Design, Simulation, and Control of a 100 Megawatt-Class Solid Oxide Fuel Cell Gas Turbine Hybrid System

Abstract

A 100 MW-class planar solid oxide fuel cell, synchronous gas turbine hybrid system has been designed, modeled and controlled. The system is built of 70 functional fuel cell modules each containing 10 fuel cell stacks, a blower to recirculate depleted cathode air, a depleted fuel oxidizer and a cathode inlet air recuperator with bypass. The recuperator bypass serves to control the cathode inlet air temperature while the variable speed cathode blower recirculates air to control the cathode air inlet temperature. This allows for excellent fuel cell thermal management without independent control of the gas turbine, which at this scale will most likely be a synchronous generator. In concept the demonstrated modular design makes it possible to vary the number of cells controlled by each fuel valve, power electronics module, and recirculation blower, so that actuators can adjust to variations in the hundreds of thousands of fuel cells contained within the 100 megawatt hybrid system for improved control and reliability. In addition, the modular design makes it possible to take individual fuel cell modules offline for maintenance while the overall system continues to operate. Parametric steady state design analyses conducted on the system reveal that the overall fuel-to-electricity conversion efficiency of the current system increases with increased cathode exhaust recirculation. To evaluate and demonstrate the conceptualized design, the fully integrated system was modeled dynamically in Matlab–Simulink®. Simple proportional feedback with steady state feed-forward controls for power tracking, thermal management, and stable gas turbine operation were developed for the system. Simulations of the fully controlled system indicate that the system has a high efficiency over a large range of operating conditions, decent transient load following capability, fuel and ambient temperature disturbance rejection as well as the capability to operate with a varying number of fuel cell modules. The efforts here build upon prior work and combine the efforts of system design, system operation, component performance characterization and control to demonstrate hybrid transient capability in large-scale coal synthesis gas-based applications through simulation. Furthermore, the use of a modular fuel cell system design, the use of blower recirculation, and the need for integrated system controls are verified.

Feedback control of solid oxide fuel cell spatial temperature variation

“…In particular, transient operation of SOFC system can be very attractive. Simulations indicate that well designed integrated SOFC systems can load follow very rapidly [4][5][6][7][8][9]. The current drawn from SOFC can be increased at the rate of electrochemistry, on the order of milliseconds, with increased efficiency at part load, and ultra low pollutant emissions for the whole range of operation (see [10] for a list of SOFC attributes).…”

Feasibility and Design Implications of Fuel Cell Power for Sealift Ships

“…As such, they are considered as potential alternative power solutions to meet future shipboard power demands with low environmental impact. Many studies on marine fuel cell applications have been published (Fontell et al 2004;Allen et al 1998;Tsourapas et al 2004Tsourapas et al , 2008Mueller et al 2008;Reenaas 2005) and several successful technology demonstrations have been showcased (Collins 2006;Hoffman 2007;FuelCell Energy 2009;European Commission Transportation Research 2009;Zemships 2009;Douglass and Partos 2003;Hammerschmidt 2006) by the academic research and industrial or development communities. Among them, the fuel cell ship service system sponsored by the Office of Naval Research (Collins 2006;Hoffman 2007;FuelCell Energy 2009) Most of the fuel cell studies and demonstration programs target auxiliary power applications, with some exceptions such as the submarine program (Hammerschmidt 2006) and small pleasure boats (Zemships 2009) where the fuel cells are used for propulsion.…”

Investigation of thermal control for different SOFC flow geometries

“…Typically, increased bulk air flow can be used to reduce temperature gradients and thermal stress [16,23,[30][31][32][33], but additional air flow comes with costs. The primary cost is the power requirement of a blower needed to push the additional air through the system.…”

“…Significant challenges arise in making SOFC systems responsive. Advanced integrated system controls, as explored in [15][16][17][18][19][20][21][22][23], are necessary in order to maintain system integrity, durability, and lifespan. Controller design is highly dependent upon the application requirements and system configuration, but generally thermal response should be damped to the extent possible, given the materials used and the high temperatures involved.…”