1. Katie S. Howe Centre for Hydrogen and Fuel Cell Research SOFC Research group www.fuelcells.bham.ac.uk www.hydrogen-wm-scratch.info Dynamic Performance of Micro-Tubular Fuel Cells

2. Overview  Starting Point –Fuel cells –Status of dynamic performance research  Experimental Work  Results  Conclusions  Next Steps

3. Starting Point: Fuel Cells  Change electrochemical energy into useful electricity  Like a battery, but not limited by how much fuel they can hold

4. Starting Point: Fuel Cells  mSOFCs –Tubular –Better thermal shock resistance –Fewer issues with sealing

5. Starting Point: Research Status Load-following capability is vital for most real-world applications In the literature:  Many papers on steady-state performance  Some modelling work on dynamic behaviour [1-3] ...but hardly any experimental results [1] Nehter, P., 2006, Journal of Power Sources, 157(1), pp. 325-334. [2] Ota, T., Koyama, M., Wen, C. J., Yamada, Y., and Takahashi, H., 2003, Journal of Power Sources, 118(1-2), pp. 430-439. [3] Serincan, M. F., Pasaogullari, U., and Sammes, N. M., 2009, Journal of Power Sources, 194(2), pp. 864-872.

6. Starting Point: Research Status  Thermal transport time dominates dynamics [4]  Readjustment time independent of step size [5]  Undershooting of voltage when current rises [5] –Size of undershoot related to step size [4] Bhattacharyya, D., and Rengaswamy, R., 2009, "A Review of Solid Oxide Fuel Cell (SOFC) Dynamic Models," Ind. Eng. Chem. Res., 48(13), pp. 6068-6086 [5] Achenbach, E., 1995, "Response of a solid oxide fuel cell to load change," Journal of Power Sources, 57(1-2), pp. 105-109.

7. Experimental Work - Method  Single cells made to in-house techniques [6] – Operated at 750  C – Fuel: 20ml/minute of pure hydrogen  Solartron TM analytical 1400 Cell Test System –Apply sets of square pulses of current  Paper submitted [7] with precise details [6] Dhir, A., 2008, "Improved Microtubular Solid Oxide Fuel Cells," PhD Thesis, University of Birmingham, [7] Howe, K. S.; Kendall, K., Transient Performance of Micro-tubular Solid Oxide Fuel Cells. Journal of Fuel Cell Science and Technology 2010,.Paper Accepted – awaiting editorial changes

8. Results Transient behaviour:

9. Results

10. Conclusions  Short re-adjustment time of <0.5s is independent of step size –Agreement with models in the literature  No under-shooting of voltage on the change –Suggests thermal transport is better than expected in these tubes

11. Next Steps  Combination of cells into small stacks –Higher powers –Dynamic performance testing of stacks  Effects of changing to a hydrocarbon fuel on transient performance

12. Acknowledgements With thanks to... My supervisors: Kevin Kendall and Stephen Decent My sponsors: RCUK and EADS Innovation Works

13. Thank you! www.fuelcells.bham.ac.uk Any questions?