Site IV.1

Health
COD
2014
Nominal Capacity
80 kWp
Yield since COD
738 kWh/kWp
Possible Gain
16% to 25%
CAPEX, OPEX
1.4 ₹/Wp, 0.2 ₹/Wp/a

Abstract

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%.

Image gallery

Main Findings

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.
Through IR inspection, several modules with warm cells, inactive strings and shading induced hotspots were detected.
Product failures at module level were detected, such as open J-boxes or hot cables at the J-box from poor soldering or clamping.

Impact on Performance

Near Shading

The losses due to near shadings (trees) could represent 7% less irradiance loss, based on a representative simulation.

Estimated Loss
≈ 7%
Inhomogeneous tilt angle

The inconsistency in the module tilt angle, combined with the deviation from the optimum azimuth, lead to ca. 3% yield loss from the optimum orientation.

Estimated Loss
≈ 3%
Soiling

An average soiling factor of 6% was determined from IV curve measurements of sample modules, before and after cleaning.

Estimated Loss
≈ 6%
Potential Induced Degradation

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.

Estimated Loss
≈ 20%
Total Estimated Energy Loss
≈ 36%

Proposed Solutions

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.