Volume 47

Integrated methanol-hydrogen-electricity conversion system with low CO2 emission for on-demand power and heat supply Xiao Li, Bin Wang, Lingzhi Yang, Yong Hao

Abstract

To address climate change, distributed energy system shall explore a synergistic pathway towards high efficiency and low carbon emissions while ensuring the continuity, stability and variety of energy supply. We propose a novel distributed energy system featuring the integration of methanol steam reforming, metal alloy-based hydrogen separation, proton exchange membrane fuel cells and CO2 capture. Methanol, as a convenient, stable, and economical medium for hydrogen storage and on-demand power generation, serves as a transition fuel between current and future energy systems. Using the toxicity-resistant LaNi4.3Al0.7, hydrogen is absorbed from methanol reformate gas containing CO and water vapor at 180 °C and then released through isothermal depressurization. Simultaneously, the tail gas from the hydrogen separation unit undergoes oxy-fuel combustion, achieving CO2 capture with low energy consumption. Subsequently, the proton exchange membrane fuel cells efficiently convert hydrogen to electricity, with the waste heat being exchanged to supply hot water. The models of reformer, metal alloy-based hydrogen separation unit and proton exchange membrane fuel cells are validated by experimental data from the literature. The analysis demonstrates that at 100 mol h-1 methanol flow rate, 250 °C reaction temperature and 8 bar absorption pressure, total electrical efficiency and total energy efficiency of the proposed system are 40.05% and 88.00%, respectively, which are 5.99 and 1.2 percentage points higher than those of the reference system with conventional pressure swing adsorption method. Meanwhile, the total exergy efficiency of the proposed system is 43.38%, which is 5.5 percentage points higher than the reference system. The system enables an efficient on-demand supply of power and heat, the potential for reducing CO2 emission, and compatibility with future energy systems.

Keywords Distributed energy, Methanol reforming, Hydrogen, Metal alloy, CO2 capture