The pursuit of grid parity is the constant mission of the photovoltaic industry, and reducing the cost of electricity (LCOE) with high efficient technologies is an essential approach for the industry to accomplish this mission. As PV modules are the core component of a PV system, the continuous improvement of module efficiency is the most direct and favorable technology route to achieve grid parity.
Development trends in Bifacial PERC
Among high-efficiency cell technologies, PERC is undoubtedly the most cost-effective. Compared with conventional cell, the production of PERC cell needs only to add rear passivation and laser slotting sections, coupled with metallization techniques. This will effectively enhance the conversion efficiency of the cells. In the past six months, the world record for PERC cell conversion efficiency has been constantly refreshed, demonstrating the strong potential upside of PERC.
Mature manufacturing techniques and reasonable capital investment can drive the expansion of PERC cell capacity. According to ASIACHEM statistics, as of May 2018, global PERC cell capacity reached 46.8 GW. Newly built or upgraded p-type monocrystalline silicon cell production lines will all adopt PERC technology. It is obvious that PERC solar cell technology is becoming a new-generation norm.
On this basis, bifacial PERC is also becoming an important route in the development of the technology. The commonly used manufacturing technology for bifacial PERC cell is to change the printing process of the PERC single-sided cell, and changing the rear surface from whole aluminum layer to a local aluminum layer. This allows incidental light on the rear surface to enter the cell from the exposed layer and create photoelectric conversion on both the front and rear sides.
In this process, with negligible increase in manufacturing cost, bifacial PERC can achieve power generation gain of 10%-25% at the system level, which will significantly reduce the LCOE of the PV system while greatly enhancing the competitiveness and development potential of PERC technology.
Bifacial PERC + half-cut technique further improve the cost performance of modules
To further realize the advantages of high power conversion of high efficiency cells, combining PERC cells with innovative module construction technique is an important upgrade route for manufacturers of PERC cells and modules. From a technology perspective to improve module output power, half-cut cell is undoubtedly a high performance and low cost product that is easy to implement in large scale production
Half-cut cell is the technique that cuts a conventional cell in half and then connecting the two halves together. Compared with conventional cell, the only operation required is to cut the whole cell into two parts by laser before string welding them. The cell splitting and transmission are fully automatic and the string welder needs only slight modification to achieve large-scale production.
Half-cut cell construction has the following characteristics:
1) As the cell is split in two, thermal resistance loss is reduced and output power of the half-cut-cell module is 5-10W higher compared to a full-cell module of the same type;
2) The hot spot temperature of the half-cut-cell module is about 25℃ lower than that of the full-cell module of the same type. This can effectively reduce the hot spot effect;
3) The half-cut-cell module can meet the 1500V system voltage design requirements and can reduce the cost of the system by about 10%.
Since half-cut module greatly enhances the output power without adding much additional cost, high-power half-cut cell module is being developed on a large scale. In 2018 SNEC, half-cut cell module was a must-have exhibit for PV module manufacturers.
At Intersolar Europe, LONGi Solar will present the new Hi-MO3 PERC Half-Cut Cell Bifacial module. The innovative combination of half-cut cell and bifacial module construction achieves front-side power up to 320W (60-cell), with bifaciality more than 75%. Under shady conditions, Hi-MO3 can deliver higher energy yield than whole-cell module array.