Abstract
Hydrogen energy is a promising source to meet the global energy demand. The adoption of hydrogen energy by society is possible with the installation and operation of reliable hydrogen infrastructures. Hydrogen has some risk factors inherently. The wide flammability range in air, high flame speed, and low minimum ignition energy cause fire and explosion accidents. In addition, hydrogen embrittlement in metals leads to ruptures in equipment and the formation of leakages. Hydrogen refueling stations, commercial hydrogen facilities, nuclear power plants, and laboratories are places that are open to accidents caused by hydrogen equipment failure or wrong human interventions. Determination of standards for safe operation and making quantitative risk analysis assessments help eliminate accidents or mitigate their damaging consequences. This chapter aims to raise awareness about the safety of hydrogen energy by addressing the risks of hydrogen, past accidents, the lessons learned, and the applicable precautions and recommendations against hazards.
TopIntroduction
The orientation to solar, hydro, wind and geothermal renewable energy sources increases with the start of depletion of fossil fuels and rising energy needs. However, they have limited use because of intermittent energy support and there are no liquid or gas fuel forms for transportation. Hydrogen has become attractive to the energy sector in recent years as a resource that provides clean energy production and is an abundant element. Hydrogen (141.9 kJ/g) has almost three times the heating value of natural gas (54 kJ/g), and since it is high flammability in the air, the energy required for the start of combustion in vehicles is lower than other fuels. Hydrogen is nitrogen and sulfur oxides-free, zero-emission fuel for the transportation sector because of the emergence of water as a byproduct of the hydrogen combustion reaction (Okolie et al., 2021). Some features of hydrogen were summarized in Table 1.
Table 1. The properties of hydrogen
| Hydrogen Properties |
| Lower heating value (LHV, MJ/kg) | 120 |
| Higher heating value (HHV, MJ/kg) | 142 |
| Density at 273 K (kg/m3) | 0.09 |
| Boiling point at atmospheric pressure (K) | 20.3 |
| Liquid density (kg/m3) | 70.8 |
| Flammability concentration limits in air (vol. %) | 4-75 |
| Diffusion coefficient in air (cm2/s) | 0.61 |
Reproduced from Rivard et al. (2019) with permission from the MDPI
Key Terms in this Chapter
Hydrogen Embrittlement: It means breaking the strength of the metal as a result of reduced energy required for the formation of cracks via the very small-sized hydrogen atoms that can easily penetrate the metals.
Safety: The whole of the conditions creates confidence to prevent injury, loss of life, or property damage caused by possible accident risks.
Flammability: Flammability is a parameter that indicates the ease of ignition of material and the intensity of heat release after being ignited.
Diffusivity: It is the diffusion rate of a substance, fluid, or heat from the high-density to the low-density region, which varies according to the media.
Minimum Ignition Energy: This term is used for flammable gases and refers to the minimum discharge energy required for gas to ignite.
Hydrogen: Hydrogen is a flammable substance with the smallest atomic number among chemical elements, releasing water when burned with oxygen.
Hydrogen Refueling Station: This infrastructure provides fuel for vehicles that use hydrogen and, in some layouts, also includes hydrogen production units within the same body.
Risk Assessment Analysis: Risk assessment is to identify risk factors and potential hazards in the current operation, take appropriate measures against hazards to eliminate or mitigate the damage that may occur, and prepare action plans.
Transportation: It is the transfer of produced hydrogen to different demand points by pipelines, cryogenic liquid tank trucks, or gaseous tube trailers.
Explosion: It is a devastating event that occurs as a result of rapid expansion in the volume due to the propensity to the powerful release of accumulated energy sourced from high temperatures or high-pressure gas into the environment.
Leakage: It is the amount of liquid or gas that escapes from a pipeline or container through the formation of a rupture, deterioration of mechanical parts, or easy evaporation.
Hydrogen Storage: This process is stockpiling hydrogen for later use by techniques such as compressed gas, cryogenic liquid, or entrapment in certain chemical compounds.