Thermo-economic analysis of a direct supercritical CO2 electric power generation system using geothermal heat

Abstract

A comprehensive thermo-economic model combining a geothermal heat mining system and a direct supercritical CO 2 turbine expansion electric power generation system was proposed in this paper. Assisted by this integrated model, thermo-economic and optimization analyses for the key design parameters of the whole system including the geothermal well pattern and operational conditions were performed to obtain a minimal levelized cost of electricity (LCOE). Specifically, in geothermal heat extraction simulation, an integrated wellbore-reservoir system model (T2Well/ECO2N) was used to generate a database for creating a fast, predictive, and compatible geothermal heat mining model by employing a response surface methodology. A parametric study was conducted to demonstrate the impact of turbine discharge pressure, injection and production well distance, CO 2 injection flowrate, CO 2 injection temperature, and monitored production well bottom pressure on LCOE, system thermal efficiency, and capital cost. It was found that for a 100 MW e power plant, a minimal LCOE of $0.177/kWh was achieved for a 20-year steady operation without considering CO 2 sequestration credit. In addition, when CO 2 sequestration credit is $1.00/t, an LCOE breakeven point compared to a conventional geothermal power plant is achieved and a breakpoint for generating electric power generation at no cost was achieved for a sequestration credit of $2.05/t.

Heat Production Performance from an Enhanced Geothermal System (EGS) Using CO2 as the Working Fluid

“…Generally, the heat production performance of CO 2 -EGSs is significantly better than that of water-EGSs, especially for geothermal reservoirs with lower permeability [18,19]. Pan et al [20,21] used supercritical CO 2 as the working fluid to study geothermal production potential using the T2WELL code (e.g., a wellbore-reservoir coupled model). Their results showed that a good thermosiphon effect was achieved when using CO 2 as the working fluid, thus significantly reducing the external cost for pumping.…”