Green Hydrogen: An Introduction

In the present energy scenario with growing environmental and climate change concerns and increasing focus on energy security, global interest in low carbon hydrogen is increasing. In an energy system focussing on accelerated deployment of renewable energy systems, the role of hydrogen for balancing it is being increasingly recognised. Hydrogen for industrial use is traditionally produced from fossil fuels such as natural gas and coal, but cleaner hydrogen can be produced from renewable energy sources. Hydrogen is a colourless gas, but many colours have been associated with it depending on the energy sources used for its production and CO2 emissions associated with it. The definition of green hydrogen is evolving, but hydrogen produced using renewable energy sources is generally considered as green. Presently, most of the hydrogen produced globally is grey as it is derived from fossil fuels without carbon capture. Hydrogen as a versatile energy vector finds several applications in industry, buildings, power, and transport sectors. Moreover, it can also be transformed into derivatives like ammonia, methanol etc. which are used as feedstocks for producing several industrial products and can also be used as green fuels, if produced from green hydrogen. Besides, substituting grey hydrogen used by the industry, green hydrogen can decarbonise many hard to abate industrial processes. However, there are several challenges associated with economically producing green hydrogen and its large-scale utilisation. This chapter discusses the above aspects of hydrogen energy in general and green hydrogen in particular in detail.