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Solar shading analysis

Understanding and Performing Solar Shading Analysis

Solar shading analysis is the detailed study of shading phenomena within the area where the photovoltaic system is positioned

Solar shading analysis involves a meticulous examination of architectural or natural elements surrounding a solar installation, determining their potential impact on incident solar radiation and whether they cast shadows on the solar panels’ capturing surfaces. This article delves into what solar shading analysis entails, the influencing factors, and strategies to mitigate its effects. Calculating photovoltaic shading is not a simple task as shadows shift position throughout the day and year due to the sun’s angle. Make sure to use a solar software that accurately assesses shading from obstacles, both nearby and distant, utilizing simple photographic surveys and creating a detailed solar diagram of the installation site.

What is Solar Shading Analysis?

Solar shading analysis is the detailed study of shading phenomena within the area where the photovoltaic system is positioned. Even a small shadow on a solar panel significantly reduces its electricity-generating capacity. This analysis predicts and comprehends how shadows will impact the solar plant’s energy production. It’s pivotal for maximizing efficiency and ensuring long-term profitability of your solar investment.

Factors Causing Solar Shading

Shading can stem from various factors:

  • Surrounding buildings: Nearby buildings, especially tall ones or those in the path of solar irradiation, can cast shadows on photovoltaic panels. This phenomenon is most notable during early morning or late afternoon when the sun is low on the horizon;
  • Trees and vegetation: Trees and other vegetation can create seasonal or daily shadows based on their position and growth;
  • Proximity of structures: Any other structures, like poles or fences, can contribute to shading depending on their height and location;
  • Terrain orography: Horizon elevations and distant obstacles diminish sun exposure hours during the day and year.

How is Solar Shading Calculated?

Solar shading calculation requires a thorough analysis of surrounding obstacles and their positions concerning solar panels. Key steps involve:

  • Site survey where an inclinometric analysis identifies potential shadow-casting objects;
  • Study of solar incidence: understanding the sun’s angle at different hours and seasons. Analyzing the sun’s path and angular changes throughout the year is crucial for determining when and from where shadows will be cast on installations;
  • Identification of shadow sources in the surrounding area, including nearby buildings, trees, mountains, or other physical structures. Temporary elements like cranes or vehicles that might affect shading during the day are also considered;
  • Measurement of azimuth and tilt: assessing shading from these sources involves measuring their azimuth and tilt, critical for calculating when and how much shadows will influence solar panels;
  • Optimization of orientation and position of solar panels: Utilizing shading data to optimize panel orientation and arrangement, including adjusting panel tilt angles and planning surrounding elements to minimize shading during critical times;
  • Long-term prediction and optimization: Shading analysis extends beyond a single-day assessment. Long-term predictions anticipate shading changes across different seasons, optimizing solar plant efficiency throughout the year.

Values obtained are integrated into a solar diagram and analyzed with dedicated solar software to verify potential shadowing during specific periods.

Solar shading on the solar diagram - Solarius-PV

Solar shading on the solar diagram – Solarius-PV


Effects of Shading on Efficiency

Shading reduces the amount of sunlight reaching photovoltaic cells, thereby decreasing their electricity-generating capacity. This phenomenon is often measured using the shading coefficient, quantifying shadows’ impact on solar panel energy production.

Shading Coefficient

The shading coefficient represents the fraction of irradiated energy net of energy lost due to shadows. This parameter assists designers in informed decisions regarding panel placement and orientation. It aids in calculating energy losses and estimating the overall plant output.

Calculating this coefficient involves a detailed analysis of sunlight reaching the panel at different times of the day and seasons. A low shading coefficient indicates a significant impact on solar energy hitting the panel and subsequently, the electricity generated.

For instance, a coefficient of 0.9 indicates that incident energy on panels is 90% of that available without shadows, implying a 10% reduction due to shading.

Spacing Between Rows of Photovoltaic Panels

When installing photovoltaic panels on a surface, one crucial aspect is the optimal distance between rows. The choice of spacing largely depends on the surface’s nature where the system will be placed. Considerations include:

  • Inclined surface: Installation on an inclined surface, like a sloped roof, typically positions solar panels in line with the roof’s tilt. In this case, row spacing isn’t usually a major concern as it follows the natural inclination;
  • Flat surface: If placed on a flat surface (e.g., ground or flat roofing), precisely calculating both panel tilt and row spacing is crucial. This prevents shading caused by the modules themselves, especially considering the sun’s angle during different times and periods.
30-35° Inclination - South Direction

30-35° Inclination – South Direction

L= latitude – D= distance between rows – β= tilt angle – g= azimuth – α= solar height

To determine the ideal distance between rows, calculating both height and distance is essential to avoid self-shading, where front modules cast shadows on the rear ones. Inaccurate row spacing might reduce overall system efficiency. Utilize specialized solar software to effectively manage shading and ensure reliable outcomes, automatically calculating minimum distances between panel rows on various surfaces—horizontal, vertical, or inclined.