Friday, January 28, 2011

Solar Water Heating Using a Unique Master and Slave Collector Design

Gordon has added solar water heating to his very very efficient home.  The system is loosely based on the our $1K solar water heating design, but incorporates some really interesting changes.

The collector uses a large "slave" collector to enclose and improve the efficiency of a smaller "master" collector.  This is design developed by Dinh Khanh some years  back and is explained in detail by William Shurcliff in this chapter of his book on solar innovations...   Basically, the larger slave air heating collector provides a warm environment for the small water heating master collector.  In Gordon's rough test, the slave collector increases the heat output of the master collector by about 50%.  This is the only application of the Khanh design that I know of, and, so far, it looks like it will do well.

The "master" water heating collector is about the top 2/3rds and the "slave" collector
extends over it and all the way to the ground.
The three small panels inside the slave are PV panels to drive the pump.

Gordon's tank and heat exchanger design are also unique.   He used a galvanized metal livestock tank lined with and EPDM liner mounted inside a well insulated wood frame.

The tank with the copper coil heat exchanger about to be installed.

The heat exchanger uses two 75 foot coils of 3/8 inch diameter copper pipe hooked up in parallel.  Using multiple small diameter coils in parallel should increase the heat transfer surface area and efficiency while still keeping the water pressure drop small.

This shows the valving that allows the heat source to be
the electric tank, solar heat, or both.
 The full story on Gordon's solar water heating system with construction details...

Details on the $1K solar water heating system...

If you have not read the story on Gordon's conversion of an old schoolhouse into a VERY low energy consumption and very attractive house, its a good one...

For the full text of the book by Dr. Shurcliff mentioned above, "New Inventions in Low-Cost Solar Heating -- 100 Daring Schemes Tried and Untried" go here...   This book is my all time favorite solar book -- it is a 1979 book and is out of print, but Dr. Shurcliff allowed me to scan it in and make it available as a free download.  The book was written during a period when many creative people were working on solar heating, and the ideas are as fresh, innovative, and interesting now as they were then.

Gary

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