China’s new bubble-lubrication system could save large ships 1.1 tons of fuel daily
Chinese engineers have introduced a second-generation bubble-lubrication system designed to enhance the energy efficiency of large commercial ships. This innovative system reportedly reduces net energy consumption by about 5%, which could translate to a savings of approximately 1.1 tons of fuel per day for a vessel consuming around 22 US tons daily.
The Shanghai Merchant Ship Design and Research Institute developed this technology, which was tested on a newly built 50,000-ton product and chemical tanker. The system works by injecting compressed air beneath the hull, creating a layer of bubbles that diminishes friction with the surrounding water.
The operational trial lasted five months and demonstrated that the bubble-lubrication system could help shipping operators lower fuel consumption without necessitating changes to their vessels’ primary propulsion systems. The institute estimates that a 5% reduction in energy consumption could save roughly one metric ton of fuel daily on a tanker of this size.
Mechanism of Bubble Lubrication
The bubble-lubrication technology is based on a principle that reduces contact between an object and the water around it. This principle is similar to that utilized by supercavitating torpedoes, which travel within a gas-filled cavity to minimize water contact and achieve high underwater speeds.
In the case of commercial shipping, the system continuously injects compressed air beneath the ship’s hull, forming a layer of microbubbles that create a gas-liquid mixture. This mixture alters the flow of water near the vessel’s surface, effectively reducing frictional resistance and allowing the ship to maintain speed with less propulsion power.
The reported 5% energy saving takes into account the additional energy required to operate the air compressors. However, the institute has not provided a detailed breakdown of the trial results.
Advancements in the Second-Generation System
This second-generation bubble-lubrication system builds on an earlier version tested on an 1,800-TEU feeder container ship. Development of the upgraded system began in May 2022, focusing on improving the earlier design’s reliance on manual operation.
The new version features an enhanced air-supply structure aimed at reducing compressor power consumption, along with automated controls and monitoring capabilities. Its intelligent control system adjusts the air volume supplied beneath the hull based on the vessel’s speed and draught.
A digital operational support system monitors and analyzes energy efficiency in real time, making the technology easier to operate under varying sailing conditions while minimizing the energy needed to generate the bubbles.
The bubble-lubrication system is designed to be compatible with various commercial vessel types and propulsion technologies, including those powered by LNG, electricity, methanol, and ammonia. While the new developments offer a solid foundation for deployment on commercial vessels, broader adoption will depend on performance across different hull designs, operating conditions, and routes.
Source: Interesting Engineering