The maritime industry is on a voyage towards a more sustainable future, with the Energy Efficiency Existing Ship Index (EEXI) as its guiding star. In this journey, hull air lubrication systems have emerged as a significant tool for achieving EEXI compliance and enhancing energy efficiency. In this article, we will explore the importance of hull air lubrication, the challenges it presents, the available technology on the market, and how it can help vessels sail smoothly within the bounds of EEXI regulations.
The Power of Hull Air Lubrication
A ship’s hull is the first point of contact with the water, and the resistance it encounters can significantly affect a vessel’s fuel consumption and emissions. Hull air lubrication is a groundbreaking technology designed to reduce this resistance by injecting a layer of air bubbles underneath the ship’s hull. The air bubble distribution across the hull surface reduces the resistance working on the ship’s hull, creating energy-saving effects.
This innovative approach minimizes the friction between the hull and the water, enhancing energy efficiency and aligning with the core objectives of EEXI compliance.
According to some studies, a hull air lubrication system can reduce fuel consumption and associated emissions by up to 10%. Moreover, a hull air lubrication system can also protect the hull from corrosion, fouling, and abrasion, which can extend its service life and reduce maintenance costs.
Challenges on the Horizon
However, applying a hull air lubrication system on a ship is not a simple task. It requires careful consideration of various factors and challenges, such as:
- The air bubble generation: An air blower or a dedicated system is used to generate air bubbles and pass them continuously beneath the ship’s surface. The air bubble generation should be optimized to achieve the desired effect with minimal energy consumption and noise.
- The air bubble outlets: Air bubble outlets are created at different locations along the bottom of the hull, symmetrically on both sides of the ship’s centre line. The air bubble outlets should be designed and positioned to ensure uniform distribution and coverage of air bubbles across the hull surface.
- The air bubble retention: To trap the layer of bubbles beneath the ship’s hull is a challenging task. The sucking effect of propeller on the bubbles and the turbulence caused by waves and currents can reduce the effectiveness of the system. Some solutions such as protruding ridges at the edges of the hull or specially designed sterns can help in trapping the blanket of bubbles.
- The ship type and speed: The hull air lubrication system until now can only be used for certain types of ships having flat bottoms. Ships having V-shaped hulls, such as certain warships or recreational vessels might not be able to reap the benefits of the system. Moreover, the system is more effective for ships operating at low or moderate speeds, as high speeds can increase the drag and reduce the stability of the system.
Technology on the Market
To address these challenges, advanced technologies for hull air lubrication have emerged:
- Microbubble Generation: Innovative microbubble generation systems efficiently inject tiny air bubbles beneath the hull to minimize friction.
- Automation and Control: Advanced control systems ensure the precise regulation of air injection, adapting to various operational conditions.
- Hydrodynamic Analysis: Computational modeling and simulations help engineers optimize the design and performance of the air lubrication system.
- Monitoring Technology: Real-time monitoring and data analytics enable vessel operators to assess the system’s performance and efficiency.
What Marine Engineers Need to Do
Marine engineers are the navigators in the journey towards hull air lubrication for EEXI compliance:
- Hydrodynamic Analysis: Conduct a comprehensive hydrodynamic analysis of the vessel’s operational profile to determine the most suitable air lubrication system design.
- Collaboration with Designers: Work closely with air lubrication system designers and manufacturers to ensure the technology is customized to the vessel’s specific needs.
- Installation Oversight: Oversee the precise installation of the air lubrication system, ensuring seamless integration with the hull.
- Performance Monitoring: Implement a monitoring system to track the system’s performance over time. Regular inspections can help detect any wear or issues that may affect efficiency.
- Environmental Responsibility: Ensure compliance with environmental regulations and monitor the release of air bubbles to minimize potential ecological impact.
- Data-Driven Decisions: Utilize data analysis to validate the improvements brought about by the air lubrication system and make informed decisions for further enhancements.
Therefore, applying a hull air lubrication system on a ship requires a lot of planning, coordination, and supervision from vessel marine engineers. They have to select the right air bubble generation, outlets, retention, and control systems for their ship’s needs and budget. They have to oversee the installation and operation of the system according to the relevant regulations and standards. They have to ensure that the system meets the specifications and requirements for EEXI compliance. And they have to evaluate the performance and benefits of the system after its application.
In conclusion, hull air lubrication is not just a compliance requirement; it’s a testament to the maritime industry’s commitment to sustainability and efficiency. With the right technology, engineering expertise, and diligence, marine engineers can propel vessels into a future where environmental responsibility and operational efficiency coexist harmoniously, all while staying in line with EEXI regulations.
Source and References:
- EEXI | Energy Efficiency Existing Ship Index – DNV
- EEXI and CII – ship carbon intensity and rating system – IMO
- A brief introduction to air lubrication systems (ALS) – TMC
- Air Lubrication System – Wärtsilä
- YouTube video 1: Mitsubishi Heavy Industries
- YouTube video 2: Alfa Laval
