The Plant is affected by soiling (pollution and bird drops), inconsistent installation angles and near shadings. Furthermore, the module power performance is significantly lower than the expected values, likely due to a combination of installation and product failures modes (mainly PID and cracks). It is recommended to (i) increase cleaning frequency, (ii) irradiation sensor re-installation, (iii) homogenize module tilt angles, (iv) install an anti-PID box to stop PID degradation and (v) conduct string reengineering based on cracks and power classes. The estimated production boost expected by the retrofitting actions lies between 16-25%.
Heavy soiling caused by nearby industrial area and bird droppings have been detected.
Due to the limited access to the roof, it is likely that the modules suffered from mechanical stress during transport, handling and installation.
A few installation failures were discovered, such as scratches in the module backsheet, disregard of bending radius and cables in contact with sharp edges and exposed to UV load.
The irradiation sensor on the plane (GTI) was poorly installed and at a different angle than expected.
The PID effect could be responsible for more than 20% of performance losses on system level. Individual module measurements showed nominal power drops higher than 55% (104W) in the modules with negative polarity.
Spikes against birds shall be installed at the upper edge of the modules to reduce bird drops (soiling).
The tilt and shading angles throughout the plant shall be homogenized.
Likewise, the irradiation sensor should be properly reinstalled to ensure accurate readings.
Increasing the albedo from 0.2 to 0.5 by painting the rooftop surface in white and adding reflective materials to the rear side of the modules, leads to an increase of the irradiation on POA of at least 1.8%.
Modules with heavy cracks shall be grouped in the same string or at least assigned to one MPPT. The grouping will be conducted based on infrared inspection with high irradiation levels and after cleaning.
Furthermore, PV modules showing power drops above the warranty conditions shall be replaced. If the replacement is not possible, the modules shall be regrouped in power classes within the same string and assigned to individual MPPT.
An anti-PID measure, such as anti-PID box, shall be implemented in order to stop or reverse the degradation.