Observer Design for a Steam Reformer Based Solid Oxide Fuel Cell System With Anode Recirculation

Abstract

In this paper we design an observer for online estimation of species concentrations in a steam reformer based Solid Oxide Fuel Cell (SOFC) system with anode recirculation and with methane as fuel. Since in SOFCs steam reforming occurs both in the reformer and in the fuel cell, a large number of concentration sensors are necessary for accurate control of critical performance variables such as utilization and steam-to-carbon-ratio. The purpose of the observer is to reduce the number of sensors required for control. In contrast to existing observers which are either designed for chemical reactors or for fuel cells exclusively, our design considers the coupled dynamics of the reformer and the fuel cell. We design an adaptive observer where the rates of reforming reactions are treated as slowly varying unknown parameters. Using a few concentration sensors we show that all other species concentrations, molar flow rates, and reaction rates in the fuel path can be dynamically estimated. Simulation results are provided in support of the proposed design.

Mathematical Modeling, Steady-State and Dynamic Behavior, and Control of Fuel Cells: A Review

“…Das and Mukherjee designed an observer for estimation of species concentrations in an SOFC with a reformer. Steam reforming in SOFCs occurs both in the reformer and in the fuel cell.…”

“…Observers have the capability to dynamically calculate the species concentrations online from available sensor data based on a mathematical model. Das and Mukherjee 133 considered the coupled dynamics of the reformer and the fuel cell. Their study showed that concentrations of all species, all molar flow rates, and all reaction rates can be estimated from measurements of (a) CH 4 and CO concentrations in the reformer and the anode chamber and (b) temperatures and pressures at the reformer and anode exits.…”

Process systems opportunities in power generation, storage and distribution

“…Arcak et al (2004) designed an adaptive observer for hydrogen partial pressure estimation in a PEMFC. Das and Mukherjee (2007) designed an observer for estimation of species concentrations in an SOFC with a reformer. Lin and Hong (2005) presented a sliding-mode state observer to estimate the unmeasurable gas temperatures inside a SOFC from measurements such as that of gas pressure.…”