Crucial Components

A rise in the uptake of good quality so­lar power projects is expected in India. To this end, there is growing demand for quality balance-of-system eq­uipment, with an increasing number of projects being installed across the country. In particular, 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, the co­st of 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.

Overview of solar cables

Cables are used to transmit power. 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 or 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 cir­cu­its, the positive and negative wires should not be laid together in the same cable. Single-wire cables with do­uble insulation offer high reliability. DC cables that connect modules as well as 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.

AC cables connect inverters to the substation. 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.

Companies specialising in solar cables adhere to certain standards for E-beam cross-linking, special purpose compo­u­nding solutions (for sheathing and insulation), conducting material, testing and ce­rtification. Since a solar plant, along with cables, has to function in an open en­vi­ron­ment over a long period, it should be able to withstand severities such as ultraviolet radiation, rain, dust, temperature va­riations, humidity and insects. Further, the­­se plants have to withstand mechanical stress due to pressure, bending or st­retching experienced during installation, as well as chemical stress caused by aci­ds, alkaline solutions and salt water.

Frequent failure on part of solar cables decreases overall project efficiency. The­refore, it is crucial to ensure their successful functioning over the desired lifespan. For the optimal performance of sol­ar systems, solar cable accessories, connecto­rs and crimping tools are used to allow fast and error-free installation. As solar projects have a minimum life of 25 years, the components used for solar projects are also expected to last that long.

Material and design for cables

It is important to use correctly sized solar cables when connecting the various components of a solar photovoltaic (PV) system. This ensures that there is no overheating and limits the loss of energy. Un­de­r­sized cables can be fire hazards. When choosing the size of the wire, the generation capacity of the solar panel and the distance between the panels and the load need to be taken into account. Cable sizes will increase with any increase in these two factors. The risk of loss is greater in the case of AC cables as compared to DC ones. 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. Copper has lower resistance than aluminium at a given temperature. Further, aluminium is a lighter and cheaper alternative for making cables than copper. The insulation and the sheath have to perform at a higher temperature range. They require high mechanical stability and flame retardation, and should be free of halogens. To meet these requirements, cross-linked polyolefin copolymers can be used.

Overview of solar connectors

Connectors used in solar power plants play an important role in facilitating connectivity throughout the system and preventing misconnection. This helps in avoi­ding loose cable ends, which can lead to energy losses and other performance is­sues. Thus, connectors provide secure and touch-proof connections between co­m­ponents. Many different versions of con­­n­ectors or standard non-connector jun­ction boxes are used in solar plants th­roughout the industry.

Similar to cables, connectors are exposed to harsh environmental conditions and me­­chanical stress. They should be able to withstand adverse conditions without getting disconnected. Hence, secure connections that can conduct current fault-free over a period of 25 years are requir­ed. These connectors should be able to meet the voltage and current requireme­nts. They should have low contact resistance and firm locking mechanisms.

Every connector needs a cable coupler. Crimping the cable coupler is an important part of connecting modules in a solar PV system. If crimping is not done properly, resistance would be higher, which wo­uld significantly reduce efficiency. Thus, crimping has emerged as a safe sol­ution for attaching connectors to ca­bles, and is being used for on-field and pre-assemb­led connections. Connectors could either be pre-installed on solar panels, or ins­tall­ed on-site. Installing them on the field re­qu­ir­es the end panels to be connected to an inverter or a combiner box. In microinverter projects, connectio­ns are made between solar panels and the microinverter. They usually have pre-installed cab­ling, and there are no field connections. Traditionally, screw terminals and spring clamp connectors have been used in solar applications. However, simple shock-proof plug connectors are rapidly taking their place. Plug connec­ters and sockets with welded cables and pre-assembled circular connection systems are also being used to save time and labour costs.

Future outlook

The restrictions imposed due to the pandemic disrupted the supply chain across all manufacturing industries. While the Covid-19 pandemic had an adverse im­pact on the cables and connectors mar­ket, it is not expected to dampen the sector’s long-term growth. Of late, inflation – particularly the rising cost of metals, electronics and fuel due to the Ukraine-Russia war – and supply chain restrictions on se­lect cities in China have emer­ged as new challenges. Within the solar sector, a significant price rise has been witnessed for solar modules, which has impacted the fi­nancial viability of entire solar projects. It remains to be seen if the price of solar ca­bles and connectors will also rise be­cause of the geopolitical tensions at play currently.

The market for cables and connectors has been growing with the 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 to reach nearly $823.7 million by 2025. The scaling up of the in­dustry is ex­pected to drive down costs, although this is subject to raw material avail­ability. Inno­vati­o­ns in technology are also expected to improve the quality of eq­uip­ment. The em­ergence of floating so­lar projects, hy­brids, energy storage and sm­ar­ter digital technologies will de­mand 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.