This document presents a methodology for estimating the key electrical parameters of solar photovoltaic (PV) cells from their current-voltage (I-V) characteristics. The methodology is non-iterative and determines the short-circuit current (ISC), shunt resistance (Rsh), series resistance (Rse), reverse saturation current (I0), and diode ideality factor (n). It applies Lagrangian interpolation and forms linear equations relating the parameters. Experimental I-V data from a silicon solar cell tested at different temperatures is fitted well using the estimated parameters. The methodology is validated against data from previous literature and can be used to analyze different PV cell performance under varying irradiance and temperature conditions.

2. INTRODUCTION
• Increasing electricity demands & fuel prices tempt us for
renewable energy sources such as wind power & solar
photovoltaic (SPV).
• Extraction of maximum power from SPV is essential for better
performance.
• SPV performance is greatly influenced by atmospheric
conditions such as solar irradiance, cell-temperature, wind
speed, etc.

3. SOLAR CELL I-V RELATION AND PARAMETERS
Solar cell single p-n junction
diode equivalent electrical circuit
• I and V cell current and voltage, respectively
• Iph photo-current
• I0 reverse saturation current
• Rse series resistance
• Rsh shunt resistance
• n diode ideality factor

4. NEED FOR THE METHOD
• ISC strongly influenced by solar irradiance
• VOC & FF strongly influenced by temperature
• Rate of change of VOC with T depends on rate of change of Rsh and Eg
with T
• Rate of change of FF with T depends on rate of change of Rse and V with
T
• Interdependency of performance on electrical parameters plays
significant role on η at different T

5. ESTIMATION METHODOLOGY: DETERMINATION
OF ISC
• At ISC point on the I-V curve
• Hence Iph = ISC (Iph photo-current)
MPP
A typical I-V characteristic of a solar cell

6. DETERMINATION OF RSH
• Use of Lagrangian interpolation formula for current
• Lagrangian multiplier
• Inverse of dI/dV at SC point gives Rsh

7. DETERMINATION OF RSE
• Following linear equations are formed as a function of Rse and n
Where
• Rse is found from,
Assumption V/Rsh >> IRse/Rsh

8. DETERMINATION OF I0 AND N
• Using Rsh and Rse, the following linear equations as a function of I0
and n are formed,
Where
• n and I0 are determined as follows,
&

9. EXPERIMENTAL
Solar Simulator
Silicon Solar Cell
A 4 x 4 cm2 silicon solar cell is tested in a solar simulator with different
temperatures of 40, 50 and 60oC.

10. I-V CHARACTERISTICS AND PARAMETERS OF A
SILICON CELL TESTED IN THE LAB
Experimental characteristics match with that of the fitted
Parameters obtained by
the proposed method

11. I-V CHARACTERISTICS AND PARAMETERS OF A
SILICON CELL OF PREVIOUS LITERATURE
Synthetic I-V characteristics match with that of the
fitted.
Ref: Priyanka Singh et al.
Solar Energy Materials & Solar cell 92 (2008)
Parameters obtained by the proposed method
Obtained parameters match
almost with those of reported at
different temperatures

12. CONCLUSIONS
• A non-iterative technique is developed for finding parameters of a
solar cell tested under different temperatures
• Technique is applicable to a Si cell with I-V data available in the
literature and a Si cell tested in our laboratory
• Technique is simple and can be employed for different PV cells tested
in different irradiance as well

13. ACKNOWLEDGEMENTS
• NCPRE, IIT Bombay for providing solar simulator through the
programme “1000 teachers training for SPV”
• SVNIT, Surat for providing the fund to attend this conference