Scatter Plot from Scientific Research

Multiple previous studies are plotted here.4,5,6,10,13,14,15,28,29Blanco et al. and Béres et al. contain different scenarios with different CO2sequestration potentials, which are plotted here with separate line segments. For each study, the plotted CO2sequestration level represents either the actual amount of sequestration found in the study (for studies a–e and h) or the upper limit on sequestration (for studies f, g, and i) in case the actual amount of sequestration is not given. In studies c, d, and e, actual CO2sequestration coincides with the upper limit imposed. For each given level of CO2sequestration, we plot only the range from the least to the greatest amount of green hydrogen production found in the study results; the number of different scenarios/results varies from a few to hundreds between the different studies. Results from the present study are plotted with green dots, shaded by (near-) optimality. For near-optimal results, both maximizations and minimizations of green hydrogen are included. With a total of 216 scenarios and three slack levels (with a minimization and maximization for each slack level), this makes for216·(1+2·3)=1,512data points, though some points are missing due to failed optimizations. For easier interpretation, the convex hulls of the four sets of points with different slack levels (optimal, 2%, 5%, and 10%) are also drawn. Only results for 2050 are included. All previous studies work with a net-zero emissions constraint given the 2050 time horizon, except Blanco et al. who assume a 95% reduction in emissions instead. We limit the inclusion of studies to only those modeling the whole European energy system, including electricity, heating, transportation, and industry sectors; whether (net) emissions from agriculture and land use, land-use change, and forestry (LULUCF) are included, however, varies between studies. Moreover, while all studies cover at least the EU, some also cover additional European countries (such as the present study). See alsoTable S1for a table with the same data on previous studies, including additional brief comments on the methodologies used. Though we report quantities of hydrogen in millions of tons (Mt), this can be converted to energy content using the lower heating value of 33.3 kW/kgH2, such that1Mt=33.3TWhfor hydrogen and1,000TWh≈30Mt.

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