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Green Building Primer

Active Solar Energy Systems: Collectors
Introduction   Collectors   Hot Water   Space Heating   Space Cooling   Resources

All active solar systems, whether they are intended to produce domestic hot water, space heating, or space cooling, need to have collectors to capture the sun's energy.

Flat Plate Collectors
Glazed flat-plate collectors are insulated and weatherproof boxes containing a dark absorber plate under one or more glass or plastic covers. Unglazed collectors, typically used for solar pool heating, have a dark absorber plate made of metal or polymer, without a cover or enclosure. This type of collector is by far the most common. With both types, small tubes run through the box and carry a fluid (either water or an antifreeze solution). As the sunlight hits the dark absorber plate, it heats up and transfers heat to the fluid passing through the tubes.


Image courtesy of NREL



Image courtesy of EERE


Evacuated Tube Collectors
Evacuated tube collectors feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and a metal absorber tube attached to a fin. The fin’s coating absorbs solar energy but inhibits radiative heat loss. The tubes are manufactured with a vacuum between the outer and inner tubes, which helps them achieve very high temperatures. They are used more frequently for US commercial applications, but are increasingly being used in residential applications.

View an animated explantion
of how solar collectors work -->

Image courtesy of EERE

Photos of the Wells house in Williamstown taken by Helena Harnik, '07.
The collectors are angled to maximize sunlight absorption during Januray and February.


Integral Collector/Storage (ICS) or Batch Collector
is an insulated, glazed box containing one or more black tanks or tubes. Cold water passes through solar collector and gets preheated. The collector is the storage tank in this system. Preheated water enters a conventional backup water heater, providing reliable source of hot water. These systems should only be installed in mild-freeze climates as outdoor pipes could freeze in severely cold weather. See the section on solar hot water in this document for more information on this type of system.