No abstract

A novel SOFC system control strategy has been developed for rapid load following. The strategy was motivated from the performance of a baseline control strategy developed from control concepts in the literature. The basis for the fuel cell system control concepts are explained by a simplified order of magnitude time scale analysis. The control concepts are then investigated in a detailed quasi-two-dimensional integrated dynamic system model that resolves the physics of heat transfer, chemical kinetics, mass convection and electrochemistry within the system.The baseline control strategy is based on the standard operating method of constant utilization with no control of the combustor temperature. Simulation indicates that with this control strategy large combustor transients can take place during load transients because the fuel flow to the combustor increases faster than the air flow. To alleviate this problem, a novel control structure that maintains the combustor temperature within acceptable ranges without any supplementary hardware was introduced. The combustor temperature is controlled by manipulating the current to change the combustor inlet stoichiometry. The load following capability of SOFC systems is inherently limited by anode compartment fuel depletion during the time of fuel delivery delay. This research indicates that future SOFC systems with proper system and control configurations can exhibit excellent load following characteristics.

Hybrid fuel-cell–gas-turbine (FC/GT) systems are technologically advanced systems that are promising for electric power generation with ultralow emissions and high efficiency for a large range of power plant sizes. A good understanding of the steady-state and dynamic performance of a FC/GT system is needed in order to develop and advance this hybrid technology. In this work, a detailed dynamic model of a solid oxide fuel cell/gas turbine (SOFC/GT) system has been developed. The system that is simulated represents the 220kW SOFC/GT hybrid system developed by Siemens Westinghouse. Results of the dynamic model and experimental data gathered during the operation and testing of the 220kW SOFC/GT at the National Fuel Cell Research Center are compared and presented.

No abstract