Albedo

What is albedo

Albedo is the fraction of incoming solar radiation reflected by a surface, expressed as a dimensionless number between 0 (perfect absorber, all light absorbed) and 1 (perfect reflector, all light reflected). The term originates from Latin “albus” meaning white, and was introduced in astronomy before becoming common in atmospheric and solar engineering.

For solar PV applications, albedo specifically refers to the reflectivity of the ground surface beneath and around solar arrays. This is critical for bifacial modules, which capture both direct front-side light and ground-reflected light hitting the rear surface. Higher albedo leads to higher bifacial gain, a key input alongside GHI and DNI in any solar yield model.

Why albedo matters

Bifacial yield. Higher albedo means higher rear-side power generation, reflected in a plant’s CUF and overall performance ratio.

Project economics. Bifacial gain reduces LCOE.

Site selection. High-albedo sites favoured for bifacial plants, which is why site survey and land feasibility studies for utility projects now record ground albedo alongside slope and soil data.

Ground preparation. White gravel and similar treatments justified by albedo-driven yield.

Albedo by surface type

Technical deep dive

Bifacial gain vs albedo

Spectral albedo

Albedo varies with wavelength. Solar cells respond to UV-VIS-NIR (300-1100 nm). Sand and soil have higher albedo at NIR wavelengths. Snow has high albedo across spectrum.

Measurement

Albedometer: paired pyranometers, one facing up (measuring incoming) and one down (measuring reflected). Albedo = downward / upward.

On-site measurement recommended for utility projects. Multiple measurements across seasons capture variation.

Cost-benefit of ground treatment

Real-world applications

Utility bifacial plant ground preparation, often planned alongside a ground mount solar layout.

Carport with white roof surface.

Floating solar with white pontoon platforms.

Agrivoltaics over light-coloured ground cover.

Snow-region bifacial installations, where tilt angle is often steepened to shed snow and maintain rear-side clearance.

Best practices

Conduct on-site albedo measurement during pre-feasibility.

Specify ground preparation to achieve target albedo.

Use white gravel for cost-effective high albedo.

Maintain ground albedo through cleaning (dust accumulation reduces albedo).

Document albedo assumption in yield models.

Indian market context

Major Indian utility solar plants increasingly specify high-albedo ground preparation.

SECI tender bid documents include bifacial gain assumptions, dependent on albedo.

NIWE data does not specifically include albedo; on-site measurement standard.

Solar yield modelling tools (PVsyst, SAM) include albedo as input.

Standards and certifications

Key takeaways

Albedo is the fraction of solar radiation reflected by a surface. Critical for bifacial solar yield: higher albedo means more rear-side power. Indian utility plants typically have natural albedo 0.15-0.30. White gravel preparation can boost albedo to 0.30-0.45, justified by bifacial yield gains of 15-25 percent. On-site albedo measurement is standard for utility-scale bifacial project planning.

Further reading

For how Albedo plays out in real projects, these guides go deeper:

• PV Yield Simulation Software 2026: Bankable Guide
• REI Expo 2026 preview: what to look for
• PVsyst Alternative 2026: 6 Tools Compared
• Photovoltaic Design Software 2026: Buyer’s Guide

Sources

• IEC TS 60904-1-2, Bifacial PV measurement.
• IEC 61724, Performance monitoring.
• ASTM E1918, Albedo measurement.
• MODIS Albedo Product, NASA.
• PVsyst albedo modelling documentation.
• NREL bifacial PV publications.
• Sandia National Laboratories bifacial studies.
• IEA PVPS Task 13 Report on bifacial.
• Manufacturer bifacial gain documentation.