Influence of the air gap between two cells of the storage battery on the thermal conditions of its operation: Numerical analysis and reliability assessment

Abstract

To control the operating conditions of battery energy storage systems (BESS), the cells are combined into assemblies and modules located mostly in a closed space limited by the battery case. There are air gaps between the cells of the battery assembly. Energy dissipation in cells leads to an intense heat removal in the closed region of the air gap. As a result, the temperature of the battery assembly increases with possible further uncontrolled thermal runaway and subsequent battery ignition. Despite the increasing number of fires and explosions of battery ESSs every year, there is still no theory providing the ability to predict the conditions of fire and explosion safety of energy-intensive energy storage systems based on storage batteries. Particularly, there are no reliable data on the temperature fields of the cells of battery assemblies during intensive charge/discharge processes.The aim of the work was to analyze the thermal conditions of operation of a storage battery consisting of two typical prismatic cells, taking into account heat transfer in the air gap between the cells. Electrothermal modeling was performed for a fairly typical battery by solving a non-stationary heat conduction equation in a two-dimensional formulation by the finite difference method. The most realistic ranges of variation in the values of influencing factors were considered. In addition, the paper presents assessment of the thermal conditions of operation of a single cell and a comparative analysis of the obtained representative temperatures with the representative temperatures of a battery assembly of two battery cells. It has been established that the temperature of the case of cells of the battery assembly is 3–7 °C (depending on current loads) higher than the temperature of the case of a single cell at equal conditions. The obtained results show the need to take into account the heat transfer between the cells of the battery assembly when analyzing the temperatures of such assemblies.