Abstract
Solid-oxide electrolysis technology (SOEC) can efficiently convert electricity from renewable sources into H2 via steam electrolysis, or syngas (a mixture of H2 and CO2) via co-electrolysis of steam and CO2. Co-SOEC provides the advantage of better thermal integration for standalone applications or with other industrial processes. In this paper two promising cases are investigated from the perspective of life-cycle assessment to evaluate the potential of reducing carbon emissions: (1) coupling co-SOEC with a cement plant, and (2) integrating co-SOEC into a biomass gasification plant. Life cycle assessment was performed based on the collection of comprehensive information regarding the electricity sources for different scenarios and a sensitivity analysis was included to verify the consistency of the results. The results show that in both cases the co-electrolysis system can be beneficial in terms of reduction of global warming potential, although it depends heavily on the geographic location and on the share of renewable energy. The highest benefits among the cases reviewed were found in the case of a coal-fed cement plant, where annual CO2 savings reached up to 2.39E + 05 tonnes CO2-eq in France with 23.6% of the electricity provided by photovoltaics (PV). In Germany, on the other hand, both cases first show benefits when the renewable share reaches a very high percentage of the electricity input: 50% provided by PV for the case of the cement plant and 82% for the case of a biomass-gasification unit. Since electricity input is the main impact concerning power-to-gas applications, the carbon content of the electricity grid mix is very important. As grid mixes become ‘cleaner’ in the future with more renewable share in the electricity generation in every country, the investigated applications are expected to provide even higher benefits.
Highlights
In a world more and more concerned with the issue of global warming and environmental pollution and with the increasing use of renewable, fluctuating sources for electricity production, highly efficient pathways are needed to help balance the production/consumption mismatches and, in particular, to store excess electricity as hydrogen or hydrocarbons, for example, for seasonal storage
In the case of Sweden with 27% of the electricity input coming from wind power, the co-Solid-oxide electrolysis technology (SOEC) process provides an impressive benefit on the global warming potential (GWP) impact (55% lower), saving 2.02E + 04 tonnes CO2-eq every year
The co-SOEC process would provide a very noticeable benefit on GWP in France where 16% of the electricity input comes from PV—the GWP in this case is 47% lower giving an annual savings of 2.28E + 04 tonnes CO2-eq As the PV share increases to 50%, this annual savings increases to 2.40E + 04 tonnes CO2-eq and to 75%, 2.48E + 04 tonnes CO2-eq are saved annually
Summary
In a world more and more concerned with the issue of global warming and environmental pollution and with the increasing use of renewable, fluctuating sources for electricity production, highly efficient pathways are needed to help balance the production/consumption mismatches and, in particular, to store excess electricity as hydrogen or hydrocarbons, for example, for seasonal storage. High temperature electrolysis (or solid oxide electrolysis/SOEC) provides a solution to produce methane through the highly efficient production of syngas from steam and CO2. Operation at high current densities increases the production rate of hydrogen and CO, and thereby improves the overall economy. Another advantageous feature of co-SOEC is the option for efficient integration with the catalytic conversion of the formed synthesis gas to methane. For this integration, it is desired that the operation of the SOEC is at temperatures below ca. Since four geographic locations were studied, the GaBi processes were listed reflecting these four countries. The nickel and aluminum oxide inputs have been considered to represent the impact of the methanation catalyst replacement, Ni–Al2O3
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