"The tubing (or heat exchanger) is filled with a liquid refrigerant material. The reflective panel focuses light and heat energy from the sun onto the piping which vaporizes the refrigerant. So far, no ice. When the sun goes down however the vapor goes through massive heat loss due to pressure differences and roughly 14 pounds of ice are produced depending on the design.
The refrigerant rapidly cools once it hits 104 degrees Fahrenheit, due to its unique properties making, it perfect for typical temperature ranges in warm climates.