Bifacial Panel

Most TOPCon modules sold between 2024 and 2026 use a bifacial design [ITRPV 2024].

In a bifacial panel, the rear side is protected by transparent glass or a transparent backsheet — not the opaque white backsheet of a conventional monofacial module. Active cells at the back capture light reflected from the roof, ground, or other surfaces beneath the panel; this contribution is called bifacial gain.

The magnitude of bifacial gain depends heavily on the albedo of the surface beneath the module. On a commercial rooftop or factory roof with exposed concrete (albedo ~0.20-0.30), estimated bifacial gain in Indonesia's tropical climate ranges from 3-8% over an equivalent monofacial module. On ground-mount installations with highly reflective surfaces — for example white gravel or geomembrane (albedo ~0.40-0.60) — the gain range can reach 10-15% [ITRPV 2024; IRENA, Utility-Scale Solar, 2023].

Tropical context note: Indonesian installations use low tilt (5-10°) because the latitude is near the equator. Low tilt reduces the exposure of the rear-side irradiance to ground reflection, pushing the bifacial gain toward the lower end of the range. Typical Indonesian surface albedos — exposed concrete 0.20-0.30; asphalt 0.10-0.15; metal roof 0.25-0.35 — are consistent with the literature placing rooftop gain at 3-8% for albedo 0.20-0.30 [multi-source, see Sources]. A 2025 Bandung field study (Universitas Widyatama, tilt 8°, n=3 surfaces) showed a 10.8% output difference between asphalt and white-painted surfaces — confirming albedo sensitivity under local tropical conditions, though without an explicit monofacial baseline [Barokah et al., R.E.M. Journal 2025, DOI:10.21070/r.e.m.v10i2.1758]. No ITB/UGM/BRIN/IESR study publishing a verified bifacial gain % against a monofacial baseline for Indonesian conditions was found as of May 2026.

The efficiency of current mainstream TOPCon bifacial modules is in the 21-23% range (front side, STC conditions) [mainstream vendor datasheets JA Solar, LONGi, Canadian Solar 2024-2026], with cell efficiency exceeding 25%.

Indonesian PLTS Application Example

For a 500 m² logistics warehouse roof in Surabaya with a concrete surface (albedo ~0.25) and a local PSH of 5.1 kWh/m²/day [NASA POWER 1984-2023], a 100 kWp bifacial system can generate an additional 3-5% of output compared with an equivalent monofacial module — equivalent to roughly 3,000-5,000 kWh of savings per year. This margin must be weighed against the price difference between bifacial and monofacial modules before finalizing the specification.