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Comment by remipch | Hacker News Reader

Exactly

This has the advantage of requiring fewer motors (only two motors for the entire panel) instead of two motors per mirror.

The disadvantage is that the light is only focused for a few hours a day.

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It is possible to make a mechanical angle bisector. Think of a compass for drawing circles but with a 3rd arm bisecting the angle. If you attach the bisector normal to a mirror, you can point one leg at the sun and the other at a target. An array of these would require linkages to aim all inputs parallel toward the sun and all outputs fixed toward the target - the outputs don't have to be parallel just have each pointing at the target. 2-axis actuation to move all mirrors as needed. Not sure if this has ever been tried, it's just an idea I had some time ago.

This is a really cool concept! The term used for connecting mirrors to rotate together is a ganged heliostat. Most papers about ganged heliostats don't do anything fancy like what you describe, but there are some patents that show a nice way of connecting the rods to give the correct angles using a slightly different concept than what you are describing [1]. I previously made a visualization of how that concept works (click and drag the sun) [2].

I've not seen exactly what you describe published anywhere, but it sounds very smular to something I thought about as well. See this 2d illustration [2]. Is this the same as what you are describing?

I had a masters student try to make it mechanically. It turns out that though it's an elegant concept, you still end up with quite a few moving parts so it's a bit tricky.

[1] https://patents.google.com/patent/US20060060188

[2] https://folk.ntnu.no/haakonjj/ganged_heliostat_illustration....

[3] https://folk.ntnu.no/haakonjj/ganged_heliostat_gear/

Nice interactive visualizations !

Yes, it might be complicated to build.

Another disadvantage being that your distance between the mirror system and the target must be fixed the same each time you setup.

This isn’t an inherently bad thing. As a marketable product this would imply a one-time manual alignment for all 48 mirrors but cheaper lifetime maintenance costs.

If you were going to sell a kit, having 48 sets of 3d printed mirror mounts of the right length for each position wouldn't be out of the question. Just a screw-on clip with the right length standoff for each mirror corner would be all you'd need. You could conceivably have different sets with different focal lengths.

I don't think it would be too fiddly done that way but it might take some work to make fine adjustments straightforward.

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