How does it work?
Skyline solar water heaters are incredibly simple and dependable. Propylene Glycol (antifreeze) is circulated through solar collectors on your roof where heat is gathered from the sun. The heated glycol flows to a special tank with an internal heat exchanger that transfers the heat to your household water. A small solar electric panel powers the system and regulates its operation, so it is completely automated and self sufficient. The system will automatically operate when there is solar energy available and the tank stores the heated water for future use and serves as a backup water heater when required.
Source: Department of Energy, Energy Efficiency and Renewable Energy 