When deciding to install a photovoltaic installation, it is worth specifying expectations regarding the performance of the PV system at the investment planning stage. When analyzing the technical parameters of modules available on the market, attention should be paid primarily to their power, but information regarding, among others, temperature coefficient, annual power decline or efficiency of photovoltaic panels.
The most important parameters of photovoltaic panels – what do they mean?
Power – MPP point and NMOT/NCOT ratio
In the case of this parameter, manufacturers usually provide information about the power at the MPP (Maximum Power Point), i.e. the peak power obtained during tests in optimal conditions, at a temperature of 25°C and sunlight of 1000 W/m². However, it is quite difficult to achieve such favorable conditions for the operation of PV installations, which is why one more parameter is increasingly used – the NMOT/NCOT (Nominal Module/Cell Operating Temperature) coefficient. The power of the panels in NMOT/NCOT means that they were tested in conditions closer to reality (including at a temperature of 20°C and sunlight of 800 W/m²). This parameter provides reliable information about what we can expect from the selected modules, and a higher NMOT/NCOT ratio simply means better performance.
Efficiency of photovoltaic panels
It is determined by manufacturers as a percentage, and on its basis the number of modules needed to service a given facility is calculated. The efficiency of photovoltaic panels is calculated by dividing the solar battery power by the solar radiation intensity.
Annual power loss
This is the module degradation factor and, because it significantly affects the nominal power of the installation, it should be as low as possible. Currently, there are panels available on the market with an efficiency of 80% after 25 years and those that will still be 82% efficient after 30 years of operation.
Temperature coefficient
This parameter determines how much the efficiency of photovoltaic panels decreases when they are exposed to temperatures exceeding 25°C. The higher it is, the more the module power decreases, and therefore the lower the temperature coefficient, the better.