1. Grid availability (GA)
This is the ratio of the actual grid availability to expected grid availability.
This is a major factor which affects the generation since without the availability of the grid, the solar projects cannot produce power and export the power.
2. Plant availability (PA).
This measures the percentage of sunlight hours when the plant was ready to produce. All components of the system should be available for effectively converting the solar radiation to electricity. This is actually calculated by getting the individual availability of components (not often followed by many).
Ex. Inverter Availability = [hours with inverter production > 0] / [hours with irradiance > 100W/m2].
Plant Availability = weighted average of all components availability
This directly affects the LCOE ( levelised cost of energy).
This is the energy production per unit of plant capacity (Kwh/kw)
4. PR (performance ratio).
This is the percentage of the received sunlight energy converted into electricity by the plant. When the project is envisaged, the design would calculate the energy production, taking into consideration the radiation, conversion efficiency of modules, efficiency of inverters, various losses in the system and weather related aspects. This (PV Syst) gives the expected generation.
Radiation is measured using pyranometers installed at site. For large installations there is a requirement of more number of pyranometer to be installed.
The actual generation is what is measured in the meter at the point of injection to the grid.
Radhakrishnan Mundoli in Solar Energy Professionals amp; Consultants