TECH 581 – Solar Energy Systems Summer 2009 Module 3-2 – Solar Electrical Effect of Temperature and Insolation on the PV I-V Curves As cell temperature.

TECH 581 – Solar Energy Systems Summer 2009 Module 3-2 – Solar Electrical

Effect of Temperature and Insolation on the PV I-V Curves• As cell temperature increases,

open circuit voltage VOC decreases substantially, while the short circuit current ISC increases only slightly.

• As solar insolation increases, ISC decreases in direct proportion, while the VOC increases only modestly.

PV perform better on cold clear days than hot days.

For crystalline silicon PV cells, VOC drops by about 0.37%/C rise in temp.ISC increasess by about 0.05%/C rise in temp.MPP slides slightly upward and left, decreases by about 0.5%/C rise in temp.

The cell temp varies not only due to ambient but also due to change in the insolation, because only a small fraction of incident insolation on the cell is converted to electricity, the rest is absorbed and gives rise to heat.

Solar Energy Systems/ J.P. Agrawal / M3_2 - page 2 The cell temp is given by:

where NOCT: nominal operating cell temp at 20C, at the solar insolation of 0.8 kW/m2 . Tamb : ambient temperature

SCNOCT

TT ambcell .8.0

20

Example:Estimate the cell temp, open circuit voltage, the max ppower output for the 150-W BP2150S module under the conditions of 1-sun insolation and ambient temp of 30C. The module has a NOCT = 47C.Solution:

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Solar Energy Systems/ J.P. Agrawal / M3_2 - page 4 The current through all cells in a module is same even though only one cell is in shade.

The ISC = 0 of the shaded cell.

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Solar Energy Systems/ J.P. Agrawal / M3_2 - page 14 Design for Photovoltaic Applications

Please read the section 9.4: pages 434 – 443.