Friday, April 29, 2011

Simple Solar Tracker - Cat Not Included

Day three of the #SnowdonBuild.

Another sunny day in North Wales, and having got the solar monitor working it was decided to have a go at a low tech solar tracker.

I particularly liked the single axis ones, where the axis of rotation is centrally down the long axis of the panel. This gives the added advantage of a steeper angle at dawn and dusk when the sun is low in the sky.

The rotating axle was made from bits and bobs lying around. It was an old length of IC tube, with a pen barrel pushed in at the top end, and a cheap screwdriver pushed in at the lower end. The pen barrel was hot-melt glued to a servo arm.

The frame work was made from two pieces of scrap wood, one notched to receive the the body of the servo and hold it in place. The screwdriver was similar to a "jeweler's screwdriver" which has a rotating end section which makes a simple bearing.

Driving the servo with the Nanode was simple - the Arduino servo library makes it very simple to set the servo to any angle between 0 degrees and 180 degrees.

The Nanode can either scan the PV angle for maximum power and then increment the angle by a few degrees per hour, to keep the maximum power output. Alternatively it can follow a pre-described tracking path of several degrees per hour, altering the angle by one degree approximately every 4 minutes.

The output mW of the solar panel was logged by the Nanode and sent up to Pachube for graphing. This simple 1W solar module model gives an example of what could be scaled up to suit a larger system.

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