I'm working on a project and currently looking for what is a suitable PV modules. I've found a good one. The data sheet of the module does not contain any information on the NOCT values. In general, how big is the difference in measurements between the STC and NOCT? Can this be determined somehow?
The performance under NOCT conditions is generally 18 to 26% less than that under STC conditions. This is because the temperature and the irradiation are usually different from STC. Higher temperatures or lower irradiations lead to lower PV capacities. You might find What is the difference between STC and NOCT in photovoltaic module specifications? helpful.
Some data sheets do not contain any information on the NOCT values. This can be determined almost exactly. There were two mathematical equations behind it. First, the temperature of the PV cell is determined. T Cell :
T cell = T environment + 1.25 * irradiation environment * ( T NOCT - 20).
T ambient and irradiation environment are respectively the temperature and the irradiation measured in the system environment . T NOCT is the NOCT temperature. This is usually in the data sheet. If not in the data sheet you can use an average value of 46 C o or 114.9 Fahrenheit. With the specific T cell one can then calculate the PV power under NOCT conditions NOCTperformance :
Power NOCT = power STC * [1+ P Tempcoef * ( T cell -25)].
Power STC represents the PV power under STC conditions. P Tempcoef is the temperature coefficient of the power. Both power STC and P Tempcoef are always included in the data sheet. As a rule, power NOCT is then about 77% of the power STC.
The data sheet of a PV module shows that the rated power at STC and the temperature coefficient of the power are 185 W and (-0.5% / C o or 31.1 / F). How is the performance at NOCT?
First you have to calculate the T cell . In the surrounding area around the module we measure the temperature and the irradiation as 30 C o or 86 Fahrenheit and 0.9 kW / m 2 respectively , for example. We would assume an average value of 46 C o for T NOCT . Therefore
T cell = 30 + 1.25 * 0.9 * ( 46 - 20) = 59.25 C o 138.65 Farenheit.
Then we calculate the performance at NOCT as follows
Power NOCT = 185 * [1+ (-0.5 / 100) * ( 59.25 -25)] = 153 W.
For this module, the performance at NOCT represents approximately 82% of the performance at STC.
I hope this helps!
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