Bifacial Module

What is a bifacial module

A bifacial solar module is a photovoltaic module designed to convert sunlight on both its front and rear surfaces into electricity. While monofacial modules absorb light only on the front and have an opaque back sheet, bifacial modules use transparent encapsulation on both sides, allowing rear cells to collect reflected, diffuse and ground-bounced light.

The additional yield depends on the bifaciality factor of the cells, the albedo (reflectivity) of the ground surface, the ground clearance, tilt angle and inter-row spacing, which is why a proper shading analysis at design stage matters as much for bifacial arrays as it does for monofacial ones. Real-world bifacial gain in Indian utility installations ranges from 8 to 18 percent annually.

Bifacial modules have rapidly displaced monofacial in utility-scale Indian solar. By 2026, bifacial monocrystalline PERC and TOPCon modules dominate ALMM-listed utility-grade products. C&I rooftop adoption is growing, particularly for carports and ground-mount installations.

Bifacial explained simply

A regular solar panel sees sunlight only on the front. Bifacial panels see light on both sides. The back cells pick up sunlight that bounced off the ground, a white roof or surrounding surfaces. Free extra electricity from light that would otherwise be wasted.

The trick is that the back side cannot have the usual black plastic back sheet. Bifacial modules use glass or transparent polymer on the back, exposing the cells to whatever light gets to them.

Why bifacial matters

Yield gain. 5 to 25 percent additional energy from the same module footprint.

Better LCOE. Higher yield reduces ₹/kWh over the project life.

Standard at utility scale. Most Indian SECI tender bids assume bifacial, and the resulting yield uplift directly raises the CUF that project economics are priced against.

Glass-glass durability. Bifacial glass-glass modules typically come with 30-year warranties.

Snow and dust shedding. Glass back surface helps in some climates.

Agrivoltaic compatibility. Elevated bifacial modules above crops capture rear-side ground reflection.

How bifacial modules work

1. Front side absorbs direct and diffuse sunlight, generating power as in monofacial.
2. Light passes through gaps between cells onto the ground.
3. Ground reflects a fraction of the light upward.
4. Reflected light reaches the rear cell surface.
5. Rear cells convert reflected light to electricity.
6. Front and rear currents combine in the cell, raising total output.

The cell itself is dual-junction-capable: doping and back-side passivation allow electrons generated at the rear to be collected. The interconnection ribbon on the back is thinner or absent in bifacial designs to minimise rear-side shading.

Technical deep dive

Bifaciality factor

Yield gain factors

Typical bifacial gain in Indian conditions

Glass-glass vs glass-back-sheet bifacial

Most utility bifacial uses glass-glass. Rooftop bifacial often uses transparent back sheet for weight reduction.

Albedo values

Real-world applications

Utility-scale solar parks. Bifacial is now standard for new ground-mount projects above 5 MW.

Solar carports with reflective surfaces underneath.

Floating solar. Water albedo of 0.10 to 0.15 plus white floating platforms.

Agrivoltaics. Elevated bifacial modules over light-coloured crop canopy.

Vertical bifacial. East-west vertical-mounted bifacial generates twin morning and evening peaks, useful for grid-balancing applications.

Snow-region installations. Snow albedo above 0.80 makes bifacial highly effective in winter.

C&I rooftop bifacial. Carports, terraces with white surfaces or surrounding reflective infrastructure.

Advantages

Higher yield from the same footprint.

Better LCOE for utility solar.

Glass-glass durability and 30-year warranty.

Reduced soiling impact (glass back surface).

Future-proof for vertical and agrivoltaic deployments.

Standard at utility scale.

Limitations

Cost premium of 3 to 8 percent over monofacial.

Yield gain dependent on ground conditions, sometimes hard to model.

Heavier glass-glass construction increases mounting cost.

Edge-clamp mounting required to avoid rear-side shading.

Requires higher ground clearance for full benefit.

Less effective on dark surfaces.

Some inverters need oversizing to handle higher DC output.

Common problems

Rear-side shading from rails or cable trays.

Mounting design assuming monofacial, blocking rear-side light.

Inverter undersized for total bifacial DC output, clipping peak power.

Soiling on rear glass in dusty conditions, sometimes overlooked in maintenance.

Bifaciality factor overestimated by EPC, leading to disappointed yield.

Glass-glass module breakage during installation due to weight handling.

Best practices

Specify minimum bifaciality factor in module purchase orders — HJT cells deliver the highest factor of any mainstream technology if budget allows.

Choose mounting that allows full rear-side exposure.

Use white gravel or paint under the array where possible.

Specify ground clearance of at least 1 metre for utility ground-mount.

Size the inverter for 110 to 120 percent of monofacial nameplate to capture bifacial gain without clipping the extra DC output.

Include rear-side cleaning in O&M schedule where practical.

Conduct annual back-side soiling check.

Comparison: bifacial vs monofacial

Indian market context

Indian utility solar PPAs increasingly assume bifacial modules. SECI and CPSU tenders default to bifacial in technical specifications.

Major bifacial manufacturers in India include Waaree, Adani Green Solar, Tata Power Solar, Vikram Solar, Goldi Solar, Premier Energies and others.

ALMM List I covers bifacial modules across PERC, TOPCon and HJT cell technologies.

C&I rooftop bifacial adoption is growing for carport and large terrace installations.

PM Surya Ghar accepts bifacial modules. Rooftop bifacial gain is limited where the roof surface is dark.

Standards and certifications

Common mistakes

Mounting bifacial like monofacial, blocking rear-side light.

Choosing modules with low bifaciality factor.

Ignoring ground albedo in yield prediction.

Inverter sized for nameplate DC, clipping bifacial gain.

Skipping rear-side cleaning.

Underestimating glass-glass module weight in mounting design.

Installing on dark tar roof and expecting 20 percent gain.

Key takeaways

Bifacial modules are the new standard for Indian utility solar and increasingly for C&I rooftop. Yield gain of 5 to 25 percent depends on ground albedo, clearance and tilt. Mounting, inverter sizing and ground preparation determine whether the theoretical gain is realised. Cell technology (PERC, TOPCon, HJT) sets the bifaciality factor and the upper bound on rear-side performance.

Further reading

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

• Cloud Solar Design Software 2026: Browser-First
• Solar Inverter Low Output, 12 Causes and Fixes India
• Solar Panel Price in India 2026: All Brands, All Wattages
• How to Maximise Solar Output in Indian Climate

Sources

• IEC TS 60904-1-2:2019, Photovoltaic devices: Procedures for the measurement of current-voltage characteristics of bifacial photovoltaic devices.
• IEC 61215, Module qualification.
• IEC 61730-1, -2, Module safety.
• IS 14286, Indian Standard for crystalline silicon PV modules.
• MNRE Approved List of Models and Manufacturers (ALMM).
• NREL Bifacial PV Performance Study, 2019.
• Sandia National Laboratories Report SAND2018-2238, Bifacial PV Modelling and Field Performance.
• Manufacturer datasheets from Waaree, Adani Green Solar, Tata Power Solar, Vikram Solar.
• IEA PVPS Trends in Photovoltaic Applications 2024.