The Acid–Base Flow Battery: Sustainable Energy Storage via Reversible Water Dissociation with Bipolar Membranes

Abstract

The increasing share of renewables in electric grids nowadays causes a growing daily and seasonal mismatch between electricity generation and demand. In this regard, novel energy storage systems need to be developed, to allow large-scale storage of the excess electricity during low-demand time, and its distribution during peak demand time. Acid–base flow battery (ABFB) is a novel and environmentally friendly technology based on the reversible water dissociation by bipolar membranes, and it stores electricity in the form of chemical energy in acid and base solutions. The technology has already been demonstrated at the laboratory scale, and the experimental testing of the first 1 kW pilot plant is currently ongoing. This work aims to describe the current development and the perspectives of the ABFB technology. In particular, we discuss the main technical challenges related to the development of battery components (membranes, electrolyte solutions, and stack design), as well as simulated scenarios, to demonstrate the technology at the kW–MW scale. Finally, we present an economic analysis for a first 100 kW commercial unit and suggest future directions for further technology scale-up and commercial deployment.

Chemical and Energy Recovery Alternatives in SWRO Desalination through Electro-Membrane Technologies

“…R-EDBM, at its current low TRL, is able to produce high energy densities (considering concentrations of 1.0 M of acid and base) approximately one order of magnitude than the ones reported for mixing salt and freshwater [72]. Most of the research works in literature to date [32,[72][73][74][75][76][77][78][79][80] use HCl as the acidic solution and NaOH as the alkaline solution, both with concentrations up to 1.0 M. Even if 1.0 M concentrations are the standard maximum so far, higher concentrations could enhance the performance of R-EDBM [72], due to higher pH gradients. Aside from HCl and NaOH, R-EDBM could recover energy from acidic and alkaline byproduct or waste streams, achieving by its integration improvements in the environmental performance of the processes.…”

“…Nevertheless, while RED is a well-developed to date technology, R-EDBM is still in the early development stages with few research publications, although its potential has been known for a long time. The couple EDBM and R-EDBM is presented as a sustainable energy storage system for RE surplus [32] configuring the so-called Acid-Base Flow Batteries. Thus, the acidic and alkaline solutions produced by EDBM will act as a charge for the battery that could be discharged in the neutralization by R-EDBM.…”

Insights and Challenges for Applying Bipolar Membranes in Advanced Electrochemical Energy Systems

“…A more recent route for BPM-based batteries is the acid/base flow battery system, using a BPM in reverse bias to charge the fluids and in forward bias for discharging. 14 , 29 , 69 , 70 Being charged from a neutral NaCl solution into HCl and NaOH, the acid/base flow batteries benefit from more abundant resources compared to the vanadium redox flow batteries. 69 The discharge mode (in forward bias) requires a membrane that is prone to water formation at the BPM interface, similar to the conditions in fuel cells.…”

“… 14 , 29 , 69 , 70 Being charged from a neutral NaCl solution into HCl and NaOH, the acid/base flow batteries benefit from more abundant resources compared to the vanadium redox flow batteries. 69 The discharge mode (in forward bias) requires a membrane that is prone to water formation at the BPM interface, similar to the conditions in fuel cells. However, as the current densities in acid/base flow batteries are typically at least an order of magnitude smaller than in fuel cells ( Figure 4 ), and as opportunities for membrane thickness tuning exist, this seems realistic for future BPM architectures.…”

Electromembrane Processes: Experiments and Modelling

“…Pärnamäe et al [8] present a perspective article with the state-of-the-art and latest developments of the AB-FB. The technology has already been demonstrated at the laboratory scale with maximum energy density and power density in discharge of ~10 kWh m −3 and ~17 W m −2 membrane, respectively.…”