Doctoral thesis: Improving the Performance of Solid Oxide Fuel Cell Systems Matias Halinen, Post-graduate Student, Aalto University Gasum Gas Fund Day Lappeenranta 17.12.2014
Outline Solid Oxide Fuel Cell Systems short introduction Objectives Results Summary Outlook
Why Solid Oxide Fuel Cells? SOFCs are high efficiency and low emission energy production technology suitable for a wide range of applications Electrical efficiency 30-60% Total efficiency >80% High temperature operation Best suited for constant power generation Distributed CHP & Prime power 100 kw, natural gas & biogas Residential CHP 1 kw, natural gas Auxiliary Power Units for Trucks & Ships 3-30 kw, LNG, diesel (sulfur-free) Portable units 200 W, propane
Solid Oxide Fuel Cell Electrochemical power source One SOFC produces <1 V 30-150 W Cells are connected in series SOFC stack higher voltage and power fuel and air delivery to electrodes Photo: Forschungzentrum Jülich
Solid Oxide Fuel Cell System Heat, steam, fuel Fuel Air Balance of Plant Fuel and air pre-heating and pre-processing Solid Oxide Fuel Cell Operating temperature 700 C Electricity & heat Heat
Objectives of the thesis work Improve the performance of SOFC systems Objectives: Develop feasible system design & components >45% el. efficiency Validate the design with a proof-of-concept prototype Develop solutions for improved operation Preventing carbon formation? Effects of stack leakages? Protection of stack from damage during system start-up? Stack temperature control?
Results
Design & Components
Design & Components Unused fuel, Steam, CO 2
Design & Components Reduce fuel & external water supply Unused fuel, Steam, CO 2
Design & Components > 50% AC efficiency Reduce fuel & external water supply Unused fuel, Steam, CO 2
Proof-of-concept: 10 kw SOFC demo unit at VTT Natural gas fuelled Warm anode gas recycle loop Grid connected Thermally self-sustained Automated, 24/7 operation Stack module by Versa Power Systems (Canada) Single 10-kW planar SOFC stack BOP MODULE STACK MODULE 4 m 1.5 m
Electric efficiency Power conversion unit 0.5 kw Air blower 0.7 kw Recycle blower 0.1 kw 70% 65% Gross DC Current collection loss 0.2 kw 60% 55% 50% Net AC Net AC power to grid 9.2 kw 45% 40% 2010 2012 2013 Stack DC efficiency Net AC efficiency Parasitic losses Electric efficiency
Improved operation Stack temperature control When stack degrades (voltage decreases), more heat is generated system operating point changes, more cooling needed stack degradation can accelerate at higher temperatures No overheating/undercooling stack longer lifetime and better performance High number of measurements needed I/O cost complex lead-ins reliability max
Improved operation 785 reduce/eliminate the need of stack internal temperature sensors Estimate the temperature by using indirect, cheap measurements outside the stack (outlet gas temperature) simple regression models based on experimental data 800 a) T MAX / C 780 775 770 Setpoint MLR est. Meas 765 1540 1560 1580 1600 Time / h T max / C 780 760 740 meas. MLR est. TC TC TC 0 500 1000 1500 2000 2500 Time / h
Summary Thesis contains readily implementable solutions to improve the performance of SOFC systems
Outlook Required know-how is available to design, construct and operate SOFC systems for the first commercial applications Durability and cost are the main challenges for wide-spread use of SOFC technology
Progress on SOFC durability Durability of the SOFC has improved steadily over years, but Each R&D cycle (e.g. materials, design) takes 2-5 years to validate Current status < 0.2 % / 1000h for best lab stacks
SOFC market status SOFCs are in the market Japan, Europe Residential microchp (~1 kw) 50,000 FC units installed in Japan USA Prime power for data centers (~100kW) Natural gas is the primary fuel for all applications Price is still high 7-8 /W for 100 kw systems 20-30 /W for 1 kw systems Subsidy programs needed 700 W residential system (Japan) 6 MW SOFC installation (USA)
Acknowledgements Funding VTT Tekes and participating companies in projects FINSOFC, SofcPower and RealDemo Gasum Gas Fund Co-authors, collagues and collaboration VTT, Aalto University, Lappeenranta Univ., Forshcungzentrum Jülich, Versa Power Systems
Thank you for your attention Questions?