Control and System Integration of an SOFC/GT-based APU with Extended Dynamic Capabilities for Military Vehicle

Principal Investigators: Jing Sun, University of Michigan, jingsun(at)umich.edu
So-ryeok Oh, University of Michigan
Student: Zhenzhong Jia, University of Michigan
Government: Herb Dobbs (Point of Contact), Joel King, U.S. Army TARDEC
Industry: Owen Taylor, Pittsburgh Electrical Engine Inc.

The SOFC/GT (solid oxide fuel cells / gas turbine) system is an appealing power generation solution for mobile applications (e.g., APUs or primary propulsion systems for military vehicles) from energy conversion efficiency point of view. The relatively poor dynamic capabilities of the SOFC/GT system, which are the results of the system characteristics and SOFC operation safety considerations, severely limit its feasibility and widespread applications to mobile platforms and must be enhanced to meet safe, efficient and fast load following requirements. To this end, two approaches are explored to extend the dynamic capabilities of the SOFC/GT system.

schematic of hybrid SOFC/GT/B systemIn the first approach (right figure), the SOFC/GT system is augmented with energy storage (e.g., battery) and the G/M (generator/motor) dual mode operation of the electric machine to ease the power tracking operation and extend the transient capabilities. Our efforts focused on studying the G/M dual mode operation and its implications on transient performance and battery requirements. Specifically, we have addressed the question of whether motoring operation can help to mitigate system shut-down, improve transient responses, and lessen the battery system requirements for both load step-up and step-down scenarios.

In the second approach, a new sprinter-SOFC/GT (referred to as S-SOFC/GT) system concept is explored. In this system, a down-sized SOFC stack, which is operated at fairly constant temperature, provides the baseline power with high efficiency. The sprinter GT-generator, which could generate substantial electric power very quickly, is used to provide the transient power for fast load following operation. Compared with the conventional systems, in which the transient performance is primarily dominated by the slow dynamic capability of the SOFC, the proposed S-SOFC/GT system has the potential to achieve: (1) fast load following by taking full advantage of the GT-generator’s fast dynamic capability; and (2) efficient and long life cycle operation by running the SOFC at fairly constant temperature.

The ultimate goal of the S-SOFC/GT approach is to establish a new SOFC/GT design framework to meet the high efficiency and long life span requirements for future mobile power applications. Specifically, to achieve the design targets of (1) maintaining fairly constant SOFC power and temperature over the entire load region; and (2) achieving fast and safe load following during transient operations.

Publications:

  • So-Ryeok Oh; Jing Sun; Dobbs, H.; King, J., "Model Predictive Control for Power and Thermal Management of an Integrated Solid Oxide Fuel Cell and Turbocharger System," Control Systems Technology, IEEE Transactions on , vol.22, no.3, pp.911,920, May 2014. doi:10.1109/TCST.2013.2271902
  • So-ryeok Oh, Jing Sun, , Herb Dobbs, and Joel King. "Dynamic Characteristics and Fast Load-Following Approach of 5kW-Class Tubular Solid Oxide Fuel Cell/Gas Turbine Hybrid Systems", International Journal of Energy Research, Volume 37, pp. 1242–1255, 2013. doi:10.1002/er.3031
  • Zhenzhong Jia, Jing Sun, So-ryeok Oh, Herb Dobbs, and Joel King, "Control of the Dual Mode Operation of Generator/Motor in SOFC/GT-based APU for Extended Dynamic Capabilities," Journal of Power Sources, Volume 235, pp172-180,2013.
    doi:10.1016/j.jpowsour.2013.01.170
  • So-Ryeok Oh, Jing Sun, Dobbs, H., King, J., "Model-based predictive control strategy for a solid oxide fuel cell system integrated with a turbocharger," American Control Conference (ACC), 2012 , vol., no., pp.6596-6601, 27-29 June 2012
    doi:10.1109/ACC.2012.6315069
  • Caihao Weng, Jing Sun, "Design of a Variable Geometry Turbine control strategy for Solid Oxide Fuel Cell and Gas Turbine hybrid systems," American Control Conference (ACC), 2012 , vol., no., pp.541-546, 27-29 June 2012 doi:10.1109/ACC.2012.6314637
  • So-Ryeok Oh, Jing Sun, Dobbs, H., King, J., "Comparative performance assessment of 5kW-Class Solid Oxide Fuel cell engines integrated with single/dual-spool turbochargers," American Control Conference (ACC), 2011 , vol., no., pp.5231-5236, June 29 2011-July 1 2011 doi:10.1109/ACC.2011.5991262
  • So-ryeok Oh, Jing Sun, Herb Dobbs, and Joel King, "Performance Evaluation of Solid Oxide Fuel Cell Engines Integrated with Single/Dual-Spool Turbochargers," Vol. 8, No. 6, 061020, IEEE Transactions on Fuel Cell Science and Technology, 2011 doi:10.1115/1.4004471
  • So-Ryeok Oh, Jing Sun, "Optimization and load-following characteristics of 5kw-class tubular solid oxide fuel cell/gas turbine hybrid systems," American Control Conference (ACC), 2010, pp.417-422, June 30 2010-July 2 2010 doi:10.1109/ACC.2010.5531015
  • Vasilis Tourapas, Jing Sun, Ann Stefanopoulou, "Incremental Step Reference Governor for Load Conditioning of Hybrid Fuel Cell and Gas Turbine Power Plant," IEEE Transactions on Control Systems Technology, Vol. 17, No. 4, pp 756-767, July, 2009 doi:10.1109/TCST.2008.2010554