A Review on Synthesis of Methane as a Pathway for Renewable Energy Storage With a Focus on Solid Oxide Electrolytic Cell-Based Processes

Abstract

Environmental issues related to global warming are constantly pushing the fossil fuelbased energy sector toward an efficient and economically viable utilization of renewable energy. However, challenges related to renewable energy call for alternative routes of its conversion to fuels and chemicals by an emerging Power-to-X approach. Methane is one such high-valued fuel that can be produced through renewables-powered electrolytic routes. Such routes employ alkaline electrolyzers, proton exchange membrane electrolyzers, and solid oxide electrolyzers, commonly known as solid oxide electrolysis cells (SOECs). SOECs have the potential to utilize the waste heat generated from exothermic methanation reactions to reduce the expensive electrical energy input required for electrolysis. A further advantage of an SOEC lies in its capacity to coelectrolyze both steam and carbon dioxide as opposed to only water, and this inherent capability of an SOEC can be harnessed for in situ synthesis of methane within a single reactor. However, the concept of in situ methanation in SOECs is still at a nascent stage and requires significant advancements in SOEC materials, particularly in developing a cathode electrocatalyst that demonstrates activity toward both steam electrolysis and methanation reactions. Equally important is the appropriate reactor design along with optimization of cell operating conditions (temperature, pressure, and applied potential). This review elucidates those developments along with research and

Remote Renewable Hubs for Carbon-Neutral Synthetic Fuel Production

“…Hence, the production of carbon-neutral synthetic fuels and feedstocks from renewable electricity has been the focus of a growing body of literature. For example, the synthesis of carbon-neutral hydrogen (Borgschulte, 2016), methane (Biswas et al, 2020), methanol (Centi et al, 2020), and ammonia (Ghavam et al, 2021) have all been considered. A number of demonstration projects have been carried out as well (Wulf et al, 2020).…”

In situ synthesis of methane using Ag–GDC composite electrodes in a tubular solid oxide electrolytic cell: new insight into the role of oxide ion removal

“…For example, an energy efficiency (dened by the energy content of methane produced to the energy input) of $95% is theoretically well predicted at the cell level. 1 This is primarily due to lower overpotential losses when using SOECs. In addition, SOECs can be used for in situ methane synthesis by electrolysing CO 2 in the presence of H 2 (from renewable sources) with the right combination of the electrocatalyst and process conditions.…”

Techno-Economic Assessment of Thermally Integrated Co-Electrolysis and Methanation for Industrial Closed Carbon Cycles

“…The appropriate heat demand can be supplied from external sources or, in the case of power-to-methane, from the exothermal methanation process that can be operated at temperatures of 250-700 • C (Götz et al, 2016;Rönsch et al, 2016). Additionally, SOEL technology provides the ability to perform co-electrolysis of H 2 O and CO 2 , thus allowing for the generation of a suitable syngas composition for the downstream methanation process (Banerjee et al, 2018;Biswas et al, 2020). These synergies allow to significantly increase the overall system efficiencies by a high thermal integration of the electrolysis and the methanation process (see Figure 1).…”