Th PV industry has increasingly been focusing on employing larger wafer based cells in pursuit of increasing module power. The main motivation for increasing module power is to reduce the cost for the balance of system (BOS). Hongbin Fang, Director of Product Marketing at LONGi Solar, one of the presenters at the TaiyangNews High Efficiency Solar conference in Dec. 2020, showed that BOS costs for a 390 W module are about $0.132/W, which can be reduced to close to $0.124/W for a 440 W module. Simply put, a gain of 50 W in module power can reduce BOS costs by about $0.008/W.
Digging deeper reveals that the main savings are coming from system design changes. String power increases with higher module power, which means that fewer strings are required to attain a specific capacity. With fewer strings, the cost for trackers and electrical component decrease as well, which is reflected as BOS savings.
There is a catch though. The module power has to be augmented without increasing its voltage; if not, the number of modules per string remain the same. That's because, the module voltage is the basis for determining the number of modules connected in a string.
Therefore, BOS cost reduction benefits can be realized only if the voltage is kept at the same level while the current of the module increases. So, building larger modules with a higher number of cells are not greatly beneficial, as this means not only an increase in module power but also a higher voltage. On the other hand, increasing the wafer size increases the cell's current, given that it is a function of surface area, while the voltage remains the same.
The text is an excerpt from the TaiyangNews Report High Efficiency Solar: Featuring PERC Modules with M10/182mm Cells Towards Very High Efficiency Products –A Conference Summary, which can be downloaded for free here.
A comprehensive overview on Value Proposition of High-Power Bifacial PERC Modules Based on M10-182mm Wafers was provided by Hongbin Fang, Director of Product Marketing LONGi Solar during the TaiyangNews High Efficiency Solar Conference; the recording can be viewed here.