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Solar tracking System for solar cells

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Hi Boncuk, I've seen people discuss blind solar tracking systems before but not seen a good working system like that yet. There are a couple of faults;

1. Your microcontroller clock, even good ones will lose or gain minutes. A good solution might be a GPS clock but the GPS module adds maybe $60 to the cost and requires the hassle of an antenna etc.

2. A problem that is not easily overcome, the highest insolation (solar brightness) quite often comes from an area of clear sky in situations where there is any cloud over the sun, so tracking the suns position like clockwork will give much less power output than a closed loop system that points the panel at the area of the sky with the most light.

So you may be building a system that is likely to be more expensive and require more high tech (things to go wrong), and will work worse at getting max power output.
 
Hi Mr RB,

thanks for your input.

My friend believes that the accuracy of the tracker will be more than sufficient at a resolution of 1/10degree.

Hi Boncuk, I've seen people discuss blind solar tracking systems before but not seen a good working system like that yet. There are a couple of faults;

1. Your microcontroller clock, even good ones will lose or gain minutes. A good solution might be a GPS clock but the GPS module adds maybe $60 to the cost and requires the hassle of an antenna etc.

A GPS receiver for just the time signal is much cheaper than one requiring determination of geographical positions. It's settled somewhere at $10.

European users might use the German time transmitter DCF77 stationed at Mainflingen (close to Frankfurt/Main) with a range of 2,500km. DCF77 modules are dirt cheap (about EURO5) and also contained in cheap kitchen clocks.

2. A problem that is not easily overcome, the highest insolation (solar brightness) quite often comes from an area of clear sky in situations where there is any cloud over the sun, so tracking the suns position like clockwork will give much less power output than a closed loop system that points the panel at the area of the sky with the most light.

This might be true, but I doubt it. The only 100% parallel light source in our solar system is sunlight. The sun's diameter is somewhat larger than the diameter of our planet. :)
I think optical sensors must be used additionally for PPT (Peak Power Tracking) anyway. PPT will take care of estimated 10% more power output than normal tracking. (My friend isn't convinced of that idea yet.)

So you may be building a system that is likely to be more expensive and require more high tech (things to go wrong), and will work worse at getting max power output.

I'm optimistic the system can be made for low budgets. :D

The software will take care of different stepper motors used individually, e.g. 1.8 deg/step instead of default setting of 0.9 deg/step.

Regards

Boncuk
 
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Wow time GPS units for $10? Can you share the info where to get them?

You are right the accuracy from the motor and mechanicals would be easy enough to obtain, provided of course you have the accurate time and day.

As for the area of sky that produces the best power output, I've seen it argued out by solar guys but haven't really tested it myself. Where I live it is hot and little cloud, and when there are clouds over the sun they are thin and fairly transparent. Or the whole sky is black and we get tropical rain haha. But is sounds like common sense if there is a dark cloud over the sun that the panel may make more power pointed at a large clear area of sky, at least that's what people say...

I guess I have a different opinion on the best way to make it, as adding a small light sensor to the panel and making it closed loop still sounds both easier and better performance. Once you already have the cost of a microcontroller in there, it can do some smart stuff based on the sensor input. A "clockwork" system just does not sound superior to me.
 
A calibrated digital compass will also be needed on the panels as feedback so that the panels are truly pointing where the software and tracker motors are trying to point them. These are affected by local magnetic effects so it is far from "simple."
 
A calibrated digital compass will also be needed on the panels as feedback so that the panels are truly pointing where the software and tracker motors are trying to point them. These are affected by local magnetic effects so it is far from "simple."


Surely that is not needed if the tracking system is on a stationary platform (like a house). As Boncuk said, once the intial lat/long and rotation is entered in, the software will then point the panel at the sun's position.
 
Think about it. If the GPS device is stationary (or even being spun around), it will read the same lat/long and time regardless of the direction it is facing. Most need to go meters away from the prior point to determine a direction. But let's say with a calibrated limit switch to indicate a completed rotation to North (or some known azimuth angle), that a starting angle position could be determined. It then becomes a dead reconing/timing system, as there is a lot of error in the motor and mechanics slewing the panels "westward" due to daily impacts of temperature, wind, and wear in the "mechanics." I've tried this and it is easy to be off by 20-degrees over the course of the day, and day-to-day it varies too. A 2-axis digital compasses such as the HMC6352 ($35 USD) helps provide feedback to the processor of where the panels are pointing in realtime. These also are not perfect. That said, it's fun to try these things. I'm "mostly" in the sun sensor camp, but I see some value in the having some programmed control, such as to set the panels vertical during precipitation and horizontal in high winds, assuming you could sense those too. ;-)
 
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It then becomes a dead reconing/timing system, as there is a lot of error in the motor and mechanics slewing the panels "westward" due to daily impacts of temperature, wind, and wear in the "mechanics." I've tried this and it is easy to be off by 20-degrees over the course of the day, and day-to-day it varies too.
...

I think we have different understandings of what Boncuk was suggesting?

In my mind he was suggesting using a microcontroller to blindly position the panel, which (by deduction) would require using a stepper motor or servo motor with an encoder, to make sure the microcontroller always positions the panel to the correct angle. That is the way I understood it.
 
Honestly the easiest and BEST way to do a PV tracker is just use 2 off green led's and either use a comparator or uC to move the tracker motor. When it is overcast the present sun's position might not be the highest current so an active sensor is the best way to track the sun. True a 2 axis system will give the most power BUT solidity of the tracker comes into question. The easiest way which most people use is an manual adjustment of the azimuth to suit the seasons, so the tracker can be made rigid to suit all weather conditions.

Personally I have seen where a person had mounted their pv panels on the roof but not flat on the roof and after a gale the pv panels were a twisted mess on the ground. Now that was 5kw of PV too, sure the insurance paid up but anyone wanting to do a tracker MUST take care and make the tracker to suit all weather conditions. Another mate has several single axis trackers with a manual azimuth setup and after a gale wind came thru, a footing of 1 metre deep by 200mm diameter of preset concrete didn't hold the trackers. Luckily he was home at the time and got to them so no real damage was done.

Now for people in high wind area's wiring the pv panels to suit a MPPT is a good solution and that is the setup I do here at home. Personally I have seen a wind generator tower of mine bend 45 degrees in high winds and we live in a gully.

Anyone wanting to do a pv tracker must take into consideration the power of mother nature and it does seem people can argue all day long which is the best way to track the sun but very few ponder on the mounts of the said pv trackers......

Cheers Bryan
 
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