Maximizing Solar Efficiency by Tackling Shading Losses in PV Systems

Energy from renewable sources is becoming increasingly popular, with solar photovoltaic (PV) technologies leading the way. As the world transitions from fossil fuels to solar power, PV technology's rapid expansion requires careful attention to factors affecting its efficiency. Shade is a key factor that can reduce power output, and efficiency, and greatly increase the overall performance of PV systems. In some PV modules, even a small shaded area can reduce energy production significantly.

Shading losses refer to the reduction in electricity generation caused by an obstruction that prevents direct sunlight from reaching solar panels. The shading on a single PV module effectively mitigates the overall electricity generation output of a module's string. When installing a solar PV system, it's important to take into account various types of shading. There are two main types of shading: dynamic and static.

Dynamic shading, such as the shadows created by drifting clouds and falling leaves, adds a dynamic element to the scene. Shading can also occur due to various factors such as snow, bird droppings, and the accumulation of dust on the surface. Static shading involves considering factors such as shade from nearby trees, buildings, chimneys, etc.

The shading of 10% of the area of a system could cause a loss of 50% in the performance of a PV system. Soiling is a prominent factor contributing to energy loss in certain areas. In regions with frequent dust deposits, the losses may lead up to 5-7%. According to an NREL study, implementing an annual cleaning on a system with a soiling loss of 1.9% would result in a reduction of the loss to approximately 1.5%. Performing two cleanings annually has the potential to decrease the average loss to 1.3%. Additionally, implementing three cleanings yearly would further limit the average annual loss to 1.2%.

Bird droppings can cause significant blockage in one or two cells, and they may not be easily washed away by rain. If a module does not have bypass diodes, the loss of operation can occur if one or two cells are completely blocked, resulting in a reduction in power generation. Snow loads are also a limiting factor. An NREL study found that fixed-tilt systems can experience losses ranging from 10 to 30% due to snow loads.

Installing bypass diodes allows for the isolation of shaded cells. These intelligent devices redirect the electrical current, effectively bypassing the underperforming cells, and minimizing their influence on the entire system. However, by implementing this approach, the output of the bypassed components will be lost. Another way to enhance the performance when dealing with shading is by implementing a module-level power electronics (MLPE) device. These include DC optimizers and microinverters that can be easily attached to individual PV modules.

DC Optimizers adjust both the output voltage and current under the influence of shading on the PV panel. When microinverters are installed, the panels are connected in parallel. It ensures that when one panel is under the shadow, every panel will function at its highest capacity without any negative effects on the rest of the panels.

In a nutshell, the performance and efficiency of PV systems can be greatly affected by shading. By understanding the mechanisms of shading losses and implementing smart mitigation strategies, it becomes possible to greatly reduce these losses and improve the overall performance and reliability of solar PV systems. Efficient system design, cutting-edge technologies at the module level, consistent maintenance, and state-of-the-art monitoring play a crucial role in effectively managing and minimizing shading losses in PV systems.