August 2021

54 n RENEWABLE ENERGY July/August 2021 www.drivesncontrols.com Floating solar plants get a helping hand from the IIoT I n recent years, countries that lack the land area to accommodate solar plants have been turning their attention to floating solar islands. Placing solar panels on islands frees up valuable land. Also, the cooling properties of water allow the panels to operate efficiently even in high temperatures. And if they are moored in reservoirs, the shade provided by the floating panels reduces evaporation, helping to conserve water. Countries including China, Japan, Taiwan, and South Korea have installed floating solar plants with a total capacity of more than 2,400MW, and an estimated value of $380m. But the greatest strength of floating solar plants is also their biggest weakness. They are susceptible to damage by rainstorms, hurricanes and extreme heat. Tidal waves, a common product of hurricanes, can destroy the panels and their cabling. During a typhoon in Japan in 2019, powerful waves caused the solar panels at an offshore power plant to collide, resulting in a fire that destroyed the plant. As well as natural disasters, environmental conditions such as humidity, strong winds, and salinity, can reduce the lifespan of electronic equipment on board the solar plants. Another significant challenge is maintenance. Offshore systems are more difficult to maintain than onshore plants. For example, in Anhui Province, China, a former opencast coal mine, now filled with water, is the location for a floating solar plant consisting of 160,000 panels. Every day, maintenance workers have to paddle out to clean and repair the equipment. These daily inspections are fixed costs regardless of the condition of the plant. Time is wasted on routine check-ups of functioning devices and, when something does fail, it takes time to reach it from the shore and make repairs. Problems can occur even when the weather is good. The cause and location of the issue cannot be easily identified from an onshore control centre, and inspectors need to check every module until the cause is identified. This is time-consuming and tedious, and the inspections can be strenuous and hazardous. Now, the Industrial Internet of Things (IIoT) is being used to overcome some of the maintenance challenges of floating solar plants. A company called GreenPowerMonitor, with headquarters in Spain, specialises in this technology, providing monitoring and control software for more than 4,000 solar power plants in 72 countries (half of them floating), with a combined generating capacity of 32GW. GreenPowerMonitor’s technology allows plant operators to monitor equipment conditions and the power being generated in real time via a Scada system, which can also perform maintenance checks when malfunctions occur. The platform can be configured to send alarms automatically and to generate maintenance tasks, which can then be tracked by the operator. Armed with knowledge of a malfunction and its location, maintenance personnel can perform repairs rapidly, being at the right place at the right time with the right tools. Central monitoring and maintenance systems of this type have been shown to increase plant efficiencies by at least 20%. The data collected via the IIoT can be used to predict potential failures of equipment by comparing its performance under different conditions. Machine- learning algorithms can be used to performpredictive maintenance. For example, if the temperature inside a solar panel increases, the lifespan of the panel can be shortened. Information from machine-learning algorithms can provide predictive insights and if a critical humidity level is about to be reached, can issue a warning or initiate remedial measures automatically. The IIoT can also be used to generate real-time predictions of energy demand and to control the power generated by grid- connected renewable sources. GreenPowerMonitor has been working with the communications specialist Moxa to develop a stable network for transporting data from offshore equipment to onshore control rooms. They have created a backup technology that avoids network disconnections and allows data to be transmitted within 20ms if the main network goes down – compared to an industry standard of around 80ms – ensuring an uninterrupted flow of data. With advances in solar technology, improved construction methods and the IIoT, floating solar power plants can now be deployed even more widely. n Generating power from solar plants located on floating islands has many attractions. But these offshore plants can be difficult and costly to maintain. A remote monitoring technology based on the IIoT is claimed to boost the efficiency of these plants by more than 20%. Floating solar power plants have many attractions – as well as drawbacks, some of which can be overcome using the IIoT, Scada and predictive maintenance technologies.