Electricity generated from renewable sources such as wind and solar power is intermittent. Electrical energy storage devices are therefore critical for effectively leveling the intermittent nature of renewable energy sources. Ultracapacitors (UCs), also known as supercapacitors, have the potential to meet the power requirements for the grid-scale renewable energy storage systems. As compared to batteries, UCs offer a higher power density, higher efficiency, and longer shelf and cycle life. Because the performance of UC depends on temperature, it is important to calculate accurately the thermal behaviors of an individual UC cell in the module composed of multiple UC cells for the efficient and reliable systems integration of UC in grid applications.

In this work, modeling is performed to study the thermal behaviors of the module composed of 18 UC cells. The thermal behaviors of the ultracapacitor cells in the module are measured during the charge/discharge cycling of the ultracapacitor module with constant-current. The charge/discharge current values examined are 50, 100, 150, and 200 A. The validation of the modeling approach is provided through the comparison of the modeling results with the experimental measurements.

Fig. 1 shows the schematic diagram of the ultracapacitor module composed of the 18 ultracapacitor cells (3.7V/3000F) from LS Mtron Ltd. (Anyang, Republic of Korea). The red dots with numbers in Fig. 1 indicate the positions for thermocouple measurement. In Fig. 2, the variations of surface temperature with time from the modeling are compared with those from the experiment during the charge-discharge cycles with the constant current of 200 A. The modeling results shown in Fig. 2 are in good agreement with the experimental measurements.