Solve PV Module Problem: Find I,V,P for 3 Conditions

[Jason03]

Im working on a problem that involves a PV module consisting of 40 cells each at .5 volts. The problem models the module as having all 40 cells in series. The PV module is connected to a 5 ohm load. The problem also says to assume that the same current and voltage flows through the PV module and load. So solve for I, V, and P.

I just need to find the current, power, and voltage for 3 conditions.

a) when in full sunlight

b) when 1 cell is in shade

c) when 2 cells are in shade.


my question is:

I know the voltage to be 20 volts in full sunlight and 19.5 volts when 1 cell is in shade...so when 1 cell is in shade I noticed the book saying that one .5 volt cell will now act as a 5 ohm reisistor...is this true...and why?

and if that is the case for 1 cell in the shade would I have a total of 10 ohms resistance to calculate the current flowing?

 

[Jason03]

any ideas?...I can understand a cell not functioning acting as a resistor...but why 5 ohms?

 

[OmCheeto]

any ideas?...I can understand a cell not functioning acting as a resistor...but why 5 ohms?

I would guess it is because that's what someone measured when they shaded an individual cell. Silicon is a semiconductor, so with no light falling on the cell, it turns into a resistor. That resistance will depend on the physical dimensions of the cell.

 

[sarah1]

its true , for this case the PV module must protect it by bypass diode