# Motor Control

• posted

Look at the pictures in your link. The back tracking example has a shorter shadow than the example without backtracking. So backtracking intercepts less light and will produce less power. The only reason I can think backtracking would be needed is if leaving parts of the panel unlit causes a problem with those solar cells restricting the current flow in the rest of the panel.

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Rick```
• posted

I believe the reason is just obtaining maximum power generation.

Increasing the panels shadowed area will decrease the power, while it is possible that the areas still exposed will produce more power if they are better aligned to the incoming light. (i.e., closer to perpendicular.)

The optimal point will depend on each particular system, of course.

R.W.

• posted

I am sorry. I meant the following link

I am looking for a generic formula that can program into my code. I am interested in back tracking because if the front panel cast shadow on to the rear panel than the rear panel will produce less power.

• posted

I think you are confused. Unless having shade on part of a panel affects the performance of the rest (as in blocking current) of the panel the energy produced will be driven by the total area of the cross-section of the light intercepted by the panels. It does not matter much what angle they are aligned to. Look at the illustrations in her paper. The larger shadow means more light is being intercepted when one panel obscures the light to the other.

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Rick```
• posted

I am sorry. I just did not get it. All I know that shadow can reduce the performance of the Solar Panel.

• posted

From what I read on backtracking, you are collecting just as much light on the panels as pointing directly at the sun and having part of one panel shadowed by part of the one in front of it. Same amount of light means same number of photo-electrons generated. The difference is that with backtracking, the light is uniform across the whole array, while direct pointing has maximal intensity over just part of the array.

Where it has the advantage is that you bias a panel to adjust its efficiency based on the light hitting the panel, and you need to bias a whole panel the same, so you can get better efficiency if the panel is uniformly lit.

• posted

That's the part I don't know about is how the panel reacts to part of it being unlit. But you are not correct in thinking the same number of photons are picked up in each case. When the panels are aligned to the sun, the total area of the sunlight being picked up is higher. The panels are loosing some in the shadows, but there are two ends that are not involved in a shadow, the end in front at the bottom which is not shaded and the end at the back that does not shade anything else. So the total area of sunlight received is higher than the area received when all of the panels are turned to prevent any shadows.

It is easy enough to draw the diagrams to show this. Or just look at the illustrations provided by the OP. I suspect the images are drawn by some program which shows the true shadows of the panels. The two cases show longer shadows on the ground for the panels aligned perpendicular to the line from the sun and which cast shadows on each other. The longer shadow on the ground clearly shows they intercept more light.

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Rick```
• posted

rickman wrote

The panels are loosing some in the shadows, but there are two ends that are not involved in a shadow, the end in front at the bottom which is not shaded and the end at the back that does not shade anything else. So the total area of sunlight received is higher than the area received when all of the panels are turned to prevent any shadows.

------------------------------------------------------------------------------ I did not understand this part. As in the diagram shows that front panel is casting shadow on the rear panel. So, the rear panel will produce less power because it is covered by the shadow. The photo cells will not produce electricity.

• posted

Backtracking would be used on very large arrays. On a very large array, the additional light collected by the first array when directly pointing at the sun is a very small part, and at some size gets surpassed by the improved efficiency over the rest of the array. The picture shows just 2 panels, which shows the effect, but you would not use backtracking on that small of an array. My guess is the method is more intended for large commercial installations of hundreds of panels, so even a 1 percent improvement in efficiency will out weigh the extra light on the first panel.

• posted

The panels that are tilted are picking up less light than the panels that are perpendicular to the light and so produce less electricity.

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Rick```
• posted

I am looking for a generic formula. Is there any that I can use for two rows or n number of rows?

• posted

Yes, calculate the effective area of the panels at various angles. This is a very simple trig function related to the sine of the angle from the panel to the light. That will tell you the maximum power level with no shadows on panels. To figure the amount of shadow cast, you will need to factor in the separation between the panels and the angle of the sun. Then it should be easy to figure out the angle of the panels to not cast shadows. Simple geometry and trigonometry. Anyone who has had high school math can figure this out.

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Rick```
• posted

Thanks! The thing is that I never went to high school. I am trying to learn science and engineering by myself.

• posted

It will be a long row to hoe if you try to apply math you have never learned. Before you try to learn science and engineering you need to know basic math. Otherwise you struggle with everything you do.

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Rick```
• posted

Struggle is a must thing if one wants to learn. I am learning at my own pace and doing whatever I can. I tried to find the material that can teach me to learn about shadow tracking but so far no luck.

If you can give me list the steps that I need to figure out the algorithm / formula for shadow tracking then I will try to convert it into a mathematical formula.

• posted

Draw a diagram of the sun and your panels. Draw the relevant lines, sun to center of panel, sun to top of panel and extend to next panel, etc. Express the angles in terms of the dimensions you know and the variables such as the position of the sun. This will require trigonometry.

To implement back tracking you will want to be able to determine the point when the shadow of one panel first falls on another. I assume this will be the same for every pair of rows. When the sun is at a higher angle than this the panels should track facing the sun as closely as possible. When the sun is at a lower angle you will need to set the panels at an angle so they do not shade one another, but just barely.

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Rick```
• posted

o:

performance of the Solar Panel.

IMHO, you should start and go on by small steps, don't try to do all the th ings at the same time. For example:

- start with moving the motor (and only the motor) the amount you want, wit h the speed you want when you want.

- connect the motor on one panel and add the algorithm to track the sun eas t-west. As a rule of thumb put the panel inclination from the ground equal to the latitude you are. If you don't understand the phrase put the panel i

- add the second panel, put them far apart enough that they don't cast shad ows to each other.

WHEN you have the system that works like this, THEN start to optimize the s ystem (power consumption of the motors, backtraking, etc.). For example if all the motor are connected to the same battery, it could be useful to not move all the motor at the same time, so the current drawn fr om the battery remains small and the battery last a little bit longer.

Bye Jack

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