Bifacial solar modules — panels that generate electricity from both the front and rear surface — have become the default technology for utility-scale solar projects in India and globally. Every major manufacturer, including Websol, now produces bifacial variants of their mainstream cell technologies.

But the marketing claims around bifacial are often ambitious. “Up to 30% additional yield from the rear side” sounds impressive — but what does bifacial gain actually look like in real Indian project conditions, and how should developers and EPCs model it in their financial projections?

This guide gives you the technical framework and real-world context to make informed decisions about bifacial technology for Indian solar projects.

What Makes a Module Bifacial?

A bifacial solar module generates electricity from both sides of the panel. The front surface works like a conventional module — absorbing direct and diffuse sunlight. The rear surface captures albedo radiation — sunlight that has been reflected from the ground or nearby surfaces back upward toward the rear of the panel.

For bifacial to work, the rear of the module must be transparent — achieved through:

• Dual-glass construction: Both front and rear surfaces are glass (replacing the opaque white backsheet used in conventional modules)
• Transparent backsheet: Some bifacial modules use a clear polymer backsheet instead of dual glass

Websol’s solar cells are designed in a bifacial architecture — where the rear passivation layer (in Mono PERC cells) allows rear-side photon capture. These cells are then assembled into bifacial solar modules with the appropriate transparent rear construction.

The Bifacial Factor: Understanding the Key Parameter

The bifacial factor (or bifaciality coefficient) is the ratio of rear-side efficiency to front-side efficiency. It tells you how much of the front-side performance the rear side can deliver under the same irradiance conditions.

A Mono PERC bifacial module with a 75% bifacial factor means: if the front side generates 100W under 1,000 W/m², the rear side would generate 75W under the same 1,000 W/m² of rear irradiance. Since rear irradiance is always a fraction of front irradiance (reflected light, not direct), the actual rear-side contribution is much lower in practice.

Albedo: The Variable That Controls Everything

Albedo is the reflectivity of the ground surface beneath and around the module. It is the single most important site-specific variable for bifacial yield.

For Indian solar project sites — which range from Rajasthan’s sandy desert to Tamil Nadu’s coastal plains to Odisha’s red laterite soil — albedo varies significantly. Rajasthan and Gujarat sites with light sandy soil routinely achieve albedo values of 0.25–0.40, strongly favouring bifacial performance. Dark basalt soil in Maharashtra or Telangana might yield albedo of only 0.10–0.15.

This is why bifacial yield modelling without site-specific albedo measurements is unreliable. Generic bifacial gain claims of “25% additional yield” are calculated under high-albedo conditions — not your specific site.

Realistic Bifacial Gain Ranges for Indian Projects

Based on field data from installed bifacial projects across Indian conditions, realistic bifacial gain (rear-side energy as a percentage of total front-side generation) falls into these ranges:

For a 100 MW utility project in Rajasthan with single-axis trackers and a well-designed bifacial system, a 10–15% net energy yield improvement over a comparable monofacial system is realistic and defensible in a yield model. Claiming 25%+ without site-specific data is not.

Factors That Affect Bifacial Gain in Practice

1. Mounting Height

Rear-side irradiance is maximised when more ground area is visible to the module’s rear surface. Higher mounting (greater clearance between module bottom edge and ground) improves bifacial gain. Trackers, which typically have higher clearance than fixed-tilt fixed-height systems, naturally favour bifacial performance.

Rule of thumb: Increase mounting height by 0.5m above minimum structural requirements for bifacial projects where land cost allows.

2. Row Spacing and Ground Coverage Ratio (GCR)

Closely spaced module rows cast rear-side shadow on each other — particularly at low sun angles. Higher GCR (modules packed more densely) reduces bifacial gain because the ground between rows receives less direct light to reflect.

For bifacial-optimised designs, GCR values of 0.35–0.45 are typically used. This is more land-intensive than monofacial designs (which can run at GCR 0.50+) — a land cost trade-off that needs to be factored into the full project economics.

3. Tracker vs. Fixed Tilt

Single-axis trackers (SAT) significantly improve bifacial performance. At low tilt angles during morning and evening hours, the rear surface is directly exposed to reflected light from a larger ground area. Additionally, trackers keep the module angle optimal throughout the day — improving both front-side and rear-side capture.

High wattage bifacial modules on single-axis trackers represent the current best-practice configuration for new utility-scale Indian solar projects.

4. Soiling and Cleaning

Bifacial modules have a rear glass surface that also collects dust. In Indian conditions — particularly in dry, high-soiling environments like Rajasthan and Gujarat — the rear glass soils at a rate that may differ from the front surface. O&M protocols for bifacial must account for rear-side cleaning, which adds complexity compared to monofacial.

5. Mismatch and Inverter Design

In a bifacial installation, different modules in the same string may receive different amounts of rear-side irradiance — depending on row position, shading from structures, and local albedo variation. This mismatch can reduce bifacial gain at the string level. Good inverter selection (particularly with module-level power electronics or smart MPPTs) partially mitigates this.

How to Model Bifacial in a Yield Simulation

Do not rely on default bifacial parameters in your simulation software. Industry-standard tools like PVsyst include bifacial modelling, but the default parameters assume generic conditions.

For a defensible bifacial yield model, you need:

• On-site albedo measurement (or satellite-derived albedo for the specific coordinates)
• Confirmed mounting height and racking geometry
• GCR and row spacing from the layout design
• Tracker parameters (if applicable)
• Soiling rate from regional data or nearby project experience

The resulting bifacial gain should be expressed as a probability distribution (P50 and P90 values) — not a single point estimate. Lenders and project finance teams will require P90 (the energy yield that has a 90% probability of being achieved) for debt sizing.

Websol’s M10 Bifacial Mono-PERC: Designed for Indian Conditions

Websol’s M10 Bifacial Mono-PERC solar cells are manufactured with a bifacial factor of 70–75%, consistent with industry-standard Mono PERC bifacial performance. Assembled into solar modules in the 525–570 Wp range, they deliver reliable front-side and rear-side performance suited to Indian utility and commercial project conditions.

For project-specific bifacial yield modelling using Websol cell and module specifications, contact Websol’s technical team for detailed datasheets and simulation parameters.