## 4 Experimental Results and Discussion  
Before each experiment, chilled water was initially introduced to reduce the temperature of the electrolysis stack below 40 \({}^{\circ}\)C. Subsequently, the hydrogen production system was started. During the initial phase of hydrogen production system startup, the electrolysis stack temperature continued to decrease slightly due to the influence of the chilled water before gradually rising again. Due to varying initial cooling conditions, each experiment could not start at the same initial temperature. However, the initial current value at the starting voltage remained relatively low and did not affect the final experimental results. When the hydrogen production system started operating, the voltage of the electrolysis stack gradually increased from the starting voltage to the target voltage over time, and the temperature of the electrolysis stack also rose slowly. Before the temperature of the electrolysis stack reached 65 \({}^{\circ}\)C, no chilled water entered the electrolyte for cooling. Once the temperature of the electrolysis stack reached 65 \({}^{\circ}\)C, the thermal control algorithm automatically activated to adjust the angle of the electric three-way valve, allowing the chilled water to enter the plate heat exchanger for electrolyte cooling. This kept the temperature of the electrolysis stack controlled within the optimal operating temperature range of 70-75 \({}^{\circ}\)C. To prevent the temperature of the electrolysis stack from exceeding the optimal operating temperature range, the target temperature was adjusted to the midpoint of the range, specifically 72.5 \({}^{\circ}\)C.  
In the experimental results, Figure 5 illustrates the temperature response of the electrolysis stack in the hydrogen production system under various thermal control strategies. It can be observed that there was a significant variation in the temperature of the electrolysis stack, varying within a range of 72.5 \(\pm\) 2 \({}^{\circ}\)C. These variations are primarily due to the delayed response of the electric three-way valve, which adjusted flow rates only after receiving output from the FLC strategy. As the electric three-way valve adjusts to the set flow rate, a noticeable temperature discrepancy occurs between the current temperature and the temperature output from the FLC strategy, resulting in suboptimal thermal control outcomes. Therefore, by using an LSTMNN algorithm to predict the temperature of the electrolysis stack after the relay is opened, followed by applying the FLC method for calculation, significant improvements can be achieved in the thermal control of the electrolysis stack compared to the original FLC strategy. The temperature prediction approach reduced the temperature discrepancy, enabling the final experimental results to maintain the temperature of the electrolysis stack within a narrower range of 72.5 \(\pm\) 1 \({}^{\circ}\)C.  
Figure 5: Temperature response of the electrolysis stack with different thermal control strategies, comparing temperature stability under various approaches and demonstrating how the two strategies affected temperature regulation. Figure 6 illustrates the power response of the hydrogen production system under two different thermal control strategies: one using FLC alone and the other incorporating the LSTMNN. From the comparison of the power outputs, it was observed that the thermal control results using FLC with the LSTMNN consistently maintained the power around 10 kW, with very minimal fluctuations upon reaching a steady state. This indicates improved stability compared to using the FLC method alone, which showed significantly reduced temperature fluctuations. Figure 7 shows the current response of the electrolysis stack in the hydrogen production system using the two thermal control strategies. The current remained stable at approximately 263 A, showing negligible fluctuations compared to results from the FLC method alone. Hydrogen production rates were separately calculated for both thermal control methods using Equation (2).