Bipolar membrane (reverse) electrodialysis acid/base flow battery for energy storage: a multi-scale model for increased efficiency

The renewable energy market is rapidly increasing. Most of renewable energy sources are intermittent, e.g. wind and solar among them. This has led to the need for new large scale energy storage systems. In this regard, the Acid/Base Flow Battery (AB-FB) represents an innovative, safe and sustainable way to store energy with high performances [1]. The energy density accumulated in an AB-FB, in the form of pH and salinity gradients, can theoretically reach 7 kWh/m8 which is higher than the values relevant to the most used technologies (e.g. pumped hydropower and compressed air). The core of the battery is the stack where two membrane separation processes are carried out: bipolar membrane electrodialysis during charge phase and its opposite bipolar reverse-electrodialysis during discharge. A stack consists of repetitive units called cells or “triplets”, composed by a cation exchange membrane, a salt solution, an anion exchange membrane, an acidic solution, a bipolar membrane and a basic solution. The aim of this work is to develop a simulation tool able to predict the operation and performances of the battery.