PEMFC STACK MONITORING

Transcription

1 PEMFC STACK MONITORING with Advanced Total Harmonic Distortion Analysis Richard Schauperl AVL List GmbH

2 BACKGROUND FUEL CELL STACK MONITORING STATE OF THE ART Measuring of individual single cell voltages or cell voltage pairs and analysis in terms of voltage drifts (CVM*) Large stack monitoring costs high instrumentation effort and elaborated wiring concepts for reliable operation (EMC**) Determination of failure causes or lifetime estimations are not possible REQUIREMENT Real time indication of critical fuel cell conditions, i.e. online monitoring Detection of cell voltage drops and its reasons set counteractions HW instrumentation for comprehensive diagnostics on stack level and also for serial application Richard Schauperl, PTE/DRF 27th April

3 AVL S APPROACH FOR STACK MONITORING THDA TM (Total Harmonic Distortion Analysis) for stack monitoring Measure no longer voltage drifts, but instead analyses effects which results from voltage drifts. In parallel the approach provides additional information towards causes of voltage drops which can t be provided by CVM. Signals are analyzed in real time, to provide online failure identification during stack operation. Dynamic failure mode detection allows immediate avoidance of potentially irreversible failures and serious lifetime consequences for fuel cell stacks. These effects are detectable in the entire stack sum signal i.e. the cabling of individual cells is not necessary. Richard Schauperl, PTE/DRF 27th April

4 AVL PEMFC STACK MONITORING THDA TM (Total Harmonic Distortion Analysis) for stack monitoring voltage measurement signal analysis on stack level FC Stack diagnostic algorithms on stack level current superimposition dryout low media liquid water on stack level Under normal operating conditions, the frequency spectrum of the superimposed current signal is identical with the spectrum of the responding voltage signal Under critical operating conditions a fuel cell distorts a superimposed signal harmonically and generates measurable spectral components. Additional spectral components (i.e. harmonics) are formed at particular frequencies during critical operating conditions. Richard Schauperl, PTE/DRF 27th April

5 PRINCIPLE OF FC-MONITORING WITH AVL-THDA THDA Total Harmonic Distortion Analysis* *patented, registered trademark Richard Schauperl, PTE/DRF 27th April

6 MATRIX EXAMPLE FOR CLASSIFICATION (SIMPLIFIED) criteria: measured physical parameter e.g. etc. effect criterion #1 criterion #2 criterion #3 criterion #4 criterion #12 low media supply o o liquid water droplets o o membrane dry out o o o o +++ sensitivity of effects to criteria: o = none, + = sensible, ++ = moderate influence, +++ = high influence rule low media (#1 & #2 & #3) and not #4 water issue (#3 & #2 & #4) and not #1 membrane issue #12 (only) METHODOLOGY Different operating conditions typical changes of electr. characteristics (collection of several criteria*) Interpretation of changes in criteria and correlation to operating conditions description with mathematical formulas * criteria are derived from FC voltage & current at four different frequencies, analysed in time or frequency domain total different criteria implemented in detection algorithms AVL THDA 6

7 THDA INSTRUMENTATION PRINCIPLE DEMONSTRATION & TESTING PHASE 1 3 output data 2 HARDWARE PRINCIPLE 1. Superimposition of a small alternating current signal burst * during operation 2. (Spectral-)Analysis of signal response = voltage (thd measurement, impedance spectroscopy, statistical parameters, ) 3. Results via CAN or RS232 interface to FC controller or GUI * i AC = typ. 1A ( 1mV/cell, sinusoidal, low frequency) Richard Schauperl, PTE/DRF 27th April

8 AVL THDA HW/SW HW and GUI, available as serial device for laboratory purpose, or product demonstration all signal processing integrated plug and play device For serial application and integration into complete Fuel Cell systems THDA requires no additional hardware. The THDA algorithms can run in the fuel cell system controller. Richard Schauperl, PTE/DRF 27th April

9 OPTION: ONLINE FAST EIS-MEASUREMENT Niquist Plot under Stable Conditons air lambda = 2.1;frequencies=6/14/26/96/1000Hz, P=500W AVL List GmbH, July Z1 Z2 Z3 Z4 Z imaginary* [Ohm] real [Ohm] On-line measurement of electrical impedance spectroscopy simultaneously scan at five frequencies ( Hz) every 0.5 sec. up to 500V max stack voltage, max 2A current superimposition changes in EIS correlates with harmonic distortion Richard Schauperl, PTE/DRF 27th April

10 ON-LINE MONITORING EXAMPLE 450A Dry + Flood + Low Media detection Dry out leads to a lower conductivity of the membrane Low media signal is indicating this effect Richard Schauperl, PTE/DRF 27th April

11 ON-LINE MONITORING EXAMPLE 450A Dry + Flood + Low Media detection Richard Schauperl, PTE/DRF 27th April

12 SPECIAL APPLICATION MULTIDIMENSIONAL THDA New approach in Austrian funded A3 FALCON project 2-dimensional distribution of failure modes for 1 cell voltage, current, temperature measurement for each segment signal analysis for each segment 2x sensor plates diagnostic algorithms for each segment FC Stack current superimposition dryout low media liquid water for each segment Richard Schauperl, PTE/DRF 27th April

13 100 CHANNEL MEASUREMENT AIR STARVATION Reduce Air Lambda stepwise 2.0, 1.7, 1.6, 1.49 (causes drop out) Voltage loss ~ 0.32V Richard Schauperl, PTE/DRF 27th April

14 SUMMARY THDA is intended to monitor fuel cell stacks in real product applications like FCEV, Range Extender, CHP, mchp, APU, THDA gives online info on state of dry out, low media, liquid water THDA offers fast EIS The laboratory THDA device is a commercial laboratory instrumentation product. AVL THDA was validated by 7 major automotive OEMs and >10 fuel cell system integrators from other industries. Outlook: in final product application THDA requires no additional hardware. THDA algorithm runs in fuel cell system controller, only a license agreement with AVL required Future developments shall increase the set of detectable failure modes, with special focus on separation of anode and cathode effects. Also the application for SOFC, SOEC and PEM electrolyzer stacks is investigated in current research projects. Richard Schauperl, PTE/DRF 27th April

15 THANK YOU VISIT OUR BOOTH E55

16 Richard Schauperl, PTE/DRF 27th April