UNSW-Martin GREEN

Innovation Changes the World MWT Technology and Its Advantages Prof. Martin Green-Chief Scientist of Sunport Power 日托光 伏首席科学家 June 04, 2019 Co nt en ts The Mass Production of MWT at Sunport Power 1 2 3 The Prospective of MWT Technology Why MWT ? Innovation Changes The World 1 Why MWT？ Innovation Changes The World 1. The positive and negative electrodes are located at the sides of rear and front (p-type wafer), respectively. 2. The connection of cells in module manufacturing is from the front of a cell to the rear side of the neighboring one by ribbons. 3. An appropriately large enough cross section of the ribbons has to be used to keep low CTM loss, especially for higher current of larger wafers. Structure of conventional H-pattern cells and their connection Innovation Changes The World The weakness of conventional modules: To meet the requirement of an appropriate cross section, a compromise for the thickness and width has to be made for the ribbons. Therefore, ◼ Shadowing at the from side is not avoidable due to the width of the ribbons, ◼ Stress on the cells due to soldering and bending of ribbons at the cell edge exists naturally, and finally causes micro-cracks. The cracks will enhance the power degradation of the modules. Any idea to reduce the shadowing and avoid the stress/cracks? Back contact Innovation Changes The World 1、 PN junction at the rear --- IBC: Started in 1970s Issue -- Cost control！ ◼ Emitter located at the backside ◼ Both the base contact grid and emitter contact grid are located at the backside. ◼ Rely on wafers of long lifetime – N-type wafers Back contact technology Innovation Changes The World 2. Emitter Wrap-through Technology (EWT) Started from 1994 The high density of holes required, normally used in thin film cells, rather than bulk crystalline Si cells. Emitter located at the front of the wafers ◼ No grid at the front ◼ The through-wafer connection is realized by doped areas ◼ All grids are located at the rear of the cell. Back contact technology Innovation Changes The World 3. Metal Wrap-through Technology (MWT) Originally publicly released in 1998 GW mass production by Sunport Power ◼ Emitter located at the front side ◼ Busbars are moved to the backside of the cells ◼ Only the fingers are kept at the front of the cells, which are connected to the backside through the holes filled with silver paste Back contact technology Innovation Changes The World 02 Mass Production of MWT at Sunport Power Innovation Changes The World The First Manufacturer on GW Scale for MWT After 7 years development, especially independent R&D, Sunport Power has built three manufacturing bases in China, covering solar cells, back sheets and modules, 1.4GW capacity for each section of the chain. Innovation Changes The World Current Status of Crystalline Silicon PV Technology Aluminum Back Field Cells Average: mono- 20.4%, poly-18.8% PERC Cells Good compatibility with conventional cells equipment (Average: mono-21.8% , poly- 19.7%) H-Pattern (p-type) (including both BSF and PERC) HIT (n-type) Only a few manufacturers achieve industrialization, high technical threshold, complex process and high cost (Average: mono-22.8%) Only a few manufacturers achieve industrialization, poor compatibility with conventional cells equipment, high technical threshold, complex process and high cost (mono- 23%)Good compatibility with conventional equipment and processing (Average: mono-22.4% , poly-20.8%) IBC (n-type) MWT (p-type or n-type) (including both BSF and PERC for p-type) (MWT + HJT for n-type) Innovation Changes The World Comprehensive comparison Technical Complexity Equipment Investment Productin Cost Conversion Efficiency H-pattern (including BSF and PERC) HIT/IBC MWT (including BSF and PERC) ★★ ★★ ★★★ ★★ MWT is the most cost-efficient approach as MWT+ is compatible with most of the other technologies. Innovation Changes The World MWT solar cells Metal Wrap Through (MWT) could increase the conversion efficiency by reducing the BUSBAR-shaded area on the front side, with both polarities at the rear side. Maufacturing Steps: 1. Design and drill the holes that go through wafers 2. Fill in with conductive paste to guide the electrode from the front to the rear side via drilled holes. 3. Insulate the back side field. As both the positive and negative electrodes are on the rear side, it s named as MWT Rear-Contact solar cell. Innovation Changes The World Customized Graphics Design on MWT Cells Innovation Changes The World MWT modules Conventional MBB Modules Internal Structure Positive and negative electrodes both on the back side of the cell. The positive and negative electrodes are located on the front and back of the cell. No Busbar on the cell surface, which increases the light area and reduces the use of silver. Positive and negative electrodes connected in series through welding the busbars on the front side of the cell, which covers the cell surface and consumes silver paste. By replacing the interconnection strip with conductive foil the series resistance of MWT modules is lower and the encapsulating loss is less. The stress of high temperature welding and the hidden crack of bad welding cannot be avoided For conventional modules, cells are connected by welding belt and then then pass through the high temperature laminating machine. With encapsulating technology alike semiconductor, MWT modules is more reliable on performance and higher on output power. Series Connection Cell Structure Encapsulation MWT module features Innovation Changes The World Benchmark series modules Innovation Changes The World SPP-FLex 1.0 Flexible High efficiency Ultra thin Light weight Easy Installation Attractive design Innovation Changes The World Excellent reliability of MWT modules A degradation of 0.39% and 0.49%,respectively. A degradation of 0.22% and 0.47%,respectively. A degradation of 0.21% and 1.22%,respectively. TC600 HF50 DH3000 Triple-time extreme testing results Innovation Changes The World High Efficiency • No main grid, output power increased by 3% on the same wafer area • Low resistance and CTM loss by using conductive back sheet Superior Warranty • 30 Years Assurance by PICC and LLOYD S • Power output no less than 80% after 30 years • Abandoning ribbon soldering, which causes strain and potential micro cracks • Highly automated module manufacturing, leading to high uniformity between each product Aesthetics Appearance • Iconic appearance without busbars • Customized cell pattern if required High Reliability The advantages of MWT modules Innovation Changes The World Output comparison between MWT and conventional modules Module Type First-year Decay Second-year Decay Liner decay Value Residue power after 25 years Residue power after 30 years MWT-Mono 2.00% 0.55% 0.55% 84.80% 82.05% MWT-Poly 2.00% 0.55% 0.55% 84.80% 82.05% Conv-Mono 3.00% 0.70% 0.70% 80.20% // Conv-Poly 2.50% 0.70% 0.70% 80.70% // More Power Generation of MWT Modules MWT/Conv 25 years 30 years MWT-mono to conv-mono +3.16% +21.93% MWT-poly to conv-poly +2.58% +21.25% Innovation Changes The World Generation and LCOE advantages within 30-year period Year MWT power output Conv-mono power output Conv-poly power output MWT-mono yield more power MWT-poly yield more power Lower LCOE for MWT-mono Lower LCOEfor MWT-poly 1 98.00% 97.0% 97.50% 1.03% 0.51% -1.02% -0.51% 2 97.45% 96.3% 96.80% 1.19% 0.67% -1.18% -0.67% 3 96.90% 95.6% 96.10% 1.36% 0.83% -1.34% -0.83% 4 96.35% 94.9% 95.40% 1.53% 1.00% -1.50% -0.99% . . 24 85.35% 80.9% 81.40% 5.50% 4.85% -5.21% -4.63% 25 84.80% 80.2% 80.70% 5.74% 5.08% -5.42% -4.83% Average of 25 years 3.16% 2.58% -3.06% -2.52% Average of 30 years 21.93% 21.25% -17.99% -17.52% Innovation Changes The World Application examples The First Top Runner Projects in Datong, Shanxi Innovation Changes The World Top Runner Project in Baicheng, Jilin Innovation Changes The World Top Runner Project in Delingha,Qinghai Innovation Changes The World Power Plant in Holland Solar Rooftop above Flower Market in Holland Family Power Station in Europe Solar Rooftop above Swimming Pool in Holland Innovation Changes The World 03 The Prospective of MWT Technology Innovation Changes The World *Cited from IHS Markit data and ITRPV 2019. MWT compatible 1.P-type BSF cells √ 2.Various passivated cells (PERC/PERL/PERT etc.) √ 3.HIT/HJT √ 4.Quasi-mono Si wafer √ 5.Back contact IBC × The compatibility of MWT Innovation Changes The World Use of Thinner and Larger Wafers: 1、 Mono wafers of 160 µm in thickness have been used Nothing abnormal in efficiency and breakage rate 2、 Mono wafers of 140 µm in thickness are under testing A little drop in efficiency (-0.2%) and rise in breakage rate (+1.5%), further optimization is in processing. Mass production in 2019 expected. 3、 Mono wafers of 120 µm in thickness are possible? Mass production expected 2020. 4、 158.75 mm wafer in use for years, 162.75 mm in trial production. Efficient way for cost reduction Innovation Changes The World Lead-free Concerns for Circular Economy in PV 1、 Economical issue – reuse of conventional materials i.e. Al frames, glass cables … 2、 Environmental issue –the recover of Lead in the modules is more and more important issue for PV. In ribbon soldering connection modules, Lead is used in the soldering materials. However, the conductive paste is Lead free in MWT modules THANKS