ClassNK accelerates support for wind-assisted propulsion systems

Urgent and collaborative action is needed if shipping is to come close to achieving the International Maritime Organization’s 2023 revised strategy for reducing greenhouse gas (GHG) emissions. The goal of achieving net-zero GHG emissions by or around 2050, while ambitious, aligns with the netzero targets expressed by countries worldwide, making it inevitable in a sense.

The maritime industry is advancing the optimization of ship operations, the use of low-carbon fuels, and the development of innovative technologies. Among these efforts, the adoption of wind-assisted propulsion systems (WAPS) as a clean technology that emits no GHG has significantly increased in development and implementation.

ClassNK published the first edition of G uidelines for Wind-Assisted Propulsion Systems for Ships in 2019 as a standard for WAPS and ships equipped with the systems, and issued an approval in principle (AiP), based on the guidelines, for the basic design of a hard sail system, which converts wind energy to propulsive force with a telescopic hard sail, and is a fundamental technology of the ‘Wind Challenger’ project that Mitsui O.S.K. Lines, Ltd. and Oshima Shipbuilding Co., Ltd. collaborated. Finally, 1st ‘Wind Challenger’ installed bulk carrier, SHOFU MARU was delivered and registered to ClassNK in October 2022.

ClassNK has continued its efforts to support the development and adoption of WAPS worldwide. To date, five AiP for WAPS have been issued, and the number of involved ongoing installation projects reaches nearly 20, and bulk carriers account for 80% of those.

Additionally, given the increasing opportunities to be involved in actual projects in recent years, ClassNK has incorporated feedback from experienced drawing reviews, surveys, and recent trends, resulting in an update to Edition 2.0 in 2023. The principal safety philosophy of the guidelines is based on functional requirements and risk assessment. Functional requirements include safety and reliability of the systems, safety and reliability for operation, resistance to failure, protection of personnel and environment, interference with ship function, and assessment of compatibility. These guidelines, following the General section, outline requirements for WAPS in Part A, for base ships in Part B, and for surveys in Part C. In addition, considering the identification and mitigation of potential risks arising from the installation of new and diverse WAPS, conducting a risk assessment has been included as one of the requirements.

As for the specific requirements for the system itself in Part A, one of the examples is loads. Four types of anticipated loads have been identified, aerodynamic loads, loads due to ship motion loads, green sea loads, and other loads. On the other hand, there should be three expected load cases: inservice, stand-by, and abnormal conditions. For each combination of these three load cases against each type of load, criteria corresponding to potential scenarios are provided. Other requirements include structural design, including yield strength, buckling strength, and fatigue strength evaluations for the structural components of WAPS, and driving and control systems, which specify the requirements for electrical, hydraulic, and control systems for operating processes such as rotation, expansion or contraction, inclination, motion, and storage.

ClassNK published ‘Guidelines for Wind-Assisted Propulsion Systems for Ships’ as a standard for WAPS and ships equipped with the systems.

With regard to the requirements for base ships in Part B, it is essential to pay attention to the following factors. The ship’s hull should be designed with consideration for the installation of WAPS and its supporting structures. For assessing the hull girder strength, the loading manual, and the loading computer, appropriate consideration must be given to the changes in the lightweight and position of the center of gravity resulting from the installation of WAPS. In addition, equipment numbers, electrical equipment, deck equipment, gross tonnage, and fire safety, as well as the effect on ship motion and blind sectors due to WAPS should be taken into account.

Here are some actual tips for WAPS installation based on ClassNK’s experience from being engaged in various projects. In terms of the arrangement, firstly, it is essential to comply with the provisions of the class rules for navigation bridge visibility in consideration of the blind spots caused by the WAPS. Navigation lights should satisfy the provisions of COLREG, on top of consideration of the shielding caused by WAPS. Depending on the case, these items must be confirmed to the flag administration. Regarding interference with cargo handling equipment or helicopter deck, confirmation for the operation at each port of call is recommended. In retrofitting, the installation is likely to bring about changes in the lightweight, longitudinal and vertical centre of gravity. In such cases, an inclining test and update of related documents are required. Besides, it is necessary to verify the risks to personnel, environment, and the structural strength or integrity of the ship that arise from the installation of the WAPS, both for the system and base ship. Ideally, a risk assessment should be carried out with the participation of stakeholders such as the WAPS manufacturer, shipowner, management company, and ship designer, once the specifications of WAPS and the specific ship for installation have been determined. The risk assessment results, which are supposed to be precautions and additional safety measures against the identified hazards, should be appropriately reflected in the designs or related manuals.

For the widespread use of WAPS as a one of the key technologies in the pursuit of achieving net-zero GHG in shipping. ClassNK strives to continue the support of their smooth implementation by establishing appropriate standards and providing reliable drawing review and survey services in line with them.