New book on sun position algorithms

[JohnCraig]

Just a quick note to say that Amazon just published my new book called Sun Position, by John Clark Craig. For most uses the 0.02 degree accuracy algorithm (1/25 of the sun's apparent diameter) is great. For demanding applications, such as state-of-the-art heliostat and other concentrator systems, the 0.00003 degree accuracy algorithm is as good as you'll find anywhere. Read more about it at Amazon... http://amzn.to/rqVnW5
Thanks!

[john p]

Isnt this all unnecessary if you just use a simple automatic electronic controlled 2 axis tracking device ?/
or am I missing something?

[JohnCraig]

Isnt this all unnecessary if you just use a simple automatic electronic controlled 2 axis tracking device ?/
or am I missing something?

The major solar projects I worked on each used a central computer to compute sun position for the site, calculate heliostat and/or photovotaic two-axis tracker aim vectors, and so on. My guess is the electronic device you are referring to probably internally uses similar algorithms to what my book provides, so the designer of such a box would need these algorithms. I've created a very small control board using a PIC microcontroller chip myself, and it used one of the algorithms from my book. The algorithms work well on just about any size computer that has floating point capability. Thanks for asking!

[john p]

Thanks for the reply. But the devices im talking about use 4 light sensing devices(LDRs or similar). and simply adjust their position until the same light is falling on each sensor,no computer or algorithims needed. We have a 2.2 kw concentrated cell panel adjusted at work on the roof using this exact same method . total cost of the electronic parts about $50. bought as 2 kits as we too lazy to design and make our own)Despite is simplicity it works perfectly and has done so for about 2 yrs now. We have used in a rather primitive way 2 car starter motors to do the actual movements.(they are cheap,reliable and very weather resistant)
Its bad points?? none that we can find.

[JohnCraig]

Interesting use of starter motors! Sounds like you've got a good handle on a solution that works for your situation. Our heliostat fields required computer control because each heliostat (mirror) had to be aimed kind of half way between the sun and the receiver on the tower. Also, on our square mile of photovoltaic trackers we found a lot of wasted energy using shadow bands and other similar sensors to what you're describing. At times the motors would run a little extra as the bright edges of a cloud confused the sensors, and it was more efficient to have the trackers aimed at the spot on the horizon where the sun was coming up, or even aimed at the sun behind the clouds while waiting for them to move on. Steady as she goes saved some motor running here and there, which adds up on a large field.

[The Only Sarge]

or one could just use this for free.....

http://solardat.uoregon.edu/SunChartProgram.html

[JohnCraig]

Nice chart. Many users would find that chart great for their purposes. My book provides the resources to allow creating such charts for those so inclined. Or tables of numbers for further analysis. Or to aim heliostats or concentrating systems in real time.

[Sunking]

Question for the MODS

Why is this thread not deleted for self promotion? I zapped it on my site.

[john p]

Its ok Sunking I dont think he will be selling many of his book to members of this site and the others he is talking about it on. To me its kind of like the solar chage manufacturer made a big deal of going from about 99.2% to about 99.6% effeciency.
The way I see trackers ,on a panel system below 20kw(bigger than most residential systems and even some small business systems) going from a 5% to .00000001 % accuracy would gan you a few more watts only. Iwould be willing to bet in just about every tracking system made their would be a backlash in the gears and motor of more than .1%

[Zaarin]

I've been working on this problem for some time now, and I conclude that trying to blindly sync the tracker with the position of the sun will not work, it will require constant re-computing due to environmental factors i.e. the wind moving the system somewhat.

Please have a look at my work in progress:

http://www.youtube.com/watch?v=JY-DhRM_Vto

I use 4 Light dependent resistors to track the sun and an Arduino.

I'm new to the forum and I'm very excited about my project, I hope you guys are doing something similar to reduce your reliance on fossil fuels.

And Merry Xmas