Process simulation of a near-zero-carbon-emission power plant using CO2 as the renewable energy storage medium

• A conceptual near-zero-carbon-emission power plant is modeled.
• Conversion of (CO2 + H2O) into ethanol through electrocatalysis route is evaluated.
• The CO2 emission of the proposed system is only 6.5% of the coal-fired power plant.

In this paper, process simulation of a near-zero-carbon-emission power plant using CO2 as the renewable energy storage medium was carried out. Liquid fuels that can be burned either in boilers or compression ignition engines to generate electricity have been the target products. The CO2 and H2O produced from combustion are recirculated back to the synthesis units, thus forming a closed cycle of “renewable energy (unstable energy supply) + CO2 + H2O → liquid fuels → electricity (stable supply)”. This novel closed loop energy storage process integrated with a 670 MW supercritical power plant was analyzed using the Aspen Plus software package. Methanol was selected as the targeted liquid fuel through three major synthesis routes: CO + H2, CO2 + H2 and CO2 + H2O, in which CO and H2 came from the electrolysis of CO2 and H2O. The performances of the three methanol synthesis routes were thermodynamically analyzed. The results show that the optimal methanol synthesis route is the direct conversion of CO2 and H2O through electrocatalysis when CO2 conversion is above 42%, while when CO2 conversion is below 42% the best choice turned out to be the CO hydrogenation. The direct conversion of (CO2 + H2O) using electrocatalysis method was adopted as the liquid fuel synthesis route for the near-zero-carbon-emission power plant. The overall CO2 emission from the near-zero-carbon-emission power plant is 44.13 kg/MWh accounting for just 6.45% of the advanced coal fired power plant.