Thermal Modelling, Management, and Electrical Safety Assessment for Containerised Vanadium Flow Battery Systems

As decarbonisation policies continue to advance, the need to enhance the utilisation of clean energy sources, such as wind and solar power, becomes increasingly critical. However, the intermittent nature of these renewable sources frequently leads to supply-demand imbalances, posing challenges to grid stability and necessitating greater long-duration energy storage capacities. Traditional energy storage technologies are limited in their storage duration, and extending this capability often requires significant increases in land use, equipment, and costs, rendering them less suitable for large-scale applications. The Vanadium flow battery (VFB), which stores energy in liquid electrolytes, presents a distinct advantage by allowing extended storage through increased tank volume without the need for substantial equipment expansion. In industrial applications, where VFB systems are typically containerised, the development of a thermal model is essential for maintaining effective temperature management during long-duration storage. Additionally, continuous electrolyte leakage may occur during VFB operation, which introduces electrical safety risks, highlighting the importance of electrical safety risk evaluation for VFB system operation. This thesis focuses on the thermodynamic modelling of a containerised commercial VFB system, utilising the model to explore thermal management performance in VFB long-duration energy storage applications integrated with photovoltaic systems and assessing electrical safety risks based on an equivalent circuit model. Specifically, this thesis includes three key aspects: 1. A dynamic thermal model is developed for containerised VFB systems, based on which thermal design options are evaluated using simulation studies. The model contains mass balance and energy balance of stacks, tanks, pipes and air temperature inside the VFB container. Simulation studies were implemented to determine the temperatures of electrolytes in the stacks, the tanks, pipes, and air temperature inside the container, in response to the ambient temperature dynamics in regions with different climates. The results indicate three important factors that can help maintain normal operation temperature range for the VFB system. Proper insulation materials and heat from inverters can help to maintain the steady-state temperature of tanks and stacks without additional heating in regions with low ambient temperatures. It is better to isolate the inverters from the inside of the container in scenarios when the ambient temperature is high. Passive cooling is not sufficient to maintain VFB normal operation for high ambient temperature range sceneries. This dynamic thermal model provides essential support for the thermal management of large-scale containerised VFB systems applied across diverse climatic conditions. 2. Using the containerised VFB thermal model developed in Part 1, this study investigates the temperature dynamics of 6-hour and 8-hour VFB systems integrated with photovoltaic sources. By examining how different operation times, load profiles, and ambient conditions affect temperatures in the stack, tank, and container, it provides critical insights into the cooling and heating requirements needed to ensure safe operation across various climates. Building on this foundation, the system is extended to explore the feasibility of a hybrid thermal management strategy, combining passive and active cooling. Because PV output fluctuates with irradiance intensity, the VFB’s charge–discharge behaviour is influenced by climatic and seasonal variations, making effective cooling essential for temperature regulation. Notably, higher-capacity systems require active cooling at lower ambient temperatures due to increased ohmic heating and greater thermal mass, whereas the heat generated by the inverter can be harnessed under cooler conditions and isolated in hotter environments. Ultimately, these findings underscore the benefits of a well-designed hybrid cooling strategy for keeping containerised VFBs within safe temperature limits while minimising auxiliary power demand, offering valuable guidance for large-scale, long-duration applications. 3. An electrical safety assessment method is proposed, drawing on a comprehensive electrical equivalent circuit model for multi-stack vanadium flow batteries that takes into account both cell voltages and the ionic resistance of the electrolyte in flow channels, manifolds, and connecting pipelines. By applying Gauss’s flux law to analyse electric field distributions during continuous electrolyte leakage, this method identifies potential electric shock risks and delineates safe operating zones under various conditions. Case studies conducted on a commercial VFB system show that, while leakage-induced electric shock risks are generally low under standard electrical configurations, certain electrical connection setups require additional safety measures to protect both the system and the public. Emphasising the importance of electrical safety evaluation and clearly defined safe zones, this approach can be adapted for electrical safety assessments of other flow battery systems.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2025

Author dc:creator

• Shu, Bing

• Vanadium Flow Battery
• Electrical Safety Assessment
• Thermal modelling
• Thermal management
• anzsrc-for: 4004 Chemical engineering
• anzsrc-for: 4008 Electrical engineering
• anzsrc-for: 400404 Electrochemical energy storage and conversion

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/31204

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/105100