With the increased interest in hydrogenas afuel, the lifecycle environmental performance of its production is gaining importance. This work presents a review oflifecycle assessments(LCA) of hydrogen electrolysis using power fromphotovoltaic(PV)conversions.The paperdiscusses the strengths and weaknesses of 13 LCAstudies andidentifies the drivers of the environmental impact.Differences in system boundary assumptions, system sizes, methods, and functional units make it challenging to establish a direct comparison of these findings.In order to simplify this process,aharmonization protocol is introducedand 13selectedLCAstudies onforsolar-poweredhydrogen productionareharmonizedfollowing the consistent frameworkthisprotocol. Theresultsfor the harmonized Global Warming Potential (GWP) range between 0,7 and 7,5 kgCO2-eq/kg H2, shown in the figure below. The differences between original and harmonized GWP in the specific cases can reach2,25 kgCO2-eq/kg H2.Due to the lack of transparencyof most LCAs included in this review, full identification of the source of discrepancy (methodsapplied, assumedproduction conditionsor other) is not possible.Yet even thehighest GWPofthis study isover 4 times lower than GWP of the grid-based electrolysis in Germany (UTCE).Based on our findings so far, the lowest GWPof hydrogenproduction is found for cases with very low emission of PV electricitysupplied to the electrolyser.Theoutcomeof this study can serve as a practicalguideline forbetter understanding of the life cycle impacts on GWPof hydrogenby makingcurrent LCAs more comprehensible.For further studieson hydrogen productionsystems,it is highly recommended to (i)dividethewhole system intowell-defined subsystems using compression as the final stage of the LCA and/or (ii) provide energy inputs/GWPresultsfor the different stagesdefined.
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