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German Aerospace Center

Hydrogen Rich Natural Gas as a Fuel for SOFC Systems Florian Leucht , Moritz Henke, Caroline Willich, Christina Westner, Josef Kallo, K. Andreas Friedrich. German Aerospace Center. Germany‘s national research center for aeronautics and space App. 7,000 people in 32 institutes at

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German Aerospace Center

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  1. Hydrogen Rich Natural Gas as a Fuel for SOFC SystemsFlorian Leucht, Moritz Henke, Caroline Willich, Christina Westner, Josef Kallo, K. Andreas Friedrich ICEPAG 2012 > Leucht > 08.02.2012

  2. German Aerospace Center • Germany‘s national research center for aeronautics and space • App. 7,000 people in • 32 institutes at • 16 national and international locations • Institute of Technical Thermodynamics • Systems analysis and technology assessment, • Electrochemical energy technology, • Thermal process technology ICEPAG 2012 > Leucht > 08.02.2012

  3. Overview • Hydrogen production from renewable sources in Germany • System model • System reaction to hydrogen • Control approaches • System efficiency with hydrogen ICEPAG 2012 > Leucht > 08.02.2012

  4. Hydrogen Production from renewable sources in Germany • Rising interest in water electrolysis • Production, storage and convertion of hydrogen into electricity interesting • Hydrogen content of 4 % in natural gas pipelines gives 15 TWh/a storage capacity • First demonstration plant inaugurated in Prenzlau Oct. 2011 by Enertrag • More demonstrations planned within a call financed by federal ministries of economics, environment and research Picture courtesy of Enertrag ICEPAG 2012 > Leucht > 08.02.2012

  5. System Model • Based on Siemens CHP100 • Tubular cells • Delivers 110 kW at atmospheric pressure 150 kW at 4 bar • Controls for: • Power • Air flow (temperature) • Fuel flow (current) • Humidification (low load) • Stack temperature (electrical heating, low load) Leucht, F. et al.: Fuel Cell System Modelling for SOFC/GT Hybrid Power Plants, Part I: Modelling and simulation framework, Journal of Power Sources, 196 (2011) 1205-1215 ICEPAG 2012 > Leucht > 08.02.2012

  6. System reaction to hydrogen • System operating at full load with pure natural gas • System does not ‘know’ about the change in fuel composition • Constant fuel flow • Fuel utilization rises up to 100 % • System would be destroyed ICEPAG 2012 > Leucht > 08.02.2012

  7. Control approaches • Standard approach: fuel flow control based on current via Faradays law • Extended by hydrogen equivalent • Determining fuel flow according to • If no information on fuel composition is available H2EQ stays fixed • Other possibilities for control input variables could be: • Temperatures (partially long time constants) • Power, voltage and current (fast response to fuel quality) ICEPAG 2012 > Leucht > 08.02.2012

  8. Combustion zone temperature • Short reaction time to changes in offgas composition • Combustion zone temperature stays stable • Power drops during transient • Bad indicator for fuel gas quality ICEPAG 2012 > Leucht > 08.02.2012

  9. Voltage • If fuel quality drops, voltage drops • Controlling fuel flow based on system voltage keeps power and voltage stable • BUT: Power is controlled via cell voltage, • If fuel control keeps voltage stable power control is useless • Fuel flow control and power control might have opposing targets ICEPAG 2012 > Leucht > 08.02.2012

  10. Delivered power • Fuel flow controlled based on delivered power • System voltage controlled to maintain safe operation point • Cell current / voltage are influenced by fuel quality • If power cannot be maintained by manipulation of voltage command fuel flow is increased. • Power stays stable, deviation from set point very small (<100 W) ICEPAG 2012 > Leucht > 08.02.2012

  11. System efficiency with hydrogen • Base case efficiency drops more than 10 % • Power set point cannot be maintained • Major problem: missing heat sink (reforming of methane) • All controls show large drop in efficiency • Fuel utilization is a lot lower than in base case ICEPAG 2012 > Leucht > 08.02.2012

  12. Summary • Power to Gas and hydrogen storage has very high potential for future power supply • SOFC systems can be operated with hydrogen rich fuels • System controls have to be able to deal with changes in fuel quality • Using system delivered power as a fuel quality indicator shows promising results • System controls need to be enhanced in order to keep system efficiency high ICEPAG 2012 > Leucht > 08.02.2012

  13. Thank you foryour attention ICEPAG 2012 > Leucht > 08.02.2012

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