It's been done a lot by the solar energy crowd, to track the sun with old 12-foot or 8-foot satellite dishes lined with aluminum foil or mirrors. I suggest doing some searches at Google Groups , and at google.com. P.S. If you do it with a large dish, like that, be careful! You might end up with a damn good "cutting torch".
Hello Andy - this link might be of some help depending upon your use and needs. How to Make a Control System for a Sun Tracking Solar Panel
I'm a bit unclear if you want a device such as an array of IR photo detectors that will track the sun and then aim the solar cells at the sun - or if you want to use solar cells to track the sun and be used either as an array to generate power or aim some other device at the sun or simply log the amount of solar energy being generated and entered into some type of log or data base. If you elaborate about your intended usage it would make things easier from this side of things to suggest some circuits or gear.
I notice from your bio that you are involved with measurement of earths gravity and magnetic field(s). I thought we were doing that with the GRACE project now???
I'm a bit unclear if you want a device such as an array of IR photo detectors that will track the sun and then aim the solar cells at the sun - or if you want to use solar cells to track the sun and be used either as an array to generate power or aim some other device at the sun or simply log the amount of solar energy being generated and entered into some type of log or data base. If you elaborate about your intended usage it would make things easier from this side of things to suggest some circuits or gear.
I notice from your bio that you are involved with measurement of earths gravity and magnetic field(s). I thought we were doing that with the GRACE project now???
Why track? Retrieve the date and time (NTP, GPS, or just a decent RTC that you set once and walk away from) and then calculate the position - It's nearly 2am here, so I haven't put a lot of thought into it, but it seems like it should be trivial to write an algorithm accurate enough for at least a few centuries.
Beat me to it. If there's one thing in the whole world that doesn't need to be verified (or tracked) by detection equipment it's the location of astral bodies at any given moment. The algorithm surely already exists and could be had for free with some well placed inquiries. One would think...
Especially since you would have to make your tracking system tolerant of clouds and overcast- you don't want it wandering around during changing conditions.
CH
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LOL ... that would be a challenge !
I was thinking of using mirrors to light a dark room with little natural light.
Andy
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I was thinking of using mirrors to light a dark room with little natural light.
Andy
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One motorized axis should be sufficient, rotating at one revolution per day. Its axis/axle would be pointed north (if in the northern hemisphere), and tilted based on your location and the time of year. You would need to be able to adjust the tilt; probably manually would be most practical. It would be like an "equitorial mount" for a telescope, which is used so that only one axis needs to be moved to track celestial bodies as the earth rotates. The fancy ones have a one rev/day motor, so that all you have to do is align the mount to north and set the tilt angle and voila.
Once you have that, you can keep something pointed at the sun. But then what are you going to do? As it rotates throughout the day, your "light collection point" would move.
I briefly considered a very similar project, a few years ago. The idea, at the time, was to use a parabolic dish and focus the light into a big bundle of finer-optic cables, so there could be some slack to allow the collection point to move. But I didn't really consider the problem of how to get the light into the cables with melting everything there.
I didn't think about using mirrors. But there is probably some relatively-simple mechanical way to use an additional mirror or two, and a few more one rev/day drive units, to make the light always end up going to the same place at the same angle.
If you rotated the tracking mirror in two axes, independently of the tracking, you could keep the reflected light pointed at one location (within some limits). But then your total collection area would vary depending on the angle of the mirror to the sun, varying the amount of light collected throughout the day. I can't quite get my head around it, at the moment. But it seems like keeping the first mirror pointed almost directly at the sun, and focusing the light to a smaller spot size early in the process, might enable it to be done better.
You might want to consider putting one or more of the mirrors on some sort of frames, so you could drill a hole in the center of each mirror and use a bolt to pull the center back slightly, to curve the mirror just a little. That way you could focus it to some degree, and wouldn't lose as much light (and then maybe you could use smaller mirrors downstream, or gain some other advantage).
I guess it might also be a lot simpler than I'm thinking. If your mirror is large enough for the amount of light you want, you could probably just tilt it off the sun by some convenient angle and then rotate it in one axis (perpendicular to sun's travel) throughout the day, at least if you wanted the light to go north or south. I'm not sure if you'd need to also rotate on an axis parallel to the sun's travel or not. (My brain's starting to hurt.)
Once you have that, you can keep something pointed at the sun. But then what are you going to do? As it rotates throughout the day, your "light collection point" would move.
I briefly considered a very similar project, a few years ago. The idea, at the time, was to use a parabolic dish and focus the light into a big bundle of finer-optic cables, so there could be some slack to allow the collection point to move. But I didn't really consider the problem of how to get the light into the cables with melting everything there.
I didn't think about using mirrors. But there is probably some relatively-simple mechanical way to use an additional mirror or two, and a few more one rev/day drive units, to make the light always end up going to the same place at the same angle.
If you rotated the tracking mirror in two axes, independently of the tracking, you could keep the reflected light pointed at one location (within some limits). But then your total collection area would vary depending on the angle of the mirror to the sun, varying the amount of light collected throughout the day. I can't quite get my head around it, at the moment. But it seems like keeping the first mirror pointed almost directly at the sun, and focusing the light to a smaller spot size early in the process, might enable it to be done better.
You might want to consider putting one or more of the mirrors on some sort of frames, so you could drill a hole in the center of each mirror and use a bolt to pull the center back slightly, to curve the mirror just a little. That way you could focus it to some degree, and wouldn't lose as much light (and then maybe you could use smaller mirrors downstream, or gain some other advantage).
I guess it might also be a lot simpler than I'm thinking. If your mirror is large enough for the amount of light you want, you could probably just tilt it off the sun by some convenient angle and then rotate it in one axis (perpendicular to sun's travel) throughout the day, at least if you wanted the light to go north or south. I'm not sure if you'd need to also rotate on an axis parallel to the sun's travel or not. (My brain's starting to hurt.)
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It might be easier to go back to the idea of using a light-reflective parabolic dish tracking the sun (using the one rev/day drive unit on a north-pointing axis [if in northern hemisphere] with a manually-adjustable tilt angle), and then just control the orientation of a reflector at the focus of the dish, so that it always points the light at the same spot, and go from there.
One more one rev/day drive unit (or maybe even some mechanical linkage) would keep the light beam passing through a single line. Then you'd just need to work out the control of the last axis, and maybe some other minor alignment details. There might even be some trivial way to do that, for all I know.
One other thing you'd need to worry about would be making sure the whole thing didn't try to track the sun when it was below the horizons, so your dish wouldn't drive into the ground. Although, thinking about it, maybe it would be a lot simpler if it could. It would only require enough ground clearance and a north-south arm to hold the primary mount, with the arm long-enough for clearances.
Again, if you start playing with a reflective parabolic dish and the sun, be extremely careful!!
One more one rev/day drive unit (or maybe even some mechanical linkage) would keep the light beam passing through a single line. Then you'd just need to work out the control of the last axis, and maybe some other minor alignment details. There might even be some trivial way to do that, for all I know.
One other thing you'd need to worry about would be making sure the whole thing didn't try to track the sun when it was below the horizons, so your dish wouldn't drive into the ground. Although, thinking about it, maybe it would be a lot simpler if it could. It would only require enough ground clearance and a north-south arm to hold the primary mount, with the arm long-enough for clearances.
Again, if you start playing with a reflective parabolic dish and the sun, be extremely careful!!
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Not that much if you install them yourself, but it can be quite a procedure depending on how your home is constructed. But they do work quite well, especially the new ones.
Sun -tubes do work acceptably, although efficacy is not actually so great - remember even a grey , overcast sky is abou t10K lux, so compared with a bright interior (office 500- domestic 300lux) these things appaer amazing. Best used only to provide incidental light to other-wise dark spaces eg interior stair landings in homes.
Back to the OP - solar tracking is actually not much used commercially, for a very simple reason: it is just not worth the effort.
If you are within 50degrees latitude of the equator then solar tracking vs. a fixed attitude, facing within 30degrees of due-South/North brings in less than 20% extra energy per year. That's also about the standard-deviation for actual insolation vs. mean solar year, so it is simply not worth the cost/effort. Just buy 110-120% of the planned collector area if you wish, it's much cheaper and will bring higher returns.
(Yes, I am an architect)
Back to the OP - solar tracking is actually not much used commercially, for a very simple reason: it is just not worth the effort.
If you are within 50degrees latitude of the equator then solar tracking vs. a fixed attitude, facing within 30degrees of due-South/North brings in less than 20% extra energy per year. That's also about the standard-deviation for actual insolation vs. mean solar year, so it is simply not worth the cost/effort. Just buy 110-120% of the planned collector area if you wish, it's much cheaper and will bring higher returns.
(Yes, I am an architect)
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