Kawasaki Heavy Industries – pushing ship design boundaries with a novel large LH2 carrier

The project was colossal in every way: not only for the size of the large liquefied hydrogen (LH2) carrier concept, but also for the technical achievement that creating this completely new vessel design represented for Kawasaki Heavy Industries’ teams of engineers and naval architects. Here’s how, equipped with NAPA tools, they overcame design challenges to make this groundbreaking concept a reality. 

With shipyards in the Japanese towns of Kobe and Sakaide, the shipbuilding division of Kawasaki Heavy Industries (KHI) specializes in high-value vessels, including LPG and LNG carriers, VLCCs and submarines. The company made headlines for building the world’s first liquefied hydrogen carrier, Suiso Frontier, which entered service in 2019.  

LH2 Carrier designed by Kawasaki Heavy Industries

With demand for hydrogen (and therefore for ships to transport it) poised to grow in a decarbonized economy, KHI set out to develop a large-scale LH2 carrier concept capable of carrying 160,000 m3 of the molecule in a liquefied state. With a length of 346 meters, the vessel is equipped with four cargo tanks, and propelled by hydrogen-burning boilers and a steam turbine.  

The challenges of novel ship design 

Designing such an innovative vessel from scratch wasn’t without its challenges. “When developing a completely new concept, there is no reference ship that can be used as a baseline,” says Ryuta Yoshida, who is in charge of the structural design of merchant ship hulls and cargo tanks at Kawasaki Heavy Industries. 

As a result, engineers and naval architects cannot rely on previous, more traditional ship designs to estimate the vessel’s hull steel weight and lightweight distribution and determine its principal dimensions. Moreover, the design featured numerous new technologies, including LH2 cargo tanks and insulation systems, which needed to be developed with careful consideration of their implications for the hull structure and the layout of outfitting.  

3D ship model of Kawasaki Heavy Industries designed by NAPA Designer

This required KHI’s teams to lead comprehensive structural studies and to manage multiple rounds of iterations throughout the design process. To overcome the challenges of novel concept design, they needed the right tools to make design processes as streamlined and efficient as possible. This is where NAPA tools came in.  

By using NAPA Steel, we were able to quickly and accurately estimate the vessel’s weight, easily create a Finite Elements (FE model), and quickly modify the model and study the structure in response to changes in the outfitting specifications, which was extremely helpful – Ryuta Yoshida, Naval Architect at Kawasaki Heavy Industries  

Rethinking the ship design process 

To fully unleash innovation, KHI’s teams needed to overcome the limitations of the conventional ship design process. Traditionally, outfitting and detailed structural design take place in the latter design phases, after the ship’s general structure has been established. But for entirely novel concepts such as the large LH2 carrier, these steps needed to happen much earlier in the process. This is essential to avoid the risk of major issues cropping up in the detailed design phases, which would require significant re-work of the entire structure.  

Ideally, developing hull forms, cargo tanks and outfitting systems all need to begin from the initial design stages. This is why Kawasaki Heavy Industry developed its “upfront design work” concept, enabled by NAPA tools. 

Detail design part of 3D model designed by NAPA Designer

In practice, KHI teams used NAPA to create a 3D model that served from the first development phases through to the initial and detailed design stages. Taking advantage of the ability to edit the model quickly, they could study hull structure design and outfitting arrangements simultaneously, with the flexibility to repeat these assessments multiple times to test different variations efficiently.  

This enabled them to study the integration of completely new technologies and systems on board with high accuracy from the early design stages and update the basic structure accordingly. NAPA Steel was instrumental to this, allowing engineers to modify the 3D model quickly and easily. “We couldn’t perform this task without NAPA,” Mr. Yoshida emphasizes. 

Arrangement of longitudinal stiffeners designed in NAPA Designer

This “upfront design” approach also enabled insights from the detailed design phases to be included in the assessment of different design variations from the initial stages. This includes considerations of construction methods and processes, as well as the arrangement of longitudinal stiffeners.

As a result, we were able to identify invisible challenges at early stages and prevent design re-work later in the process. – Ryuta Yoshida, Naval Architect at Kawasaki Heavy Industries

Building on a success story

Improving the design process was a success: KHI’s large LH2 carrier concept obtained approval in principle (AiP) from ClassNK in April 2022, providing third-party validation of the initial design and its safety. “Without NAPA, it would have been difficult to implement a design process that required repeated structural studies from an early stage,” Mr. Yoshida added.  

The NAPA tools also provided a shared database that allowed teams at Sakaide and Kobe to work concurrently, thereby boosting efficiency. 

Going forward, Kawasaki intends to expand the use of NAPA tools beyond hull structure design, and harness their potential to support the development of cargo tanks. This would involve parametric modeling for tanks, FE model output and weight estimations at an early stage. The company is also planning to use NAPA Viewer to facilitate internal model reviews.  

By doing so, Kawasaki is building the foundations for business success, as the energy transition will increase demand for highly innovative ships. “Due to the transition towards a decarbonized society, the development of ships powered by new fuels and of new fuel carriers is already actively underway. Creating these new ships involves juggling a large number of research and design elements, but 3D model-based design using NAPA will help manage that complexity,” Mr. Yoshida concluded.