The Solar Foundation: Solar Structures Need Attention

As India’s solar march has gone on, from 2 GW to a possible 42 GW by the end of this year, it’s interesting to see just what got the headlines within the sector.

Solar Structures Need Attention

It has undoubtedly been modules, cells and inverters, in that order. What has been missed out is in fact, as important. Yes, we are talking about the structures that hold it all together, or the module mounting structures (MMS). Speaking to many of the firms in the business, one gets the impression that ignoring the whole business of solar structures is a bad idea, and its time the industry, and the powers that be took a closer look at it. Coming at a time when extreme weather events are no longer ‘once in a century’, or even ‘once in a decade’, the foundations or structures on which the whole solar system rests, have never been more important. So here’s a start.

R.K. Singh: The 5 Point Checklist for 2020

Also Read

Samarth Dakshini, Director at Rajasthan based structures firm Raydean, adds that “ Many EPC players and especially small system integrators in today’s market do not provide the attention required for structural stability and safety. In this cut throat competition industry many players are looking to cut corners for saving costs and unfortunately they try to do that in BOS , specially Module mounting structures because many end customers and some times even installers are hardly aware about the design aspects of MMS and they look at it as simple fabrication which has to be carried out in trial and error methodology , although the cost of MMS is hardly even 10% of the total project cost “.

The quality issue is flagged as a serious problem by both EPC’s we spoke to as well as structure manufacturers, who invariably blamed cost pressures on the mistakes made.

Today, Tata Blue Scope has seen enough potential in the market to launch a special steel, ILIOS®, targeted specifically at the racking market. Manufactured from cold rolled Zn/Zn-Al coated products with reference to Indian standard IS 15961:2012 and Australian standard AS 1397, the steel offer higher corrosion resistance, weight optimization and quick installation. It offers greater load carrying capacity with a lighter weight with 550 MPA reducing tonnage per MW by up to 50% according to the firm. The firm claims that It lasts for upto 4 times longer than ordinary galvanized steel. ILIOS® stays close to customers through its plants located in Chennai (Tamil Nadu), Bhiwadi (Rajasthan) and Pune (Maharashtra).

So What Can Go wrong

Saving too much on the structure can lead to many problems. More than a few manufacturers and EPC contractors point to the extensive damage faced by the storms, and cyclones recently in some solar parks. Although overall damage has been at acceptable levels, overall.

Rananjay Singh, Marketing Head at Gensol, which has been involved with projects over 10 GW in India, says that “At the time of evolution of industry, Stakeholders/Developers were focused on components and critical Spares, which have a direct contribution to Power Generation. Though the entire market was evolving it would be unfair to say that stakeholders did anything wrong deliberately, or compromised on quality of structure. As the industry has evolved, participants have realized that with a life of 25 years, structures have to withstand and support, otherwise even if good quality modules and inverters are sourced, they will not be able to generate power. Structures today have evolved to provide options like fixed tilt structures, seasonal tilt structures, and finally, tracker mounted structures, which track the movement of the sun everyday. These structures all come with their own strength, weight and design requirements today, be it for ground mounted, or rooftop situations. Design in particular is a sore point with many contractors and manufacturers. Rananjay adds that common structure related issues like rusting, corrosion, bending of structure due to wind speed, pile cap, weak foundation, O&M and especially challenges in extreme weather conditions can all be planned for at the design stage itself.

Prakhar Agrawal, Director, R R Ispat, (Hira Group), another manufacturer and EPC contractor adds that “ while planning for a PV plant, though issues of structural stability and safety get adequate attention but adaptive engineering new engineering structures and ideas are not taken considered. Today there are wind speed and galvanising norms such as 150 km /hr and minimum 85 microns for design too. But contactors should be given more freedom and adaptive design for better quality. Galvanising structure are the most important thing, as it increases life and quality overall. New light weight materials that cut cost are yet to stand the test of time.”

Rattan from Tata Bluescope echoes this sentiment, saying that “there should be no compromise on design and quality of the mounting structures chosen. Solar module mounting structures contribute to only 7% of the entire Solar Plant cost. However if chosen the wrong structure, it may have an adverse impact on the overall installation.”

The Standards and Innovations

Like every part of the solar supply chain, structure manufacturers too have faced cost pressures. That has led to some good, and sometimes more questionable decisions. However, the relative indifference to tracking structural evolution means that that the specifications or standards, demanded of modules, cells or inverters, are not as strict for structures, leaving a lot of scope for mistakes. Most of the standards being prescribed today, when they are actually prescribed, are from specifications in 2011-12. Since them many changes have happened globally, as well as domestically. An interesting example is galvalume, introduced in India by JSW steel, which is a special type of galvanisation on steel that extends both the life of the product and its look. Cost issues have prevented the firm from making as much progress as it would like to with the product. It’s a challenge that Tata Blue Scope faces with its own offerings too, though the firm does claim to have crossed 1.2 GW in installations using its products.

Gensols’s Rananjay points out that while MNRE does not specify standards here, “there are standards available for each and every material and their withholding capacity . But some of biggest PSU players like NTPC etc have their own standards laid down for all items such as module mounting structure, civil work etc, which helps”.

Hira Group’s Prakhar adds that the experience in the past 12 months has only gone to show that extreme weather events are going to be more frequent now, which makes a strong case for fresh standards and norms, especially for large scale PV plants.

Ajay Rattan, lists down the basic standards that are expected today, once factors like wind speed have been taken into account. “It is encouraged and to be sure that the design has been certified by a recognized Lab/ Institution . Suitable fastening arrangement such as grouting and calming should be provided to secure the installation against the specific wind speed. The steel mounting structures shall be as per latest IS 513:2003 and galvanization of the mounting structures shall be in compliance of latest IS 277:2018 and Zinc and Aluminum Alloy coating as per IS 15961:2012. Structural material shall be corrosion resistant and electrolytically compatible with the materials used in the module frame, its fasteners, nuts and bolts etc. The fasteners used should be made up of stainless steel. The structures shall be designed to allow easy replacement of any module output from the SPV panels. Regarding civil structures the developer needs to take care of the load bearing capacity of the roof and arrange suitable structures based on the quality of roof. The total load of the structure (when installed with PV modules) on the terrace should be less than 60 kg/m2. The minimum clearance of the structure from the roof level should be 300 mm”.

Raydean’s Samarth adds that “For many years the industry at large had only indicative specifications, leaving it to the bidders to ensure safety and quality of MMS. Can you imagine that in case of say modules or inverters? But now recently MNRE has laid down strict specifications and standards for solar module mounting structures used for Solar water pumping systems. These standards are laid down for prestigious KUSUM scheme, in which farmers are about to get 30 Lakhs Solar water pumps through various subsidies. But we as a manufacturer feel that still lot needs to be done . There have to be first BIS or equivalent standards in place and then there has to be minimum qualifying criteria for manufacturing of MMS, with lot of impetus on testing and checking by the governing bodies.“

On the issue of innovation, the focus has obviously been on reducing weight and increasing strength at the same time, preferably at a lower cost. While not every innovation has achieved all three objectives, but the broad consensus in India remains with galvanized steel use. Samarth goes on to warn that “a design based only on experience and trial and error would never withstand the tough weather conditions etc. Only a qualified design done keeping all site conditions in mind while following basic minimum standards (such as BIS) ensures full reliability, but sadly that is not the case many times. GI based structures are still very relevant in many projects, ‘one size fits all’ philosophy doesn’t work here”.

Samarth, along with some other EPC and manufacturer’s we spoke to, regularly cited the experience with the recent cyclones. “A common mistake is non-adherence to specified material grades etc. by the manufacturers. As observed over the years one major mistake which installers do is to ignore the importance of foundation of the structures, they again and again lean towards saving cost in civil works i.e foundations , be it in a utility scale project, Solar rooftops or Solar water pumping systems. According to reports coming from various sites after two consecutive high wind cyclones in different parts of the country, the structures along with the system have been uprooted along with their foundations, showing the low standards of Civil work done. Footing or foundation of any MMS is an integral part of the design , if you pay attention to what is seen above the ground and de-grade what is below the ground , there is no point in putting a well designed / manufactured structure.

Pawan Pandey, Founder and CEO at Tanash Energy, who has been involved with projects worth over 700 MW has this to say. “ Lack of engineering (designs are copy paste), extreme focus on weight reduction of steel in projects due to cost cutting caused by low tariffs , leads to shortcuts like low thickness material usage, little or no proper code(standard) defines for engineering, no proper analysis on load test and wind test. When the total cost of steel use in a project is 5 to 6% which is quite reasonable, we shouldn’t look to cut costs here. Pawan makes a strong case for higher government involvement, be it in laying down minimum standards, ensuring better supply of raw materials as well as funding to manufacturers to ensure the market is well supplied with quality components”. Pointing out how as ‘recently’ as 2016, the 650 MW Adani project In Tamil Nadu sourced a major part of its MMS requirements from China, he makes a strong case for ensuring more players on the manufacturing side, especially with their own steel making facilities.

The Future

As a product that offers one of the highest warranties among assets being built today, Solar power installations have big promises to keep. Module Mounting Structures are literally the edifice on which these promises are built, as weak stuctures, poor alignment, or too little ground clearance can all lead to serious damage to the structures. Government agencies need to draw up a modern, more specific set of standards and norms, going beyond prescribing galavanised steel of a certain standard or even advising not to go with aluminium frames in coastal areas, for instance. A recent SECI tender document that we evaluated specifies a module efficiency of 80 percent at the end of 25 years, and 90 percent at the end of 10. While asking for a 5 year warranty on the structure.

As solar technologies are evolving, with larger modules, higher energy density, so too have structures, be it lighter, or stronger. In rooftop solar, solar tiles have already made their appearance, BIPV (Building Integrated PV systems), where the solar roof replaces the roof altogether , and many other options like floating solar have already started making inroads in India . There is a real case to establish standards before a few failures draw the need to do it. As some of our participants in this story have also indicated, extreme weather events in the past two years have also indicated that mistakes have been made, though thankfully not leading to damage and wastage at a scale that would be considered disastrous yet.

Importantly, the tools to design and plan batter are far better today. As Gensol’s Rananjay says, “Earlier data was available for shorter tenure. Now a days a lot of technical and site-based data is available, hence design and implementation can be certainly improved more easily”.

Both utility, and rooftop solar have their own unique demands, and specific requirements, that need to be met, to ensure a clear, uninterrupted run of productivity and growth. After all, as Prakhar Agrawal said to us ” A tree’s beauty lies in its branches, but its strength lies in its roots”. Solar structures are the roots on which everything hinges. It’s time to take them far more seriously .