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MOL's sails rise to the challenge

MOL copyJapanese operator Mitsui OSK Lines (MOL) has had wind propulsion in its sights for a long time. In 2009, it joined forces with the University of Tokyo in forging the Wind Challenger Plan to explore the energy saving potential of sails on its vessels. 


However, with the global economy still mired in recession after the events triggered by the collapse of Lehman Brothers the year before, MOL decided instead to prioritise the more expedient option of slow steaming and the plan was

placed on the back burner.


Then, in 2013, it received a fresh injection of support when it was chosen to receive a ‘Subsidy for Next generation marine environment-related technology research’ by Japan’s Ministry of Land, Infrastructure, Transport and Tourism. Further impetus came with the 2015 Paris Agreement, when MOL began considering the potential for GHG reduction by using wind for the generation of renewable hydrogen. 


Two years later, in collaboration with shipyard partner Oshima Shipbuilding, the Wind Challenger Plan had evolved into the Wind Challenger Project.


Bulk carrier

The project’s primary aim is to develop an extraordinarily large rigid wing sail (height: 60m, breadth: 15m, thickness: 3m) for a bulk carrier, located at the forecastle of the ship, which can be rotated according to the wind direction or retracted telescopically to a reef sail. 


After being granted Approval in Principle (AiP) by ClassNK in October 2019, the concept moved to the detailed design stage and in late 2020 came the announcement that MOL had reached a deal with Tohoku Electric Power Co for an 87,396dwt coal carrier. 


Based on the Wind Challenger concept, the Oshima-built vessel is scheduled for delivery during the third or fourth quarter of 2022. According to the project’s research, the initial ship will save an estimated average of 4-7% in fuel. MOL tells The Naval Architect that this single sail configuration should have little effect upon the vessel’s hydrodynamics.


However, it is planned that subsequent ships could be fitted with as many as four Wind Challenger sails, for a combined average fuel saving of 14-28%, which will require more careful stability considerations, particularly the righting moment. MOL and Oshima plan to run further verifications of the system’s GHG reduction effects ahead of the 2022 delivery date, which will factor in the motion characteristics, main engine and the customer’s operational patterns. 


The remaining power will come from what MOL calls “conventional fuel” although does not specify whether this would be HFO with scrubbers or Low-Sulphur Fuel Oil.


The sail itself consists of a rigid wing sail of closed skin with a crescent wing section. A telescopically retractable steel spar and fibre reinforced polymer (FRP) blade will be lifted by a hydraulic cylinder inside the spar, with the spar’s rotation enabled by a mechanical gear on the upper deck. 


Concept illustrations suggest the sail will be reduced to around one quarter of the surface area when in reef sail mode, which would be deployed during strong winds or when the vessel is in port. The sail area and direction will be automatically controlled.


Zero emission concept

But while the Wind Challenger’s ambitions might appear comparatively modest that’s really only half the picture. In parallel, MOL has been developing a zero-emission sailing ship concept, a project known as Wind Hunter, which will take surplus wind energy acquired by the sails and convert it into hydrogen.


A Wind Hunter ship would have two methods for propulsive operation. In the event of strong winds, excessive energy, i.e. greater than that required for the ship’s cruising speed, would generate electricity driving an electrolysis device and thereby hydrogen gas. 


This gas would in turn be attached to toluene held in storage to create methylcyclohexane (MCH). Despite being far less regularly mentioned in discussions of Power-to-X options, MCH offers superior energy density to liquid hydrogen without the toxicity of ammonia while being capable of storage as a liquid in normal conditions.

The MCH would then be stored in a dedicated tank. Should there only be weak winds then the energy deficit required to achieve cruising speed would be supplied by a fuel cell via electric motor-driven propellers. This fuel cell would be powered by hydrogen gas derived from the MCH.


Presently, Wind Hunter is in Phase 1 of its development; a test project in which a water electrolyser, hydrogen storage alloy, fuel cell, generator turbine and electric propeller have been installed on a 40ft yacht for a series of exercises. 


This stage, which is expected to be completed at the end of this year, will be followed up to 2024 by a program of larger demonstrations, as well as the preparation of an optimised weather routing system. 


MOL will also seek to collaborate with various authorities and discuss with candidate shipyards. It is projected that the first Wind Hunter vessel would enter service in 2030.