Fraunhofer Energy AllianceFraunhofer ISE
The exhibit shows an arrangement of 4 battery cells within a phase change material (PCM) composite developed at Fraunhofer ISE. The PCM allows a passive temperature control of the batteries. During operation the PCM stores the dissipated heat of the batteries. When the batteries are resting or operating at low load, the heat is released to the environment and the battery cells.
If the PCM is heated up above the melting temperature a phase change from solid to liquid takes place. At the same time the PCM temperature remains constant, thus achieving effective cooling of the batteries.
Besides the constant temperature of the phase change the main advantage of the PCM is the high storge density and capacity. The developed material has a melting enthalpy of approx. 140 kJ/kg. For comparison, liquid water would have to be heated by approx. 33 K for the same storage capacity.
To remain the position of the PCM during phase change it is shape stabilized and processed into a composite material. Accordingly, the phase change only occurs within the composite material. There is no need for an encapsulation like it is used in common PCM applications.
The developed composite material is particulary suitable for the reduction of temperature peaks and fluctuation as well as for achieving a more homogeneous temperature distribution within a battery module.