10 Practices to avoid for best-in-class solar O&M

Indian solar industry has grown tremendously over the last decade, a trend that is expected to continue in the coming years. India has become one of the cheapest producers of solar power worldwide. While this cost reduction was driven mainly by the falling module prices, increased competition and aggressive bidding had led many developers to cut down on their O&M budget. Lower O&M budgets can downgrade the sophistication of O&M practices.

Here’s a list of 10 items that lean O&M teams should avoid ensuring best-in-class O&M with a limited budget.

01. Improper maintenance of pyranometer 

The angle at which the pyranometer is installed should be the same as the tilt at which solar panels are installed to find the PR ratio (=Specific Energy Output/Radiation per sq m per day). Many times, the angle of the Pyranometer is changed so that less radiation falls on it as a result of which, the input of the Pyranometer reduces, and therefore PR increases. Other than this, pyranometers must be cleaned regularly but this practice is not followed everywhere. As a result, the dust gets settled on the glass and less radiation falls on the Pyranometer. This again results in faulty data on its PR ratio. Abnormally high PR (>85%) is an indication that the pyranometer may not be recording correct radiation.

02. Ignoring safety measures on-site

The site team often ignores safety measures while performing O&M activities and risks their lives. Technicians may not be wearing all safety gear like helmets, shoes, working gloves, working jackets, etc. For instance, if a cable is broken and needs to be fixed, the technician may not use insulated tools or rubber gloves or goggles. If the cables are live, they might injure the technician involved in the process and can even be a cause for death.

03. Lack of proactive testing

SCADA and monitoring software used in O&M have their own limitations and do not give the developer an understanding of the module level defects in the plant. Many times, critical damages like cell cracks, hotspots, PID or even module and string isolations can go unidentified for long periods. Therefore, it is important that the O&M team conducts periodic testing of the modules - including IV curve measurements, EL imaging, and drone-based thermography. Below is an EL image of a module with PID and a power loss of 55.79%.

04. Improper handling of cables

The cables in the solar power plants are located under the modules very near to the ground surface. These plants are in open areas where there’s a lot of vegetation. Over time, these cables hide inside the thick bushes and this causes difficulty in O&M of the cables. 

Many times, it has also been observed that the cables are dangling and not laid properly in the conduits. This can possibly invite multiple ground faults and is a safety risk.

05. Improper labeling of cables

When a plant is established, all the cables are labeled for future reference and data is fed in SCADA accordingly. As time progresses, many labels get damaged or disrupted, as a result of which, whenever a fault occurs on the cables, it becomes quite difficult to identify the cable and resolve the issue. If the cables are labeled correctly, the resolving process takes around 1-2 hours which might extend to 2-3 days if not labeling is not proper. Therefore it is important that the labels be restored periodically. (Labelling is missing - in the caption)

06. Improper cleaning frequency and methodology

Key problems with cleaning

• In some places, cleaning is done during peak hours. This practice is detrimental for the modules because during peak generation hours, the temperature of the modules is very high and the cold water will cause this high temperature to fall quickly, leading to thermal stress. 

• Cleaning frequency and methodology should be derived from the nature of soiling observed on the site. For this, soiling loss measurement can be done at regular intervals. For example; High TDS level could lead to scaling of modules; Sticky dust might need cleaning with IPA solution

• Mopping from the edges to remove dust deposition may not be done properly which reduces transmission

• Uneven soiling occurs if there is no proper cleaning 

• Discoloration might also occur due to cleaning of modules with hard water

• The cleaning of modules may be done with brushes and hard detergents which leave scratches on the modules.

07. Improper module handling

The workers involved in cleaning the modules may damage the modules by kneeling, dropping other equipment, walking or climbing on the modules, leading to micro-cracks.

08. Improper collection of plant data

For preventive maintenance of the plant, certain data sets need to be collected and analyzed at varying frequencies. For instance, daily global horizontal irradiance, maximum DC/AC power, generation start and stop time, DC generated at strings should be collected on a daily basis while net energy generated at the inverter, net energy fed at the meter, normalized energy generated, monthly DC energy loss are calculated on monthly basis. Some data is also collected on a yearly basis like annual average performance ratio, annual average plant availability avoided CO2 consumption, etc. It has been seen that this data is not maintained in plants and therefore many problems may not be detected in a timely manner. This is one of the major practices in O&M that needs to be corrected for the proper functioning of solar power plants and increasing the plant lifespan.

 09. Inadequate inventory availability

Inadequate inventory can prolong the downtime as the site team may not have the right materials to fix a problem. Since most plants are located at remote locations, the restoration of inventory may take a longer time, hence leading to a longer breakdown. Certain equipment and components are a must, however, it is a common observation that these components either may not be present at the site or may not be available in sufficient quantities. Some of the critical inventories are MC4 connectors, string cables,  string fuse, inverter dc fuse, etc.

10. Preventive maintenance not based on proper root cause analysis

When an issue is detected by the O&M teams, it is often resolved on a short-term basis and the O&M teams fail to build a preventive plan based on proper root cause analysis, which sometimes further escalates the problem. An example of this is a plant in Rajasthan where the module mounting structures did not provide a scope of expansion to the modules. As a result, the frame of the modules started bulging due to excessive heat in the region, causing moisture penetration within the modules, reduced insulation resistance and repeated tripping of the inverters. In order to resolve this issue, the O&M teams bypassed the GFDI to prevent the tripping of inverters instead of solving the problem of insulation resistance and module expansion. By-passing GFDI further led to excessive Potential Induced Degradation in the plant leading to power loss. A preventive plan based on proper root cause analysis could have reduced this power loss significantly. 

To conclude, O&M is not just grass-cutting, cleaning, and security. O&M is responsible for maintaining overall plant efficiency and energy delivery along with minimizing losses in the plant. It ensures ease of operations, safety, and reliability of equipment involved in the plant. With certainly added care during O&M, the plant lifespan can be increased significantly.