Specific types of shading are indeed more problematic for solar panels and can severely impact their performance. The main types of shading and their relative impact are as follows:
Types of Shading That Affect Solar Panels
1. Hard Shading
- Hard shading occurs when a solid object completely blocks sunlight on part of a solar panel, such as from chimneys, satellite dishes, dense tree branches, or nearby buildings.
- This type of shading can cause severe effects, potentially shutting down entire strings of cells or panels and reducing output dramatically. Even shading a single cell can reduce the output of the whole panel by 50-80% or more because of the series electrical connection of cells.
2. Partial or Soft Shading
- Soft shading partially reduces sunlight, such as from light cloud cover, atmospheric haze, or sparse tree foliage.
- It generally causes a uniform reduction in power output across affected cells but is less severe than hard shading.
3. Dynamic Shading
- Dynamic shading changes throughout the day or across seasons, caused by moving shadows from clouds or seasonal tree leaf changes.
- This shading is unpredictable and challenging to mitigate without advanced system design and technology.
4. Edge Shading
- Edge shading affects the perimeter of solar arrays and is caused by roof edges, mounting hardware, or self-shading from nearby panel rows.
- Though often unavoidable, it can be minimized through careful layout and design.
5. Uniform Shading
- Uniform shading affects the entire solar array equally, such as from heavy cloud cover, dirt, dust, or snow.
- It tends to cause a proportional drop in production but doesn’t cause the disproportionate losses associated with partial shading.
Why Some Shading Types Are More Problematic
Because solar cells within a panel are connected in series, shading even a small part causes a “bottleneck” effect, much like a clog in a pipe reduces overall flow. The shaded cell limits the current through the string, reducing output of the entire panel and sometimes the entire string of panels.
This leads to what’s known as the “Christmas light effect” — if one cell or panel in a series string is shaded, it can reduce or shut down power flow like one burnt-out bulb in a string of Christmas lights.
Mitigating Shading Effects
- Bypass Diodes: Most modern panels have bypass diodes that allow current to flow around shaded cells, preventing complete shutdown but still causing some power loss.
- Module-Level Power Electronics (MLPEs): Devices like microinverters or DC optimizers enable each panel or even each cell to operate independently, reducing shading impact.
- System Design: Careful placement of panels to avoid common shading, using stringing configurations, and regular maintenance to keep panels clean can mitigate shading losses.
Summary Table: Types of Shading and Impact
| Shading Type | Cause Examples | Impact Severity | Characteristics/Notes |
|---|---|---|---|
| Hard Shading | Chimneys, dense tree branches, buildings | Very High | Can shut down entire strings; severe output loss |
| Soft Shading | Light clouds, haze, sparse leaves | Moderate | Uniform reduction; less severe overall |
| Dynamic Shading | Moving clouds, seasonal foliage | Variable/Unpredictable | Changes throughout day/season; hard to predict |
| Edge Shading | Roof edges, mounting hardware | Moderate to Low | Usually minimized by design |
| Uniform Shading | Cloud cover, dirt, snow | Proportional reduction | Affects whole array evenly, less disproportionate |
In conclusion, hard shading and even partial shading of single cells or panels are the most problematic types because they can disproportionately reduce the output of an entire panel or string. Dynamic shading adds complexity but varies in impact. Strategies such as bypass diodes, MLPEs, and careful system design help mitigate these losses.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/are-there-specific-types-of-shading-that-are-more-problematic-for-solar-panels/
