A case study conducted at a 30 MW PV project developed by China Guodian Corporation (CGC) compared the performance of p-type PERC and n-type TOPCon modules under the same installation conditions. The study demonstrated an increased energy yield of just 5% for the n-type modules, over a two-week period in February 2023.
The 30 MW project studied was developed by CGC in Jixian, Tianjin Province. The project features 20 MW made up of two different 545 W, p-type PERC modules from unnamed manufacturers, with the remaining capacity made up of 555 W n-type TOPCon modules supplied by JinkoSolar. All of the modules are installed on fixed tilt racking at a 30 degree angle, and connected in strings of 26 modules with one 225 kW string inverter for every 17 strings.
The performance of the two module types was analyzed during the first two weeks of February 2023. During this period, the n-type modules were shown to have generated an average of 169.53 kWh per kW installed, a 5.02% increase on the 161.43 kWh/kW achieved by the best-performing p-type module at the site.
N-type advantage
Module manufacturer JinkoSolar, which supplied the n-type modules to this project, says this data illustrates the reported advantages of TOPCon over PERC in action. The manufacturer cites the n-type modules’ higher efficiency and better bifaciality as key reasons for the increased performance. Better bifaciality (around 70% for PERC and 80% for TOPCon) could account for a yield increase of 1- 1.5%.
With only two weeks of data, collected during the coldest part of the year in Tianjin Province, other advantages are more difficult to take directly from this case study. However, JinkoSolar also cited its n-type modules’ lower degradation rate – 1% in the first year followed by 0.4% per year as likely to bring a yield increase of around 1.8% over PERC’s typical degradation of 2% in year one followed by 0.45% per year.
Finally, it cited the lower temperature coefficient of n-type modules – 0.29% performance loss per C of temperature increase, versus 0.35% for PERC modules – as responsible for a further 2% yield boost, noting that this advantage would be more visible at the project studied in the summer months when temperatures can reach 30 C and higher.
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