Electrical and thermal analysis of an intermediate temperature IIR‐SOFC system fed by biogas

Abstract

The fuel cells are well placed in the panorama of sustainable energy options owing to some of their important characteristics, such as low environmental impact, in terms of both polluting gases emissions and noise pollution, and the high-energy conversion efficiency.Among the different fuel cells according to the type of electrolyte and the operating temperature, the high temperature fuel cells (Solid Oxide Fuel Cells [SOFCs], and Molten Carbonate Fuel Cells [MCFCs]) obtain the highest performance values in terms of energy conversion efficiency [1,2], power density output, stability, useful life, and versatility with regard to the use of fuels. Furthermore, the use of fuels derived from a renewable source, which can feed the SOFC, is particularly interesting. Compared to conventional technologies SOFCs are able to convert various fuels, such as biogas [3][4][5] or syngas [6][7][8] deriving from biomasses, into electric energy distributed where it can be used with high efficiency. In addition, Solid Oxide Cell can produce alternatively electric energy (Fuel Cell mode) and hydrogen (Electrolytic Cell mode) [9].This type of fuel cell has the peculiarity of generating thermal energy, which can be used for cogeneration purposes. Advances in the chemistry and processing of materials are enabling a reduction in the operating temperature of SOFCs in the so-called intermediate temperature region (IT) between 500 and 750°C [10,11].The use of new materials, which work best at intermediate temperature, involves a series of advantages, such as: minor sealing problems, smaller number for Balance of Plant components, simplified thermal management, faster phases of startup and shutdown, and the achievement of a higher thermo-mechanical stability of the fuel cell and a reduced degradation of both the fuel cell and the components of the system that contains it.In recent years there have been a number of theoretical and experimental studies of IT-SOFC energy systems fed by biofuels [12]. The risk associated with the direct use of biofuel (e.g. biogas, bio-alcohols, biodiesel, etc.), which MODELING AND ANALYSIS AbstractAn Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) system fed by not conventional fuels such as biogas can produce electric energy with high conversion efficiency and thermal energy. Inside the energy system, the methane in the biogas is mixed with steam, and then it is converted into carbon monoxide, hydrogen and carbon dioxide through steam reforming and water gas shift chemical reactions in an indirect internal reformer (IIR) mostly and in the SOFC anode minimally. The chemical energy of the electro-oxidation of hydrogen and carbon monoxide produced is directly converted into electric energy in the fuel cell anode. A part of the anode exhaust gas can be recirculated at the IIR inlet and the percentage of this recirculated anode exhaust gas together to the fuel utilization factor influence the performances (electric and thermal powers and efficiencies, primary energy saving and first law efficiency) of t...

Key Parameters of Proton‐conducting Solid Oxide Fuel Cells from the Perspective of Coherence with Models

“…With this in mind, proton‐conducting SOFCs were proposed which have a lower activation energy of proton transport . Proton conductors also are expected to open the way to SOFCs being run at low to intermediate temperature ranges . A key advantage of H+SOFC over standard oxygen ions conducting SOFC is 100% utilization of fuel; thus, there are no anode recirculation solutions needed .…”

Design and Implementation of the Off-Line Robust Model Predictive Control for Solid Oxide Fuel Cells

“…In general, methane can be synthesized, as a major product or a by-product, from many chemical processes, or even formation process [8]. In addition, methane in biogas can be directly fed to SOFC under dry conditions; however, there is a risk that is associated with contaminants in biogas when it is introduced to commercial SOFCs while using Ni-YSZ anode [9,10]. Therefore, either commercialized material development or fuel processing with cleaning technologies is required.…”

Yb-Doped BaCeO3 and Its Composite Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cells

“…Fuel cells have many merits, such as diversity of fuel options, being environmentally friendly and having high energy efficiency [1,2,3,4,5,6,7,8]. BaCeO 3 and SrCeO 3 -based perovskite oxides have excellent protonic conductivities under hydrogen- or water-containing atmosphere at 400–1000 °C [9,10,11,12,13,14,15].…”