Performance analysis of direct air capture-based renewable power-to-methanol (P2M) system in different regions of China: An annual intermittency investigation

The direct air capture (DAC) integrated power-to-methanol (P2M) is a promising approach to reverse the carbon emission and energy demand. However, the intermittent character of renewable power and low response speed of DAC bring operation challenge. To evaluate the overall performance under different response time-scale, in this study, the operation strategies based on DAC stages, the number of its units are proposed from the view of reducing the energy storage of battery (strategy Ⅰ) or enhancing the amount of methanol production (in strategy Ⅱ) according to the fluctuating renewable power. Then the annual overall system performance is further distinguished in regions located at Northwest China, which own excellent renewable energy resource and have unsatisfactory wind, solar power curtailment rate. Results present the number of running DAC units ranges between 8 and 33, simultaneously the running quantity of total occupies 72.1 % and 89.0 % yearly under strategy Ⅰ and Ⅱ respectively in Urumqi. The daily averaged amount of captured CO₂ are 1297.5 and 1784.1 mol respectively at a typical day, showing the greater quantity of running DAC units is the main reason resulting the lower storage capacity of CO₂ and higher storage capacity of battery. Furthermore, the maximum captured CO₂ amount appears in Lhasa, which reach 800.3 t corresponding to the methanol productions are 523.3 t under strategy Ⅱ. The electricity transferred to the external gird takes a large proportion (i.e., exceed 75.0 %) in all selected regions, further proving the superior potential of DAC-based P2M system while dealing with the abandoned renewable electricity.