer ISE, Freiburg Workshop»Start-Stopp-Phänomene und Strategien für PEMFC«11 th December 2014, Fraunhofer ISE, Freiburg International Workshop»Experience with Test Procedures for PEMFC Stacks«20 th & 21 st January 2014, Fraunhofer ISE, Freiburg Workshop» Zulassung Zertifizierung Normung Sicherheit und Qualität in der Wasserstoff- und Brennstoffzellentechnik«24 th & 25 th February 2014, ZSW, Ulm Please get more information at our booth in hall 2, D11 31

32 Thank you for your attention! I am happy to answer your questions. Ulf Groos Head of Department Fuel Cell Systems Fraunhofer Institute for Solar Energy Systems ISE Phone Fax ulf.groos@ise.fraunhofer.de 32

33 Let us join together to build our future. 33