WE-NET Home Page/Summary of Annual Reports 1998

3.5 Safety measures and assessment

3.5.1 R&D Goals

The research and development of the WE-NET has been launched in FY 1993. The WE-NET project will construct a clean energy network on a worldwide scale, where hydrogen will be produced by employing various kinds of renewable energy such as hydropower, solar in areas blessed with these energies.

On the total WE-NET system, we must establish a unified safety scheme. On each WE-NET systems, we must establish and improve specific accident analysis codes and specify safety features or functions to keep safety.

Therefore, in the first phase, we plan to implement research regarding the following items and descriptions:

(1) Identification of Guideline for System Safety Design

We will conduct a survey on safety ideas, safety goals, safety design guidelines and accidents, as well as on laws and regulations, specifications and standards which are applicable to hydrogen energy systems.

For each component of the WE-NET systems, we will identify postulated accident scenarios, and estimate their effects on humans and structures with the objective of specifying the safety requirements required for each component of the system. Referring to various information regarding safety obtained during the period of phase I, we will make the safety design guidelines for the WE-NET system.

(2) Analyses on Accident and Safety

We will correct data to be used for analyses on various accidents and safety and propriety simulation models for application to typical cases will be developed. For these models, we will develop two simulation models that predict the dispersion characteristics following the spillage of liquefied hydrogen and predict the explosion and ignition of the hydrogen -air mixture. Furthermore, we study integration of these two models to estimate the total effect of liquid hydrogen leakage consistently.

Considering the above-mentioned goals of phase I and development achievements until FY 1997, the following items and descriptions was identified as the agenda for FY 1998 (the last year of phase I). Investigation of safety technologies for dispersed use of hydrogen started from FY 1998.

(1) Identification of Guideline for System Safety Design

We will survey liquefied natural gas facilities and hydrogen facilities at high temperature and high pressure whose safety measures may be similar to those for liquefied hydrogen facilities. For these facilities, we will gather and classify safety information including safety ideas, goals and design guideline. Studying various information regarding safety obtained during the period of phase I, we will make the safety design guidelines for the WE-NET system.

(2) Analyses on Accident and Safety

We have developed simulation models that predicts the dispersion characteristics following the leakage of liquefied hydrogen and estimates the effect of the explosion and ignition of the hydrogen-air mixture. We will study to improve these models and study to integrate these two models to estimate the total effect of liquid hydrogen leakage.

On the other hand, we will make experimental plan for the characteristics of leakage, distillation, dispersion of liquefied hydrogen and hydrogen explosion scheduled in phase II. These experiments will be done to verify the simulation models.

(3) Safety Technologies for Dispersed Use of Hydrogen.

We will correct and study the safety technologies for dispersed use of hydrogen (including small scale hydrogen production, transportation and storage).

3.5.2 Results in FY 1998

(1) Identification of Guideline for System Safety Design

We conducted a survey on manuals, laws, regulation, specifications and standards which are applicable to domestic and foreign hydrogen energy systems. With various information regarding safety obtained during the period of phase I, we made the safety design guidelines for the WE-NET system. For each component of the WE-NET systems, we surveyed postulated accident scenarios.

(2) Analyses on Accident and Safety

We improved the simulation model that predict the dispersion characteristics following the spillage of liquefied hydrogen by taking in turbulence model and also improved the simulation model that predict the effect of the explosion and ignition of the hydrogen-air mixture by expanding predicting area. Furthermore we studied to integrate these two models to estimate the total effect of liquid hydrogen spillage. Consequently, we got two calculation results for two supposing phenomena and it was shown that the modes can use consistently. We made precise experimental plan for the characteristics of leakage, distillation, diffusion of liquefied hydrogen and hydrogen explosion scheduled in phase II.

(3) Investigation of Safety Technologies for Dispersed Use of Hydrogen.

We studied the technical standards applied to LPG or LNG filling station for automobile as a research on safety technologies for dispersed use of hydrogen.

3.5.3 Future Plan

We made the safety design guidelines for the WE-NET system in phase I that shows various items that are needed to check at the construction of each WE-NET systems. But we must show the concrete conditions such as setting safety equipment or distance of unit to unit and so on. Therefore we will study to make the safety design standards for the WE-NET system.

We have studied the simulation models that predict the dispersion characteristics following the spillage of liquefied hydrogen only theoretically.

So, we will make experiments regarding these phenomena to get more realistic information. And we will verify the simulation model with the results of the experiments and improve the accuracy of the model.

On the other hand, for hydrogen explosion we have studied detonation as that gives the maximum damage. But it is well known that the possibility of detonation of hydrogen occur in an open space is very low and it is thought that the possibility of deflagration of hydrogen occur in an open space is rather high. Therefore, we will study deflagration and develop the simulation model of that. And we will also make experiments regarding these phenomena to improve this model.

If the detonation should happen, the damage from it is predicted very serious. So, we research the transition condition of deflagration to detonation. With these studies, we will establish the evaluation method of safety to the supposing phenomena. The results of the evaluation of safety by the established method will be reflected to the safety design guidelines and/or the safety design standards for the WE-NET systems.

Regarding to the safety technologies for dispersed use of hydrogen, we will watch the states or situations change of each systems and will propose the adequate guidelines.