Solar hot water technology

Solar hot water technology is fairly basic or even low tech, and comprises a set of well tested designs, responding to different climates and uses.

Basic solar water heaters technology

Over 30 million of solar hot water heaters have been put in Chinese homes, and many more millions worldwide. Solar hot water heaters is a proven and tested technology, even in cold and cloudy climates.

Sophisticated solar hot water systems cost several thousand dollars - a lot more than conventional gas or electric systems - but they can reduce heating bills by half or more, saving money over time. See: Solar costs and payback.

The solar water heaters technology

Solar water heaters technology is truly simple, and hasn't change much over the two last decades.

These systems have now better circulating pumps, better heat exchangers, better valves, and other better components, but the technological core remains the same, mainly at the solar collectors level...

It's true that there are now more efficient solar panels (the tube solar), but on the whole the solar hot water technology remains rather low-tech - only more efficient in their designs for colder climates.

Solar water heater technology designs for colder climates

There are two main types of designs for colder climates: the drai nback, the glycol (and other antifreezing closed loop).

These designs require more efficient solar panels (evacuated-tubes) and a larger number of components: pumps, controllers, antifreezing fluids...

Solar water heater technology designs for moderate and hot climates

In moderate and hot climates the thermosyphon design is largely dominant.

The batch (or ICS) design is losing market share, though used by many DIY enthusiasts (due to its extreme simplicity). It's basically a system for solar water heating in moderate climates.

The active solar design is also largey used in moderate climates.

The differences

Most solar systems use flat solar panels or tube solar panels.

Some use pumps (active systems, including the drainback design) while others are based on gravity or natural convection (passive systems).

Some use anti-freezing fluids (glycol design...), while others use potable water at the collector level.

A system uses an integrated tank (the batch solar system), another a well insulated storage tank on the top of the collector (the thermosyphon system), while the others use auxiliary or backup tanks and well separated storage tanks.