Abstract
Power generation using gas turbine power plants operating on the Brayton cycle suffers from low efficiencies. In this work, a solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency. The SOFC system utilizes four heat exchangers for heat recovery from both the turbine outlet and the fuel cell outlet to ensure a sufficiently high SOFC temperature. The power output of the hybrid plant is 37 MW at 66.2% efficiency. A thermo-economic model predicts a payback period of less than four years, based on future projected SOFC cost estimates.
Highlights
Fuel cells are electrochemical devices that convert the chemical energy in a fuel into electricity without direct combustion
Solid oxide fuel cells (SOFC) are best suited for stationary power generation. They operate at temperatures between 600–1100 °C and have been tested at operating pressures up to 15 atm [1]. Because of their high temperature and pressure exhaust, SOFCs are considered ideal for integration in hybrid power generating systems, where their outlet gas streams are expanded in a gas turbine (GT) to produce additional power
The SOFC model is validated using experimental data published in References [21,30,31]
Summary
Fuel cells are electrochemical devices that convert the chemical energy in a fuel into electricity without direct combustion. Song et al [12] and Calise et al [16] modeled part load operating conditions of hybrid plants Both found that the best control strategy for part load operation was simultaneously varying the air and fuel flow rates while maintaining a constant air/fuel ratio. SOFC results in better thermodynamic performance, but add significantly to the system costs since the SOFC cost dominates the capital cost in new hybrid systems They discussed the inherent difficulty in selecting a gas turbine for small scale operation since their efficiencies decrease as the system scales down. Large scale gas turbines already exist in these plants, and the objective is to select an optimally sized SOFC stack that best matches the existing system. A thermo-economic model is developed for this system to optimally size the SOFC stack to obtain the most cost effective performance of the system
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