| Work Detail |
Indian scientists have developed six different strategies for reconfiguring solar modules on degraded photovoltaic assets. Their analysis shows what conditions make reconfiguring a low-performing solar plant profitable. Researchers at the Indian Institute of Technology Bombay have analyzed the techno-economic feasibility of upgrading photovoltaic (PV) plants with degraded modules by reconfiguring them. The team modeled a commercial-scale photovoltaic plant in Python and investigated different reconfiguration strategies and degradation modes, analyzing the economic feasibility of the project for India and the United States. In several likely scenarios, reconfiguration may be the only option left for plant operators to improve energy production with existing modules, the group states. In this document, reconfiguration is defined as changing the electrical positions of PV modules within a block connected to a string monitoring box (SMB) to improve the performance of the entire PV array. The same process could be repeated for other blocks connected to other SMBs to achieve performance improvements at the central inverter or plant-wide level. The simulated utility-scale plant was based on 315 W modules, with 30 connected in a daisy chain, giving a total power output of 9.45 kW. Another 10 panels were connected in parallel to the SMB, achieving a power output of 94.5 kW, while 10 SMBs were connected to a central inverter for a total power output of 945 kW. The utility-scale plant had 30 of these inverters, giving a plant capacity of 28.35 MW. Different types of degradation Initially, two modes of degradation were investigated. The first was a reduction in shunt resistance (Rsh), typically caused by potential-induced degradation (PID) in hot and humid climates. The second was an increase in series resistance (Rs), typically caused by corrosion, interconnect degradation, or solder joint problems. In both cases, the team attempted to reconfigure the systems by grouping similar modules into new strings. However, this only resulted in an improvement in the first case (2.72%), while performance worsened in the second (-0.64%). Following this experiment, the team focused solely on non-uniform current reduction cases, such as those involving a PID degradation of Rsh, as reconfiguration was found to have potential in those cases. Six different strategies—named C1, C2, C3, C4, C5, and C6—were outlined for the proposed scenarios, with varying cost burdens. Overall, C6 requires reconfiguring 10% of the modules, C5 20%, C4 40%, C1 50%, C2 80%, and C3 90%. The group explained that strategy C1 requires choosing the top 15 modules from each chain and creating new chains, while C2 divides each chain into five sets of six modules each and calibrates these sets in descending order of average fill factor (FF) for all sets generated from the 10 chains. Furthermore, C3 divides the chain into 10 sets of 3 modules each and sorts these sets in descending order of average FF for all sets generated from the 10 chains. In addition, C4, C5, and C6 have different module values ??and the associated module swaps required. Results The analysis showed that strategy C6 helped improve performance by 0.3212%, while C5 and C4 gained 0.9899% and 2.4053%, respectively. C1 gained 2.713%, and C2 and C3 gained 3.65% and 3.7923%, respectively. From an economic perspective, strategies that require different panel replacement rates are more viable when module costs are lower. If 100% of the modules in a 30 x 10 array had to be repositioned, 150 swaps would be required, and with 10 people, it could be completed in one day, the academics explain. Assuming that the labor cost in India is $0.74/h and $7.25/h in the United States and an 8-hour work day, the labor cost per module swap in India is $0.198/module and $1.93/module in the United States. Thus, 100 people could reconfigure the entire 28.35 MW plant in approximately one month. Based on these results, the team concluded that reconfiguration can make economic sense when several key conditions are met, such as a small sample of IV at the module level, low labor costs, and a short payback period. Reconfiguration would also be feasible when there are cracks in the cells or permanent fouling due to cementation, the group concluded. Their work was presented in “ Viability of performance improvement of degraded Photovoltaic plants through reconfiguration of PV modules”, published in Solar Energy . |
