What is the best size for solar cell in future? 188mm will be the #1.
China's key silicon wafer suppliers are scrambling to release plans for larger silicon wafers. The largest silicon wafer size has reached 210mm, but is the larger the silicon wafer better? What silicon wafer size is the best choice? my idea is that 188mm cell will be the first and best choice.
For 210mm cells, if they follow the traditional 6-column packaging method, the modules are too wide, it is with a width of more than 1.3 meters. And such a wide modules will cause container loading to become a serious problem. The inner height of the container's highest dimension is only 2.69 meters. If the width of the modules has reached 1.3 meters, the stacking of the two pallets of modules and the height of the pallet will definitely not be fitted into the container.
It is precisely because this problem cannot be solved that TrinaSolar’s 210 mass-produced module specifications have adopted a 5-column, 3-cutting cells packaging method, and the width is controlled as 1.1 meters. However, there are new problems. According to the component circuit design, the optimal packaging method must be an even-numbered column. For odd-numbered packaging methods, a "jumper wire" must be added to make up an even number form. This "jumper wire" is costly and will increase the overall width of the glass, EVA and backplane by 1.2cm, and consumes an extra bus bar with a total length of 2 meters (due to jumpers, the odd-numbered 210mm modules are estimated to cost an extra 1$ per piece). Another small problem is the 3-cutting cell packaging problem, all cells are cut into three parts, and the cutting damage on both sides of cells. And no matter how it is packaged, there seems to be a risk of leakage. 210mm can bring some "flux value" in the manufacturing process, but the packaging problems caused by the excessive silicon chip will take away a lot of related value.
What is the best? I think the optimal width of photovoltaic modules may be about 1.2 meters. I just read First Solar's 2019 annual report and telephone conference memo. Their performance in last year was very good. This is related to the protection of the US policy and also to their series 6 products. Related to the great success, their Series 6 orders have exceeded 15 GW, and their production capacity is completely out of reach. The production capacity in 2020 and 2021 is already full, and the production capacity is basically full in the first half of 2022. It should be said that the version design of Series6 is not only feasible, but also very popular. The length and width are 2009mm×1232mm.
If you reverse the optimal size of photovoltaic modules, and at the same time you need to ensure an even-numbered array of 6 columns, the optimal silicon wafer size may be between 180 and 190 mm.
If we use 188mm silicon wafers, we can still use the even-numbered array package with 6 rows of cells. If it is a 72-Cells module, the length and width are: 1172×2316mm. The current photovoltaic module production line is compatible with 1.2×2.4m modules. Except for the stringer, the other parts of the related equipment has no need to make any changes. The size of 1.17 meters wide by 2.3 meters long can be accepted by the market. The effective packaging cell area is 2.53 square meters, and the total power of the module can reach 570 watts, which is 16% higher than the 50 cells module with 210mm cells and 28% higher than the 72 cells module with 166mm cells. I truly believe, with the further improvement of battery efficiency, the 72 cells module with the 188mm silicon chip can challenge 600 watts of package power in the near future.
What we really need is not larger silicon wafers, but larger PV modules! Under various objective conditions, we should enlarge the module area as much as possible, so as to effectively save the cost of the power station. As discussed above, we need to ensure that the module width is less than 1.2 meters and is an even-row package (or six-row package is the most appropriate). The optimal silicon wafer size pushed back is a value between 180~195mm. I personally like the size of 188mm very much, 188 is the luckiest number in Chinese, and it sounds nice, memorable and lucky!