The heat from the user's head is transferred to the PCM by conduction through a heat sink extending over the user's head. No power is needed for the cooling system. The temperature in the user's head is kept just above the PCM temperature, so the user would not suffer from an uncomfortable and dangerous warm environment in the head that will affect the user's alert. The cooling unit is able to provide comfort cooling up to 2 h when the PCM is completely melted. The stored heat of the PCM bag would then have to be discharged by immersing it in water for about 15 minutes to solidify the PCM before reusing it. The PCM hull cooling system is simple and has potential to be implemented as a practical solution to provide cooling comfort to motorcyclists.