Lifetime Capacity – An Important Performance Metric for SOEC Stacks
Rainer Küngas, Peter Blennow, Thomas Heiredal‐Clausen, Tobias Holt Nørby, Jeppe Rass‐Hansen, Poul Georg Moses · ECS Transactions · 2019
Haldor Topsoe has commercialized a system for on-site CO generation based on solid oxide electrolysis technology under a tradename eCOs™. A single eCOs™ module is capable of producing 96 Nm 3 CO per hour at 99.5% purity, and larger units consisting of several modules and higher CO purities are available on demand. In this patented system, the electrochemical conversion of CO 2 into CO is carried out in solid oxide electrolysis stacks. The parameters used to evaluate the performance of SOFC stacks typically include area-specific resistance (measured in Ω cm 2 cell area), stack efficiency (measured in %), stack cost (e.g. USD/kW or USD/stack), degradation rate (typically measured in %V/1000 h), and stack lifetime (measured in hours). It is common practice in the field to use the above performance metrics also to describe stacks operating in SOEC mode. This manuscript will highlight how this practice may provide a skewed picture of stack performance, and that for the commercialization of SOEC technology, a number of additional performance metrics need to be considered. In particular, the importance of lifetime capacity, i.e. the total amount of product produced by a stack (measured e.g. in Nm 3 gas or mol product per stack), is highlighted. Examples of alternative ways to maximize stack lifetime capacity will be described.