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Blackened aluminum collector cups are the heart of the solar energy collector developed by the International Solarthermics Corporation.
The firm claims such cups provide a larger collector surface from a smaller area than the conventional black surface which is flat. The sups allow for a reduction in total area and size for the collector unit. A blower circulates air behind the class and over the cups, forcing heated air into rock storage inside the a-frame housing, 05/1975. Photographer: Norton, Boyd. Original public domain image from Flickr
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