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Topic: Follow the sun (Read 547 times) previous topic - next topic


Apr 16, 2018, 08:00 pm Last Edit: Apr 16, 2018, 09:09 pm by vinceherman
Where will you be traveling?

In the southern USA there is about a 10-12% loss if you simply lay the panels flat instead of tilting them optimally.  You have more loss the further north you go.

Edit: my math is suspect.  might be more loss.  checking.

Edit2:  I got this formula for the flat efficiency vs optimal tilt - cos(x) where x is the latitude of the location.  But then it got confusing with tilt of the earth, time of the year, time of the day.
But if you have one panel at the optimal tilt and another panel of the same dimension flat, the flat one will produce about cos(x) as much power as the tilted one.
In Cleveland OH, at about 41.5 latitude, a tilted panel will be 100% and a flat panel will be about 75% efficient.
In Austin Tx, at about 30.25 latitude,  a tilted panel will be 100% and a flat panel will be about 86% efficient.

If your application is dependent on these numbers, do the math yourself.  It has been a loooooong time since I was in trig.  :)


The sun shines from a 47 degree sector, no matter where you are. Aim the panels at the middle of that sector, if it is going to be stationery.

Well, if you live outside the polar circles, you'll miss some sun. But in that case it really pays off tracking the sun during the day. In Northern Finland you get sun 24 hours per day in the summer. Or rain.

If you ask for help and write 'u' instead of 'you' because you think it's convenient, I will write 'no' instead of 'yes'. For same reasons.


Well, let's see, if it's a 10% loss by going with a fixed orientation versus tilty tracky, then adding a 7th panel at a 17% gain would be a net of 7% plus the much greater ruggedness of the system.


I have a Basic Stamp that I could use but I would like to use the Arduino Due for this purpose.
It must lift all of the solar panels to get the best position so to get the most sun. I'll always face the panels south so I get the most sun. I'm using 6 panels but I will only need 1 circuit. They will all be connected by linear actuators to be tilted to get the most sun. I figure to only use 3 photo resistors, bottom, middle and top, but the panels must come to rest on the roof when the motor home is turned on to move to another area. I'm too old to climb up ladders to manually tilt each solar panel. I don't want you to design the system but only to point me in the right direction , sorry for the pun.
I've never used the Arduino Due but look forward in using it.
Thank You,   GettingTooOld
From this info i assume that the aim is to park the motor home facing South and then raise a set of 6 panels from flat on the roof to an angle sufficient to maximise input.

If the panels are to track the sun from East to West is not really indicated it seems more about the increasing trouble of climbing up to set the panels in position.
It seems that there may already be a manual system in place to to this but this needs clarification!

If this is so then a motorised system with limit switches would be all that is needed to raise the panels and a system setup so you can not drive untill the panels are down and locked in place.

Hi TuffGettingOld how bout some more input.



Apr 17, 2018, 05:19 am Last Edit: Apr 17, 2018, 10:59 am by TomGeorge
If all  you are doing is standing the panels up from a flat storage position, you may only need to sample once an hour when you get the array up to its optimum position.
I'm not sure but I think some of the posters here have not realized the camper will never be parked dead level or in due South position.
Look up tables and assuming where the sun will be is hopeless.
You need to find your geological position on the earth and local time.

The az/el of the sun tells you that, and is daylight saving free.

If you are parked in a valley, then look up tables will at the start and end of the day, have the panels pointing into the valley sides, not the top of the valley where even though the sun has gone behind them, will be the highest energy vector.

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....


If you're only going to park and tilt the panels up then 1 tilt angle will do for days. It takes 6 months for the sun to go from winter low angle to summer high angle of 46 degrees difference. What latitude you're at determines where the low and high are but it's 6 months to get that much change, 183 days for 46 degrees, almost 4 days per degree in tilt angle needed. You can sense the sun or know your latitude and what day it is, which requires less wiring, etc.

You might consider adding side panels to reflect light onto the panels when the sun is off to east or west. Even paper white reflects 51% of light energy.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.


Apr 17, 2018, 02:51 pm Last Edit: Apr 17, 2018, 03:12 pm by vinceherman
Here is a set of articles on the very subject:

Edit: Aw snerk.  he went with manual tilting.  I got to that site by clicking the link with this image:

I cannot find reference to that hardware on their site.

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