How to calculate Solar Panel Efficiency in Shaded space

1. Efficiency Decrease due to Shading

The efficiency of solar panels can decrease between 25% and 50% in shaded conditions, depending on various factors. Here is specific experimental data and theoretical analysis supporting this range:

2. Impact of Shadow Coverage Area

• Small Area Shadows: When the shadow coverage is less than 5 cm², the output power of the solar panel is minimally affected.
• Medium Area Shadows: With shadow coverage around 10 cm², the output power drops significantly, data shows an approximate 26.5% decrease.
• Large Area Shadows: When shadow coverage exceeds 20%, the output power can drop as much as 77.9%.

3. Experimental Data

• Experiment 1: At a study conducted by National Semiconductor, a traditional solar power system exhibited a 35% to 40% decrease in power when parts of the panels were shaded.
• Experiment 2: In a funded study in Inner Mongolia, shaded solar panels showed currents of only 50% or lower compared to normal panels, leading to daily losses exceeding 30% of the system’s output.
• Experiment 3: In complex shading conditions, the output characteristics of solar panels displayed significant fluctuations, revealing multiple peaks and valleys, leading to unstable system output.

4. Theoretical Analysis

• Current and Voltage Changes: Partially shaded cells experience a drastic drop in current, leading to an overall reduction in the series link’s current. Voltage is also impacted, though typically less than current.
• Example: When the shaded area is 20%, the current approaches zero and voltage declines, significantly dropping the overall output power.

5. Solar Panel Efficiency in Shaded Calculation Formulas

Output Power Under Shadows

Output power under partial shading:

Pshaded = Punshaded × (1 - (Ashaded / Atotal))

• P_shaded: Output power under shade.
• P_unshaded: Output power under unshaded conditions.
• A_shaded: Shadow coverage area.
• A_total: Total area of the solar panel.

6. Example Calculation

Assuming a solar panel with a total area of 1 m², an output power of 150 W under unshaded conditions, and a shadow coverage area of 0.2 m²:

1. Calculate Output Power Under Shade:
   Pshaded = 150 × (1 - (0.2 / 1)) = 150 × 0.8 = 120 W
2. Calculate Efficiency Decrease:
   Efficiency Decrease = (Punshaded - Pshaded) / Punshaded × 100% = (150 - 120) / 150 × 100% = 20%

7. Overall Conclusions：Solar Panel Efficiency in Shaded space

• Efficiency Decrease Range: Experimental data and theoretical analysis indicate that solar panel efficiency reduction typically ranges between 35% and 50% under shaded conditions.
• Small Area Shadow: Efficiency reduction is almost negligible when the shadow area is less than 5 cm².
• Medium Area Shadow: Efficiency decreases around 26.5% when shadow coverage is approximately 10 cm².
• Large Area Shadow: Efficiency can decrease up to 77.9% with over 20% shadow coverage.
• Specific Values: A decrease range of 35% to 50% mainly applies under medium area shading conditions (10% to 20% coverage).

8. Improvement Measures

• Optimized Design: By optimizing the layout and connections of solar panels, shading impacts can be mitigated.
• Use of Smart Bypass Diodes: Utilizing smart bypass diodes and Maximum Power Point Tracking (MPPT) algorithms can help improve system efficiency under shading.
• Proper Site Selection: Aim to select installation locations that are unobstructed to maximize solar panel efficiency.
• Regular Maintenance: Conduct periodic inspections and cleaning of solar panels to ensure surfaces are free from dust and obstructions, improving overall system performance.

Conclusion

In summary, the efficiency of solar panels typically drops between 25% and 50% in shaded conditions, especially with medium area shadows (10% to 20% coverage). This efficiency decrease results from significant changes in current and voltage due to local shading effects, and the complex characteristics of multi-peak output performance. Taking appropriate optimization measures can effectively reduce the impact of shading on solar panel performance.