Experimental analysis of operating time improvement of fast charging power device with composite phase change materials

The popularity of electric vehicles has led to an urgent need for high-power fast charging piles. However, increasing the charging power leads to a large amount of heat from the power device, which greatly restricts the operation time of the charging piles. An innovative hybrid thermal control system for power devices by combining liquid cooling and composite phase change material (CPCM) is proposed, and the operating time for the power device is evaluated by measuring the critical time that the power device reaches its thermal hazard temperature threshold caused by overheating. It is demonstrated that the maximum operating time of the power device improves significantly with the CPCM coating, and the effects of the phase transition temperature, coating thickness, and thermal conductivity of CPCM on the maximum operating time of the power device are studied. Compared with the single liquid system, the maximum operating time of the power device is extended by 910 s after adding CPCM at the heat flux of 2.7 MW/m(3), and the energy consumption ratio (ECR) of the cooling system is decreased by 81.99 %. A larger extended operating time of 1180 s is found as the addition of CPCM with a phase transition temperature of 52 degrees C, which is about 6.9 times higher than the single liquid cooling. Increasing the CPCM thermal conductivity from 6.05 W/(m<middle dot>K) to 8.99 W/(m<middle dot>K) extends the operating time of the power device from 1110 s to 1560 s, and a decrease from 0.428 W/h to 0.305 W/h for the ECR of the cooling system is also found. Increasing the CPCM coating thickness from 3 mm to 7 mm increases the maximum operating time from 1110 s to 1230 s, but a further increase in the CPCM coating thickness gives less improvement in the ECR of the cooling system. In addition, the temperature difference of the power device with and without CPCM is analyzed to reveal the mechanism of CPCM in improving the charging time of the high-power fast charging piles.