AKA: Solar thermal panels
Asolar collector consists of a network of pipes through which water (orin colder climates, antifreeze) is heated. Collectors come in varioussizes, with 4 by 8 feet (1.2 x 2.4 m) the most common.
On atypical summer day (sunny and warm), the fluid in the collectorsreaches 140°F to 180°F (60°C-80°C). On a clear winter day (sunny andcold), it can reach 120°F to 150°F (50°C-65°C). When it´s cloudy andwarm, collectors can reach 70°F to 90°F (20°C-30°C), and when it´scloudy and cold, 50°F to 60°F (10°C-15°C). As long as the temperaturein the collector is greater than that of your incoming cold water(usually about 50°F; 10°C), your solar hot water system is saving youenergy.
Several types of solar collectors are on the market.Flat-plate are thin (3-4 in.; 7-10 cm), black, and covered with glassto hold in the sun´s energy.
Inevacuated tube collectors, a glass tube surrounds each individual pipein a vacuum. This nearly eliminates the influence of ambient airtemperature. Evacuated tubes perform better than flat-plate collectorsin cloudy weather, and can achieve higher temperatures compared toother collector types, but are typically more expensive. All activesystems and some thermosyphon systems may use either flat platecollectors or evacuated tube collectors.
A third type, calledintegrated collector storage (ICS) or batch, combines the solarcollector and storage tank into one unit. An ICS panel can resemble aflat-plate collector with greater depth (6 in.; 15 cm). A simple batchheater can be a tank within a glazed box.