- Successful Development of a Compact and Lightweight Onboard Liquid Hydrogen Supply System -

UIWANG, South Korea – August 25 – The Korea Railroad Research Institute (KRRI) (President: Sagong Myung) has developed an onboard liquid hydrogen supply system (hereinafter “the developed system”), a core technology for hydrogen-powered railway vehicles, as part of efforts to establish a sustainable, eco-friendly railway transportation system.

Liquid hydrogen is produced by cooling gaseous hydrogen to ultra-low temperature of –253℃. To supply it stably to a fuel cell, multi-stage control technologies such as vaporization, pressure regulation, and temperature controlare essential. In the early stages of development, each of these functions was built into a separate module, resulting in bulky systems that were difficult to mount on trains.

The newly developed system incorporates a compact control unit that integrates pressure, flow, and temperature control into a single device. Compared to the previous modular approach, the system reduces volume by 10% and weight by 5%. As a result, it achieves more than double the driving range per refueling compared with existing hydrogen trains.

The system is designed to stably power four 95 kW fuel cells (380 kW total), reaching a level suitable for application in actual railway propulsion systems.

To improve thermal insulation in hydrogen storage tanks, the system employs a Kevlar-based* support structure. This design provides effective insulation under cryogenic conditions while enhancing durability.
* Kevlar: A high-performance synthetic fiber that is five times stronger than steel, lightweight, and highly heat-resistant, widely used across industries.

The hydrogen vaporization unit adopts a dual heat-source system, combining the conventional electric heating method with the use of external ambient heat. This approach improves vaporization efficiency while balancing energy consumption.

Vaporized hydrogen is recirculated through pipelines back into the storage tank, where it passes through a heat exchanger to help vaporize additional liquid hydrogen. During this process, the generated pressure is used to maintain and supply the 17 bar operating pressure required by the fuel cells, forming a Pressure Build-Up (PBU) system.

This design enables stable operation without relying on liquefied hydrogen pumps or compressors, which are not yet commercially available for mobility applications. As such, it represents a key technology for improving the overall efficiency and reliability of the system.

The research was conducted as part of KRRI’s Basic Research Program under the National Research Council of Science & Technology (NST, Chairman: Kim Young-sik) through the project “Development of Compact and Lightweight On-Board Liquid Hydrogen Supply System Technology.”

Unlike gaseous hydrogen, liquid hydrogen can be stored safely at atmospheric pressure and has about 1/800th the volume, making it highly advantageous for railway transport.

KRRI, in collaboration with its joint research partner Parity Co., Ltd. (CEO: Kim Sa-soon), has developed the on-board liquid hydrogen supply system and is currently conducting certification testing.

The developed system can be applied immediately to trains and is expected to accelerate the conversion of aging diesel trains to liquid hydrogen propulsion.

※ Relevant Research Project
Project Title: Development of Compact and Lightweight Onboard Liquid Hydrogen Supply System
Research Period: January 2025 – December 2026
Project Leader: Dr. Kim Gil-dong, Principal Researcher at KRRI

Dr. Kim Gil-dong, Principal Researcher at KRRI, said “We plan to verify the performance of this core technology through various tests by 2026 and apply the propulsion system to existing hydrogen trams for demonstration research.”

President Sagong Myung of KRRI said, “KRRI will lead in developing technologies that build a sustainable railway environment. We will continue to prove the feasibility of hydrogen-based urban transport and establish the technological foundation to lead the era of new energy transition.”





Press Contacts

Sunghyun Baek, Ph.D.
Korea Railroad Research Institute
baeksh@krri.re.kr
+82 31 460 5162