This paper presents basic understanding needed for safely utilizing hydrogen as energy resources. There have occurred a number of disasters caused by accidents in systems using hydrogen. Each of those disasters has contributed to the progress of science and/or technology. The hazards of hydrogen are attributable to its characteristics, and reliable methods for protection against such hazards are indispensable for appropriately making use of hydrogen. The importance for establishing reliable technology on hydrogen utilization is not to neglect but to understand the hazards of hydrogen.

Although hydrogen is expected as clean energy it potentially has an explosion hazardous nature due to a wide range of explosion limit and a small value of minimum ignition energy. In this paper ignition, combustion, explosion and detonation characteristics of hydrogen-air and hydrogen-oxygen mixtures are presented with their data such as ignition temperature, explosion limit, minimum ignition energy, detonation parameters etc.. Based on these data safety evaluation procedures are described from the point of view of prevention, protection and mitigation of accidental explosions.

Liquefied hydrogen is mainly utilized for propellant of the space rocket in Japan. However its mass consumption is expected as a clean energy, a high purity gas and a extremely low temperature refrigerant. In this report industrial production scheme and safety control for the liquefied hydrogen plant are described from the writer’s experience. Improvement of the safety control will be required more and more on a large quantity of hydrogen handling.

Steam reforming catalysts which is used fuel cells have life. Sulfur is a severe poison for steam reforming catalysts because sulfur compounds are strongly chemisorbed on the metal surface. The impact of sulfur poisoning in determining reformer life is confirmed. Poisoning effects are often correlated with the poison concentration in the feed gases, which is the important parameter in practical operation.

I will report the case study on the hydrogen energy system in a Japanese typical city. This city has 300 thousands populations and its area is 260 km². If the energy requirement that is equivalent to 30 thousands Tera Joule including electric generation, might be converted to the hydrogen energy system, the annual hydrogen supply shall reach to 180 thousands tons and about 15% of the carbon dioxide emission shall be reduced. One of main technical issues is the design of total system constitutions in consideration of the treatment of the boil off-gas evolved in handling of Ii quid hydrogen. For the realization of the hydrogen energy system in the near future, the development of hydrogen utilization will be essential that advantages of the hydrogen will be attained.

In the air, on the sea and on the land, engines for transportation have abruptly changed in the last 50 years since the WWII. For example, concerning the railway locomotive, it changed to the electric train from the steam locomotive in Japan. Also in many other countries, diesel engine locomotives and electric locomotives are expanding their use. The reasons were economy and environment.

During this time,the internal combustion engine technologies develops amazingly include lean bum in spark ignition engine, and high pressure fuel injection, multiple fuel injection and bulk combustion in diesel engine and others.

The candidates of new prime mover for the next century are being researched and proposed by several researchers. Although the ultimate zero emission fuel will be hydrogen, its production without any emission have been tried in Japan. All these activities for future prime movers proceeding with dreams of engineers.