3 Physical Obstructions That Impact Utility-Scale Solar Farms: Part 2

There are many types of issues that reduce the performance of utility-scale solar farms. Previously, in Part 1 of this series, we explored three common faults that reduce power production, such as hotspots and string faults. In this blog, we want to cast light on other types of issues that lower the power production of PV arrays. We’re talking about physical obstructions, and in this case, when we say “cast light,” we literally mean it. 

A physical obstruction refers to a situation where a PV module is partially or fully blocked from receiving direct sunlight on all its cells. 

While forms of physical obstruction reduce power production, they differ in their causes, effects and remedial actions. Besides reducing the power of the directly blocked cells on the panel, these issues can have an additional effect on overall performance since the cells and the panels are interconnected in strings.   

1. Shading

Shading occurs when a physical object is casting a shadow on part of the PV module. When a module is shaded, the affected cells produce less electricity. In severe cases, shading can activate bypass diodes within the module to isolate the affected cells and prevent overheating and damage, but this may further reduce energy production.

Possible causes: There can be several root causes for the creation of shading:

• Objects inside the solar farm such as shelters, utility poles and antennas. 
• Self-shading in some hours of the day, when the sunlight angle causes each row of modules to cast partial shadow on the adjacent row of modules.
• Weather conditions such as haze or clouds. Clouds can be uniform or dynamic in their effect depending on if they are heavy or partial and moving.
• Nearby buildings or thick tree branches. These are less common in utility-scale solar farms which are usually located in vast open fields.

Remedial actions: 

• Solar farm design – To prevent or minimize shading from adjacent rows or objects, the PV arrays and their mounts are placed with optimal orientation and tilt, as well as sufficient spaces between rows and between row edges and obstructing objects. 
• Aerial thermal inspections – Conducting inspections in various seasons and times of day provide accurate detection of shading issues across the solar farm.
• Elevated mounting solutions – Considering higher mounting structures or tracking systems that adjust the modules angle throughout the day.
• String configuration – Connecting modules with similar shading conditions on the same string to prevent mismatch power issues.
• Micro-inverters and power optimizers – Optimizing the performance of each module separately. 

2. Soiling

Soiling refers to the accumulation of material that partially or fully covers the surface of solar modules. This obstruction reduces the amount of sunlight reaching the photovoltaic cells, diminishing the energy output of the system. Soiling typically builds up gradually and can lead to long-term performance issues if left unaddressed.

Possible causes: there are several different sources of soiling:

• Dust and pollen – In dry and windy environments, dust, dirt and flowers’ pollen particles can settle on the surface of panels, gradually blocking sunlight.
• Ice and snow – Uncleared ice and snow can accumulate and block the sunlight.
• Bird droppings – Flocks of birds can leave droppings that obscure sections of the module’s surface and reduce exposure to sunlight.
• Urban pollution – In areas with heavy pollution or near industrial zones, airborne pollutants such as soot or grime can settle on the PV modules.
• Irrigation: In agricultural areas, water used for irrigation or nearby sprinklers can splash onto panels, carrying dirt and leaving behind mineral deposits as the water evaporates.

Remedial actions: 

Operation & Maintenance crews need to schedule regular periodic cleaning to remove soiling from the surface of the modules, ensuring maximum sunlight absorption. Many teams are using robotic cleaning tools that are built to clean the modules most efficiently while keeping the surface from damage.

O&M teams are conducting drone thermal inspections to determine the optimal cleaning frequency against the energy gains, especially when the soiling occurrence is dynamic and depends on seasonal elements.

3. Vegetation

Vegetation refers to the excess growth of grass and plants to a point in which they cast a partial shadow on some of the modules, or pose a risk on the modules, their infrastructure and the O&M workers in the solar farm.

 Potential damages: 

• Reduced energy output due to shading.
• Overheating cells can overheat and even cause a fire in extreme cases. 
• Electrical risk to electrical cables, switches and circuits that support the solar modules that may lead to short-circuiting or power surges.
• Pests and rodents can hide within the excess vegetation and risk the equipment and wiring.
• Increase in maintenance cost.

Remedial actions: 

Similar to soiling, O&M teams can conduct frequent drone-based inspections to accurately identify vegetation issues in their large utility-scale solar farms.

Many of them are also deploying electric lawn mowing robots that automatically trim the grass and plants and lower the chance of human error. It is usually combined with chemical methods to control the growth of weeds. 

Some solar farm owners are enhancing soil health through advanced vegetation management methods. In some places they turn the site into an agri-solar farm by growing vegetables underneath the PV arrays, and even employing sheep to graze the excess grass.

Frequent Inspections Help Optimize Solar Power Production

The huge size of utility-scale solar farms makes drone-based thermal inspections a necessary tool in accurately detecting the locations of shading, soiling and vegetation issues and determining their effects on your power generation.

vHive offers autonomous multi-drone solar inspections and analytics to provide a comprehensive view of your solar farms’ power anomalies. The clear insights help you prioritize and expedite corrective maintenance work to ensure your performance is always at its peak.

Are you ready to optimize your solar farm’s performance? Book a demo today to see how our autonomous drone solution and AI-driven analytics can transform your solar farm.