1. 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 V OC decreases substantially, while the short circuit current I SC increases only slightly. As solar insolation increases, I SC decreases in direct proportion, while the V OC increases only modestly. PV perform better on cold clear days than hot days. For crystalline silicon PV cells, V OC drops by about 0.37%/  C rise in temp. I SC 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.

2. Solar Energy Systems/ J.P. Agrawal / M3_2 - page 2 The cell temp is given by: where NOCT: nominal operating cell temp at 20  C, at the solar insolation of 0.8 kW/m 2. T amb : ambient temperature 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 30  C. The module has a NOCT = 47  C. Solution:

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4. 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 I SC = 0 of the shaded cell.

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14. Solar Energy Systems/ J.P. Agrawal / M3_2 - page 14 Design for Photovoltaic Applications Please read the section 9.4: pages 434 – 443.