PSI - Issue 60

Ram Niwas Singh et al. / Procedia Structural Integrity 60 (2024) 411–417 RNSingh/ Structural Integrity Procedia 00 (2023) 000 – 000

412

2

1. Introduction to Hydrogen economy Over the last few centuries rapid industrialization has been the main driver for the growth. Setting up of steel, cement, fertilizer and other industries required intense source of energy, which was readily provided by fossil fuels. As industrialization became more wide spread with more countries opting for it to improve the living standards of their population consumption of fossil fuels increased many times over a very short period (Statista 2024). This meant that the fossil fuel resources were getting diminished at a much faster rates than they were replenished by nature. Fossil fuel propelled economy resulted in sharp increase in CO 2 concentration in atmosphere (Climate 2023) and mean temperature of the earth (Earth) over the last few centuries coinciding with pace of industrialization. Thus, we are staring a situation of rapid depletion of fossil fuels at one hand and irreparable damage to the environment due to continued reliance on it as a source of energy and input to various industrial processes. The effect of global warming is a reality and to arrest its effects on climate change, United Nations has identified 17 Sustainable Development Goals (SDGS). Goal 7 aims to provide clean and affordable energy to all (SDGS). The approach to reverse the effect of global warming on climate change is to reduce CO 2 emission by finding suitable replacement for fossil fuels as a source of heat and reactants in various industries. Accordingly, global targets are being set to reduce CO 2 emission and each country is exploring clean energy options to achieve net zero emission. Hence, renewable energy sources like solar and wind are clean energy options and had seen rapid deployment over the last decade (IEA 2022). The variation in day night and seasonal availability of the renewables is proposed to be tackled by complimenting it with energy storage devices and developing transnational grids. Hydrogen can be used a fuel for generating heat, electricity and for storing energy (Abe 2019, Sergey 2021, Edwards 2007). One of the options is to use a combination of Hydrogen, renewables and energy storage systems to meet the energy requirement optimally without causing any further damage to the environment. Four pillars of hydrogen economy are hydrogen generation, storage, transportation and consumption (Abe 2019, Filippov and Yaroslavtsev 2021, Edwards 2007). Due to its smaller size hydrogen can permeate through materials used to store it resulting in its loss. The understanding of hydrogen permeation through materials requires knowledge of hydrogen solubility and its diffusivity. Hydrogen is known to embrittle material under certain conditions (Lee 2016, Marchi and Somerday 2012). Overall life cycle cost of technologies used in hydrogen economy will depend on the performance of the material of construction used. This article summarizes various methods of hydrogen generation, storage and transportation and forms used to bring out the environment in which the materials in hydrogen economy will be exposed to, types of hydrogen / hydride embrittlement and its mechanism and recommendation for materials scientists and engineers to pursue research and development work in this rapidly evolving area. 2. Hydrogen generation, storage & transportation and use Hydrogen can be generated by partial oxidation of coal and oil or steam methane reforming with/without carbon capture, water electrolysis with electricity provided by nuclear, solar, wind, hydro and wave, water splitting using heat from nuclear and solar sources and Biomass fermentation, fragmentation and pyrolysis (Ajanovic 2022, Holladay 2009). The steam methane reforming reaction given in Eqn. 1 is performed between 300 to 1100 °C and under pressure up to 100 bar (higher pressure improves yield but at lower pressure rate of transformation is higher especially at lower temperatures) (Ajanovic 2022, Holladay 2009, Okere and Sheng 2023). CH 4 +2H 2 O=CO 2 +4H 2  H o 298 =165 kJ /mol (1) The thermo-chemical method of producing hydrogen uses a reactor to perform multi-stage reactions with no net consumption of chemicals. The input is water and high temperature heat and output is hydrogen, oxygen and low temperature heat (Ajanovic 2022, Holladay 2009). One example of the thermo-chemical method of hydrogen production is Sulphur iodine process involving Bunsen Reaction occurring at 120°C, HI decomposition occurring at 450°C and sulfuric acid decomposition occurring at 850°C as shown in Eqns. 2-4, respectively (Ajanovic 2022, Holladay 2009).