Improving both energetic and kinetic performances of osmotic battery for grid energy storage

• Main Authors: Li, Dan, Mo, Zijing, Fane, Anthony G., She, Qianhong
• Other Authors: School of Civil and Environmental Engineering
• Format: Article
• Language: English
• Published: 2025
• Subjects: Engineering; Osmotic battery; Energy storage system
• Online Access: https://hdl.handle.net/10356/181991
• Institution: Nanyang Technological University

Osmotic battery (OB), alternating the operation of reverse osmosis (RO) for charging and pressure-retarded osmosis (PRO) for discharging, is an emerging grid-scale energy storage system (ESS) that offers complementary advantages over other existing grid ESSs. OB utilizes osmotic pressure difference of two solutions as a media for energy storage. However, OB faces the issue of energetic-kinetic trade-off generally applicable in all the ESSs. This study aims to quantitatively analyze this trade-off in OB and to develop effective strategies to address this issue. Our analyses suggest that this trade-off can be addressed by (1) raising the initial high-salinity solution concentration (cHS,0), and (2) using more water permeable osmotic membranes with a suitable high-salinity solution. For example, increasing the cHS,0 from 1.2 M to 2.4 M increases energy density from 0.5 to >1.0 kWh·m−3 along with an enhanced power density and a stable high roundtrip efficiency (RTE) above 66 %, albeit requiring membranes with substantially improved mechanical strength. Furthermore, using high-permeance nanofiltration-type osmotic membranes with divalent high-salinity solution could improve the peak power density to above 50 W·m−2 while maintaining energetic performance. This study not only offers effective strategies to ease the energetic-kinetic trade-off but also recommends important directions for developing future osmotic membranes for OB.