The increase in solar power installations and awareness regarding optimal solar generation has shifted the focus to advancements in balance of system (BoS) component technologies. The importance of junction boxes in improving the quality of solar power is being realised by the solar industry. Junction boxes live in the shadow of their more famous BoS peers. Although small and simple in design, junction boxes simply cannot be ignored because of their use cases. A junction box is an enclosure on the module where the PV strings are electrically connected. It houses the electrical parts of solar panels and protects them from external harm. The junction box makes it easier to connect the solar panels to the array through connectors. Another critical function of the junction box is to protect reverse current. The junction box helps keep corrosive elements away from the wires and conductors. It has high temperature resistance, water resistance, ozone resistance and other important properties.
Therefore, a junction box is able to enhance the efficiency of solar panels by optimising and stabilising the power generated by the system, and making the power safe for further use. Types of junction boxes
There are four types of junction boxes – silicon, non-silicon, curtain and explosion-proof. For solar power systems integrated into building structures, specific solar PV junction boxes are available. Junction boxes are manufactured using two technologies – soldering and clamping. In soldering, the foils from the solar panels are soldered to the diodes in the junction box, which is then filled with a material to allow heat transfer. The latter involves clamping the foils to the wires.
Issues and challenges
Despite quality checks, failures have been reported in some cases. The primary reasons for failure are burnt bypass diodes, low power and high energy stress on the system. The melting of plastic components, broken latches and the separation of external connectors are other factors. Since junction boxes function in high temperature environments, extreme heat can have an adverse impact. In some cases, operations and maintenance companies have faced issues while replacing junction boxes or sourcing key components used in them.
Over time, the technology for junction boxes has evolved to deal with modules offering greater output. These modules generate more heat and thus require junction boxes that can withstand that kind of heat. To this end, cool bypass switches have been introduced to replace the traditional diodes.
Due to the increasing use of bifacial modules, junction boxes have to deal with even more output resulting from generation on both sides of the solar module. Moreover, to prevent shading at the back new junction boxes of comparatively smaller size have come into the market.
Smart junction boxes are now entering the market and their market share is expected to increase going forward. Companies are developing junction boxes that can be integrated with solar panels for monitoring, optimisation and rapid shutdown abilities. Moreover, in the future, communication with solar modules will become possible with the help of junction boxes integrated with Wi-Fi technology. These junction boxes would enable tracking, monitoring and control of output from individual modules. Also, the voltage, current and temperature parameters would be read and analysed to determine whether servicing of parts is required with the help of junction boxes. If the temperature rises beyond a level or a fire erupts in a junction box, the communication thread would help in shutting down the modules immediately. Smart junction boxes would also feature removable covers that enable easy technological upgrades.
The International Technology Roadmap for Photovoltaic, 2019 has highlighted key future trends for junction boxes. One, the internal electric connection of bypass diodes would be done mainly by soldering. Welding would gain market share over the next few years while the use of clamping would reduce going forward. In addition, the report has highlighted that the now prevalent single junction box concept would be replaced by multiple junction boxes in the coming years due to a shift from fuel cell module concepts to half cells.
The report has also highlighted that despite the emergence of smart junction boxes, standard junction boxes would continue to dominate the market over the next 10 years. By 2030, the market share of smart modules would slowly grow to 20 per cent. A similar trend would be seen in junction boxes with module-level monitoring and shutdown capabilities. Their combined share in the world market was around 5 per cent in 2019 but is expected to grow to approximately 20 per cent by 2030. Standard junction boxes without such capabilities would remain mainstream.
Going forward, the most interesting trend in this space would be the juxtaposition of microinverter technology with junction boxes. Such junction boxes are likely to gain traction with the growing uptake of microinverters. According to experts, this technology would further simplify the installation of solar plants.
In sum, given the numerous technology advancements, the solar industry is expected to give greater importance to junction boxes for improving the quality of solar plants.
By Sarthak Takyar