how about sunpower plant ?

Question

how much is their power?

Answer 1

According to Wikipedia, the solar constant has been measured as 1366 watts per square meter, normal to the earth's "surface" at the Stratosphere. Since very little of this energy is impeded on a clear day, we can use this value at the actual surface. Now, we start with correction factors... The inclination of the Earth's axis causes an annual deviation from the normal of
L-23.5cos(360t/365.259) So the radiation impinging normally at your latitude at true local Noon on any given day will be 1,366cos(L - 23.5cos(360t/365.259)) W/m^2. Because of atmospheric refraction, the sun is visible for 204° of arc (max) per day, giving another correction factor of
cos(360*180(h-12)/(24*204)), -0.8 < h < 18.8 hours local

All of this assumes a system lying flat on the ground. A gimballed system can correct for both these factors, but at a cost of collector size and system complexity.

The efficiency of the system will probably run between 25 and 50%, depending on processes used