There is a strong emphasis on scaling up solar power in India. With an increasing number of projects being installed across the country, there is more demand for quality equipment. Cables and connectors form a crucial supporting network in the solar power generation set-up. Since such systems comprise a large number of electrical connections, they are also vulnerable to energy losses at contact points. To limit these losses, long-lasting and secure cable connections with low contact resistance are required. Meanwhile, connectors are needed to facilitate and ease the installation process.
Although these components account for a small share in the total capital cost, frequently replacing them can add up to a significant amount over the life of the solar plant. Thus, proper selection and sizing of cables and connectors is important for optimising costs and for ensuring a well-functioning system.
Cables are an essential part of the solar power system as they are used to transmit power within it. There are two types of cables used in solar power plants – direct current (DC) and alternating current (AC). DC cables directly connect solar panels to junction boxes and inverters. They can be of three types – earth wires, single-core wires and twin-core wires. Special extension cables are used to connect the positive and negative cables to the junction box (or directly to the solar power inverter). To avoid earth faults and short circuit, the positive and negative wires should not be laid together in the same cable. Single-wire cables with double insulation offer high reliability.
In India, electricity is more commonly transmitted in AC form. Thus, inverters are used to convert DC power into AC. Solar systems with single-phase inverters require three-core AC cables and those with three-phase inverters require five-core AC cables. AC cables connect inverters to the substation. Meanwhile, DC cables that connect modules with the junction box and the solar power inverter are two-core cables comprising a current-carrying live wire and a negative wire, which are protected by an insulation layer.
Since the solar plant and the cables have to function in an open environment over a long period, they should be able to withstand severities like UV radiation, rain, dust, temperature variations, humidity and insects. Further, these plants have to withstand mechanical stress due to pressure, bending or stretching as experienced during installations, as well as chemical stress caused by acids, alkaline solutions and salt water. Thus, it is crucial to ensure their optimal functionality over the desired life the span. For the optimal performance of solar systems, solar cable accessories, connectors and crimping tools are used to allow fast and error-free installations. As solar projects have a minimum life of 25 years, their components are also expected to last as long.
Undersized cables can be a potential cause of fire. Using the right size of cables ensures that there is no overheating and it limits the loss of energy. While choosing the size of the wire, the generation capacity of the solar panel and the distance between the panels and the load needs to be taken into account. Cable sizes will increase with the increase in generation capacity and the distance from the load to the panel. The risk of losses is greater in the case of AC cables as compared to DC cables. DC main cables are designed to ensure that the generation loss is lower than 1 per cent of the peak power output from the solar project. This requires cables to have a low ohmic resistance. Besides length and cross-section area, this resistance depends on the material used in making these cables. Typically, aluminium and copper are used to make solar cables.
Some of the key players in the cable market are RPG Cables, Cable Corporation of India Limited, Nexans, Phoenix Contact, General Cable (Prysmian Group), Amphenol Industrial, Taiyo Cable Tech, Eldra B.V., KEI Industries, the Lapp Group, KBE Elektrotechnik, QC Corporation, Yueqing Feeo Electric, Siechem Technologies, Changzhou Painuo Electronic, Dynamic Cables, JainFlex Cables and RR Kabel.
Connectors provide secure and touch-proof connections between components. They facilitate connectivity throughout the system and also prevent misconnections. They help avoid loose cable ends, which can lead to energy losses and other performance issues. Connectors are exposed to harsh environmental conditions and mechanical stress, and should be able to withstand adverse conditions without getting disconnected. Hence, secure connections are required to conduct current fault-free for 25 years. These connectors should be able to meet the voltage and current requirements. They should have low contact resistance and firm locking mechanisms.
Connectors could either be pre-installed on solar panels or they can be installed on site. End-panels have to be then connected to an inverter or a combiner box, and these connections are often carried out on the field. In microinverter projects, connections are made between solar panels and the microinverter. These connections are usually pre-installed with cabling, especially in the case of plug-and-play integrated solar modules. Traditionally, screw terminals and spring clamp connectors have been used in solar applications. However, simple shock-proof plug connectors are fast taking their place. Every connector needs a cable coupler. Crimping the cable coupler is an important part of connecting the modules in a solar PV system. If crimping is not done properly, it would lead to higher resistance, thus significantly reducing the efficiency. Crimping has emerged as a safe solution for attaching connectors to cables, and it is being used for on-field and pre-assembled connections.
There are some connectors that are more dominant in the market such as the MC4, a common connector manufactured by Multi-Contact globally. This unit comprises a 4 mm single-contact cylindrical plug and socket shell design. MC3 is the 3 mm version of the MC4 device. MC4 components and compatible models are used in the majority of solar panels. Other common connectors are offered by Amphenol, Tyco, MC3 and Radox, among others.
Market overview and outlook
The restrictions imposed due to the pandemic disrupted the supply chain across all manufacturing industries. While there has been an adverse impact of the Covid-19 pandemic on the cables and connectors market, it is not expected to dampen the sector’s long-term growth.
The market for cables and connectors has been growing with a rapidly expanding solar segment. As per an industry report, the global market for solar cables reached a valuation of $613.3 million in 2019. It is expected that the market will grow at an average annual growth rate of about 7.7 per cent up till 2025 to reach nearly $823.7 million by 2025.
The scaling up of the industry is expected to drive down costs, although it is subject to raw material availability. Innovations in technology are also expected to improve the quality of the equipment. The emergence of floating solar projects, hybrids, energy storage and smarter digital technologies will require more innovation in the cables and connectors space. Going forward, the demand for different kinds of solar cables and connectors is also expected to evolve with the emerging needs and applications in the solar power space.
By Meghaa Gangahar