FROM NATURAL GAS TO GREEN HYDROGEN

Abstract

Since hydrogen usually exists on Earth as part of a compound, it has to be synthesized in specific processes in order to be used as a product or energy source. This can be achieved by different technical methods, and various primary energy sources, – both fossil and renewable fuels, in solid, liquid or gaseous form, – can be used in these technical production processes. Hydrogen has only a very low volumetric energy density, which means that it has to be compressed for storage and transportation purposes. The most important commercial storage method, – especially for end users, – is the storage of hydrogen as a compressed gas. A higher storage density can be achieved by hydrogen liquefaction. Novel materials-based storage media (metal hydrides, liquids or sorbents) are still at the research and development stage. The storage of hydrogen (for example, to compression or liquefaction) requires energy; work is, in present, on more efficient storage methods. Unlike electricity, hydrogen can be successfully stored in large amounts for extended periods of time. For example, in long-term underground storage facilities hydrogen can play an important role as a buffer store for electricity from surplus provided by renewable energies. At present, pure hydrogen is generally transported by lorry in pressurize gas containers, and in some cases also in cryogenic liquid tanks. Moreover, local/regional hydrogen pipeline networks are available in some locations. Another solution for storage and transportation are Liquid Organic Hydrogen Carriers (LOHC) that can use long pipe networks and ships. In the near future, the natural gas supply infrastructure or oil (transportation pipelines and underground storage facilities) could also be used, in specific conditions, for the storage and transportation of pure or blended hydrogen with methane. This could be essential for transition because most important primary energy source for hydrogen production currently is natural gas, at 71%, followed by oil, coal and electricity (as a secondary energy resource). Steam reforming (from natural gas) is the most commonly used method for hydrogen production. In this new light, the article explores the trend and prospects for hydrogen, presented in the literature, as a source of energy competing with gas and oil resources in the global energy system of the future.