Low-carbon methanol production using solar thermal energy: A techno-economic assessment

Abstract

This work presents a techno-economic and greenhouse gas emissions assessment of a proposed low-carbon methanol production process. The process takes a novel low-carbon methanol production method and reduces its emissions further by integrating a solar thermal energy (STE) system to provide for its electricity requirements. The authors investigate three different scenarios for the STE system, analysing the effects of solar irradiance design point, and the impact of thermal energy storage on system performance. Case-1 (15.57 MW) was designed for daytime operation and sized for the maximum annual solar irradiance, with Case-2 (24.91 MW) incorporating thermal energy storage to enable 24-hour operation. Case-3 (48.66 MW) also utilised thermal energy storage to enable 24-hour operation, but was sized for the minimum annual solar irradiance. The methanol process and the STE system were modelled in Aspen Plus and Aspen HYSYS, with the simulation data being used with mass and energy balances to conduct a techno-economic and greenhouse gas emissions assessment. The standalone methanol plant was estimated to emit 0.37 t CO₂/t CH₃OH, with the integration of the STE system reducing this to 0.29 (Case-1), 0.23 (Case-2), and 0.10 (Case-3), resulting in one of the lowest emitting traditional methanol production methods available. The cost of abatement of these remaining emissions through carbon capture and storage was also considered. The economic analysis found that the integrated processes in Case-1 and 2 were financially viable, resulting in a net present value of $247 million and $72 million respectively. The net present value was reduced to $185 and $21 million when considering the cost of carbon capture and storage. Conversely, the net present value for Case-3 was negative, requiring an increase in the price of methanol to $\sim$$600/t, and a reduction in the cost of capital to $\sim$8%, to become financially viable.