Solar Hot Water Panels

A solar hot water panel is simply a type of solar thermal energy collector. Typically a central component in residential solar hot water systems, it functions by collecting the sun's radiant heat energy and transferring it to the heat absorbing liquid flowing within it (generally water or antifreeze depending on the application). There are basically two types of solar hot water panels specifically, plate collectors and evacuated tube collectors (see the general description of solar thermal collector operation on our residential solar systems page)

Medium to High Performance Panels

Standard Flat Plate Collectors - The performance of these solar hot water panels depends greatly on the materials used in their construction. For instance lower performance can be expected from using a black polymer for the collector plate. Much higher performance is gained from metals (especially copper). Of course, this increases the cost/price of the unit.

The next generation of flat plate collectors is starting to employ very advanced technologies. For example, new glazing materials are being integrated that essentially operate like a one-way mirror for thermal energy. This glass allows solar energy in, but when the collector plate heats up and starts to re-radiate infrared energy, the interior side of the glazing reflects the heat back onto the collector plate. This forces the efficiency of the of the collector upward as it will heat faster and stay hotter longer, extending its useful operating time to earlier and later hours of the day.

Very High Performance Panels

Evacuated Tube Solar Collector - Given the different types of panels, the most efficient is the evacuated tube solar collector. This latest generation of collectors has multiple longitudinally oriented absorption tubes within vacuum sealed external glass tubes. The absorption tube has a metal fin that runs down its length. A special coating simultaneously captures solar thermal energy and suppresses its re-radiation away through the collector's glass tube(s). This configuration gives these panels very high efficiency ratings due to very low heat loss characteristics. Commonly found in commercial (e.g. laundromats) and or colder climate residential installations these collectors can be used to heat air or water. Thermal ratings are in the 25 - 28 kBTU/day range. They tend to be very expensive but can produce temperatures that significantly exceed the boiling point of water.