By

Gaurav Kumar

&

Dr. Ashish K. Panchal

S V National Institute of Technology,

Surat

A PROCEDURE FOR FINDING SOLAR CELL PARAMETERS AT DIFFERENT

TEMPERATURES

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.

SOLAR CELL I-V RELATION AND PARAMETERS

• 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

Solar cell single p-n junctiondiode equivalent electrical circuit

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

ESTIMATION METHODOLOGY: DETERMINATION OF ISC

• At ISC point on the I-V curve

• Hence Iph = ISC (Iph photo-current)

A typical I-V characteristic of a solar cell

MPP

DETERMINATION OF RSH

• Use of Lagrangian interpolation formula for current

• Lagrangian multiplier

• Inverse of dI/dV at SC point gives Rsh

DETERMINATION OF RSE

• Following linear equations are formed as a function of Rse and n

• Rse is found from,

Where

Assumption V/Rsh >> IRse/Rsh

DETERMINATION OF I0 AND N

• Using Rsh and Rse, the following linear equations as a function of I0 and n are formed,

• n and I0 are determined as follows,

Where &

EXPERIMENTAL

A 4 x 4 cm2 silicon solar cell is tested in a solar simulator with different temperatures of 40, 50 and 60oC.

Solar Simulator Silicon Solar Cell

I-V CHARACTERISTICS AND PARAMETERS OF A SILICON CELL TESTED IN THE LAB

Experimental characteristics match with that of the fitted

Parameters obtained bythe proposed method

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)

Obtained parameters match almost with those of reported at different temperatures

Parameters obtained by the proposed method

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

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