In general, at the inception of initial commissioning there are no documented energy output performance data, and all measurements taken must be based on real-time, instantaneous power output values of various solar power subsystems.

Dynamic Solar Power Output Performance Measurement Procedure

Please refer to Chapters 8 and 9 for additional recommendations as to how dynamic field testing can involve use of advanced wireless intelligent submetering technology and can be used to test and dynamically validate functionality of solar power PV modules, strings, and subarrays.

1. Measurement of peak DC power output: This value is the sum of all PV modules’ PSTC value (which is power measured under Standard Test Conditions (STC) measured at 25 °C), as shown on the manufacturer's module specification or the module nameplate.

2. Calculation of solar irradiance factor Ki: Solar irradiance is measured by a pyranometer. Irradiance readings are displayed in watts per square meter (W/m2). When measuring solar irradiance, the pyranometer plane and inclination angles must be exactly the same as the PV module arrays, with the same azimuth and tilt angle. Note: Irradiance factor Ki is obtained by dividing measured under STC irradiance which is 1000 W/m2 at sea level and 25 °C.

3. Calculation of PV module temperature factor KT (see Chapter 4): PV cell temperature Tc is measured by an infrared thermometer (IRT), which is targeted at a module. The KT, the temperature coefficient CT listed in the PV module specification (generally −0.003/°C to − 0.005/°C for mono-crystalline cells).

4. Calculation of solar power system derating factor Ks: This factor is a product of all solar power system derating factors, such as module nameplate tolerance, module mismatch inverter coefficient of efficiency module soiling, wiring losses, shading, system availability, sun tracking efficiency, and aging-efficiency loss factors. These are reflected in National Renewable Energy Laboratories’ (NREL) web-based PV Watts II calculation.

Evaluation of Ranges Degradation Factors

The following are ranges of various degradation factors:

1. Module nameplate DC tolerance:

2. Verify performance factor assigned to the PV module manufacturer's product quality, which involves electrical test performance, electrical output performance sorting, PV module batching, and quality assurance methodology.

3. Module mismatch:

4. Verify derating multiplier is associated with ohmic resistive variations inherent in each PV module. Numerous parameters that result in varying electrical output of muddles are inconsistencies in solar cell fabrication, cell crystalline structure, and intercellular soldering.