Solar hot water heaters range from the very simple (for hot and moderate climates) to the fairly complex (for colder climates):
- the batch systems (an ultra-simple system for moderate climates);
- the thermosyphon systems (for moderate and hot climates);
- the drainback systems and glycol and other closed loop systems (for cold climates).
Batch solar System Design
The batch system (or ICS) is the simplest and the most direct heirs of the first solar water heaters.
It combines a solar panel and a storage tank into one single unit; in its most simple version is a mere water tank within a glazed box.
See, for details:
Batch solar water heaters
The Thermosyphon System
Thermosyphon solar systems are simple, very efficient and very popular in moderate and hot climates.
They are cheap and do not include pumps or special controls; they can be installed in colder climates when equipped with small circulating pumps (to move water and to prevent freezing problems). That's a simple design.
See: Thermosyphon Systems
Glycol and other closed Loop Systems
Cold climates require more complex solar water heaters.
One of the most popular systems for cold climates - the closed loop systems - comprises an antifreezing fluid (glycol, usually), a differential controller, a storage tank, a heat exchanger, sensors and valves.
Like glycol and other closed loop systems, drainback systems are designed for cold climates. They offer low maintenance, long lifespan and reliability.
See, for details: Drainback solar design