Solar Hot Water Collector Types

So you’ve decided on the type of solar water-heating system for your home: direct-gain or heat-exchange. Now you must decide on the type of solar collector you will be using to heat your fluids. Taking note that a heat-exchange system uses a roof tank to warm and store your hot water, and that the separate tank systems require solar collectors, your two viable options are between a flat-piece or evacuated tube collector.

Flat-piece collectors are insulated and glazed 4x10 foot black boxes that have copper wires of small diameter running through them. A typical residential home would require 1-3 flat-piece collectors, a system that has been well tested for its effectiveness. The evacuated tube collectors, or ETs, are newer in design (circa 1970s) and comprise several sealed glass tubes of 4 to 6 inches by 7 feet which are vacuumed for high insulation. A typical residential home would take on 12 to 24 ETs that are serially linked and connected to a copper head that is insulated, which allows heated water to run to and from the water heater.

In comparison, both collectors function well and many homeowners are satisfied with their ability to provide for their necessary hot water needs. The flat-piece collectors have the advantage of being less costly and having an impressive track record of usability. But the flat-piece collector’s cost may fluctuate with the price of copper as the flat-piece collector takes on quite a bit of copper component in its design.

If you prefer the ET collector, you should find an installer who is experienced and well versed with this type of solar collector. When you are more familiar with the options, you will make a better choice of installation for your solar system. Factors which may sway you into choosing ETs include:

- Better insulation than flat-piece collectors

- Better performance in cold weather (assuming it still gets sunlight during non-freezing daytime hours)

 - Ability to rotate sideway to catch more sunlight (especially important if the roof is not facing south or the solar window is blocked)

- More polished and aesthetic ally attractive than flat-pieces, which, being open, are subject to condensation on their glass pieces, making them less attractive than ETs

- Ability to raise them when on a roof with a mount or rack in cold climates, which is best to limit snow accumulation. This is because the snow will run through the rounded gaps. This is known as snow loading

-  Raised or racked ETs have a wind loading that is lower than that recorded on flat-pieces, even if the flat-pieces are also racked

- ETs weigh less than flat-pieces, placing less stress on the roof