Energy, exergy and pinch analyses of a novel energy storage structure using post-combustion CO2 separation unit, dual pressure Linde-Hampson liquefaction system, two-stage organic Rankine cycle and geothermal energy

The cost of electricity production and its purchase price markedly differ at different hours of the day; therefore, the idea of storing electricity during off-peak hours (low price) and its use during peak hours (high price) is discussed. In this study, a novel integrated structure for separating CO2 from the output smoke of a power plant using a chemical absorption unit via the post-combustion and CO2 liquefaction method by the dual pressure Linde-Hampson liquefaction system during off-peak hours is developed. The low-temperature organic Rankine cycle and the gas turbine power production unit are used to produce power during peak hours. The post-combustion CO2 separation unit produces 9307 kmol/h CO2 from the power plant's output smoke by absorbing 249.6 MW heat flow from the geothermal energy and 24.42 MW power. At hours when the energy demand is low, the produced CO2 is converted into condensed liquid form by receiving 18.31 MW power. When the demand for electric energy consumption is increased, this integrated structure produces 11.61 MW power. The multi-functional LCES system round trip and baseline LCES system exergy efficiencies are 36.75% and 58.48%, respectively. The exergy analysis results illustrate that the highest exergy destruction contribution in the equipment belongs to the fractionating columns (48.52%), heat exchangers (43.62%), and compressors (2.86%). The heat exchanger network related to the HE12, HE15, HE16, and HE18 multi-stream heat exchangers are extracted by pinch analysis. The sensitivity analysis illustrates that the exergy efficiency of the power generation cycle, baseline LCES plant, and multi-functional LCES structure increase up to 33.19%, 60.87%, and 21.14%, respectively when the pumped pressure of liquid carbon dioxide at peak consumption increases from 80 bar to 120 bar. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study proposes a novel integrated structure for separating CO2 from the output smoke of a power plant during off-peak hours using a chemical absorption unit and CO2 liquefaction method. Power is produced during peak hours using a low-temperature organic Rankine cycle and gas turbine power production unit. The exergy efficiencies of the multi-functional LCES system and baseline LCES system are 36.75% and 58.48% respectively, with sensitivity analysis showing the highest exergy destruction contribution in the equipment related to fractionating columns, heat exchangers, and compressors.