Introduction：
To investigate the outdoor performance of both technologies, especially in a humid rooftop field environment, an experimental study on the energy yield performance of TOPCon PV modules in comparison to BC modules was carried out in Laizhou, China’s Shandong Province.
15 units each of Jinkosolar 585W TOPCon modules and equally rated BC modules were installed on a residential rooftop with a tilt angle of 20°. An optimum for front side power generation was reached as shown in Figure 1.
The energy generated was measured by DC meters at a 1-min interval, with data from each panel including DC voltage, current, power, module temperature, irradiation on front side, wind speed, orientation, ambient temperature, relative humidity and atmospheric pressure collected each day commencing 1st June. After one month of operations, the TOPCon module initially showed a yield gain of 1.7% when compared to the BC equivalent.
Results and Analysis:
In the case of back contact (BC) cells, all electrical contacts are located at the rear side of the device, resulting in stress concentration, back side deformation or bending and a rise in local temperature. This deformation in temperature resulting from stress concentration on the rear side will negatively affect the performance of the cell, a phenomenon clearly observed during days of higher temperatures in Laizhou, where temperatures could reach 38-39 degrees Celsius and module temperature up to 55 degrees Celsius at noon.
This stress-induced damage tends to propagate, with a high possibility of back surface bending or even breakage during transportation, loading/unloading, handling and initial stages of installation.
Conclusion
With TOPCon and Back Contact two of the industry’s new mainstream cell technologies, this study compared their respective energy yield in a rooftop scenario deemed optimal for BC technology. Results indicated that the TOPCon module produced a 1.7% higher energy yield performance, based mainly on its low-temperature, greater stability and reliability.
