Thermo-electric coupling characteristics and operation parameters optimization of high-voltage electric heating elements for molten salt thermal energy storage

In recent years, molten salt thermal energy storage technology has been widely applied in renewable energy consumption. Molten salt electric heaters (MSEHs) serve as key devices for electricity-to-heat conversion in thermal storage systems. Compared with conventional low-voltage MSEHs, high-voltage MSEHs can be directly supplied by 10 kV or 6 kV power systems, enabling more efficient and scalable integration with industrial high-voltage distribution infrastructure. However, electric heating elements in high-voltage MSEHs are prone to dielectric breakdown and resistance wire fusing during operation. This study developed a coupled thermo-electric model to quantify the temperature and electric field distributions for electric heating elements with different diameters. The results indicate that the element diameter exerts a dual influence on heat conduction and electrical insulation performance. As the element diameter increases from 20 mm to 40 mm, the maximum internal electric field strength decreases from 1.29 kV/mm to 0.76 kV/mm, while the maximum internal temperature rises from 800.5 °C to 947.7 °C. Furthermore, high-voltage breakdown tests indicate that the 40 mm element is better suited for 10 kV heaters. Moreover, the overheating behavior of electric heating elements under varying heat transfer coefficients and surface power levels was investigated. Finally, a neural network model was introduced to predict the maximum element surface temperature and the maximum electric heating wire temperature under varying operating conditions. Based on the prediction results, the appropriate operating range of the electric heating element was determined, providing guidance for selecting operating conditions in high-voltage electric heating elements.