Power-to-methane via co-electrolysis of H2O and CO2: The effects of pressurized operation and internal methanation

Ligang Wang*, Megha Rao, Stefan Diethelm, Tzu-En Lin, Hanfei Zhang, Anke Hagen, François Maréchal, Jan Van herle

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

This paper presents a model-based investigation to handle the fundamental issues for the design of co-electrolysis based power-to-methane at the levels of both the stack and system: the role of CO2 in co-electrolysis, the benefits of employing pressurized stack operation and the conditions of promoting internal methanation. Results show that the electrochemical reaction of co-electrolysis is dominated by H2O splitting while CO2 is converted via reverse water-gas shift reaction. Increasing CO2 feed fraction mainly enlarges the concentration and cathode-activation overpotentials. Internal methanation in the stack can be effectively promoted by pressurized operation under high reactant utilization with low current density and large stack cooling. For the operation of a single stack, methane fraction of dry gas at the cathode outlet can reach as high as 30 vol.% (at 30 bar and high flowrate of sweep gas), which is, unfortunately, not preferred for enhancing system efficiency due to the penalty from the pressurization of sweep gas. The number drops down to 15 vol.% (at 15 bar) to achieve the highest system efficiency (at 0.27 A/cm2). The internal methanation can serve as an effective internal heat source to maintain stack temperature (thus enhancing electrochemistry), particularly at a small current density. This enables the co-electrolysis based power-to-methane to achieve higher efficiency than the steam-electrolysis based (90% vs 86% on higher heating value, or 83% vs 79% on lower heating value without heat and converter losses).
Original languageEnglish
JournalApplied Energy
Volume250
Pages (from-to)1432-1445
ISSN0306-2619
DOIs
Publication statusPublished - 2019

Keywords

  • Energy storage
  • Power-to-methane
  • Solid-oxide eletrolyzer
  • Co-electrolysis
  • CO2 utilization
  • Pressurized operation
  • Internal methanation

Cite this

Wang, Ligang ; Rao, Megha ; Diethelm, Stefan ; Lin, Tzu-En ; Zhang, Hanfei ; Hagen, Anke ; Maréchal, François ; Van herle, Jan. / Power-to-methane via co-electrolysis of H2O and CO2: The effects of pressurized operation and internal methanation. In: Applied Energy. 2019 ; Vol. 250. pp. 1432-1445.
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title = "Power-to-methane via co-electrolysis of H2O and CO2: The effects of pressurized operation and internal methanation",
abstract = "This paper presents a model-based investigation to handle the fundamental issues for the design of co-electrolysis based power-to-methane at the levels of both the stack and system: the role of CO2 in co-electrolysis, the benefits of employing pressurized stack operation and the conditions of promoting internal methanation. Results show that the electrochemical reaction of co-electrolysis is dominated by H2O splitting while CO2 is converted via reverse water-gas shift reaction. Increasing CO2 feed fraction mainly enlarges the concentration and cathode-activation overpotentials. Internal methanation in the stack can be effectively promoted by pressurized operation under high reactant utilization with low current density and large stack cooling. For the operation of a single stack, methane fraction of dry gas at the cathode outlet can reach as high as 30 vol.{\%} (at 30 bar and high flowrate of sweep gas), which is, unfortunately, not preferred for enhancing system efficiency due to the penalty from the pressurization of sweep gas. The number drops down to 15 vol.{\%} (at 15 bar) to achieve the highest system efficiency (at 0.27 A/cm2). The internal methanation can serve as an effective internal heat source to maintain stack temperature (thus enhancing electrochemistry), particularly at a small current density. This enables the co-electrolysis based power-to-methane to achieve higher efficiency than the steam-electrolysis based (90{\%} vs 86{\%} on higher heating value, or 83{\%} vs 79{\%} on lower heating value without heat and converter losses).",
keywords = "Energy storage, Power-to-methane, Solid-oxide eletrolyzer, Co-electrolysis, CO2 utilization, Pressurized operation, Internal methanation",
author = "Ligang Wang and Megha Rao and Stefan Diethelm and Tzu-En Lin and Hanfei Zhang and Anke Hagen and Fran{\cc}ois Mar{\'e}chal and {Van herle}, Jan",
year = "2019",
doi = "10.1016/j.apenergy.2019.05.098",
language = "English",
volume = "250",
pages = "1432--1445",
journal = "Applied Energy",
issn = "0306-2619",
publisher = "Pergamon Press",

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Power-to-methane via co-electrolysis of H2O and CO2: The effects of pressurized operation and internal methanation. / Wang, Ligang; Rao, Megha; Diethelm, Stefan; Lin, Tzu-En; Zhang, Hanfei; Hagen, Anke; Maréchal, François; Van herle, Jan.

In: Applied Energy, Vol. 250, 2019, p. 1432-1445.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Power-to-methane via co-electrolysis of H2O and CO2: The effects of pressurized operation and internal methanation

AU - Wang, Ligang

AU - Rao, Megha

AU - Diethelm, Stefan

AU - Lin, Tzu-En

AU - Zhang, Hanfei

AU - Hagen, Anke

AU - Maréchal, François

AU - Van herle, Jan

PY - 2019

Y1 - 2019

N2 - This paper presents a model-based investigation to handle the fundamental issues for the design of co-electrolysis based power-to-methane at the levels of both the stack and system: the role of CO2 in co-electrolysis, the benefits of employing pressurized stack operation and the conditions of promoting internal methanation. Results show that the electrochemical reaction of co-electrolysis is dominated by H2O splitting while CO2 is converted via reverse water-gas shift reaction. Increasing CO2 feed fraction mainly enlarges the concentration and cathode-activation overpotentials. Internal methanation in the stack can be effectively promoted by pressurized operation under high reactant utilization with low current density and large stack cooling. For the operation of a single stack, methane fraction of dry gas at the cathode outlet can reach as high as 30 vol.% (at 30 bar and high flowrate of sweep gas), which is, unfortunately, not preferred for enhancing system efficiency due to the penalty from the pressurization of sweep gas. The number drops down to 15 vol.% (at 15 bar) to achieve the highest system efficiency (at 0.27 A/cm2). The internal methanation can serve as an effective internal heat source to maintain stack temperature (thus enhancing electrochemistry), particularly at a small current density. This enables the co-electrolysis based power-to-methane to achieve higher efficiency than the steam-electrolysis based (90% vs 86% on higher heating value, or 83% vs 79% on lower heating value without heat and converter losses).

AB - This paper presents a model-based investigation to handle the fundamental issues for the design of co-electrolysis based power-to-methane at the levels of both the stack and system: the role of CO2 in co-electrolysis, the benefits of employing pressurized stack operation and the conditions of promoting internal methanation. Results show that the electrochemical reaction of co-electrolysis is dominated by H2O splitting while CO2 is converted via reverse water-gas shift reaction. Increasing CO2 feed fraction mainly enlarges the concentration and cathode-activation overpotentials. Internal methanation in the stack can be effectively promoted by pressurized operation under high reactant utilization with low current density and large stack cooling. For the operation of a single stack, methane fraction of dry gas at the cathode outlet can reach as high as 30 vol.% (at 30 bar and high flowrate of sweep gas), which is, unfortunately, not preferred for enhancing system efficiency due to the penalty from the pressurization of sweep gas. The number drops down to 15 vol.% (at 15 bar) to achieve the highest system efficiency (at 0.27 A/cm2). The internal methanation can serve as an effective internal heat source to maintain stack temperature (thus enhancing electrochemistry), particularly at a small current density. This enables the co-electrolysis based power-to-methane to achieve higher efficiency than the steam-electrolysis based (90% vs 86% on higher heating value, or 83% vs 79% on lower heating value without heat and converter losses).

KW - Energy storage

KW - Power-to-methane

KW - Solid-oxide eletrolyzer

KW - Co-electrolysis

KW - CO2 utilization

KW - Pressurized operation

KW - Internal methanation

U2 - 10.1016/j.apenergy.2019.05.098

DO - 10.1016/j.apenergy.2019.05.098

M3 - Journal article

VL - 250

SP - 1432

EP - 1445

JO - Applied Energy

JF - Applied Energy

SN - 0306-2619

ER -