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# Solid State Solar Tracker

Double Fresnel solid state solar tracking?
 (+3, -2) [vote for, against]

One big problem with solar is that efficient operation requires mechanical solar tracking.

Suppose one had a dome shaped collector, fresnel-principle patterned to focus sunlight from pretty much any direction. The focal point should track along a fixed path over the course of a day, and the track itself would be slightly different each day. However - and this is key to the idea - the tracks would generally NOT significantly overlap so long as the focal point is small compared to the focal length.

Now place a second fresnel lens or miror beneath the dome. Design this one with tracks matching the tracks of concentrated light, and design each spot along the track to re-direct the incoming light toward a single focal point, where a fixed solar collector (Photovoltaic or thermal) collects the energy.

One issue - it has to be designed for a specific latitude.

 — TomRC, Feb 19 2009

Would a series of vertically-stacked domes (like two or three), each less 'humpy' than the last, not do the same thing?
 — Texticle, Feb 19 2009

 I'm pretty sure this won't work, but I don't have a solid argument why.

 I think the problem is you have considered the sun as a point source of light with a single emitted ray of light, when it actually acts more like a bunch of parallel rays of light.

I can't see how a stationary reflector/refractor that reflects/refracts all the rays of light (with angle A) to a stationary focal point, can also reflect rays of light (with angle A+x) to the same focal point.
 — xaviergisz, Feb 20 2009

I'm pretty sure the conflict occurs between focal point and focal length. In order for the lower mirror/lens to effectively intercept and redirect the beam, it will have to be at the focal point of the upper lens, or it will have to be shaped locally specifically to redirect the incoming light.

If the lower mirror is at the focal point, it will have to be locally convex in order to avoid spreading the light. It will also, however, have to be generally concave in order to be at the focal point of the upper lens for the entire day. This obviously presents a conflict.

If the lower mirror is not exactly at the focal point of the upper, it will have to have be of a specific shape, such that the incoming light is focused on the receiver. This shape, in general, will be incompatible with the general arc required to track the sun across the sky. You could have a system that worked at 12:00 and 12:30, say (for a given mirror element size), but at 12:15 the light would be caught between the two and extremely scattered.
 — MechE, Feb 22 2009

What you have described here sounds like a universal collimator, which, as I think I have said recently, is optically and thermodynamically illegal.
 — notexactly, Apr 22 2019

 //universal collimator// Nothing is stated about unreal efficiencies.

 Just dreaming but a liquid crystalline structure that that loss heat to alter internal reflective angles. A morphing lens might be possible.

Solid but dynamic.
 — wjt, Apr 25 2019

 A plastic bag full-ish of water which could manipulated (clockwork?) into various shapes to guide the rays towards the solar collector?

 Or, my dumbness, a tinfoil. cone of more than 45 degrees should catch pretty all the rays.

The tricky bit is keeping those sneaky photons getting out of the cardboard box.
 — not_morrison_rm, Apr 26 2019

//(clockwork?)// batons and struts of copper-aluminium-nickel muscle possibly.
 — wjt, Apr 26 2019

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