Integrated technological and economic feasibility comparisons of enhanced geothermal systems associated with carbon storage

Enhanced geothermal system (EGS) demonstrates low carbon intensity for supplying electricity but it has not been widely developed commercially. Although the engineering feasibility of different operational strategies has been illustrated, the energy industry is still ambiguous in economic aspects; in particular, incorporating carbon policies into the decision-making process is necessary. In this study, an evaluation framework from technical and economic perspectives considering the impact of carbon credit is introduced for the first time to compare six EGS working schemes including two well configurations and three flow strategies. Afterwards, sensitivity analyses are performed with respect to six technical parameters and four economic constraints. Key findings in this study prove that mixed CO2-water horizontal-well-EGS achieves the most profitability with an NPV of $35.3 million. CO2-EGS can produce the greatest geothermal power and carbon storage, but the high CO2 consumption is a major obstacle to achieving profitability. Compared to water-EGS, mixed CO2-water EGS shows a greater profit gained the advantage from carbon storage even with less geothermal energy harvesting. Regarding various well types, the horizontal well system can earn more profits than the vertical well system if the thermal breakthrough is not serious. The sensitivity analyses suggest that the parameters that dominate fluid injection amount and flow rate shall be assigned the highest priority. The electricity market price is another critical factor, and a mixed CO2- water EGS project is recommended to start according to the rising trend of the electricity sale price. This study provides an informative decision-making strategy for EGS stakeholders.