Interim field-test data from the Beijing Center for Photovoltaic Testing and Evaluation show that Trina Solar’s Vertex N-Type TOPCon modules delivered 2.90% more energy than the reference TBC modules during a six-month trial in the harsh conditions of the Tengger Desert.
The test site, near Wuwei in Gansu Province, is exposed to intense sandstorms and large day-to-night temperature swings. The results highlight the value of high bifaciality and strong low-irradiance performance when selecting modules for desert projects.
Test site and demanding operating conditions
The test site is located near Wuwei, Gansu Province, where the Tengger and Badain Jaran desert regions meet. It is one of China’s leading locations for reproducing the demanding conditions faced by utility-scale PV systems on sandy and gravel terrain.
- More than 50 days of sand and dust storms each year.
- Day-to-night temperature differences of up to 30°C.
- Summer sand-surface temperatures above 60°C.
- High ground reflectance, increasing irradiance on the rear side of bifacial modules.
- Frequent low-light conditions around sunrise and sunset.
- Low temperatures and frost during colder periods.
- Cloudy days and periods of reduced solar irradiance.
Together, these conditions provide a realistic year-round test environment for desert solar projects.
Why bifacial TOPCon modules perform well
Laboratory measurements conducted before the field trial identified two principal advantages of the Vertex N-Type TOPCon modules:
- High bifaciality: the rear side can convert a greater share of sunlight reflected from the ground.
- Strong low-irradiance response: output remains more stable during mornings, evenings and cloudy periods.
The open, reflective terrain around Wuwei supplies continuous rear-side irradiance, allowing bifacial modules to generate additional energy.
The measurements showed a direct relationship between reflected irradiance and additional energy yield: as rear-side irradiance increased, so did the benefit of the bifacial design.
A clear advantage during low-irradiance hours
The TOPCon modules’ advantage over the TBC reference became more pronounced when solar irradiance fell below 200 W/m².
| Period | TOPCon energy-yield advantage over TBC |
|---|---|
| 08:00–09:00 | 7.98% |
| 18:00–19:00 | 7.78% |
These low-light periods can also coincide with higher electricity demand, potentially increasing the commercial value of the additional energy in markets with time-variable pricing.
Total energy-yield gain of 2.90%
Across the full test period, the Trina Solar Vertex N-Type TOPCon modules maintained stable performance and produced 2.90% more electricity than the TBC reference modules. They achieved this result despite dust and sand accumulation, large temperature fluctuations, frost, and continuously changing irradiance.
The data indicate lower relative operating losses and more stable production under difficult field conditions.
Implications for module selection
As large-scale solar development expands across desert regions, module selection can no longer rely only on nameplate power or laboratory-measured front-side efficiency. Developers should assess total lifetime energy yield under the site’s actual operating conditions.
The Wuwei results suggest that the combination of high bifaciality and good low-irradiance response can give TOPCon modules a meaningful advantage at open sites with high ground reflectance, including:
- Sandy deserts.
- Open gravel and rocky terrain.
- Dry and semi-arid regions.
- Reflective coastal or clay-rich areas.
- Plants using elevated mounting structures that allow irradiance to reach the rear side of the modules.
Conclusion
The Tengger Desert trial found that Trina Solar Vertex N-Type TOPCon modules generated 2.90% more electricity than the TBC reference during the test period. Their advantage rose to 7.98% in the morning and 7.78% in the evening, driven by high bifaciality and improved low-light response.
For desert and other high-reflectance sites, procurement decisions should therefore consider actual energy yield, bifacial performance, low-irradiance response, thermal losses and mounting conditions—not front-side efficiency or nameplate power alone.
Source: Trina Solar field-test results from the Wuwei desert site, July 2026.