Question

1.The realistic power output of a crystalline solar module operating at 65 degree C as a percentage of its rated nameplate power output is approximately what % of STC?

2. If a STC value for Voc is 20V and Isc is 4A and irradiance is at a half sun, what would be the approximate Voc and Isc?

Answer 1

The electric output performance of crystalline silicon and thin film PV modules are generally measured under standard test conditions (STC), ensuring a relatively independent comparison and output evaluation of different solar PV modules.

STC is an industry-wide standard to indicate the performance of PV modules and specifies a cell temperature of 25°C and an irradiance of 1000 W/m2 with an air mass 1.5 (AM1.5)spectrum.

However, the temperature coefficient also tells you that efficiency increases in temperatures lower than 25°C. So, in most climates, the efficiency will balance out over the long run.

(1) In many instances, a solar cell can get as hot as 65°C, causing the panel to become less efficient and therefore produce less power. If a panel with a temperature coefficient of -0.4%/°C were to reach an extreme heat of 65°C, it would reduce output by as much as 26% (-0.4% x 65). However, there are more variables involved than simply the coefficient value, and the equation is a little more complicated.

(2) Voc= temperature coefficient(T[STC]-T[ambient])+ Voc rated

same for Ioc

every solar panel will have a temperature coefficient. The temperature coefficient represents the rate at which the panel will underperform at each increase in degree Celsius (°C). Most panels have a temperature coefficient of between -0.2% /°C to -0.5%/°C, when tested under standard laboratory conditions, where ambient temperature is set to 25°C. The closer the temperature coefficient is to zero, the better the panel will perform when the temperature rises. All solar panel manufacturers are required to provide the temperature coefficient figure.

Voc= 0.2(25-12.5)+20 =22.5V

Ioc= 0.2(25-12.5)+4 =6.5A

the ambient temperature is 12.5 because it is half of the irradidiance of the sun means generally half the temperature of the STC.