Abstract
Hydrogen is a promising energy carrier in the clean energy systems currently being developed. However, its effectiveness in mitigating greenhouse gas (GHG) emissions requires conducting a lifecycle analysis of the process by which hydrogen is produced and supplied. This study focuses on the hydrogen for the transport sector, in particular renewable hydrogen that is produced from wind- or solar PV-powered electrolysis. A life cycle inventory analysis is conducted to evaluate the Well-to-Tank (WtT) GHG emissions from various renewable hydrogen supply chains. The stages of the supply chains include hydrogen being produced overseas, converted into a transportable hydrogen carrier (liquid hydrogen or methylcyclohexane), imported to Japan by sea, distributed to hydrogen filling stations, restored from the hydrogen carrier to hydrogen and filled into fuel cell vehicles. For comparison, an analysis is also carried out with hydrogen produced by steam reforming of natural gas. Foreground data related to the hydrogen supply chains are collected by literature surveys and the Japanese life cycle inventory database is used as the background data. The analysis results indicate that some of renewable hydrogen supply chains using liquid hydrogen exhibited significantly lower WtT GHG emissions than those of a supply chain of hydrogen produced by reforming of natural gas. A significant piece of the work is to consider the impacts of variations in the energy and material inputs by performing a probabilistic uncertainty analysis. This suggests that the production of renewable hydrogen, its liquefaction, the dehydrogenation of methylcyclohexane and the compression of hydrogen at the filling station are the GHG-intensive stages in the target supply chains.
Highlights
Hydrogen has been attracting attention as a clean energy source in part because of its flexibility as an energy carrier; it can be produced from a variety of industrial processes and consumed by a variety of end-users
SustainRabeiglitayr2d0i1n7g, 9t,h11e0N1 G reforming hydrogen supply chain, hydrogen production via steam refo1r1moifn2g6 of natural gas (NG) was the most greenhouse gas (GHG)-intensive process which account for 60% of the total GHG emissions
To better understand the potential role of hydrogen energy in decreasing GHG emissions in Japan, a WtT life cycle inventory (LCI) analysis was carried out for renewable hydrogen supply chains originating in Australia and Norway
Summary
Hydrogen has been attracting attention as a clean energy source in part because of its flexibility as an energy carrier; it can be produced from a variety of industrial processes and consumed by a variety of end-users. Hydrogen can be produced from hydrocarbon feedstocks via chemical processes (e.g., steam reforming of natural gas (NG) and coal gasification), and by using electricity to power the electroylysis of water [1,2]. Micro fuel cell combined heat and power (FC-CHP) systems could decrease household energy use owing to their high gross energy efficiencies (the sum of power generation efficiency and heat production efficiency) [14]. Megawatt-class hydrogen energy systems have been installed around the world in data centers, hotels and many other commercial facilities to combine distributed renewable energy resources—such as solar photovoltaics (PV) and wind turbines—and measures to ensure a stable energy supply—such as battery storage, and water electrolyzers, storage tanks and fuel cells for hydrogen production, storage and use, respectively [15,16,17,18]. In terms of power generation, a commercially operated 12 MW hydrogen turbine began operating in Italy in 2009 [19,20]
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