With improvement of PV technology and deep promotion of ‘Top Runner’ plan, China PV industry starts to enter high-efficiency products’ competition era. Recent years, module enterprises continue attempting application of new packaging materials, use cell of higher efficiency, optimize module manufacturing technologies etc, continue transfer conversion efficiency of c-Si module and optimize performance of modules. Bifacial double-glass modules, halfcut-cell modules, overlapped-cell modules, and multi bus-bar modules etc. high efficiency modules technologies come out one after another.
Among, overlapped technology, as one of mainstream high efficiency module technologies, has aroused general concern. Bus-bar connection structure is used between cells in traditional modules. Using of large numbers of bus-bars increase internal losses of modules and reduce conversion efficiency of modules. Meanwhile, single piece cell’s difference under series structure, influence of back current to modules will increase, so that hot spot, which it produced, would damage modules, or even influence running of whole PV system.
Overlapped-cell modules use sawing technology to saw cells which bus-bars are redesigned to small pieces which figures are reasonable, to overlap every small piece and welding to series, after series and parallel typesetting to lamination to modules, so that cell will interconnection in a more intimate way. In the same measurement, overlapped modules can place 13% more cells than conversional modules. Besides, because of optimization of this module structure, which uses no welding strip design, greatly reduce line loss of modules and greatly increase output power of modules.
Higher efficiency, less loss, overlapped technology no doubt will bring revolutionary influence to China high efficiency module packaging technology. Especially under the situation of China module market price gradually goes down, cost reduction and efficiency increase of module field become a must. In hence, enterprises in PV industry should vigorously promote technology R&D and large scale manufacture of overlapped-cell modules.
Seraphim Solar promoted Eclipse series modules which applied overlapped technology in Mar, 2016. By using electrical design of no bus bar and innovativeness, Eclipse reduces modules internal loss and effectively increases module power, single piece module maximum power output increases more than 15%, module of same 60-pc type can reach more than 320W. Eclipse new technology and process can also combine current high efficiency cell technology. On 2017SNEC, Seraphim Solar promoted two new Eclipse modules, which matched module products of black silicon and PERC technology, respectively and uses module product of HJT cell.
In Feb, 2017, Dongfang Electric, Zhonghuan Semiconductor, SunPower and Yixing Development Zone signed contract and started DZS Solar high efficiency overlapped solar cell module project. It is reported that, the project introduced overlapped module technology which original created by DongfangSunPower and verifiedmaturity in North America market, to construct 21 mono-Si and multi-Si module production lines which all applied overlapped technology. Total investment of the project is about CNY 5bn. By the end of 2017, it will construction 730MW high efficiency overlapped solar cell module capacity. After all put into operation, it will form 5GW high efficiency overlapped solar module capacity.
GCL System Integration founded special science and technology R&D team of high efficiency sawing technology and high efficiency overlapped technology since 2014. Diamond high density module which it promoted applied innovative overlapped technology and displayed on 2016SNEC. Besides, on 2017SNEC, Jolywood, Solaria, Eging Photovoltaic Technology, SF-PV, ZhongliTalesun and Longi Solar etc. companies all displayed overlapped modules products.
However, large scale mass production of overlapped-cell modules still has some problems. Firstly, technology threshold of overlapped modules is quite high, how to ensurereliability of cell connection in packaging process is the key of the technology; secondly, overlapped modules need to use new devices and materials to manufacture, the cost is relatively high. Besides, overlapped modules existing risk of patent dispute. In hence, when module manufacturers are doing R&D and production, they have to pay attention to strengthen patent application and protection and avoid patent conflict.