Analysis of Three-Stage Preheating Strategy and Heat Transfer Mechanism of Metal-Supported Solid Oxide Electrolysis Cell System

This study details the dynamic model of a metal-supported solid oxide electrolysis cell (MS-SOEC) system, which includes a metal-supported stack, evaporator, heat exchanger, and associated heaters and blowers, forming an integrated electrolysis and thermal management unit. A novel, three-stage cold-start strategy is proposed to ensure a safe thermal ramp-up from room temperature (303.15 K) to the target operating temperature (873.15 K). By leveraging the internal heat generated during the second stage, this strategy reduces the total preheating time by approximately 46 min and improves the startup efficiency by 27.7% compared to a conventional approach relying solely on external heaters. Adhering to these parameters effectively suppresses thermal shocks, keeping peak conduction heat transfer below 7000 W and ensuring both a safe and efficient startup. The system employs a dual-side proportional-integral-derivative (PID) controller control strategy targeting a fixed heating rate of 2 K/s during the ramp-up. The effectiveness of this control is demonstrated as the PID signals for the fuel and air-side heaters drop from a peak of 14 200 during the initial startup to 300 and 100, respectively, at steady-state. This drastic reduction highlights the heat exchanger's high efficiency in reclaiming reaction heat and minimizing the external power demand once operational.