solar trackerusing microcontroller

[hinakadevalec]

I want to design dual axis solar tracker using LDR/photosensor with microcontroller .i m having solar panel of 1kw capacity. there are total 5 panel each having 252w .total weight of structure is also very high near about 300kg. so please suggest me the required mechanical structure to rotate the panel and provide me information regarding complete circuit for tracker circuit using sensor and microcontroller.at presently image can not attached herewith.

 

[doraemon]

Hello!

Why a dual axis? As far as I know, earth is spinning around a single axis, so one axis solar
should be sufficient.
As for the mechanical structure.... the only sensible reply is "it depends". Are your panels
rotating individually or are they mounted on a single structure together in which case you move
the whole structure?

Dora.

 

[Warpspeed]

Dora is quite right, and also one complete revolution of the earth always takes exactly 24 hours.
So all you need to do is drive your panels with one motor and one gearbox maybe 180 degrees in 12 hours east to west,, then drive it back the other way west to east for 12 hours at night, at the same speed.
Pretty easy if you use stepper motors.
And you don't need any sun sensors.
It tracks even in thick fog, then when the sun comes out its right there pointing exactly where it should be.

Then about every two months just alter the tilt angle slightly to correspond to the seasons.

 

[BradtheRad]

You must create a support frame that will withstand strong winds. It will be very difficult to maneuver 5 large panels if they are fastened together. A strong wind will apply enormous force on them, just like an airplane wing. They are likely to break up.

Install each panel on its own support frame. Space them a few feet apart so none shades another.

If you are ingenious, you can attach a long arm so it spans all 5 panels. Then when you move the single arm, it pivots all panels simultaneously.

 

[doraemon]

Hello!

You must create a support frame that will withstand strong winds.

Indeed. I tend to forget the hardest part of the problems and focus on detail. Maybe that's
what we can cal a typical engineer behavior.

Dora.

 

[Warpspeed]

I started to do all this myself a couple of years ago, but other projects have gradually pushed it onto the back burner.

What I did was source a reasonably large industrial gear motor with a high reduction gear ratio, these come up on e-bay all the time.
But if you are patient, you will be able to get one one fairly cheap. This one set me back $26.00

That will give you a super strong cast iron gearbox casing, a massive support bearing and a pretty stout shaft, on which to hang your counterbalanced solar panel array.

Toss the original drive motor away, but keep the toothed plastic motor coupling.

Get yourself a stepper motor with another high ratio reduction gearbox and mount it on the back of the big gearbox using a flat plate, and the original toothed motor coupling.
Its mechanically fairly simple to do, but very robust.

You then drive the stepper from a constant frequency source such as a crystal oscillator and a frequency divider.
Now the actual frequency is less important than the fact that it is always constant and never drifts.

So the big gearbox might ideally rotate 180 degrees in 12 hours, but that is not important.
Suppose it only rotates 168 degrees in 12 hours with the particular crystal, divider, stepper, and gear ratios that you end up having.

As long as you reverse the direction EXACTLY every 12 hours, it will track pretty well, it will be a few degrees short at either end of travel, but that will not matter. Its not a cumulative error.

In fact less than 180 degrees rotation is actually desirable, because the solar array needs to clear the mounting post. I may need to modify this to do that....

To get a pretty accurate 12 hour reversing signal, which is very important, all you need is one of those cheap on/off appliance timers.
It will already have a lithium backup battery, so its ideal. Just program it for forwards at 6am and reverse at 6pm.
It will track the sun for months without needing any correction.

Its a bit of effort to accumulate all the parts, but once you have those, the whole timed tracking system becomes very simple and very reliable.

Here is the original three phase motor on the left, the stepper motor and gearbox on the right enclosed in a PVC weatherproof housing, with the plastic shaft coupling.
Behind is the the big gearbox.

Stepper is 200 steps/revolution (at 3.125Hz =16 seconds/rev)
Stepper gearbox is 100:1( 26.67 minutes/rev)
Big gearbox is 54:1(24 hours per rev)



At the other end in another weatherproof PVC housing are two hall effect limit switches, just in case the timer fails to reverse the action.

This also automatically re synchronizes the system if stepper motor power fails.

Also can be seen the keyed drive flange which supports the weight of the solar array.

The big gearbox bolts to this thick wall galvanized steel 4" x 4" post. Its two metres tall and there is 1.5 metres below ground set into a lot of concrete.

The half inch rectangular plate on top is angled at 38 degrees which is the latitude for Melbourne.

That is as far as I have come with it so far, but it has been running in mock up, and it does track the sun amazingly well..

 

[hinakadevalec]

Hello!

Why a dual axis? As far as I know, earth is spinning around a single axis, so one axis solar
should be sufficient.
As for the mechanical structure.... the only sensible reply is "it depends". Are your panels
rotating individually or are they mounted on a single structure together in which case you move
the whole structure?

Dora.

Hello! As it is single structure mounted on single frame. as it is has to track from est to west on single axis so it is same like as single axis tracker . we can put another dc motor for horizontal movement of panel . i m trying to attach image in forum but it is not uploaded

 

[BradtheRad]

i m trying to attach image in forum but it is not uploaded

The "Add an Image" button is the most convenient and reliable method. Go to Advanced mode if you do not see it below the Quick Reply Window.

Only certain graphics formats can be uploaded.

After upload is successful, then copy the entire BBC window. Paste into your message.

 

[doraemon]

Hello!

Hello! As it is single structure mounted on single frame. as it is has to track from est to west on single axis so it is same like as single axis tracker . we can put another dc motor for horizontal movement of panel . i m trying to attach image in forum but it is not uploaded

So basically it rotates around a vertical axis which gives you the sun direction, and you need another motor for the panel inclination, is that right?

By the way, you may also consider making a completely fixed panel. All the solar power plants work that way.

Dora.

 

[Warpspeed]

I was going to add a second stepper motor and gearbox to this, but may not bother.

The idea was a second stepper motor (and dual gearboxes) driving a crank. The crank does one revolution every 365 days and drives a connecting rod that causes the panels to nod up and down with the seasons.
Up 22 degrees at mid winter, down 22 degrees at mid summer, and parallel with the axis of east west rotation at the equinoxes.

 

[KlausST]

Hi,

two axis:
one left - right for a day.
but isn´t there an additional axis over a year. winter- summer?

By the way, you may also consider making a completely fixed panel. All the solar power plants work that way.

Good point. With tracking you optimize the power output. On the other hand the control unit and the motors draw current.
Maybe the benefit is just as much as the power for the motors. Especially on cloudy days.... So maybe there is no overall benefit.

Additionally the tracking needs a lot of mechanics, and maintenance, and repair...

The question is: is the tracking worth the effort?

Klaus

 

[Warpspeed]

My tracking motor is 5v at 100mA, solar panels installed on it are expected to be rated at several hundred watts.

Maintenance and repair is only likely to occur from storm damage.
The gearboxes turn very slowly, wear is negligible.

Is tracking worth the effort ?
Probably not.
But only because the cost of solar panels has now decreased so dramatically. Simulations here suggest a two axis tracker benefits about 32% in power output from having the same number of panels fixed in position.

Its a lot easier to just install about one third extra panels, and the cost of doing that will probably now be a lot cheaper than a tracker, unless you build it all yourself.

It is the main reason this project is on hold.
I will probably finish it eventually, mainly for the technical challenge but its not a priority.