YANMAR Technical Review

Abstract

Amid a rapid upsurge in global efforts to reduce GHG emissions, hydrogen is increasingly being recognized for its potential as a clean energy source able to replace fossil fuels.
Yanmar Power Technology Co., Ltd. is working to become a global leader in the green powertrain technology business by 2050, including through the development of powertrain technologies that use hydrogen as a fuel.
This article describes the development of a maritime hydrogen fuel cell system, its use in a hydrogen-powered test boat, and the world’s first 70 MPa high-pressure hydrogen refueling of the boat.

1.Introduction

Amid a rapid upsurge in global efforts to reduce greenhouse gas (GHG) emissions, hydrogen is increasingly being recognized for its potential as a clean energy source able to replace fossil fuels. In the maritime sector, the International Maritime Organization (IMO) adopted a GHG strategy in 2018 that sets a target of reducing total annual GHG emissions from international shipping by at least 50% (compared to 2008) by 2050 as part of a wider goal of phasing out emissions as soon as possible in this century⁽¹⁾. Moreover, recent times have seen moves toward bringing forward the timeframe for achieving these goals, and in Europe and America there has been an acceleration of efforts to reduce the emission of nitrogen oxides (NO_X), including in cities, environmentally protected areas, and large ports^{(2) (3) (4)}.
It is against this background that work on the maritime use of hydrogen fuel cells has picked up pace, especially in ferries or in tugs and other vessels used in port operations. This includes a number of projects in Japan and elsewhere seeking to develop fuel cell vessels with the aim of having them enter service in the first half of this decade^{(5) (6) (7) (8)}.

2.Potential Use of Hydrogen as Fuel

Inspired by its vision of becoming a global leader in green powertrain technologies by 2050, Yanmar Power Technology has been developing technologies for using hydrogen as a fuel (see Fig. 1).

As part of this development work on marine electrification, Yanmar hopes to start by equipping small vessels with hydrogen fuel cells in the comparatively near future (see Fig. 2).

3.Progress to Date on Maritime Hydrogen Fuel Cell Systems

Through its participation in research commissioned by Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and in projects funded by the Ministry of the Environment, Yanmar has been engaged in the development of technology for maritime hydrogen fuel cell systems, including the field testing of a test boat and work on how to supply vessels with hydrogen (see Fig. 3). In FY2020, this included the development of a system based on the fuel cell unit from a Toyota MIRAI car, the construction of a test boat equipped with this system and a high-pressure hydrogen tank, and the commencement of operational trials^(9)(10)(11). In FY2021, the test boat was used to successfully complete the world’s first 70 MPa high-pressure refueling of a moored vessel from a mobile hydrogen supply station⁽¹²⁾. The test boat was also the first such vessel to comply with the MLIT’s safety guidelines for hydrogen fuel cell boats and it has been used to identify and address the specific issues facing such vessels with a view to their practical deployment⁽¹³⁾.

4.Yanmar EX38A Hydrogen Fuel Cell Test Boat

4.1.Vessel Overview

This test boat was built on the base of an EX38A pleasure boat made by Yanmar Marine International Asia (see Fig. 4). To ensure a pleasant vessel interior, all of the main components are housed internally below deck, including the fuel cell system, high-pressure hydrogen tank, lithium-ion battery, and propulsion motor (see Fig. 5).

4.2.Fuel Cell System

The fuel cell system used in the test boat is based on that from a Toyota MIRAI, with modifications to the cooling system and to the equipment configuration and layout to comply with the MLIT safety guidelines for hydrogen fuel cell vessels and to satisfy onboard space constraints (see Fig. 6). One such modification was that the test boat used a seawater heat exchanger for the stack coolant in place of the air-cooled system used in the MIRAI. This allowed for downsizing of the heat exchanger and reduced the rise in stack temperature that occurs when operating at high electrical output for extended periods of time. Meanwhile, integrated monitoring and control of the fuel cell system is performed by a power management controller that also covers the lithium-ion battery and propulsion inverter. While propulsion load can vary suddenly due to driver input or sea conditions, the test boat is able to maintain steady cruising performance by using its lithium-ion battery for power assist and regeneration together with automatic mechanisms such as reducing propulsion power when the motor speed limit is triggered.

4.3.High-Pressure Hydrogen Refueling

Ensuring a long operating time for a fuel cell boat requires either fitting a larger hydrogen fuel tank or filling the tank to a higher pressure. In the test boat, hydrogen storage is provided by four MIRAI tanks installed side-by-side and connected in parallel that can be filled to a high pressure of 70 MPa. To allow for refueling of the fuel cell boat from a commercial mobile hydrogen station at this high pressure, Yanmar developed a hydrogen refueling system relay facility that is suitable for attachment to such stations. The system is made up of several high-pressure refueling hoses connected together as well as the refueling port, high-pressure hydrogen piping, and the emergency release coupling from a fuel cell vehicle (see Fig. 7). Note also that refueling from the mobile hydrogen station was undertaken with special permission obtained following consultation with the Ministry of Economy, Trade and Industry (METI); Osaka Municipal Fire Department; Osaka Ports and Harbors Bureau; MLIT; and Japan Coast Guard.

The test program performed refueling under a variety of different initial tank pressures and using different filling rates, collecting data such as the tank temperature when the target pressure was reached. In one example with an ambient temperature of about 26 °C, the tanks were filled at a rate of 5 MPa/min from an initial tank pressure of approximately 6 MPa, reaching the target pressure of about 74 MPa without exceeding the upper limit for tank temperature of 85 °C (see Fig. 8). Note that, because the capacity of the accumulator in the mobile hydrogen station is inadequate for the size of the test boat tanks, the tanks are first filled to about 50 MPa and then the accumulator is repressurized so that it can continue filling up to the target pressure. Accordingly, although this makes the refueling time seem quite long, the issue should be resolved when stationary hydrogen stations are installed for maritime use.

4.4.Operational Testing

Fig. 9 shows the results of testing conducted to assess the load-tracking performance of the system during operation. With the maximum output limit for the hydrogen fuel cell system set at 184 kW (92 kW × 2), the motor speed was rapidly increased so that the propulsion load reached 110% (275 kW) of the rated motor power. Most of the load is supplied by the output of the fuel cell system while the propulsion load remains below the output limit. Once it exceeds this limit, however, the propulsion load is augmented through power assist from the lithium-ion battery.

5.Conclusions

Yanmar has been developing and testing hydrogen powertrains based on its recognition that hydrogen can serve as a clean energy source able to replace fossil fuels. The work has included the announcement of plans for the early commercialization of a hydrogen fuel cell system in 2023. This article has described the first demonstration boat to officially comply with the "Safety Guidelines for Hydrogen Fuel Cell ships" of the Ministry of Land, Infrastructure, Transport and Tourism, and the world's first filling a boat with 70MPa high pressure hydrogen. This article shows the possibility of the hydrogen fuel cell system as the next generation powertrain for marine business. With a view to leveraging this maritime experience to expand to a wider range of applications for the technology in stationary power generation and other non-maritime applications, Yanmar also recognizes the need to work closely with government and industry partners, including in the area of standards setting in advance of similar such measures in Europe and Americas. In addition to this collaboration with industry and government players, it also hopes that these efforts will advance Yanmar Group’s goal of helping to forge a hydrogen future.

References

• (1)IMO, ACTION TO REDUCE GREENHOUSE GAS EMISSIONS FROM INTERNATIONAL SHIPPING, 2018
• (2)MLIT News Release, Agreement to Strengthen Targets for Reducing Greenhouse Gas (GHG) Emissions from International Shipping
  https://www.mlit.go.jp/report/press/kaiji07_hh_000221.html in Japanese
• (3)City of Amsterdam, Clean Air Action Plan, 2019
• (4)San Pedro Bay Ports, Clean Air Action Plan, 2017
• (5)HySeasIII, https://www.hyseas3.eu/
• (6)FLAGSHIPS, https://flagships.eu/
• (7)Nippon Yusen News Release, Demonstration Project Begins for Commercialization of Vessels Equipped with High-power Fuel Cells
  https://www.nyk.com/news/2020/20200901_01.html in Japanese
• (8)Iwatani Corporation News Release, Commencement of Development of Hydrogen Fuel Cell Ship and Marine Fueling Station
  http://www.iwatani.co.jp/img/jpn/pdf/newsrelease/1402/20210721_news.jp.pdf in Japanese
• (9)Maruyama, et al., Journal of the Japan Institute of Marine Engineering, Vo. 56, No. 5 (2021) p.51-56 in Japanese
• (10)Maruyama, et al., The Journal of Fuel Cell Technology, vol. 21, No. 3 (2022) p.59-64 in Japanese
• (11)Maruyama, et al., Journal of the Hydrogen Energy Systems Society of Japan, vol. 47, No. 2 (2022) p.116-121 in Japanese
• (12)Yanmar Holdings News Release, Yanmar Conducts World’s First 70 MPa High-pressure Ship Refueling with Hydrogen
  https://www.yanmar.com/jp/marinecommercial/news/2021/10/13/98421.html in Japanese
• (13)MLIT News Release, Safety Guidelines for Hydrogen Fuel Cell-powered Boats https://www.mlit.go.jp/maritime/maritime_tk7_000040.html in Japanese

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The original technical report is written in Japanese.

This document was translated by Innovation & Technology Division, Technology Strategy Division.