The performance of a solar project depends not only on its equipment, but also on its manufacturing process. As new and emerging technologies are applied in manufacturing, the equipment quality improves and so does overall project performance. Various national and international standards are in place to maintain the quality of solar power equipment and projects. With the implementation of these standards and the adoption of cutting-edge technologies to construct a solar plant, the output from the plant can be optimised.
The high direct current (DC) load in Indian solar power projects impacts the health of equipment such as inverters. Thus, solid state inverters are installed at these plants. These can sustain for a longer period of time while improving the quality of generation. A key emerging trend in the inverter space is the growing presence of string inverters. Earlier, they were only used in distributed rooftop solar power generation systems, but now they are becoming popular in the ground-mounted segment as well, with 30-35 per cent of ground-mounted projects now using string inverters.
In addition, several innovative technologies are being deployed in order to effectively monitor solar plants. A key monitoring technique that is gaining traction is I-V curve diagnostics, which tracks real-time plant performance. I-V curve diagnostics can carry out online analysis on entire strings with advanced diagnosis algorithms. It also helps scan and identify the strings with low performance or faults. This assists in achieving proactive maintenance, improving operations and maintenance efficiency and reducing operating costs. Further, I-V curve diagnostics uses maximum power point tracking (MPPT) to sustain power generation for a long period.
For monitoring inverters, either power line communication or wireless communication technology can be used. Typically, sub-gigahertz communication is used to monitor a large number of inverters in a plant, as it allows meters to transmit data to distant hubs without using a lot of power. Further, less cabling in plants results in fewer cable-related faults.
Another key factor governing solar plant performance is the quality of solar modules being used. Continuous technical innovation in solar modules has significantly improved the performance of solar plants in recent years. There are various types of solar modules – multi crystalline, monocrystalline and mono-PERC. Of these technologies, multi crystalline solar modules remain the most popular choice in India due to lower cost although monocrystalline is catching up with a reducing price gap. Mono-PERC is also increasingly gaining prominence. In addition, there are bifacial modules and heterojunction technology though their deployment is limited in the Indian context. Mono-PERC is emerging as a better alternative since it gives more output per square metre. Overall, the weight associated with each watt of generation is reducing as the thickness of wafers is reducing. While lower thickness of wafers and modules would warrant an equipment upgrade, it will also increase the chances of damage. Further, micro-cracks in panels is a persistent issue, which adds to the damage.
Half-cut cells are another type of solar cells that are slowly gaining traction. These cells provide several benefits over traditional solar cells. Most importantly, these cells offer improved performance production numbers. Besides, half-cut cells are more durable than traditional cells since they are smaller in size and more resistant to cracking. Full cells and cut cells are other technology innovations. Cut cells have lower resistive losses, higher output and greater shading tolerance as compared to conventional cells.
The domestic content requirement (DCR) mandate is a part of many government tenders. This is expected to boost domestic manufacturing in India. While module manufacturing standards have been put in place by the government, their implementation needs to be improved with close monitoring. Also, safety and design standards have been established for module testing, but there are no official testing standards for cells in place. The specifications for manufacturing of solar cells depend on the company and the criteria agreed upon by their manufacturers. In India, there are more than 150 certified module manufacturers with a production capacity of over 10 GW. While there are standards in place for materials used by these manufacturers, there needs to be better monitoring to make sure that those materials are being actually used in solar plants.
In the context of solar inverters, there are many standards that have been prescribed by the Ministry of New and Renewable Energy. These include standards related to interconnectivity, ingress protection rating of inverters and efficiency of MPPT. However, there is a lack of testing infrastructure for inverters in the Indian solar segment. The industry has come up with only two tests so far, for anti-islanding and safety, which are mandatory for all solar inverter manufacturers.
There is also the issue of making sure that these tests are being properly carried out by manufacturers. The standards of the Bureau of Indian Standards (BIS) are very similar to the International Electrotechnical Commission standards. However, there is a need for tests specific to Indian conditions to ensure better monitoring and improved performance over a period of time. When all manufacturers adhere to the BIS testing standards, there will be uniformity in surveillance. Even though the industry is currently struggling due to lack of testing infrastructure, the situation is expected to improve in the near future.
When it comes to equipment manufacturing, countries with lower-cost products along with economies of scale have a competitive edge in the industry. Due to their expansive supply chain, these countries are able to manufacture cost-effective products. The DCR component in Indian tenders is expected to give domestic manufacturers a greater role in the solar industry, which will further drive investment. The non-utilisation of existing production capacity is a key challenge faced by the domestic industry. Greater investment in the segment will help in the expansion and proper utilisation of the existing production capacity. Another key challenge faced by local manufacturers is that large developers usually opt for Tier-rated products. However, it is difficult for small manufacturers to cope with various types of costs such as the ones associated with warranty insurance and bankability reports in order to receive Tier I rating.
Various implementation challenges also exist at the project site. The actual installation is devoid of a lot of basic requirements such as earthing and laying of communication cable. Surge protection devices are also mostly absent. Guidelines given by manufacturers are often not followed during implementation due to the associated costs. There is an urgent need for knowledge sharing, information exchange and training to overcome these challenges.
In conclusion, while rapid progress is being witnessed in the solar power segment, there are still many challenges when it comes to implementation, system monitoring and standard compliance. Going forward, manufacturers, project developers and engineering, procurement and construction companies need to work together to ensure the optimal performance of solar plants and build quality assets that perform well for at least 25 years.
Based on a panel discussion between Kostubh Mehta, Senior Manager, Solar Inverters, Delta Electronics; and Bhupendra Rawat, Head, Business Development, RenewSys India (Enpee Group) at a Renewable Watch conference on “Solar Plant Performance”