Sunday, September 05, 2010

Progress Report

It is the end of another summer of free solar heat for our pool.

The DIY Parabolic Solar Heater has worked well again this year. A plan book showing how to build the project yourself has been published and has been selling well - thank you for your support! This project is entirely self funded and your purchase of the plan book helps to support my work.

I can report that the problem of back heating has been completely solved. Last year I had reported that under certain conditions, notably when the array was not powered and was tilted off vertical, at some point in the day, the semi-focussed rays of the sun would land on the backs of the reflectors. This back heating caused them to permanently distort.

The fix turned out to be to paint the backs of the reflector sheets with bright white exterior grade latex paint. Three coats of latex were applied to new reflector sheets last fall and all the sheets in the array were replaced with these back painted reflectors. Almost one year later, there is absolutely no distortion of the reflectors - none whatsoever. The white paint reflects and dissipates the heat. Normally the acrylic mirrors used for the reflectors are received from the manufacturer with a gray coating on the back of the mirror.

Another small improvement was to make the cross pipe safety straps adjustable. This was done so that they could be adjusted tight after any maintenance that involved removing the cross pipes. Adjustable stainless steel radiator hose clamps were cut and flattened and joined to the strap material with nylon bolts.

An adjustable safety strap is shown installed on a cross pipe. All the safety straps in the array have been replaced with these improved versions. There have been no blowouts this summer from boiling during stagnation conditions (when the main water pump was not running and the sun was focussed on the collector tubes).

I am working on several other improvements and two other applications for the solar parabolic array. More about these shortly.

Thanks once again for your interest and support. 

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