Tuesday, August 30, 2011

Solar concentrator - parabolic trough

I have been thinking about taking a cheap 10 to 20w solar panel and directing a lot more light to it via a parabolic trough. People seem to be doing this using simple convective liquid cooling and upping the amount of light by a factor of 5 to 10. Here is a company doing it commercially link It's an extreme example - there is a smaller domestic application to be had.

Or flipping the original idea around, it could be that the main purpose of the device is to pump heat via a liquid - using a small integrated solar panel. An easy unit to relocate if cooling is built in too.

I like the idea of a trough over a dish, as is it will track the sun fairly well during the day, and just need monthly angular adjustments of inclination.

I don't want a point focus like a normal parabola, so by using chunky segments on the reflector (could be cheaper to make) I can spread the reflected light over the surface of the panel.

I did some experimenting in Google Sketchup with reflective angles versus the width of each segment on the parabola and came up with the following diagram:
It looks like the rule of thumb is to make the higher ribs about half the width of the solar panel, but lower down it becomes less important, so the same width is ok. There is a portion directly below the panel that will be shadowed.

Here's my concept:

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