First, let’s look at south and central Florida. For that area, a direct or open loop system would be perfect. Direct/open loop means the water goes directly into the copper tubes in the collector and from there down into the tank. This type of system is the most efficient on the market. The number of freezing nights in Florida is few, but freezes do happen. Freeze protection for this system is provided by a flush valve. If temperatures drop to near freezing, the valve opens up and allows warmer water to flow through the collector. This kind of system is highly efficient, but would not work in those climates which would bring most Floridians to their knees (or perhaps scurrying for the nearest cocoon.) For our next example, let’s pick Wisconsin. Obviously some wimpy little flush valve would not work in any part of this state.
A solar thermal system will work just fine way up north, but a more appropriate type would be either a drainback or a closed loop system. A drainback system simply means that whenever the system is not running, all the water drains out of the collector – so no freezing. A closed loop system – equally appropriate for a cold climate – means the only thing that circulates through the collector is an anti-freeze solution which after having collected heat flows back to the tank and transfers its heat to the water. So… no freezing. Yes, antifreeze is nasty stuff, so every system where it is used is double walled for extra protection. There are systems available for every climate. For an excellent primer on solar water heater systems, go to www.fsec.ucf.edu. Click on “Solar Thermal”, then “applications”, then “solar heating options in Florida”. This should say “solar heating options for Anywhere” as all major types of systems well explained… with diagrams.