soLAR DESIGNS for water heating

Five Main Solar Designs

Solar hot water heaters range from the very simple, for hot and moderate climates, to fairly complex solar designs for colder climates:

- the batch solar design (an ultra-simple system for moderate climates);
- the thermosyphon design (mainly for moderate and hot climates);
- the solar active design (or solar open-active systems, for moderate and hot climates);
- the drainback solar design (cold climates);
- the glycol and other closed loop designs  (anti-freezing pressurized solar hot water design for cold climates).

Batch solar Designs

The batch solar design (or ICS) is the simplest and, in a way, the oldest solar hot water heater system.

It hasn’t pumps, separated storage tanks or anti-freezing.

It combines a solar panel and a storage tank into one single unit, and in their most simple version, it is a mere water tank within a glazed box.

See, for details:
Batch solar water heaters

Image: EERE

Thermosyphon Design

Thermosyphon solar designs are simple, very efficient and very popular in moderate and hot climates.

They are cheap and they not include pumps or special controls, and can also be installed in colder climates when equipped with small circulating pumps (to move water and to prevent it from freezing).

See:  Thermosyphon design

Active Solar Design

If you live in a moderate or hot climate, without freezing problems, you may choose a simple solar system composed by panels, a simple pump and using water as the liquid medium. Such design is technically called an active solar system, or an open-loop direct system. See: Active Solar Designs

Glycol solar and other closed Loop Designs

Cold climates require more complex solar designs. Batch systems are clearly inadequate in freezing conditions, and the thermosyphon design can be too simple.

One of the most popular solar designs for freezing climates comprises a relatively complex system with an antifreezing fluid (glycol, usually), a differential controller, a storage tank and also a heat exchanger, sensors and valves.

See, for details: Glycol solar design and other closed-loop systems
Image: Southwest Gas

Drainback solar designs

Like glycol and other closed loop systems, the drainback design responds to cold climate needs. They aren't as complex as other cold-climate solar water heating systems, and offer low maintenance, long lifespan and reliability.

See, for details: Drainback solar design