Operating Principles, Performance and Technology Readiness Level of Reversible Solid Oxide Cells

The continuous increase of energy demand with the subsequent huge fossil fuel consumption is provoking dramatic environmental consequences. The main challenge of this century is to develop and promote alternative, more eco-friendly energy production routes. In this framework, Solid Oxide Cells (SOCs) are a quite attractive technology which could satisfy the users’ energy request working in reversible operation. Two operating modes are alternated: from “Gas to Power”, when SOCs work as fuel cells fed with hydrogen-rich mixture to provide both electricity and heat, to “Power to Gas”, when SOCs work as electrolysers and energy is supplied to produce hydrogen. If solid oxide fuel cells are an already mature technology with several stationary and mobile applications, the use of solid oxide electrolyser cells and even more reversible cells are still under investigation due to their insufficient lifetime. Aiming at providing a better understanding of this new technological approach, the study presents a detailed description of cell operation in terms of electrochemical behaviour and possible degradation, highlighting which are the most commonly used performance indicators. A thermodynamic analysis of system efficiency is proposed, followed by a comparison with other available electrochemical devices in order to underline specific solid oxide cell advantages and limitations.