I'm going to put my raspberry pi zero in a water/air tight box outdoors, but I'm worried that it might overheat with it preforming tasks all day and sitting in the sun. Considering that, I want a way to cool it down without breaking the water seal. That makes a fan, not an option. Can anyone tell me how to cool it down without a fan? I don't think a heat-sink is enough to solve the problem because there is no airflow to transfer heat to.