Saturday, January 11, 2014

georgesworkshop diy weatherproof solar tracking sensor housing

A brief video tour of the solar sensor housing (radome) I made from a standard plastic outdoor electrical box and a hobby store transparent globe.

I had written previously about the housing here.

This sensor housing is mounted on a moving part of the georgesworkshop gen2 solar trough heater. It finds the position of the sun and steers the solar array toward it. A very simple commercially available circuit (US$35) provides all the brains that is required. The entire array uses only a small amount of 12 volts DC and can operate from a gel cel for a week or from a small solar PV panel. I used this array for solar heating of a swimming pool.

In this long view you can see the two locations I tried in the large array (click to enlarge photo).

Of the two spots, I now prefer the one at the top of the motor drive (the right lower arrow). Initially, I had decided to mount the sensor at the top left, since this was the earliest corner of the array to receive morning light and it worked fine.

I could have chosen any of the top or bottom hangers in the array to mount the sensor housing. There was an interesting failure that happened at the top left.

Lessons learned:.In a new appendix for the upcoming book, I discuss various things that went wrong with the gen2 design in the interest of sharing ideas that might improve your efforts. At left is the draft outline. I might add a few more things.

Here is a draft excerpt about melting the sensor housing, for your enjoyment:

"Appendix A - Lessons from Experience
In this section, I share with the reader some of the things that went wrong which were only evident with the passage of time.

Melting the sensor housing I wrote in the sensor section that the sensor housing should be located on a moving part of the array.
On the large swimming pool heater array, I chose to locate the sensor on a hanger at the top west end of the array since this corner received light first in the morning.

Here you can see that sensor backlit by concentrated sunlight streaming out of focus onto the solar sensor and its mount. This happens because I don’t have the array tilted quite high enough for my latitude.

Another view from the other side which shows the de-focused beam heating the side of the box and the deformation of the seal at the top.


Once the top of the Leviton box was removed, I could see that the side wall had deformed as well as looking a bit charred on the outside.

So the moral of the story might be to avoid the focus at the top of the array if possible? Having the sensor on a lower hanger might slightly shade a bit of the reflector but that location keeps the sensor housing out of the concentrated beam. Putting the sensor housing at the top of the motor drive arm, as I did with the Alternative 2 Round Sensor housing also protects the sensor from the beam."

As I said in the last post, I am going to be away from the workshop for a week.

Thanks for your interest.

George Plhak

[to the gen2 intro and reading list]

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