This design improves the performance of conventional water heating collector by extending the area of the collector to include an air heating collector that warms the area around the water heating collector to reduce heat losses from the water heating collector.
explained in detail in Shurcliff's book: New Inventions in Low-Cost Solar Heating
Gordon's original article on his implementation of the design along with construction details is here..
Its been two years and Gordon has a good report on the things that worked and the things that did not work so well and had to be fixed or improved.
The report covers: performance, a new differential controller, pumps, backup water heaters, and some plumbing issues....
All good stuff to know if you plan to use this design.
March 31, 2013