The growth of solar power in India has led to a drop in solar energy prices. Thus, it is incumbent upon solar plant operators to reduce their cost of operations. One of the ways to effectively bring down operational costs is automation of electrical balance of plant systems. Automation in solar technology can be classified into five broad categories – supervisory control and data acquisition (SCADA)/ distributed control system (DCS), operations and maintenance (O&M) automation, automation in plant installation, automation in balance of systems (BoS) and automated communication systems.
SCADA/DCS solutions
SCADA is a control system architecture, which uses computers, networked data communications and graphical user interfaces for high-level process supervisory management. In solar plants, SCADA includes monitoring of power generation, energy exported to the grid, the environment ambient temperature, irradiation and equipment health. SCADA is one of the first steps in solar plant automation and provides a vast scope for plant optimisation through data analytics, IoT and feedback mechanisms.
DCS is similar to SCADA in terms of functions, but is more useful in the context of a utility grade solar plant, where the control room is not remote. It uses multiple servers, creating a decentralised system of process monitoring and data acquisition. It provides a higher degree of redundancy compared to SCADA, and is more advanced. In addition to performing all functions under SCADA, DCS can go a step further and control the processes, which can lead to better plant performance. Both SCADA and DCS communicate on a dedicated intranet, a very expensive option, or the internet, which is cheaper and prevalent. This makes them vulnerable to cyberattacks though cybersecurity options can be incorporated in these systems.
The world’s largest solar power plant, the Adani solar plant in Kamuthi, Tamil Nadu, uses ABB’s SCADA solution. This solution connects panels, inverters, transformers, switchgear, substations and the grid, with meteorological stations, to provide a complete view of the performance of the entire plant. The SCADA solution also provides a unique integrated alarm system that ensures quick and speedy identification of plant issues. This helps ensure timely diagnostics and optimum power generation at all times.
There are several global companies providing SCADA/DCS solutions for solar plants, including ABB, Rockwell Automation and Emerson Process. Many Indian companies including Larsen & Toubro (L&T) and Ilogicon are also offering SCADA solutions. The presence of multiple SCADA/ DCS solution providers indicates that the market is quite mature and is bound to grow further given India’s appetite for solar power plants over the next few years.
O&M automation
Solar plants require regular scheduled maintenance, which includes site inspection, detailed visual inspection of components, manufacturer-specific inverter inspection, tracker inspection and data acquisition system inspection. This helps take immediate action in case of an emergency. Apart from this, they require regular cleaning as the film of dust accumulated on the face of photovoltaic (PV) panels. Many of these tasks can be automated through various systems, thus reducing the failure rate, downtime and cost of operations.
One of the most popular technologies used for this purpose is remote monitoring. This includes monitoring of a PV plant from a remote location in real time and ensuring an appropriate/quick response in case of any untoward incident. Remote monitoring also extends to monitoring underperforming components, automatic ticketing systems, detection of soiling, total and partial shading of strings, and aging. The main players in this market are ABB, Tata Power and Rockwell Automation. Alion energy provides robotic PV cleaning solutions, another example of automation in the solar plant’s O&M. These solutions are yet to gain commercial success due to their high costs, especially in a price sensitive market like India.
Automation in plant installation
This is a fairly new concept introduced by Alion Energy. The company has developed a solar installation solution, which automates the installation of PV cells in utility grade solar projects. In the process of installation, metal posts, racks and cable trenches found in conventional plants are replaced with extruded concrete rails. Then solar panels are installed by a robotic vehicle, which increases the speed of installation. This installation also facilitates automated cleaning by robots.
Automation in BoS
BoS refers to the supporting equipment and auxiliary components used in a plant. It includes energy storage systems, which go a long way in improving the plant reliability, and handling the variability and uncertainty in solar power generation. Therefore, the automation of storage systems is important for smooth plant performance. This includes automated disconnects to protect the operators and assets and aid in fire suppression. Major players in the storage system automation space are AES Corporation, Grenzebach, Schiller Automation and L&T.
Automated communication system
In transmission systems, the main transmission lines are largely equipped with fibre optic cables and integrated into the earth (optical ground wire cables), and the substations are accessible through broadband communication systems. The two communication technologies that cater to application-specific needs are synchronous digital hierarchy and multiprotocol label switching-transport profile. At the remote ends of the power transmission system, where the installation of fibre optic cables or wireless solutions is not economical, substations are connected through digital high voltage power line carrier systems.
Meanwhile, the proliferation of distributed energy resources is impairing the power quality of the distribution network. To quickly respond in critical situations, system operators need to integrate the decentralised wind and solar generation with the energy management system, and thus into the communication network of the power utilities. As the local environment of these systems varies widely, it is crucial that the right mix of communication technologies is deployed, tailored as per the utility’s needs and the availability of the necessary infrastructure and resources such as fibre optic cables, frequency spectrum for wireless technologies, and quality and length of the power cables for broadband power line carriers. The isolated decentralised renewable energy projects also require an advanced communication system, wherein intelligent devices record energy supply and consumption data in real time and adjust the grid voltage automatically. One such solution is the advanced metering system, which can help remotely communicate with energy meters without the need for manual intervention. The data collected through the automatic meter reading system is transmitted via the general packet radio service modem using the transmission control protocol or internet protocol and inserted into a structured query language server database at the data centre.
Issues and challenges
While solar power automation systems have huge benefits, they also face a set of issues and challenges. Automation in plant installation is not cost effective in India, and thus its growth in the country has been restricted so far. Further, solar plants with storage systems have not grown at the same pace as distributed solar installations due to the sheer volume and cost involved, thereby resulting in low market penetration. Moreover, automated cleaning of solar panels has not picked up pace in the country. Despite these challenges, SCADA/DCS solutions and remote monitoring are being widely adopted.
The way forward
Automation technologies such as SCADA/DCS solutions and remote monitoring have multiple applications in solar power plants.
An emerging trend is the use of drones, mainly in cleaning and visual inspection of PV panels. Aerial Power has launched an automated drone that can clean solar panels without using water. Through this solution, the company claims to save up to 60 per cent in maintenance cost in arid regions. Another company, SenseFly, has developed a drone that can visually inspect hotspots and determine if cleaning is required or not. The Australian Renewable Energy Agency has collaborated with Australian National University to develop a cost-effective robotic inspection system using drones. Thus, the use of drones may increase in the near future owing to the reduction in the cost of drone technology and increased standardisation in solar plants.
Going forward, automation technologies are expected witness a significant growth in adoption, given the increasing solar capacity in the country. The growth of solar storage systems will also drive BoS automation. However, automation in PV plant installation and automated cleaning of panels may not pick up pace in India in the near future.