(486a) Design and Control of An Energy Integrated Solid Oxide Fuel Cell System

Solid Oxide Fuel Cells (SOFCs) are a promising class of high temperature fuel cells that can be used for Combined Heat and Power (CHP) generation, and stand-alone applications. The high operating temperature of the SOFC stack allows for energy integration with an (endothermic) fuel processor (external or internal to the fuel cell), that could result in high energy efficiencies. However, high operating temperatures also result in drawbacks that include material mismatches, sealing issues and proper material selection; all these should be taken into consideration during the design of a SOFC system.

In this study we consider an integrated fuel cell/external fuel processor system for in situ hydrogen generation (using methane stem reforming) and power production. Methane is fed in the fuel processor where a hydrogen rich stream is obtained. Subsequently, it passes through the SOFC where electrochemical reactions produce power output. Heat exchangers are placed to recover energy available from hot streams and transfer it to the cold streams.

The goal is to design an optimal energy integrated configuration, minimizing external energy demand. The proposed energy integrated configuration is designed based on pinch analysis. The resulting configuration is used for dynamics and control studies. We develop a control strategy where performance, stability and operational feasibility of the energy integrated system are taken into consideration. We control the output power (the primary objective) through the electrical side of the energy system, the fuel utilization (to prevent fuel starvation) through the fuel processor's inlet flow rate, the SOFC's temperature (to avoid the existence of hot spots) through the air inlet flow rate and the fuel's processor temperature by manipulating the external energy input. The process heat exchangers are controlled through hot streams' bypasses.

A power demand scenario is considered and the operability and performance of the integrated system is evaluated for a combination of linear and nonlinear model-based controllers. Simulations demonstrate good operability and performance in a wide range of power demands.