Electric Power Generation, Specific Capital Cost, and Specific Power for Advanced Geothermal Systems (AGS)

Abstract

Advanced Geothermal Systems (AGS) generate electric power using a closed-loop system, by circulating a working fluid through a long wellbore and extracting geothermal heat only through conduction from rock surrounding the wellbore. Quantitative evaluations of electric power and cost are not available. In this paper, we simulate an AGS for a wide range of system parameters after modifying the existing genGEO simulator by replacing the porous reservoir with one or more horizontal lateral wells which are spaced apart to limit thermal interference. Our results include the computation of the electric power generation, capital cost, specific capital cost (SpCC) (i.e., dollars per Watt), and the specific power (i.e., Watts per well meter). We find that using CO2 as the working fluid rather than water increases the electric power generated from the system. Additionally, for any vertical well length, there exists an optimal lateral well length, an optimal mass flowrate, and an optimal well diameter which minimize cost. We also show that ideal well costs and high geothermal gradients significantly decrease the overall cost.