STEADY STATE MODELING AND ANALYSIS OF A DE-COUPLED FUEL CELL - GAS TURBINE HYBRID FOR CLEAN POWER PRODUCTION By GARRETT SCOTT HEDBERG A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN MECHANICAL ENGINEERING WASHINGTON STATE UNIVERSITY School of Mechanical and Materials Engineering MAY 2017 © Copyright by GARRETT SCOTT HEDBERG, 2017 All Rights Reserved ii © Copyright by GARRETT SCOTT HEDBERG, 2017 All Rights Reserved i To the Faculty of Washington State University: The members of the Committee appointed to examine the thesis of GARRETT SCOTT HEDBERG find it satisfactory and recommend that it be accepted. _____________________________ Dustin McLarty, Ph.D., Chair _____________________________ Cecilia Richards, Ph.D. _____________________________ Jacob W. Leachman, Ph.D. ii ACKNOWLEDGEMENT Wow, I guess I do not know where to begin. There is so many people to thank and give credit to for this work. I could not have done it alone. First, I must thank my family Scott, Chris, Madi and Justin. You guys have been the rock for which I could stand on and have always encouraged and pushed me to be the best person I can be. Thank you for always being there, even if you were 1500 miles away. I love you guys. Next, I want to thank my advisor, Dr. Dustin McLarty. I remember you outlining this idea on the first day I arrived in Washington. We weren’t sure what results we were going to get, but I’d say it worked out well right? Thank you for continuing to push me even when I thought we had reached the finish line. I want to thank you also for taking a chance on me when you were just starting your own career at WSU. Even though a Ph.D. wasn’t what I decided on you were still supportive of my choice and a constant source of information for the endless questions I asked figuring out the dFC-GT. You were a great advisor and I can’t wait to see the results that start pouring out of the lab. Speaking of, I should thank everyone in the CESI lab at WSU: Nate, Nadia, Kevin, Marshall, Haley, Jeff, Ashley and Nathanael. You all definitely made coming to work so much more fun and enjoyable, while also being awesome coworkers and answering my basic MatLab© syntax questions. Thanks, and I can’t wait to see what the future holds for you all! I want to give some final shout outs to my friends in Washington, Minnesota, and wherever else you may be. It’s hard to accomplish anything alone, and knowing there’s friends like you in my corner allowed me to continue forward even when I wasn’t sure where I was going. iii STEADY STATE MODELING AND ANALYSIS OF A DE-COUPLED FUEL CELL GAS TURBINE FOR CLEAN POWER PRODUCTION Abstract by Garrett Scott Hedberg, M.S. Washington State University May 2017 Chair: Dustin McLarty This thesis introduces a de-coupled fuel cell-gas turbine hybrid arrangement that removes the fuel cell stack from the turbine working fluid, retains the high efficiency thermal integration of a topping cycle, and does not employ the high temperature heat exchangers of a bottoming cycle. The distinguishing feature of the system is the solid-state oxygen transport membrane used to create a secondary oxidant stream without significantly affecting turbomachinery performance. The secondary oxidant stream is re-pressurized and diverted to a solid oxide fuel cell. Excess hydrogen from the fuel cell supplies the combustor, which heats the oxygen-depleted air and drives the turbomachinery. The fuel cell operates in a thermally sustaining condition with direct and indirect fuel reforming providing the thermal management. Thermodynamic models developed in the Clean Energy Systems Integration Lab (CESI) at Washington State University identified the design conditions and characterized the system performance within the design space. Analysis indicates greater than 75% fuel-to-electric efficiency is achievable, with higher efficiency possible through co-production of hydrogen. The iv potential to retrofit existing turbine systems, particularly micro-turbines and stand-by ‘peaker’ plants, with minimal impact to compressor stability or transient response is a promising pathway to hybrid fuel cell/turbine development that does not require bespoke turbomachinery design. Economic analysis of the developed system showed its potential to compete in the power energy market as an alternative power generation device. v TABLE OF CONTENTS Page ACKNOWLEDGEMENT .......................................................................................................................... iii Abstract ................................................................................................................................................ iv LIST OF FIGURES Page ................................................................................................... x LIST OF TABLES Page ............................................................................................................. xii 1. Introduction .......................................................................................................................................... 1 1.1. Thesis Outline ................................................................................................................... 4 2. Background ........................................................................................................................................... 6 2.1. Fuel Cells: ......................................................................................................................... 6 2.1.1. Fuel Cell Structure ........................................................................................................ 7 2.1.1. Steam Reformation ....................................................................................................... 9 2.1.2. Fuel Cell Types ............................................................................................................ 10 2.1.3. Solid Oxide Fuel Cells (SOFC) ...................................................................................... 10 2.1.4. Thermodynamics of Fuel Cells .................................................................................... 12 2.1.5. Fuel Cell Losses ........................................................................................................... 15 2.2. Gas Turbines ................................................................................................................... 18 2.3. Heat Exchangers ............................................................................................................. 19 2.4. Oxygen Transport Membrane ........................................................................................ 20 vi 2.5. Hybrid Systems (FC-GT) .................................................................................................. 21 2.5.1. De-Coupled Fuel Cell Gas Turbine .............................................................................. 22 2.6. Economics....................................................................................................................... 25 3. Literature Review ................................................................................................................................ 28 3.1. Modeling Approaches .................................................................................................... 28 3.1.1. Fuel Cells ..................................................................................................................... 28 3.1.2. Gas Turbines ............................................................................................................... 29 3.2. FC-GT Hybrids ................................................................................................................. 29 3.2.1. FC-GT Economics ........................................................................................................ 32 3.3. System Pressurization .................................................................................................... 32 4. Component Models ............................................................................................................................ 35 4.1. Compressor/Turbine Model: .......................................................................................... 35 4.2. OTM MODEL: .................................................................................................................. 36 4.3. Fuel Cell Model: .............................................................................................................. 37 4.4. Combustor Model .......................................................................................................... 40 5. Steady State Analysis .......................................................................................................................... 43 5.1. Design Space Investigation ............................................................................................. 44 5.2. Sensitivity Study ............................................................................................................. 53 vii 5.3. Fuel Cell and OTM Relationship ..................................................................................... 55 5.4. System Pressurization .................................................................................................... 56 5.5. Micro-turbines ................................................................................................................ 58 5.6. Hydrogen Co-Production