Site I.7

Health
COD
2018
Nominal Capacity
70 kWp
Yield since COD
465 kWh/kWp
Possible Gain
14% to 18%
CAPEX, OPEX
0.2 ₹/Wp, 1.2 ₹/Wp/a

Abstract

The PV plant shows high levels of soiling caused by bird droppings and a significant amount of inactive cells strings partially induced by soiling. During the assessment installation failures of the DC cabling were detected as well module damages and near shading. It is recommended to (i) change the module tilt to 15°, (ii) increase the cleaning frequency to three times per month, (iii) increase the albedo using white gravel, (iv) relocate the shading objects and (v) replace modules with performance drops beyond manufacturer ́s guarantees. The estimated production boost caused by the retrofitting actions lies between 14% and 18%.

Image gallery

Main Findings

Heavy soiling caused by bird droppings has been detected. A large amount of birds coming from the wasteland Ghazipur nearby, gather on the rooftop system every day.
The near shadings were ignored during the design phase of this system.
A significant amount of modules with inactive cell strings were detected. This effect is mainly caused by shading and heavy soiling.
Scratches at the backside were detected posing safety risks and increasing the risk of inverter disconnection due to loss of insulation.
The installed irradiation sensor is from a different technology, and has a different tilt angle. The module temperature sensor is not properly fixed.
A significant number of connectors showed overheating due to improper installation.

Impact on Performance

Soiling

Soiling measurements were conducted measuring both the short circuit current and nominal power before and after cleaning at irradiations higher than 800W/m2. The estimated soiling factor is in the range of 8 – 9%.

Estimated Loss
8%-9%
≈ 8.5%
Inactive Cell Strings

Modules with inactive cell strings underperform 33% to 66% depending on the amount of affected strings. The extrapolation of the inspected sample to the whole system leads to a loss of 5% on system level.

Estimated Loss
≈ 5%
Total Estimated Energy Loss
≈ 13.5%

Proposed Solutions

The cleaning cycles shall be increased and defined based on a soiling study that adjusts the cleaning needs to each season.
Spikes against birds shall be installed at the upper edge of the modules.
The irradiation sensor should be properly reinstalled and it should be of the same technology as the modules.
The modification of the tilt angle to 15° leads to a performance boost of around 2.2%.
Increasing the albedo from 0.2 to 0.6 by covering the ground with white gravel leads to an increase of the irradiation on