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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.
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Would a series of vertically-stacked domes (like two or three), each less 'humpy' than the last, not do the same thing? |
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I'm pretty sure this won't work, but I don't have a solid argument why. |
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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. |
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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. |
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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. |
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