When Do Bifacial (Double-Sided) Panels Make Sense? Antalya Guide

A bifacial panel is a double-sided solar panel that can generate electricity from both its front and rear surfaces. The front face takes direct sun, while the rear face makes use of light reflected from the ground and surroundings. In Antalya, bifacial panels make the most sense in ground-mounted plants, elevated structures and carport applications. On a flat tile roof, the rear face's contribution usually stays limited.

What is a bifacial panel and how does it work?

The back of a standard (monofacial) panel is covered with an opaque backsheet. In a bifacial panel the rear surface is closed either with a transparent layer or with a second sheet of glass (glass-glass, "G2G"). The cells are also built to collect light arriving from both sides. n-type cell technologies such as TOPCon suit this double-sided operation; we described this structure in our what is a TOPCon panel article.

The additional energy produced by the rear face is called "rear-side gain". This gain is not a fixed value; it varies with what is under and behind the panel. In datasheets you see two separate values: the bifaciality factor, which shows how efficient the panel's rear face is relative to the front, and the total power in particular gain scenarios.

Four factors that determine rear-side gain

1. Albedo (ground reflectivity): Dark soil and green vegetation reflect little; light-coloured concrete, gravel or a white membrane reflect more light.
2. Mounting height: The higher the panel rises above the ground, the more evenly light reaches the rear face and the less the effect of its own shadow on the ground.
3. Tilt and row spacing: As the gap between rows grows, the indirect light reaching the rear face increases, but so does land use.
4. Obstructions behind the panel: Mounting profiles, cable trays and closeness to the roof surface reduce rear-side gain.

Therefore the question "by what percentage does a bifacial panel produce more?" has no single answer. The same panel gives a noticeable gain in good conditions and a very small one in poor conditions.

Datasheet values: bifaciality and rear-side gain

The examples we obtained from manufacturer documents are as follows. The comparison given belongs to two products; no generalisation can be made for all models.

The electrical values of the TommaTech G2G model are the same as the single-sided TT605-144TN10 (Pmax 605 Wp, efficiency 23.42%). The difference shows up in weight and warranty: the single-sided model weighs 29.0 kg with a 15-year product warranty, while the glass-glass model weighs 33.0 kg with a 25-year product warranty. A 4 kg difference per panel means 80 kg over 20 panels (calculation). This matters for roof load-bearing capacity.

Why does a bifacial panel give limited benefit on a roof?

On most residential roofs, panels are mounted parallel to the roof surface at a height of a few centimetres. On a tile roof, because the back of the panel is very close to the tiles, little light reaches the rear face. The situation is similar on a trapezoidal sheet roof. Many villa and apartment roofs in Antalya are one of these two types.

On a flat terrace roof, if the panel is raised on a tilted structure, the situation changes somewhat. A light-coloured or white surface reflects more light to the rear face. Even so, the additional gain still depends on the roof edge, the parapet and the shade of other panel rows.

For this reason the main reasons for choosing a bifacial panel in roof projects are these:

• A product warranty of up to 25 years thanks to the glass-glass construction (the TommaTech G2G example).
• The mechanical and structural differences that come with closing the rear face with glass instead of an opaque layer.
• Special cases with high albedo and raised mounting, such as a white terrace.

In return, the additional weight, the need for different mounting hardware and the price difference can reduce the gain in a roof application. The calculation must be made for the roof. We covered the difference between roof and ground in a broader view in our roof solar plant vs ground-mounted solar plant article.

Bifacial panels in ground-mounted plants and carports

In ground-mounted plants, panels are installed at least several tens of centimetres above the ground with wide gaps between rows. This structure increases the light reaching the rear face. Covering the ground with light-coloured gravel, or working with dry, light-toned soil, raises albedo.

A similar structure is seen in agricultural land and irrigation systems in Antalya. Around Korkuteli and Elmalı, light-coloured soil surfaces that dry out in summer are advantageous for reflectivity. According to PVGIS data, annual specific yield is 1,719 kWh/kWp in Elmalı and 1,655 kWh/kWp in Korkuteli. Still, ground reflectivity varies with season and land cover; for this reason the assumption must be checked on site.

In carport (car park canopy) applications, panels sit above the vehicles, at least 2-2.5 m above the ground. This height increases the light reaching the rear face, and the gain rises if the ground colour is well chosen. You can find detailed information in our carport and car park solar energy article.

Example calculation: how much is the rear-side gain worth?

To make the gain concrete, let us consider a hypothetical 100 kWp ground-mounted plant. According to PVGIS 5.3 data, annual specific yield in Antalya city centre with a single-sided panel at optimum tilt facing south is 1,656 kWh/kWp. In that case annual production with a single-sided panel is 165,600 kWh. For rear-side gain we use not a real measured value but only scenario figures.

This table shows what a bifacial panel's price difference is to be weighed against: the additional production accumulates over the project's life. However, the real gain is revealed by an on-site albedo measurement and a project-based simulation. For this reason, instead of statements like "X% additional production" in a quotation, the assumption used for the calculation should be written down.

Selection summary by application type in Antalya

This table is for preliminary assessment only. For the final decision, the panel price difference, the albedo measurement and the roof's load-bearing capacity should be compared together in writing.

Checklist before buying a bifacial panel

1. Has a realistic albedo assumption been written for mounting height, row spacing and ground surface?
2. Does the panel's datasheet clearly state the bifaciality factor and rear-side gain scenarios?
3. Has the glass-glass model's weight been assessed together with the roof's load-bearing capacity?
4. Have the product warranty and performance warranty been written separately?
5. Has the main equipment such as the panel, inverter and battery been manufactured within the last five years? (Unlicensed generation regulation, 2 April 2026 amendment.)
6. Does the inverter's input current accommodate the current raised by the rear-face contribution?

Because rear-face contribution increases panel current, the inverter's MPPT current limits must be checked for this. This calculation is made at the project stage. If you want to see which panel makes sense for land, a roof or a carport, you can contact us for a free site survey.

Conclusion

A bifacial panel does not promise additional return in every project. It gives a meaningful gain in high-mounted ground plants, carport structures and flat terrace roofs with a light-coloured surface. In close-to-roof mounting on tile or sheet roofs, the rear face's contribution stays small; in that case the long warranty and durability of the glass-glass construction stand out more. For the right decision, calculate albedo, mounting height, weight and price difference together; do not read the highest-gain scenario in the datasheet as a guaranteed result.

#Technology#Bifacial#Double Sided Panel#Albedo#Ground Mounted Solar#Carport