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(MHIET), part of Mitsubishi Heavy Industries, Ltd. (MHI), has been working on the commercialization of hydrogen combustion engines as a key product to support MHI Group’s MISSION NET ZERO declaration which aims to achieve net zero emissions by 2040.

In 2021, MHIET developed technologies to achieve stable combustion of 100% hydrogen in a single-cylinder engine with a cylinder bore of 170 mm and a piston stroke of 220 mm developed from its GSR engine series through testing at the Japanese National Institute of Advanced Industrial Science and Technology (AIST).

As the next step towards commercialization, the construction of a 6-cylinder hydrogen engine generator set (Note 1) with a power of 500 kW and a hydrogen supply facility to supply hydrogen gas to high pressure delivered on trailers to the reduced pressure generator has been completed. Starting with a trial using Japanese town gas, MHIET aims to confirm stable combustion at 100% load while running on hydrogen this fiscal year.

As part of this series of tests, a thorough evaluation of the new hydrogen engine will take place, including combustion stability, performance and reliability. Taking into account the characteristics of hydrogen (Note 2), an assessment of the safety and other performances required for a generator set will also be carried out. The use of green hydrogen (produced from electricity from renewable energies without CO₂ emissions) is planned for testing.

By basing the entire development process, from design to evaluation, on a single principle, it is possible to quickly implement improvements discovered by evaluation. MHIET aims to accelerate the commercialization process and is targeting fiscal year 2026.

Reciprocating engines have a unique structure allowing them to burn a variety of fuels. Hydrogen engines are considered a promising technology for the energy transition that aims for carbon neutrality. In particular, generators using a hydrogen engine can thus contribute to the carbon neutrality of distributed electricity systems because they emit zero CO.₂ while meeting energy needs. Through demonstration tests, MHIET strives to contribute to achieving a carbon neutral society by expanding the use of hydrogen.

• 1A set of equipment required to generate electricity using a hydrogen engine, including a generator mounted on the engine output shaft, auxiliary equipment (piping systems for fuel gas, lubricating oil, cooling water, intake and exhaust gases, and a generator control panel) required to operate the generator set, as well as the enclosures that house and protect the generator and ancillary equipment.
• 2Compared to natural gas, hydrogen is highly combustible and can ignite with energy equivalent to static electricity and a wider combustion range. Additionally, because the molecules are small and leaky, hydrogen engine generator sets require strict safety measures such as redundant leak prevention, leak detection, safe shutdown of the integrated system, and ventilation to avoid gas accumulation.

Previous versions of MHIET’s hydrogen engine development

1. Stable combustion of 100% hydrogen on a single-cylinder engine

MHIET Conducts Combustion Test for Hydrogen Engine with Pure Hydrogen – Joint Project with AIST to Achieve Stable Combustion of 100% Hydrogen Fuel for Carbon-Free Hydrogen Economy

Test of a single-cylinder engine (cylinder bore 170 mm, piston stroke 220 mm) modified from a 4-stroke MHIET gasoline engine from the GSR series offered in 6 to 16 cylinders at the Japanese National Institute of Science and Technology advanced industrial technologies (AIST). As part of a joint research project with AIST, stable combustion of 100% hydrogen fuel was achieved.

2. Functional test of city gas and hydrogen dual fuel on a commercial gas engine for cogeneration system

Successful completion of a test operation of a mixed combustion of city gas and hydrogen in a commercial gas engine for a cogeneration system – Nominal operation at a hydrogen mixed fuel combustion rate of 35%, a first in Japan

Toho Gas and MHIET successfully ran on a 35 volume percent hydrogen fuel blend in a trial, the first in Japan. The test was carried out at the Toho Gas Technical Research Institute in Tokai, Aichi Prefecture, using one of MHIET’s existing gas engines.

3. Enables stable combustion of up to 50 volume % hydrogen for a 5.75 MW gas engine cogeneration system

MHIET achieves stable combustion of up to 50 volume % hydrogen on a single-cylinder test engine

Using a KU series gas engine (3.65~5.75 MW), a proven model in various industries, a single-cylinder engine developed on the basis of a 5.75 MW cogeneration system was tested. With the aim of reducing CO₂ emissions, stable combustion with up to 50 volume % hydrogen admixtures at a power equivalent to its rated power has been verified.