Analysis of the work of a “renewable” methanol production installation based ON H₂ from electrolysis and CO₂ from power plants

This article presents a thermodynamic analysis of a system for producing “renewable” methanol from H₂ generated from electrolysis, fed by surplus energy from a 40 MW wind farm WF during the night valleys and from CO₂ captured from a power plant's flue gas. A methodology determining the energy efficiency of the entire methanol production and purification installation was developed, as well as a methodology for determining the efficiency of its components, i.e. the hydrogen generator HG (η_HG) and the methanol generator MG (η_MG). A number of effective ways to improve these efficiencies were proposed and analyzed. To evaluate the cooperation of the HG with a WF, a number of indicators were introduced: an indicator of the maximum working time utilization, a rated power index for the generator, an energy storage indicator, and an indicator for the working time with nominal power. The listed efficiency and indices were determined as a function of the nominal power of the HG in relation to the nominal power of the WF (in a range from 1 to 45%). The energy efficiency of the entire system under study, η, ranged from 45.5% to 52.9% with a MG efficiency of 69%–69.64%. The use of heat from compressed gases increased the efficiency η by 0.98 p. p. Relative to the best variant, while the use of compressed gas heat, waste heat from the methanol production and purification installations, and the use of the chemical energy of residual gases gave a possibility of achieving an efficiency exceeding 60% (60.4%).