Optimization of Pressurized SOFC-ICE-Turbo Hybrid Generation System

Abstract

While renewable energy sources are a clear pathway to net-zero emissions, the use ofhydrocarbon fuels is still widespread. In the interim high efficiency hydrocarbon power generation systems are required. Solid Oxide Fuel Cell (SOFC) technology is a low emissions alternative to internal combustion engines, being both more efficient and able to run both fossil fuels and hydrogen. SOFC research has made several advancements in recent decades that has further increased their performance and reduced their cost, making them a more viable market alternative. Research has shown SOFC pressurization and hybrid generation increases power density, efficiency, and flexibility. A shift towards pressurized systems running as hybrid generators with internal combustion engines (ICE) has become a viable option to produce >70% efficiencies. However, unlike previous concepts involving gas turbines, ICEs don’t pressurize the system. SOFC/ICE hybrids, therefore, require high efficiency electric compressors. This study was focused on the evaluation and optimization of two-stage motored turbochargers within a pressurized SOFC/ICE generation system with key variables of air flow rate, operating pressure, and stack current. First, the motored turbocharger was experimentally validated at increased temperatures to simulate second stage conditions. Then the performance data was incorporated into a system model to optimize the performance of the hybrid SOFC/ICE system over a range of operating conditions. The results showed that the air compression was the most important factor for optimizing the system efficiency with a peak efficiency of 68% achieved at 220 kPa and 80 g/s with a current draw of 35 A.