photovoltaic current

[Pooja-S]

Ben, which context you are referring to?

[RTSLVU]

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@Pooja-S wrote:

RTSLVU, I appreciate your reply. But can you give me an example of how the design of the panels and wiring of the array can be corrected. Consider my program itself. Also please consider the shading. How can this be done. Thanks.

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I really can not make sense of you pogrom... But there is no easy solution to the shading issue beyond mounting the panels so they so not get shaded and configuring the array to minimize the chances of the entire array going down. I don't really think you could simulate or even calculate this because it has a lot to do with how the shadow hits the panels and how the panel is constructed.

I learned this from experience testing a small array. During the afternoon power would start to decline when it should have been going strong. Then we would suddenly lose almost 50% power, then that would creep up to almost 90% loss. There was a telephone pole casting a shadow that would slowly sweep across the array. The only solution was to move the array. If you look at one simple panel, you have a bunch of solar cells connected in series. If one gets shaded then it becomes and open circuit so the entire panel has no output. Now scale that to a large series array of panels. If one panel gets shaded the entire series has no output. Larger panels like a large array would have their cells (or panels in an array) wired in a series parallel configuration so it would take a much larger shadow to bring the whole system down.

You really need to get some panels out in the sun and cast shadows on them to see what I mean. Because a long thin shadow that only covers 10% of the total area can bring the entire output to 0 but a large shadow covering 50% of the panel vertically could only reduce output by a 50%, cover that same panel 50% horizontally and you are at 0 again.

[Pooja-S]

is my program good so far? the scale of the graph etc..

[Pooja-S]

Hi Zach, yes which constants to use from the datasheets. Also please take a look at my program, how does the shading(area) connected. & how can we find the voltage at max power, max power, current at max power from my program. Thanks loads.

[Pooja-S]

Hi all, pls see my program, i highlighted in red. I am unable to connect the wires, getting errors. How can we connect the index array, & array max & min.  consider my program. Thanks.

[Pooja-S]

This is my program. Why i am not getting the graph CURRENT AND POWER correctly. Please somebody help me.

i have attached a pdf file. This contains the specifications of a solar cell. How to i use it ?Help please.

[johnsold]

What do you think is not correct about the graphs?  If you select Autoscaling for both X and Y axes, the graphs seem quite reasonable.  the way it is set up you are only plotting the data for one cell not an array of cells.

Lynn

[Pooja-S]

Dear Lynn, can u please see the attachments. These are the values for a silicon solar module, i want to extract only values for a cell. Since there are 36 cells connected in series, i guess we should divide all every values by 36 to obtain values for a cell. Right? But if you see my program, i am confused where values of Pmax, Voc, Isc, Is .... should be fed as constants.

[Pooja-S]

sorry 1 missing attachment the specifications of a solar module, i need to extract values to get solar cell values, and use it in my program.

[johnsold]

1. Where did you get the values in the case structures in the nnn.vi? It looks as though you are trying to model the behavior of a diode, but I think there may be some errors.  For a diode Is (saturation current) is typically on the order of 1E-12 but you have values which look more like the forward voltage drop.  What you have labeled IL looks like Is.  I have no idea what the top case structure represents.

Edit: The labels were far away from the structures they identify.  I have not sorted everything out yet.

2. kT/q = 26 mV is valid for Si.  I think you may need other values for other materials.  It has been a long time since I looked at the behavior of semiconductors at this level, so I may be mistaken.

3. Your loop stops when the value in the voltage shift register exceeds the value you call IL, but which looks like the voltage across a diode. For your solar array you probably want the Voc value of the array.

4. You could combine all three case structures into one with three outputs.  The case structure should be outside the loop since nothing in it will change after the lop starts running.

5. Similarly, if G, Area(Shading), and dV do not change during a run, the terminals should be moved outside the loop.  The entire Efficiency calcuation does not change.  It should be outside the loop.  Why do exactly the same thing hundreds or thousands of times?

Until I better understand your program I cannot answer your questions directly.

Lynn