Temperature Coefficient

Hi,

I'm new to the PV technology and just have a few questions about the "Efficiency" and "Temperature Coefficient".

1. I understand the Efficiency is calculated based on Maximum/Nominal Power  and incident radiation under STC. If the power output is 200 W for a 1 m2 panel under 1,000 w/m2 condition, the efficiency is 20%. I assume when operating under the actual weather condition when the solar radiation is 500 w/m2 on the panel surface, theoretically the panel output would be 500 W * 20% = 100 W, is this correct? Or efficiency actually has changed?

2. Temperature Coefficient only affects Maximum/Nominal Power, right? Use the example above, the Nominal Power is 200 W, efficiency 20%. Assuming the temperature coefficient is -0.5%/C. Assuming the weather condition is: 600 w/m2 incident radiation and the cell temperature is 45 C. Under this condition, the power loss would be -0.5%/C * (45 C - 25 C) = -10%. So the Nominal Power would now be 200 W * (1-10%) = 180 W. This is Nominal Power though. The actual panel output at this time would be 600w/m2 * 20% = 120 W. Is above logic all right?