126 Chapter 10 Figure 9 Behr refrigerant-based battery cooling system. Courtesy MAHLE International GmbH. ZĞĨƌŝŐĞƌĂŶƚĂƐĞĚĂƩĞƌLJŽŽůŝŶŐ^ĐŚĞŵĂƟĐ ŽŶĚĞŶƐĞƌ sĂůǀĞ ŽŵƉƌĞƐƐŽƌ &ĂŶ džƉĂŶƐŝŽŶ ǀĂƉŽƌĂƚŽƌ ŚŝůůĞĚ ŝƌ ,ĞĂƚĞĚ ŝƌ ĂƩĞƌLJWĂĐŬ Figure 10 Direct refrigerant-based cooling schematic. attached to the lithium-ion cells. In actual usage, direct cooling is much more feasible with an air-cooled system where the thermal system can be designed such that the air is either pushed or pulled directly across the cells. Refrigerant-based cooling systems are yet another method for thermally managing a battery system.
Refrigerant-based systems have many of the same benefits as liquid-cooled systems, but tend to have a slightly higher cost. On the positive side, they eliminate the risk of liquid leakage into the battery pack. One such example is the system introduced by the Behr Group, now MAHLE International GmbH, who introduced a refrigerant-based cooling system targeted at HEV- and EV-type batteries (Behr, 2010) ( Figures 9 and 10 ). Heat pipes have been discussed and evaluated for various lithium-ion-based battery thermal management systems, but as of today have not yet been able to offer either the performance or the cost advantage to make them worth investigating for large energy storage systems.
In principle, the heat pipe combines two different thermodynamic principles, thermal