*2.4. Hybrid Cooling Systems*

Some hybrid BTMSs combine natural air convection with liquid and thermoelectric cooling systems [45]. With a thermoelectric cooler (TEC), all the processes concern transformations from electricity to heat and vice versa. These systems can work like coolers as well as like heaters (useful for those technologies that have to work in the extremely lowtemperature environment). Lyu et al. compare the temperature reached by a cylindrical lithium-ion cell if it is cooled with air, with liquid, and finally with a hybrid BTMS, which combines air and liquid cooling methods and a TEC system. Results show that during the test with air-cooling, the cell temperature increases with the voltage, and the higher is it, the faster the temperature rising. With the liquid-cooling, it is shown that the cell temperature and the water temperature rise almost together and with a more moderate trend. Lower cell temperatures can be obtained using the hybrid TEC system.
