1. MODEL-BASED DETERMINATION OF HYDROGEN SYSTEM EMISSIONS OF MOTOR VEHICLES USING CLIMATE- CHAMBER TEST FACILITIES Dr. Martin Weilenmann

2. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 2 Basic question What means system emissions of H 2 vehicles? System emissions may occur While parking: leakage At start up: density check, de-aerate While running: poisoning purge At shutdown: system ventilation What quantitative amounts are evaporated?  Safety  Efficiency Chassis Dynamometer needed

3. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 3 Second question How to measure them? Based on mass balance in a test cell In a closed test cell Difficult to realise In a ventilated test cell if All in- and out- flows are known (mass flow) Concentrations of all in and out flows are known

4. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 4 Subsequent questions How to reach satisfactory accuracy? What requirements to the test cell? Exterior ventilation Interior ventilation What requirements to the sensors/analysers? Accuracy Sampling rate Positions How to process data?

5. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 5 Test cell overall sketch

6. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 6 Test cell Mass balance – exterior ventilation Mass balance Test cell with controlled overpressure  only one inflow Measure total volume flow and H 2 concentration (+ p,T)

7. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 7 Test cell Mass balance – exterior / Interior ventilation As pressure remains constant: Inflow = outflow But, what about outflow concentration?  Precondition: interior ventilations so high that chamber shows a homogenous concentration Climate machine Vent for car Under floor!

8. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 8 Test cell Mass balance – Interior ventilation Test with blowing a Helium balloon at time = 0  some 10 – 30 s

9. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 9 Test cell Mass balance – exterior / Interior ventilation If interior ventilation homogenizes concentrations within seconds and if exterior ventilation is significantly slower (air exchange rate of several minutes)  chamber concentration is homogenous and equals outflow concentration(s)

10. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 10 Test cell Mass balance – validation Blowing a Helium balloon with known mass of Helium Chamber volume known Ventilation known

11. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 11 Sensors Analyser properties Gas chromatograph for H 2 (RGA3) ppb range 10 ppb detection limit 2 minutes sampling rate  Mass balance in discrete form Ambient H 2 concentration monitored before and after the test and considered as constant

12. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 12 Data processing Discretize mass balance equation Most simple: assume time step T (here 2 min) to be small compared to system dynamics. Implicitly assume all concentration signals to be almost constant during one time step

13. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 13 Data processing Discretize mass balance equation II More advanced: solve mass balance equation for each time step correctly.  Need to know (assume) the signal shape of the vehicles emissions t1t1 T+t 1 ? t1t1 t1t1 t1t1 Most probable Extreme cases

14. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 14 Data processing Discretize mass balance equation III Constantly emitting source: Early peak: Late peak:

15. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 15 Results Comparison of approaches Maximal theoretical error: -12... 14 %

16. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 16 Results Integral values Emissions in the range of mg/min are detectable

17. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 17 Conclusions System emissions can be monitored with A standard chassis dynamometer in a standard climate test cell plus a H 2 sensor in ppb-range If: Internal ventilation is high (within seconds) and External ventilation is slower than sampling time Flows of mg/min are detectable.

18. M. Weilenmann et al. Empa, Materials Science & Technology, Ueberlandstrasse 129, CH-8600 Duebendorf, www.empa.ch/abt 137 18 Thanks To all partners and funding agencies To you!