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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.
Brian
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.
Brian
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Signing UpStep 1Basic 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!
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!
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I think if you pause the video from time to time it is easier to understand what he means. Brian
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.
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.
http://www.eastcoastsolarsystems.com/heliostats/ .
Check it out.
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.
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.
"Equation of Time" heliostat.
http://www.redrok.com/neat.htm#US4368962
The gears and stuff calculate the "Equation of Time".
The heliostat head is quite close to a Silbermann
heliostat which is driven with a constant speed
clock drive which is good for a few days but needs
mechanical adjustments. See:
http://www.redrok.com/main.htm#mechanical
Hultberg fixes these errors.
Duane
http://www.redrok.com/neat.htm#US4368962
Just click on the patent # and Google opens the
full patent. Hultberg shows 2 embodiments one with
1 crank and the other with 2 cranks. Presumably
the 2 crank version is a bit more precise.
Duane
But I am puzzled as to WHY Hultberg went to all the trouble and expense of inventing this machine and patenting it. The patent reads like something from the 19th Century, but actually it was filed in the 1980s. The cog-wheel technology shown in the diagrams was already being replaced by computers. (Actually, in one of the claims, computers are mentioned. It looks like he realized at the last minute that this new technology was about to supersede his invention, so he tried to claim it too.)
I doubt very much that any of these machines have been made except for Hultberg's own prototype.
Fun, though.
David
I didn't make fun of "temperament". In the context, it made good sense. But it implied that the sun's motions are governed by unpredictable whim, which is not true.
(Incidentally, my Spanish is quite good. I studied Spanish Language and Literature at university.)
In my last post to him, I suggested he should try his idea and see what happens. Maybe you should, too. I have no idea what Wikipedia may say about it, but I do know that Wiki has been proven wrong many times.
This is his baby. Constructing a prototype would not be difficult or expensive. I think he should do so. If it works, he might make a fortune with it. If it doesn't, I'll try not to gloat too much!
Nobody here has put anyone down, except you in this last post to me. Do you really want me to sit by and say nothing when I *know* that his idea won't work, and that others here may be wasting time and money trying to copy it?
When you say "...Just take a clock mechanism,..." etc, lacks to add "put the array over an equatorial mount". If you omit this step, the device does not function. You think the following thing: during a single day, and especially considering only the diurnal hours, the displacement of the sun in the sky is practically circular, be in winter or in summer. Therefore, an equatorial mount is the unique thing that does you need to trace it. You can be sure that it will not be set apart of its path more than some seconds of arch.
An equatorial mount or assembly is one whose axis of turn is parallel to the terrestrial axis, that is to say that is oriented in north-south direction, and inclined with regard to the horizontal one angle equal to the latitude of the place.
I live in Argentina, south of South America. Then, I speak Spanish. Therefore my English is not good, pardon. I use http://freetranslation.com/ and then I apply corrections according to the little thing that know of the language.
Thanks also for the cam-and-lever mechanism idea. I did not think this, I only thinked combined movements, this is much simpler. But one must say that even this method is not the last word as for an exact position, because the displacements of the terrestrial axis are not contemplated in the equation of the time, due to they are erratic and unpredictable. Obviously, the differences are despicable for the almost totality of the applications.
I did something seemed to what you suggest, three or four years ago, and functioned here in the backyard of my house, approx. 32º of south latitude, in full autumn. At least, functioned between the hours 11 and 13 approximately. As soon as it have time I will try to refloat the apparatus and I will it to work several days. It does not contemplate the annual displacement of the sun, that is to say that in this epoch I would have that to adjust the north-south inclination of the mirror almost daily.
If you read and analize carefully my assertion "...during a single day, and especially considering only the diurnal hours, the displacement of the sun in the sky is practically circular..." you must realize that this is true.
My mirror did not direct the sunlight toward the pole, directed it approximately up, but similarly would be able to have directed toward any side, inside the practical limits of the construction of the apparatus, and of the laws of the reflection (example, is impossible reflecting it more than 90 degrees of the mirror's surface)
But I insist, my mirror function ALWAYS because the mounting is equatorial and during some few hours the north-south displacement of the sun in the sky is despicable. Its path is practically circular.
With the 48 hours arrangement, once aimed the ray of sun light in the desired direction, the mirror will remain all the time (we say some hours) aiming at the bisector (bisectriz in Spanish) of the angle formed between the sun and the object to illuminate.
Babylon English-Spanish
despicable
adj. despreciable, astroso, bajuno, desdeñable, indigno, menospreciable, ruin, vil, zurriburri
English_Spanish by Jaime Aguirre
despicable
s.- sabandijaadj.- despreciable | vil | ruin | menospreciable | desdeñable | execrable
An English -> Spanish Dictionary (G...
despicable
(adj.) = despreciable, vil, infame
Ex: Gestation, menstruation, & pregnancy were often considered shameful and despicable.
About thinking in 3D, really is difficult and sometimes conducts to serious errors. For that reason (among others) the models from buildings from the plans are manufactured.
But sorry, I think you are in error and I am in the good way.
Perhaps you know the saying: "if you think as me, we will be friends; if you don't think like me, we will be doubly friends, because together we will be able to find the truth"
http://www.earlytech.com/common/show_image.phtml?Id=491390987&Item_Name=Heliostat+by+Silbermann+1843 shows how the geometry works. I do not understand it at all so I asked for an explanation and here is what I got as an explanation:
"The heliostat in that link needs to rotate at half the speed of the sun because it is trying to keep the direction of reflection constant. If you are just trying to keep a telescope or camera pointing directly at the sun then you need to rotate at the same speed. So it depends what you are trying to do, if you want to redirect the sunlight to a fixed point where you can use it to do work then 15o/hr is going to be wrong" So it appears the 48 hour thing is a hundred years old! Are you still so certain?
Brian
I managed to see the 1843 machine to which Brian referred. For some reason, the link would not work for me yesterday. Actually, the image shows a collection of machines made by Silbermann, who was a famous maker of these things at that time.However, I cannot see any reference to a mirror turning once every 48 hours. The machines have an ingenious mechanical device for bisecting the angle between the directions of the sun and the target. The basic mechanism, defining the direction of the sun, rotates once every 24 hours.
I suspect that the person who wrote the "explanation" for Brian knows even less about the thing than Brian himself does.
I am beginning to wonder if the 48-hour machine is something like Leonardo da Vinci's helicopters - imagined and maybe drawn, but never made and tested.
Back to our discussion. For simplicity, imagine that you are at the earth's South Pole. The earth's rotation axis is vertical, with the Celestial South Pole directly over your head. Suppose the date is December 22, the summer solstice, so the sun is moving horizontally 23.5 degrees above the horizon. Suppose that the target at which you want to reflect light is in a horizontal direction, as seen from your mirror.
At some time of day, the sun will appear to pass directly above the target. The bisector of the angle between the directions of the sun and the target will be pointing 11.75 degrees above the horizon, or 78.25 degrees from the vertical axis of the earth.
12 hours later, the sun will be 23.5 degrees above the horizon in the opposite direction. The target is still where it was originally. So in what direction does the bisector now point? Almost over your head, that's where! it will be only 11.75 degrees from the vertical axis of the earth, at the same azimuth as the target.
So the angle between the earth's axis and the direction of the bisector - along which the mirror must point - varies between 78.25 degrees and 11.75 degrees during the day. So it is absolutely certain that the mirror can *not* be fixed to a polar axis, rotating only about it.
The same situation occurs, but is less simple to describe, for any other location on the earth. It is not peculiar to the poles.
As I have said so many times, please DO THE EXPERIMENT. HAZ LA PRUEBA. Forget about everything that I and others have said. Learn from actual observation. That's science.
Best wishes.
David
Where you say " ...it will be only 11.75 degrees from the vertical axis of the earth",
you must say "...it will be only 11.75 degrees south of the intersection of the meridian of the place with the heavenly equator"
That is, in my latitude, "it will be approx. 21.25 degrees north of the zenith." You cannot see it?
If I could send you a drawing, I believe that you would understand it. But you have said me that cannot receive it.
A drawing would be misleading because it is two-dimensional. We MUST think in three dimensions. Use a globe instead.
Why do planes flying between Europe and the west coast of North America go way to the north over the arctic? Because that's the shortest route. Look at a globe (NOT a map) and you will see this is true. The mid-point of the journey between Vancouver, on the west coast of Canada, and London, England, is close to the Arctic Circle, over northern Canada, even though both cities are close to the same latitude of 50 degrees north. This shortest path is called a "Great Circle".
If the earth were transparent, an observer at its centre would see the direction of the mid-point of this Great Circle route as the bisector of the angle between the directions of Vancouver and London.
The same is true of the situation I hypothesized above. In three dimensions, the angle between the target, on the horizon, and the sun, 23.5 degrees above the opposite horizon, is in a *vertical* plane, which also includes the axis of the earth. The bisector of the angle is only 11.75 degrees from the axis and the celestial South Pole.
It is essential in this problem to think in three dimensions and to consider Great Circles, rather than straight lines, as the shortest distances between points.
Yes?
While it travelled by train to my house I fell in account of which is YOUR problem: you don't know what signifies "equatorial assembly". I will explain it you, to see if you understand of a good time: the axis is PARALLEL TO THE TERRESTRIAL AXIS, which can be expressed also (I believe to have said before but it does not matter) in the following way:
- It is oriented in north-south direction (or south-north, is equal)
- It is INCLINED with regard to the horizontal plane of the place an angle equal to the LATITUDE OF THE PLACE; the highest part (if there are it) is the one that aims at the most nearby pole.
Do you understand now? If don't, don't continue, we finish here.By the previous thing, already you will have realized that your affirmation "The angle that includes the directions of the sun and of the receiver is in a VERTICAL plan, that includes also the axis of the land and the south pole" is false, and is the origin of YOUR CONFUSION.
And I believe that we can give for finished the discussion. Too much time we have dedicated him.
Un abrazo.
Osvaldo J. Schiavoni