Researchers from Skoltech, Sirius University, and Zhejiang University have proposed a new approach for analyzing and optimizing the long-term operation of vanadium flow batteries across a wide range of ambient temperatures. The developed model, validated by experimental data, allows for accurate prediction of system efficiency and energy capacity, which is critically important for their integration into power grids and for use in industrial energy storage systems within Russia’s climatic conditions. The results, which can enhance the reliability and economic viability of large-scale vanadium-based energy storage systems, have been published in the Applied Energy journal.
Vanadium flow batteries are considered one of the most promising solutions for creating large-scale energy storage systems. Their key advantages are long service life, the ability to fully discharge without degradation, and flexible scalability to meet the needs of power systems. One of the main indicators of such batteries is their energy efficiency — the ratio of energy delivered during discharge to the energy spent on charging. The higher this indicator, the lower the losses and the more economical and reliable the system, which is especially important for the operation of large-scale systems supporting power grids and managing load.
Thermal processes play a special role in battery operation. During charging and discharging, the system can release a significant amount of heat, and this directly affects the temperature, hydraulic properties, and stability of the system. Large energy storage systems are often placed outdoors, making them vulnerable to seasonal temperature fluctuations. Previously, the authors had already developed a non-isothermal model that allows real-time tracking of key system parameters, including temperature, voltage, and power. However, until now, no comprehensive study had been conducted on how exactly all these factors affect the overall energy efficiency of the battery under real operating conditions.
“In the course of the research, an analytical formula for determining the equilibrium temperature of the battery, which establishes itself during long-term operation, was derived for the first time. This tool allows for a quick assessment of the system’s thermal state and prevents overheating without the use of complex computations. The model was validated on a 5 kW experimental setup and showed high accuracy: The calculation error for voltage was less than 2%, and for temperature — less than 3%,” commented the study’s lead author, Stanislav Bogdanov, a junior research scientist at the Skoltech Energy Center.
The systematic study revealed conflicting trends: While the system’s energy efficiency decreases with increasing pump power due to increased hydraulic losses, the absolute energy output can increase thanks to more intensive electrolyte pumping. Low temperatures allow for achieving high power due to better cooling but require more energy to pump the viscous electrolyte. Conversely, high capacity and efficiency are achieved at room temperature, but power has to be limited to avoid overheating.
“The presented method serves as a tool for informed decision-making. For example, maximum power is the priority for emergency grid startup, while maximum efficiency is key for daily peak shaving. Our research provides practical recommendations for selecting optimal operating modes for industrial energy storage systems based on vanadium flow batteries,” noted Mikhail Pugach, a senior research scientist at the Skoltech Energy Center, co-author, and leader of the project and the study.
