Do Solar Panels Need Direct Sunlight?

Solar panels are widely recognised for their ability to convert sunlight into electricity, but a common question is whether they require direct sunlight to function effectively.

While solar panels perform best under direct sunlight, they can still generate electricity in less-than-ideal conditions. This article explores how different lighting conditions affect solar panel performance and the implications for their use in various environments.

Solar panels generate electricity through photovoltaic (PV) cells, which convert light into electrical energy. The more light PV cells receive, the more electricity they can produce. However, the type and intensity of light can vary significantly depending on weather, time of day, and geographical location.

Key Points

Photovoltaic Effect: PV cells use the energy from photons (light particles) to knock electrons loose from atoms, creating an electric current.

Efficiency: The efficiency of this process depends on the intensity and quality of the light hitting the PV cells.

Performance in Different Lighting Conditions

1. Direct Sunlight

Optimal Condition: Direct sunlight provides the most intense and concentrated light, making it the ideal condition for solar panels.

Maximum Output: Under direct sunlight, solar panels operate at their highest efficiency, often close to their rated capacity.

Clear, Sunny Days: Performance peaks during clear, sunny days, especially around midday when the sun is highest in the sky.

2. Diffuse or Indirect Sunlight

Scattered Light: Diffuse sunlight occurs when sunlight is scattered by atmospheric particles, such as clouds or dust, resulting in less intense, but more evenly spread light.

Reduced Output: Solar panels can still produce electricity under diffuse light, but at a reduced efficiency compared to direct sunlight.

Overcast Days: Panels can generate about 10-25% of their typical output on overcast days, depending on the cloud cover density.

3. Shaded Conditions

Optimisers: Are installed in areas likely to receiving any of the following forms of shading, to prevent the entire string ceasing to operate – these devices greatly increase production in any of the following circumstances:

Partial Shading: When part of a solar panel or array is shaded, the overall performance drops significantly because most panels are wired in series, and shading one part can reduce the output of the entire string.

Bypass Diodes: Modern panels often include bypass diodes to minimise the impact of shading by allowing current to bypass the shaded cells.

Obstructions: Shade from trees, buildings, or other structures can significantly reduce energy production.

4. Low-Light Conditions

Morning and Evening: During early morning and late evening, the angle and intensity of sunlight are lower, leading to reduced solar panel output.

Winter Months: Shorter days and a lower sun angle in winter can also lead to decreased energy production.

5. Artificial Light

Minimal Production: Solar panels are not designed to be efficient under artificial light. While they can produce a small amount of electricity from strong artificial sources, it is negligible compared to natural sunlight.

Factors Affecting Solar Panel Performance

1. Panel Orientation and Tilt

Optimal Angle: Solar panels perform best when they are oriented towards the sun. In the UK, this typically means facing south and tilting at an angle roughly equal to the latitude of the location.

Adjustable Mounts: Some systems use adjustable mounts to optimise the angle of the panels throughout the year.

2. Weather Conditions

Temperature: High temperatures can reduce the efficiency of solar panels. Panels are more efficient in cooler conditions as long as they receive sufficient light.

Snow and Ice: Snow can block light from reaching the panels, but many panels are designed to shed snow quickly. Ice can also reduce efficiency by covering the panel surface.

3. Geographical Location

Latitude: Closer proximity to the equator generally means more intense and consistent sunlight.

Climate: Locations with frequent cloud cover or heavy pollution may experience reduced solar panel performance.

Maximising Solar Panel Efficiency Without Direct Sunlight

1. Advanced Technologies

Bifacial Panels: These panels can capture light from both the front and back sides, making them more effective in diffuse light conditions.

PERC Cells: Passivated Emitter and Rear Contact (PERC) cells improve efficiency by capturing more light and reducing electron recombination losses.

2. System Design and Installation

Optimisers and Microinverters: These components help manage shading and improve the efficiency of each panel individually.

Regular Maintenance: Keeping panels clean and free of obstructions maximises light absorption.

3. Energy Storage Solutions

Battery Storage: Pairing solar panels with battery storage systems allows you to store excess energy generated during peak sunlight hours for use during low-light conditions.

Conclusion

While solar panels perform best under direct sunlight, they can still generate electricity in diffuse, shaded, or low-light conditions. Advances in technology and thoughtful system design can help mitigate the impact of less-than-ideal lighting, ensuring that solar panels remain a viable and efficient source of energy in various environments.

Further Guidance

What Are Solar Panels?