Abstract Body

At the heart of global efforts to achieve carbon neutrality lies the imperative to harness clean energy sources like hydrogen. However, the widespread adoption of hydrogen as a fuel has been constrained by the cost challenges associated with its production and transport.

To reduce transportation costs, it is necessary to transport hydrogen in liquid, which has a small volume (1/800 of that of a gas). Therefore, pumps capable of handling liquid hydrogen are needed at all points in the hydrogen supply chain.

However, liquid hydrogen is difficult to handle because of its extremely low temperature of 20 K under atmospheric pressure and its unique properties of low density, low viscosity, and low latent heat of evaporation. When considering pumps driven by motor that use liquid hydrogen as the working fluid, a particular problem is the low latent heat of evaporation. In other words, the low latent heat of evaporation means that the heat generated inside the motor can easily gasify liquid hydrogen. If a large amount of liquid hydrogen gasifies due to heat loss in the motor, transport efficiency will naturally be reduced.

To solve this problem, TORISHIMA PUMP MFG.CO., LTD., in collaboration with Professor Taketsune Nakamura of Kyoto University National University, has developed a centrifugal submerged pump incorporating high-temperature superconductivity.

As shown in Figure 1, this pump is surrounded by a vacuum double-shell insulated vessel and filled with liquid hydrogen. The pump and motor are completely submerged in this vessel. The motor section is kept in a cryogenic environment at all times, allowing the use of high-temperature superconducting motors.

Since the pump is equipped with a high-temperature superconducting motor, gasification of liquid hydrogen due to heat loss in the motor can be minimized. This improves the efficiency of liquid hydrogen transport and contributes to hydrogen cost reduction. This system is very rational in terms of liquid hydrogen transportation.

We have made a prototype pump equivalent in size to that expected in a commercial plant and conducted an operational test using liquid hydrogen at JAXA (Japan Aerospace Exploration Agency)’s Noshiro Rocket Testing Center in March 2024. As a result, a maximum rotational speed of 5,000 min-1, a maximum flow rate of 30.5 m3/hr, and a maximum pressure of 1.6 MPa were achieved, making it the world's largest centrifugal pump for boosting and transporting hydrogen. It is also the first industrial pump equipped with a high-temperature superconducting motor.

This development is a major breakthrough not only in the mass transportation of hydrogen, but also in the industrial application of high-temperature superconductivity.

※This development is supported by a Japanese governmental agency, NEDO (New Energy and Industrial Technology Development Organization) grant "Development of Technologies for Building Competitive Hydrogen Supply Chain".