Table of Content:
- Introduction
- How much does shading affect solar panelefficiency?
- What are the different types of shading?
- Methods to avoid shading Losses of solarpanels
- Conclusion
Introduction
In the world of solar panels, shading isthe greatest adversary. It can lead to reduced output and affect the efficient operation of systems. Therefore, shading issues must be thoroughly considered before installing solar photovoltaic arrays.
How much does shading affect solar panel efficiency?
Some experts suggest that shading could potentially reduce the output of solar photovoltaic systems by up to 40%. Interestingly, even if only 10% of the panels are shaded, efficiency may drop by 50%. This is due to the way solar cells are connected within the system.
Traditional solar panel arrays are connected in a series of parallel "strings." If one string is affected by shading, the loss can propagate to other parts. To prevent complete failure of all cells, installations typically include bypass diodes. These diodes reroute the current, bypassing underperforming cells. However, while this prevents the entire array from failing—similar to how one bad bulb in a string of Christmas lights doesn't affect the whole string—it does limit the energy of the cells and reduce the voltage of the entire string.
In this regard, inverters play a crucial role. They must balance optimizing the voltage of underperforming strings or maximizing the energy collected by unaffected strings. Regardless of the approach chosen, inverters must decide between two inefficient options.
What are the different types of shading?
Temporary shading: Includes temporary shading caused by snow, bird droppings, and fallen leaves. Dust accumulation may also result in temporary shading.
Self-shading: This type of shading affects the installation system's racks and may be caused by the preceding row of modules. Therefore, module row layout is crucial in system planning.
Building shading: Objects such as chimneys, satellite dishes, antennas, and roof structures may cause shading on buildings.
Positional shading: Encompasses any shading caused by surrounding environments, such as trees and other nearby buildings.
Direct obstruction: Any object close enough to directly obstruct the solar system may have the greatest impact on its efficiency.
Methods to avoid shading Losses of solar panels
To avoid shading of photovoltaic panel arrays, the following measures can be taken:
1.Conduct shading analysis before construction:
Before building the power station, a comprehensive shading analysis should be conducted. This includes investigating potential shading sources in the surroundings, such as high-voltage lines, railings, vegetation, and existing buildings (including planned buildings). By taking necessary measures, such as adjusting installation positions, shading effects can be minimized.
During surveying and installation, consideration should be given to the annual growth of vegetation and whether tree canopies and branches will cause shading. If shading issues are anticipated, pruning or removing trees should be considered. Additionally, terrain changes should be considered to prevent shading from affecting sunlight exposure to panels, including shading in both north-south and east-west directions, as well as shading from different heights within the same row.
2.Keep solar panels clean:
Regularly cleaning the surface of solar panels is an important step in maintaining the efficient operation of solar energy systems. Cleaning can prevent bird droppings, dust, and shading from trees affecting the panels, ensuring adequate absorption of light. Furthermore, installing panels in locations with minimal shading can significantly reduce the impact of shading on power generation efficiency.
3.Avoid artificial obstruction:
During the design and installation of solar systems, avoid installing fences or erecting bird deterrent poles around solar panels. Additionally, during maintenance, be careful to avoid inadvertently causing shading, such as drying clothes or placing items on the panels. This ensures optimal performance and efficiency of the solar energy system.
4.Use multiple MPPT inverters:
Considering the use of multiple MPPT inverters to reduce the impact of shading on solar panels is an effective strategy. MPPT inverters are critical components in solar systems, with the primary function of monitoring the output voltage and current of solar panels and adjusting the operating point in real-time to ensure maximum power output.
By using multiple MPPT inverters in the system, solar panels can be divided into multiple independent strings, each controlled by a separate MPPT inverter. This means that even if some panels are shaded, other unaffected panels can maintain efficient power generation. Each MPPT inverter can independently track and maximize the output power of each panel, thereby minimizing the impact of shading on the overall power generation of the system.
Additionally, a multi-MPPT inverter system can overcome mismatch issues caused by shading. Since each inverter operates independently, even if some parts of the panels are shaded, the entire system is not affected, ensuring maximum overall efficiency of the solar panels. However, it is important to note that using a multi-MPPT inverter system will increase the cost of the system, so when deciding to adopt this design, site conditions and budget constraints need to be considered comprehensively.
5.Run solar panels in parallel:
It is well known that shading-covered photovoltaic modules significantly reduce the power output of the entire string. However, shaded panels within one string do not affect the power output of parallel strings. This means that strategic grouping can be adopted: modules affected by shading can form one string, while modules unaffected by shading can form another string, thereby maximizing the overall energy generation. By connecting panels to different strings separately, shading effects can be minimized.
For small residential solar systems, using parallel-operated solar panels with microinverters may be a more cost-effective option. Although this approach may increase the initial cost of the system, it provides greater flexibility and reliability, as each panel can operate independently without affecting the performance of the entire system due to shading or faults in other panels. Therefore, for small residential systems, using parallel-operated solar panels with microinverters may be a reasonable and effective choice to improve the overall efficiency and reliability of the system.
6.Use solar panels with strong shading resistance:
Maysun Solar's IBC (Interdigitated Back Contact) solar panels demonstrate powerful shading resistance with their unique full-back contact technology and cutting-edge design.
These panels utilize full-back contact technology, allowing normal flow of positive and negative metal electrodes even when shaded, while eliminating resistance on the front, effectively reducing damage from hot spots to components and thereby reducing the risk of power station operation.
The front features a design with no metal electrodes, expanding the range of light absorption. Even if some cells are shaded, other unshaded cells can continue to generate current, ensuring high-efficiency power generation for the entire panel.
With no obstruction from metal gridlines on the front, light loss is reduced, increasing the illuminated area by 2.5%. This feature forms the unique high short-circuit current technology characteristic of IBC cells, making their cell density 5-8% higher than that of Perc and TOPCon cells, with superior power generation performance.
Additionally, the shading-resistant characteristics of the front with no metal electrodes allow for a wider range of light absorption, with a spectral absorption range of 300nm-1200nm, resulting in early morning startup and late evening shutdown of the panel, with a power gain of more than 2.0% compared to Perc and Topcon panels.
Therefore, Maysun Solar's IBC solar panels provide a reliable solution for the efficient operation and stable power generation of solar energy systems, with their outstanding shading resistance, extensive light absorption range, and excellent power generation gain.
7.Using Bypass Diodes and MOS to Mitigate Shading Effects:
When solar panels are partially shaded, bypass diodes and MOS (Metal-Oxide-Semiconductor) play a crucial role. They allow the current to bypass the shaded portion, maximizing the efficiency of the unshaded areas. Traditionally, bypass diodes were employed to address this issue, but they faced challenges such as reduced efficiency and limited adaptability in complex shading conditions. However, a new solution, MOS (MOS Bypass Switch), offers a fresh perspective. By efficiently controlling current flow and quickly adapting to changes in light conditions, MOS mitigates the impact of shading, ensuring continuous power generation and enhancing the reliability and lifespan of solar panels. Maysun Solar's solar panels are equipped with MOS technology for optimal performance.
Conclusion
In the design and installation of solar panels, reducing shading is one of the key factors to ensure efficient system operation. By taking appropriate measures, such as conducting shading analysis before construction, regularly cleaning solar panels, and avoiding artificial obstruction, the impact of shading on solar systems can be minimized. Additionally, using solar panels with strong shading resistance, such as Maysun Solar's IBC solar panels and utilizing MOS technology, can further improve system stability and power generation efficiency. Therefore, when designing and installing solar systems, it is essential to thoroughly consider shading issues and select appropriate solutions to ensure continuous and stable power generation and contribute to the future of sustainable energy.
Reference:
Lee, S. (2023) 'Avoid solar panel shading: How to minimize its impact,' Velo Solar, 20 February. https://www.velosolar.com/solar-panel-shading/.
Boiler Guide Limited (no date) Solar PV and shading | Solar Guide. https://www.solarguide.co.uk/solar-pv-and-shading.
Opie, N. (2022) 'Limiting shading losses to maximize solar power output,' Ratedpower, 15 February. https://ratedpower.com/blog/shading-losses/.
Staff, A. (2024) Shading losses in PV systems, and techniques to mitigate them. https://aurorasolar.com/blog/shading-losses-in-pv-systems-and-techniques-to-mitigate-them/.
Solving PV module shading problems with the help of MOS（MOS bypass switch) - a new idea from Maysun Solar (no date). https://www.maysunsolar.eu/blog/pv-module-shading-problems-with-the-help-of-mos.
IBC Solar Panel, IBC Solar Module Manufacturer | Maysun Solar (no date). https://www.maysunsolar.eu/ibc-series-solar-panel.
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