Saturday, July 6, 2013

A Test of Reflective Surfaces In Front of Vertical Solar Collectors to Improve Performance

I like my 100 sqft vertical collector that is integrated with the south wall of the house.  It provides our solar water heating and also some solar space heating. It provides excellent performance all winter, and does not have any tendency to overheat in the summer.  The boss says it looks nice.

The one downside of this collector is that in the late spring, the sun is getting up higher in the sky, which reduces the effective area of the collector, and there is still some need for space heating.  So, it would be nice if it could put out a bit more heat in the late spring.

This test looks at adding several types of reflective material on the ground in front of the collector to improve late spring and summer output.  A near horizontal ground reflector works well under these circumstance because the sun is hitting the collector nearly straight on.

The reflective materials include bright white rocks, a white painted reflector board, and at a flat board covered with highly reflective aluminized Mylar.  The results for each of these was measured -- the chart at the end shows how the did.

White reflective rocks
The radiation intensity was measured at each of the blue tape squares on the collector.

White painted board as reflector
The aluminized Mylar reflector was made by just applying the Mylar film over the white board.

This chart shows how the materials compared.

How each of the materials compared as reflectors
The first black bar is a baseline and was done with black weed fabric on the ground in front of the collector.

As expected, the aluminized Mylar does the best, but the white board also does well, and even the white rocks provide some useful gain.

For all the details on using these materials and actual percentage improvements...


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