Critical Links

Trends in the solar cables, connectors and junction box industry

A solar balance of system (BoS) en­com­passes several elements that play a significant role in ensuring sm­ooth and efficient transmission and delivery of power by a solar module. Cables, connectors and junction boxes are key elements of the BoS. The photovoltaic (PV) junc­tion box is an enclosure on the module where the PV strings are electrically conn­ected. The presence of diodes in ju­nction boxes ensures that the flow of po­wer rema­ins unidirectional, preventing power from feeding back into the panels. Diodes also prevent damage and corrosion of the module and counteract low efficiency outcom­es. While there are several types of junction boxes in the market, next generation technologies are rapidly being adopted in the form of smart junction boxes and auto cut-off junction boxes. These technologies are in the resear­ch and development stage and can be ex­pected to be developed over the coming few years. Renewable Watch looks at the upcoming trends, challenges and recommendations for the market of junction bo­xes, cables and connectors in India…

Upcoming changes in the segment

The solar market is expected to witness the onset of higher efficiency PV modules with 600 W plus capacity soon. With such ad­vancements in the wattage of modules, the type and quality of junction boxes re­quir­ed in the market would need significant impro­vements. Junction boxes would also be required to support the increasing ca­pacity of string inverters and central inver­ters. Fur­ther, bigger installations due to inc­reased module Pmax are also expe­cted in the coming months. This can po­t­e­n­tially impro­ve return on investment and levellised cost of energy. Better quality ju­nction boxes and connectors would also lead to lower overall operations and maintenance activities and project execution time.

Split junction boxes are slowly replacing traditional/conventional four-rail junction boxes in higher wattage modules with double glass or twin type assemblies. When the wattage increases, more rated current is required from split junction boxes and th­eir diodes to meet the module current re­quirement. Split junction boxes also save cable lengths, thereby reducing product cost, lowering module losses and increasing performance efficiency. Over the coming years, junction boxes are expected to en­tail enhanced carrying capacity for PV connectors.

Increased insulation thickness for solar cables may also make them relatively long­er lasting. Compact and robust designing of BoS elements would also lead to inc­re­ased efficiency and optimised costs. Com­pa­ct structures can reduce the shading eff­ect on the rear side of bifacial modules and allow usage of an optimal volume of silicone glue inside the junction box, en­abling an overall reduction of PV model cost. Us­age of integrated module type du­al chip di­odes, which have superior heat dis­sipation abilities and excellent switching responses over conventional diode packages, can be expected. Cables and con­n­e­c­tors that meet lower contact resistance re­quireme­nts can reduce module losses. Pr­o­ven and ad­vanced grade engineering plastics may be widely used for better performance un­der harsh environmental conditions.

Potential modes of failure

There exist several scenarios in which junction boxes, cables and connectors may fail or underperform. Bypass diodes and junction boxes can burn due to lightning strikes and other secondary surge impacts. PV connectors may get burnt due to poor cri­m­­ping out of unauthorised and manual rework. Partial or incomplete mating of co­un­terparts during commissioning can also lead to failure of PV connectors due to bu­rns. Another potential risk is the cross-mating of PV connectors, which may lead to high contact resistance. Improper connections caused by tightening issues during re­work is also a cause for concern. While over-tightening leads to stress on the module, under-tightening may create IP issues. Solar cables may also get damaged due to sharp edges.

Technical specifications and recommendations

There are several technical specifications that can be taken into consideration to im­p­rove the output of solar modules. Ensur­ing the availability of connectors in a pre-a­s­s­embled state would greatly ease the as­s­embly at site in case of any rework activities. Certain parameters such as the use of material grade equipment with advanced grade engineering plastics are also recom­m­­ended. Double insulation and EBM cro­ss-linked cables and wires may be utilised for better product life and performance in har­sh conditions. Finally, upgrading the pro­­duct licences of junction boxes, conne­ctors and cables to the latest available versions is important. Fine-tuning test specif­ica­tions according to the respective IEC standards can ensure better product relia­bi­lity and life cycle. All components must be tested and certified as per established international standards. n

Based on remarks by Manjunath Reddy, Managing Director, DhaSH PV Technologies Private Limited, at the “BoS for Solar Power Plants” virtual conference organised by Renewable Watch




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