Long-term performance of PEM fuel cells with dry cathode supply and anodic fuel recirculation

Zentrum für BrennstoffzellenTechnik Long-term performance of PEM fuel cells with dry cathode supply and anodic fuel recirculation Sönke Gößling ZBT GmbH Carl-Benz-Straße 201 47057 Duisburg Germany Telefon: +49-203-7598 1171 Telefax: +49-203-7598 2222 www.zbt-duisburg.de s.goessling@zbt-duisburg.de

Long-term performance of PEM fuel cells with dry cathode supply and anodic fuel recirculation the role/importance of long-term tests long-term tests with dry cathode supply and anodic fuel recirculation basic structure of the test rig historical outline of the long-term tests at ZBT test rig improvements; learning the hard way latest last long-term test and improvements at ZBT 2

the role/importance of long-term tests the fuel cell life time is an essential part on its way to a viable product the requested lifetime equals the operation time of its application the minimal requested lifetime is (no explicit definition/source found) portable applications: 2000 h mobile applications: 4000 h domestic energy supply: 40000 h 3

long-term tests with dry cathode supply and anodic fuel recirculation In scientific publications long-term performance of PEM fuel cell components is usually presented on the basis of highly sophisticated test environments real life applications usually try to reduce the balance of plant components and more often rationalize the humidifier for portable and mobile devices the anodic supply is usually realised with a recirculation or dead end and a purge è We do long-term tests with a dry cathode supply and anodic fuel recirculation 4

basic structure of the test rig long-term test with operating conditions typical for portable devices dry cathode supply / anodic recirculation weekly online electrochemical impedance spectroscopy short stacks of 5 cells three stacks with individual media supply fuel cells verified results for long-term tests Task: comparing stack components (MEA, gaskets, bipolar plates) or operational topics like media supply independently from any outside influences 5

basic structure of the test rig 3x parallel 6

historical outline of the long-term tests at ZBT first long-term test in 2007; the aim were current ripple purposes the degradation was to high and made any conclusion impossible attempt to reduce the degradation and increase current ripple effect in test #2 & #3 after the current ripple project, the focus of the test rig changed to degradation of fuel cell and its components the parallel operation of three short stacks enables qualitative conclusions, even if the setup of the test rig and environmental conditions change # current [ma] runtime [h] Degradation [µv/h] cathod humidity [%] cathode stochiometry 1 800 612 185.6/284.3 85 2,7 2 400 2133 78.3/75.5 85 5,4 3 400 2999 62.0/45.4 41 1,7 4 400 768 various operatin conditions 5 400 913 29.7/27.8 0 2,2 6 400 3298 17,2/15,1 0 2,2 7

historical outline of the long-term tests at ZBT 8

test rig improvements; learning the hard way rust, caused by stainless steel parts have been welded and the acid cleaning has been refrained 9

test rig improvements; learning the hard way blocked flowfield channels the combination of teflon tubes and quick-couplers cause small shred of teflon that can block single flowfield channels 10

test rig improvements; learning the hard way rust, caused by stainless steel parts have been welded and the acid cleaning has been refrained 11

test rig improvements; learning the hard way rust, caused by stainless steel parts have been welded and the acid cleaning has been refrained 12

test rig improvements; learning the hard way rust, caused by stainless steel parts have been welded and the acid cleaning has been refrained 13

test rig improvements; learning the hard way 14

test rig improvements; learning the hard way 15

voltage/cell [mv] results the long-term test 680 670 660 650 640 630 620 610 600 Stack 2 Stack 3 NO pollution 450 400 350 300 250 200 150 100 50 pollution [ug/m^3] 590 20.10.2010 19.11.2010 19.12.2010 18.01.2011 17.02.2011 19.03.2011 date 0 16

latest last long-term test and improvements at ZBT Online EIS 17

latest last long-term test and improvements at ZBT decreasing membrane resistance sensitive for pollution increasing dc-resistance 18

Zentrum für BrennstoffzellenTechnik thank you for your attention Sönke Gößling ZBT GmbH Carl-Benz-Straße 201 47057 Duisburg Germany Telefon: +49-203-7598 1171 Telefax: +49-203-7598 2222 www.zbt-duisburg.de s.goessling@zbt-duisburg.de