An example system includes a housing configured to house a portion of an electric machine and a heat transfer material, the heat transfer material is configured to contact a conductor of the portion of the electric machine and to remove heat from the conductor and transfer heat to the housing. The system includes a coolant configured to remove heat from the housing. An inner surface of the housing comprises a plurality of structures configured to increase an inner surface area of the housing, wherein the plurality of structures are configured to contact the heat transfer material.