Support Structures

Need for cost-competitive tracking and mounting systems

Module mounting structures have an important part to play in the functioning of a solar power plant, in the case of both utility scale as well as rooftop. They are the supporting structures that hold solar panels to the ground. In order to harness solar power efficiently, mounting structures need to be manufactured and installed at sites in a specific way. For further increasing the irradiation received by panels, solar trackers can be used to follow the sun’s movement. However, the quality of mounting structures is often compromised to cut costs and solar trackers witness limited uptake due to their high price.

Mounting structures

Mounting structures need to be durable to be able to bear the weight of solar panels, high wind speeds and a range of temperatures. In order to adapt to topographical features and weather conditions at site, module mounting structures require customisation. These structures can be set up for rooftop plants, ground-mounted solar, carport and sun tracker solutions. Mounting structures have evolved over the years in terms of weight, material, adaptability and cost.

A solar power plant is designed to last about 25 years, making the supporting structure a crucial factor in its long-term performance. It is thus important to choose the correct type of mounting structure. There are five types of mounting structures: Roof-mounted racks, ground-mounted racks, top-of-pole-mounted racks, side-of-pole-mounted racks and tracking system-mounted racks. Of these, four are fixed-angle type and one is variable-angle type.

Roof-mounted racks are used for rooftop solar projects. They can be fixed or adjustable and even be installed with a solar tracker. Ground-mounted racks are usually adjustable and allow panels to tilt up or down for maximum solar absorption. There are two varieties of pole-mounted racks. While one allows the solar panel to sit on top of a pole, the other elevates it several feet off the ground. Tracking system-mounted racks can be used for solar tracking systems and solar water pumping systems.

Tracking solutions

Solar tracking systems allow modules to move in such a way that they continuously face the sun. This helps maximise the irradiation received by the solar array.

There are two types of solar trackers: Single axis and dual axis. The single-axis type track the sun from east to west, rotating on a single point, moving either in unison, by panel row or by section. Dual-axis trackers rotate on both the X and Y axes, making panels track the sun directly. Even though single-axis trackers collect less energy per unit as compared to dual-axis trackers, the former have shorter racking heights. Thus, they require less space to install and are easier to operate and maintain.

Single-axis trackers can further be categorised as centralised and decentralised. Centralised trackers use a single motor to power a driveline between rows that move an entire segment of panels while decentralised systems have one motor per tracking row. In some cases, trackers with motors are present on each set of racking. This makes the rows more flexible to adjustment and they are able to track other modules independently. In spite of these merits, a dual-axis solar tracker outperforms a single-axis tracker by producing 30-45 per cent more energy. This is due to its ability to accurately follow the sun’s arc.

Demand and significant players

In recent years, the demand for mounting structures has increased. Most of the demand is in conjunction with other components of a solar power plant. For instance, in the case of balance of system (BoS) tenders, the successful bidder is often also responsible for the design and construction of the module mounting structure for solar panels, including the fixing of modules with the module mounting structure and module interconnection. However, some recent tenders have specified the need for procuring module mounting structures. In July 2019, Bharat Heavy Electricals Limited (BHEL), issued a tender inviting bids to supply module-mounting structures for the Neyveli Lignite Corporation of India’s solar projects in the state of Telangana. Following this, in September 2019, Rajasthan Electronics and Instruments Limited (REIL), a government-owned manufacturer of electronic products, issued a tender to procure solar photovoltaic (PV) module mounting structures for modules of 250 W, 300 W and 335 W. The total number of module-mounting structures to be procured is 270.

In light of the growth of the solar power segment, the majority of steel giants around the world have started supplying mounting structures. JSW Steel Coated Products Limited is one such example. Pennar Industries derives over 30 per cent of its business from its solar mounting structure division. Ganges Internationale and the SNS Corporation are two other leading players in the mounting structure space. Some other large players are Tata International, Jakson, Neuvosol, Metalkraft, Strolar, and Solar Mounting System Solutions.

KavitsuRobotronix Private Limited and German PV tracker company DEGERenergie GmbH had announced plans to set up a solar PV tracker manufacturing facility in Satara, Maharashtra, through a joint venture called KAVITSU DEGER India Private Limited. While 70 per cent of the production was planned for single-axis trackers, 30 per cent was for dual-axis trackers.

According to the contract agreement, DEGER would share its patented maximum light detection sensor, which is 45 per cent more productive than a regular PV system. Other popular manufacturers and wholesalers of solar trackers are Amberroot Systems, Ephysx Technologies, Greenera Energy, Hyquip, Infinite Solar, ERCAM, Arctech Solar, Kaizen Imperial, Milman Thin Film Systems, Nordic (India) Solutions, Parco Engineers, and SAG Steel.

Key concerns and challenges

Besides being a key component in functioning, module-mounting structures make up a significant share of the cost of a solar project. Typically, mounting structures can cost up to about 10 per cent of the total system cost of a large solar power plant and about 15 per cent for smaller power plants. Unlike most BoS components such as inverters, cables and transformers, mounting structures are not bought from suppliers. The designing of mounting structures is taken up by engineering, procurement and construction (EPC) companies. According to a study undertaken by PV Diagnostics, there are two types of structural issues: design/installation, and operations and maintenance (O&M).

Issues often arise due to faulty practices followed at the time of designing and installing a solar plant. The primary causes for this are ignorance on the part of EPC companies involved or wrong considerations taken during the designing level. There may be a variable structural tilt causing unwanted shadows on other panels and a difference in radiations received across panels.

Apart from generation loss, this causes accelerated degradation due to angle mismatch and different temperatures in affected panels. As a result, mounting structures may become unstable or may have loose braces, making them unable to deal with high wind speeds and changing weather conditions. At times, clamps, nuts and bolts at cross-bracing are not properly screwed. Further, even the braces are sometimes improperly tightened. Faults can arise in drivelines if there is less ground clearance or if the driveline slips due to slotted joints. Other O&M issues could arise owing to poor site conditions and inappropriate assumptions taken at the time of designing.

Outlook

Manufacturers of solar components are constantly trying to improve the efficiency of solar power generating systems. While one part of this endeavour is to improve the panel technology to get higher yield per unit area compared to competing modules, the other is to install quality solar trackers that make solar panels follow the sun’s path, thereby optimising irradiation. While solar trackers increase efficiency and reduce the manual upkeep of panels, their use remains limited due to a considerable rise in the total project cost and the addition of a moving part, which may cause problems on breakdown. Meanwhile, there has been a surge in the demand for mounting structures in tenders. This, coupled with falling module and inverter prices, has shifted the focus on the development of mounting structures while optimising cost. If strict quality checks are put in place, this may lead to more advanced and cost-competitive products.

By Meghaa Gangahar

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