Testing the Waters with Floating Solar Plants

Article by King Wu, Software R&D Manager Energy Sector, Moxa, Inc.

Over the past few years, countries that lack the land mass required for solar plants have turned their attention to the water-based alternative: floating solar islands. By placing solar panels on floating platforms in the sea, lakes, reservoirs, and rivers, valuable land is freed. In addition, as the cooling properties of water allow the panels to perform well even in high temperature ranges, they are able to function efficiently under duress. Another benefit is that the shade provided by the floating panels reduces evaporation, helping the reservoirs that host them conserve water.

At present, countries including China, Japan, Taiwan, and South Korea have installed floating solar plants with a total capacity of 2,400 MW — enough to power 240,000 households. The winning characteristics of floating solar farms have attracted investments from countries like the Netherlands, France, Singapore, India, Vietnam, Thailand, and Sri Lanka, with an estimated value of US$380 million.

Though floating solar plants are on the rise in the green-energy industry, their greatest strength is also their biggest weakness. The floating solar plants’ susceptibility to natural phenomena such as rainstorms, hurricanes, and extreme heat is hindering their progress. Tidal waves, a common product of hurricanes, often contribute to irreversible damage to the system’s floats, cables, and wires. The prime example is the 2019 typhoon in Japan. High-intensity waves caused the solar panels to slump together causing a fire that destroyed the offshore power plant.

This incident has brought the construction method used in the floating solar plants to the foreground of discussion. Besides unpredictable natural disasters, regular environmental conditions near water bodies, such as humidity, strong winds, and salinity, can reduce the life span of onboard electronic equipment and consequently, the plant. Hence, the durability of the equipment used and the construction methods are two of the main areas of focus when building a floating solar plant.

Another significant challenge is the daily maintenance of plant assets. The offshore floating systems are more difficult to maintain than their onshore counterparts based on accessibility alone. Since the latter can be accessed by motor vehicles whereas the former requires a boat, making daily maintenance a considerable challenge.

As the technology matures, plants are becoming bigger in size, making this already difficult task a near-impossible one, leading to dire consequences. For example, the floating solar plant in Anhui Province, China, utilizes a coal mine pit filled with water to host 160,000 solar panels. Maintenance workers use paddle boats to repair the equipment and clean the pond every day. When a typhoon hits, bringing with it torrential rainfall and tidal waves, workers’ lives are put in harm’s way.

Traditionally, power plants have relied heavily on regular inspection of sites, which involves assigning on-duty employees to perform daily inspections of each and every piece of equipment. As a result, these inspections become fixed expenditures regardless of the equipment condition. Time is often wasted on routine check-ups of functioning devices, and, when something does break down, on traveling between the shore and the deployment site for the correct repair tools. Another common scenario is unexpected power deficiency even on a sunny day.

Since a malfunction, the cause, and the location of the problem cannot be easily identified from the onshore control center, inspectors must check each and every floating module until the issue is found. It is like trying to find a needle in a haystack, time-consuming and tedious. In addition, the limited transport options and other factors such as the climate and the direction of the water stream make inspections strenuous and hazardous, reducing maintenance proficiency.

In recent years, the Internet of Things (IIoT) is being used in floating solar plants to overcome maintenance challenges. As one of the initial providers of IIoT-based solutions, Moxa has first-hand experience with the effective use of IIoT to improve operations and maintenance in green-energy projects.

In the past decade, Moxa has worked with GreenPowerMonitor, a DNV GL company, a world-renowned independent software vendor for over 2,000 solar power plants worldwide. The IIoT connectivity solution is able to create a system that allows owners to monitor the power generation and equipment conditions through a SCADA system in real-time. It can also perform maintenance checks on devices when a malfunction occurs.

The SCADA platform will be configured to automatically send an alarm and generate a maintenance task on the system, which can then be tracked by the owner. Armed with the knowledge of what and where the malfunction is, inspectors can repair the devices in a timely manner by being at the right place with the right tools at the right time. Experience has shown that the efficiency of a power station with a central monitoring and maintenance system can increase by at least 20% compared to others without such a system.

Furthermore, the data collected through IIoT can be used to preemptively determine the potential failure rate of equipment in close proximity to water bodies by comparing its performance under different circumstances. New Machine Learning algorithms can be deployed to enable owners to perform predictive maintenance on their equipment to avoid permanent damage.

For example, when the temperature inside a device rises due to increasing humidity, the life span of the device could be significantly shortened. Information from Machine Learning algorithms can help the owner gain predictive insights into their devices. And, when a set humidity state is about to be reached, a warning can be issued or corresponding measures can be automatically initiated.

IIoT’s predictive abilities can also be applied to green energy forecasts and grid-connected technology to get real-time predictions and effectively control power generation from grid-connected renewable energy sources. To take this leap, first and foremost, we need a stable network for data transportation from remote offshore equipment to the onshore control center.

GPM and Moxa have created a connection backup solution to prevent complete network disconnection in situations like this. This solution allows the data to be transmitted via a backup channel within 20 milliseconds while the network is being restored as opposed to the industry standard of 80 milliseconds, ensuring an uninterrupted flow of information.

With new advancements in solar technology, improved construction methods, and the IIoT, floating solar power plants may finally break free from the restrictions that are preventing them from greater adoption worldwide.

Learn more at www.moxa.com/en/solutions/power.

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