Modelica-based 1-D dynamic modeling and thermodynamic analysis of power-to-gas systems through solid oxide electrolysis and CO2 methanation

•A detailed dynamic model is developed for the power to gas system using Modelica.•Steady-state location of the reaction hot spot is analyzed by sensitivity analysis.•Optimum inlet temperature of the SOEC was fitted for different supply powers.•Optimum H/C ratio is identified to balance the CH4 yiel...

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Bibliographic Details
Published in:Energy conversion and management Vol. 317; p. 118730
Main Authors: Yin, Ruilin, Chen, Liangyong, Nižetić, Sandro, Sun, Li
Format: Journal Article
Language:English
Published: Elsevier Ltd 01.10.2024
Subjects:
Dynamic analysis
Energy storage
Methanation
Power-to-gas
Renewable energy
Solid oxide electrolysis cell
Solid oxide electrolysis cell
Methanation
Renewable energy
Power-to-gas
Dynamic analysis
Energy storage
ISSN:0196-8904
Online Access:Get full text
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Summary:•A detailed dynamic model is developed for the power to gas system using Modelica.•Steady-state location of the reaction hot spot is analyzed by sensitivity analysis.•Optimum inlet temperature of the SOEC was fitted for different supply powers.•Optimum H/C ratio is identified to balance the CH4 yield and CO2 conversion rate.•Some special transients of the hot spot temperature’s response are revealed. Power-to-gas (PtG), consisting of water electrolysis and CO2 methanation, is regarded as a promising technology for energy storage and carbon utilization. However, the PtG system is faced with frequently varying loads due to the non-dispatchable renewable power input. To support its efficient transient operation and control, this work was focused on development of novel dynamic model of PtG system that includes solid oxide electrolysis cells (SOEC) and tube bundle methanation reactors (MR), using an object-oriented language Modelica. The equations for each component in the system are derived based on the mechanisms of electrochemical/chemical reactions, gas flow, and heat transfer. The developed models are then utilized for numerical studies and thermodynamic analysis with both steady-state and dynamic simulations. The steady-state study is conducted including a sensitivity analysis with various input conditions and an energy analysis. The sensitivity analysis shows the variation of the reaction rate along the axial direction of the one-dimensional MR tube, as well as the shift in the position of the reaction hot spot. The optimum SOEC inlet temperature is fitted, adapted to different belonging powers. Moreover, the H/C ratio of MR is determined as 8.4 through a trade-off between the CO2 conversion ratio and CH4 yield. The dynamic simulations in response to the power disturbance have demonstrated the disparate time scales of flow and heat transfer, as revealed by a multi-domain analysis of heat transfer, mass transfer, and chemical reactions. The concentrations and temperatures of products along the MR tube axis exhibited different variation trends. In the dynamic response to the electricity input disturbance, the axial position of the hot spot temperature gradually crawls over time, and exhibits an interesting transient phenomenon of initial inverse response. The results in this paper lay a solid foundation for a dynamic control design and efficient operation of the PtG system.
ISSN:0196-8904
DOI:10.1016/j.enconman.2024.118730