Sunday, March 17, 2013

Adding Glazing to the Off The Shelf Solar Water Heating System Collector

This is an update on the project to develop a simple, efficient, low cost and reliable DIY solar water heating system that is easy to install because it uses all off the shelf parts.

The system uses an unglazed pool heating collector because it is inexpensive, easy to install, and allows the system to qualify for the federal tax rebate.  The performance of this collector is good for warm and moderate climates, but falls down during the winter in cold climates.

This update covers adding glazing to the pool heating collector to improve its performance when when its cold and for part sun conditions.
The pool heating collector with glazing.

The glazing used is SunTuf corrugated polycarbonate, which was chosen because it is tough, long lived, readily available (eg Home Depot), and has a high service temperature.  The glazing is supported by a simple frame that just plunks down over the collector -- the weight of the glazing assembly is supported by the collector manifold, and the glazing assembly is held down by a couple of straps in the same way the the collector itself is held down.  The whole glazing assembly for the 4 by 10 ft collector is light weight and can be handled by one person.

The glazing includes some openings at the bottom and at the top that allow a controlled amount of air to circulate between the glazing and the absorber.  This is to mellow out the temperature that the collector gets to if the collector is stagnated (no water flow).   The idea is to keep this air flow small enough to not significantly effect collector performance, while at the same time keeping stagnation temperatures within bounds.

The link below gives all the details on the construction.

The performance of the system is definitely improved with the glazing in place.  For some conditions that are typical of moderate to cold climates, the improvement is of the order of 50% in heat output.
The link below gives complete performance details, and compares the performance of the glazed and unglazed pool heating collector to commercial flat plate and evac tube collectors on both heat output and heat output per dollar of collector cost.

Comparing efficiency of several collectors to our collector.

All the details on the updated collector with glazing...

The main page for the Off The Shelf DIY Solar Water Heating System....

Comments, suggestions, questions are most welcome.

March 17,2013

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