Synergistic integration of a gas turbine and solid oxide fuel cell for improved transient capability

Abstract: A theoretical solid oxide fuel cell–gas turbine hybrid system has been designed using a Capstone 60kW micro-gas turbine. Through simulation it is demonstrated that the hybrid system can be controlled to achieve transient capability greater than the Capstone 60kW recuperated gas turbine alone. The Capstone 60kW gas turbine transient capability is limited because in order to maintain combustor, turbine and heat exchangers temperatures within operating requirements, the Capstone combustor fuel-to-air ratio must be maintained. Potentially fast fuel flow rate changes, must be limited to the slower, inertia limited, turbo machinery air response. This limits a 60kW recuperated gas turbine to transient response rates of approximately 1kWs−1. However, in the SOFC/GT hybrid system, the combustor temperature can be controlled, by manipulating the fuel cell current, to regulate the amount of fuel sent to the combustor. By using such control pairing, the fuel flow rate does not have to be constrained by the air flow in SOFC/GT hybrid systems. This makes it possible to use the rotational inertia of the gas turbine, to buffer the fuel cell power response, during fuel cell fuel flow transients that otherwise limit fuel cell system transient capability. Such synergistic integration improves the transient response capability of the integrated SOFC gas turbine hybrid system. Through simulation it has been demonstrated that SOFC/GT hybrid system can be developed to have excellent transient capability. [Copyright &y& Elsevier]