Power output of a solar panel if a complete row of cell is shadowed

[fozia.jehan]

Homework Statement

I have to analyse the power output of a solar panel using a basic electrical engineering circuit analysis of a solar module if a complete row of solar cells in it is shadowed (For example, such shading might be caused by dust that slides down the surface of inclined panels.) will the power be zero or not?

Homework Equations

The Attempt at a Solution

I am taking a single solar cell as simply a dc current source, whose output is proportional to the incident solar irradiance and so with the shading the power of that cell will decrease accordingly. I am assuming that the solar cells are connected in series in the panel and so the total power will be zero if a complete row is shadowed, because in series connection the total current is equal to the least current produced by a solar cell in the panel. I know the circuit diagram of a single solar cell (a current source in parallel with the dark current diode) but can't figure out how to draw the circuit for a series of cells and also how to present my answer. Any help will be greatly appreciated.

 

[Delphi51]

It depends on how the cells are connected. Perhaps the rows consist of X cells in series, and the Y rows are connected in parallel. Then the other Y-1 rows would carry on producing power while only the shaded row's output is lost.
What if the cells of a column are connected in series and the columns are connected in parallel? Then the answer depends on how the dark cell in each column behaves - does it allow current to flow through it with little resistance like a diode?

 

[fozia.jehan]

Oh. I was thinking that in practice all the solar cells are connected in series in a panel, and then you can connect these panels in series and/or parallel. Am I wrong?
Another thing is how to represent them in a circuit diagram?

 

[Delphi51]

I don't know how they are connected. I think the output voltage is typically 12 or 24 Volts, suggesting about a dozen or two cells in series. You may find this information on an RV forum.

 

[CWatters]

Perhaps see "By-pass diodes"...
http://www.solar-facts.com/panels/panel-diodes.php

 

[fozia.jehan]

thanks delphi and cwatters.. have searched the web a lot in order to find an electrical circuit diagram for many cells connected in series or parallel but couldn't find one.. do you guys have any idea where can I find it?

 

[CWatters]

The link I posted shows panels in series. Only two panels but more would be connected the same way.

 

[Delphi51]

There is a lot of discussion about how to connect multiple panels on the web but not much about how individual cells are connected within a panel. There is some in the wikipedia article "solar panels". There cannot be a definitive answer because different panels will be made in different ways to produce the size and voltage the customer requires. If you can't get more particulars, you must assume that some cells are connected in series - call them rows - and some rows are connected in parallel. That will enable you to answer the question. The link to bypass diodes may be very helpful, but remember it is probably the solution to the problem you are identifying in your answer.