CHAPTER 2  >  ACTIVITIES  >  PROBLEMS  >  PROBLEM 8
Characteristics and maximum power point of PV cells
A small photovoltaic panel consisting of 21 cells arranged in series is exposed to sunlight. (The surface area of a single cell is about 15 cm^2.) It is connected to a load resistor with variable resistance.
Voltage and electric current for the load resistor have been measured for different values of the resistance (see graph). Irradiation was about 60 W/m^2 for the first, 200 W/m^2 for the second, and nearly 400 W/m^2 for the third (the highest) curve.

a. Determine the short circuit current for these three cases. How large is the open circuit voltage?
b. Determine the resistance values of the load resistor that would lead to voltages of 2.0 V, 4.0V, …, 10.0 V for the three characteristic curves.
c. Calculate the electric power of the panel for a voltage of 4.0 V and for 8 V for the three cases of characteristic curves.
d. Determine the maximum values of the electric power for the three cases. What are the values of the load resistance for the maximum power point for the three curves?
e. Determine the efficiency of the panel for maximum power point conditions for the three cases.
f. Use the model of PV cells represented by the equivalent circuit shown above to generate characteristic curves. [I_L: light current proportional to irradiance; I_D: diode current; R_S: series resistance.] Adjust the parameters of the model to fit the measured values (PV_Characterisitcs.xls).


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