Low Tech HELIOSTAT. How Do I Attach the Suntracker?





Introduction: Low Tech HELIOSTAT. How Do I Attach the Suntracker?

I recently made a solar accumulator which is a limited heliostat, I guess. It can only send the light to somewhere on the axis of the equatorial mount.
The new heliostat is different. It should be able to send the light just about anywhere you want and keep it on that spot as long as the sun shines.
This feature could be massively useful for solar cooking (multable heliostats shinging light on one area) water heating or solar lighting, (shining the light into dark corners or northern windows).
I want low tech ones that poor people who do not have computers can make.
I am pretty sure this works now after making a little model. I am using gimbals on the real thing having seen a problem on the model. Thanks to all who helped me choose gimbals for where it joins to the equatorial mount!
The theory follows on the next couple of pages.

Step 1: Basic Optics

When sunlight hits a mirror, it bounces off at the same angle as it hit the mirror.
The plane of the mirror is exactly at right angles to a line bisecting the bouncing lightrays. I think we should focus on the bisecting line!
If we allow the mirror to swivel on its centre point, and tie the corners of the mirror to somewhere on that line and keep it taut, the mirror will point at the correct angle to send the light to the target!

Step 2: Like a KITE

If we get 2 similar elastic bands and tie them together, and tie ones end to the sun pointer and the other ones end to the target pointer, where the bands are tied to each other will define a point on the bisecting line.
Furthermore, the kite mirror will now be pointed in the right direction as long as the sunpointer follows the sun.

Step 3: Put It on Equatorial Mount!

If the bands do not work, you could try a spring loaded spool of thread with 2! threads coming off the spring in the middle. One thread in place of one band and one in place of the other. This will keep the "kitemirror" taut.
Here is what it might look like on equatorial mount.
It might work better if the fixed target pointer comes up through the middle but it makes for a more difficult to build device.
The sun pointer moves during the day, the bands move as it does so, and the centre and the mirror is moved as the bands move too.
Perhaps a device with 2 pointers was used by The Archimedes Heat Ray to aim it and keep it on target?
Archimedes was a whiz with parabolics too so his heat ray mirrors might have been concentrating mirrors.

Step 4: Gimbal the Start of a Practical Heliostat

I have been hunting for ways to turn the idea into reality. Many thanks to people who answered my forum question. The universal joint answer led me to a gimbal as my solution!
While searching for a metal ring to make a gimbal, I made one from wood.
I stuck mylar to a rectangular piece of plywood for the outside and used stiff wire and screws to attach the gimbal section. I hope that it is close to equatorial mount.
Since taking the photos, I have added a target pointer.
I have not yet decided how to attach the sunpointer.

Step 5: How to Set Up and Adjust Equatorial Mount?

If the equatorial mount is pointed exactly north (in the northern hemisphere) and in line with the axis of the earth, then all is rosy.
How can we get it to this state? It is hard to find exact north! I suggest the first thing to do is get the heliostat set up pointing up at exactly at your latitude no of degrees. Point it approximately north.
Over the course of the day, as it turns the reflection will move a little. You can use this movement to readjust the mount until it is perfect. I have not yet figured the movement out because I have not yet made one! Perhaps this work can start tomorrow!



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    Nice effort! For anyone looking for a turn-key solution, see the H1 heliostat over at http://www.lightmanufacturingsystems.com/heliostats . It uses a metalized PET mirror, which is unusual.

    I have been working on this for  about 7 months now.  An equatorial mount does work at equinox as you say with a 48 hour rotation or any day with a 24 hour rotation if the target is in line with the polar axis (principle of coleostat). At redrock heliostat website, 3 mechanical heliostats are shown: Focalt, Gamby, and Silberman.  The last two suffer from gimbal lock when the sun and target are closer than 30 degrees, there is a good article on this in Wikipedia.  I have not been able to understand the Focalt mechanism yet. It seem as if the tape, rubber band and corkscrew methods might also have mirror control problems at low sun, target angles.

    Daniel Murphy's latest work can be seen on this video.   (I have other easier projects where I can contribute more!)
    I think if you pause the video from time to time it is easier to understand what he means. Brian

    Good to hear from you!  I abandoned it for a while.  I think last time I emailed with you we noticed that a reference picture of a Gamby had the equatorial axis  pointing the wrong way.  Correct? 
    But really glad that you have made progress.
    When we know the problems beforehand, we can make arrangements to move the target or heliostat  to get round  the problem during year!
    I have made progress on tracking (turning the equatorial mount)!  I have a fuller sized image at http://solardesign.ning.com/photo/liquid-piston-tracker and I may do an animation too.


    I have been looking into a heliostat on equatorial mount with a 48 hour rotation. I have not been able to conduct experiments due to clouds. Even if the 48 hour rotation does not work perfectly, it may be part of the solution. If it is "nearly right" then all that is needed is a 24 hr rotation for the sun pointer to make fine adjustments to the angles of the mirror. This means no huge swings on the gimbal (perhaps a small ball joint is all that is needed). Like the ball joint in a tractor 3 point linkage. What do you think?

    Hello, I had a similar idea a time ago, and I never got to develop it totally. Seemed in its objective, but nothing with the rubber band. The equatorial mount by itself is sufficient. If the sun takes 24 hours a turn, we only needed a mechanism that gives a turn in 48 hours. for example, the hour axis of a clock, geared down four times. In this way, if at sunrise dawn? we put the mirror to 45 degrees on this axis, so that the reflected ray upwards vertically, at noon the mirror will have to be horizontal, and to the dusk again to 45 degrees in the opposite direction. This approach must be duplicated symmetrically to the equatorial axis, so that the following day the process can be repeated. But the sun is not easy to convince, and it is guided by its own temperament. It would be necessary to make almost daily adjustments to the approach, because there are no mechanic ways to follow the sun in the sky. Pardon my "automatic translator" English.

    Sorry. The 48-hour rotation idea won't work, except in one case. That case is if the date is one of the equinoxes and the target direction is on the celestial equator. In other situations, it may seem to work at sunrise and sunset, but not at other times of day.

    For example, suppose you are on the equator at an equinox, so the sun rises due east, rises straight up the eastern sky, passes overhead at noon, then goes vertically down the western sky to sunset. And suppose you want to reflect light due north, horizontally. At sunrise, the mirror must point horizontally north-east, so light from the sun on the eastern horizon will be reflected to the north. And at sunset the mirror must be aimed north-west. So, you might say,the mirror turns 90 degrees in 12 hours, so that's 48 hours per revolution, with the axis of rotation vertical.

    But that would mean that at noon the mirror is pointing due north, aimed horizontally, and that won't work at all! In order to reflect light from the overhead sun toward the northern horizon, the mirror would have to be aimed upward at 45 degrees. Your 48-hour rotation won't do that.

    We have discussed some heliostat designs that work. A mirror that rotates once every 48 hours won't. Sorry!

    And it *is* possible to follow the sun mechanically. It doesn't have any "temperament". Its motions are highly predictable.

    I don't agree.

    If the assembly is equatorial, my 48 hours rotation idea functions EVER, be equinox or solstice or intermediate. Your assumption of an equatorial subject is yours, not mine. Please rethink that thing.

    About the "equation of time", that is to say the movements of the sun in the sky, the mechanical complexities of a device that keep in mind them, they are larger than what a person can confront. Or, if you prefer it, the relation cost / benefit is too high so that be worth while.