Power supply characterization of baseload and flexible enhanced geothermal systems

Abstract

We investigated the techno-economic feasibility and power supply potential of enhanced geothermal systems (EGS) across the contiguous United States using a new subsurface temperature model and detailed simulations of EGS project life cycle. Under business-as-usual scenarios and across depths of 1-7 kilometers, we estimated 82,945 GW and 0.65 GW of EGS supply capacity with lower levelized cost of electricity than conventional hydrothermal and solar photovoltaic projects, respectively. Considering the scenario of flexible geothermal dispatch via wellhead throttling and power plant bypass, these estimates climbed up to 184,112 GW and 44.66 GW, respectively. The majority of EGS supply potential was found in the Western and Southwestern regions of the United States, where California, Oregon, Nevada, Montana, and Texas had the greatest EGS capacity potential. With advanced drilling rates based on state-of-the-art implementations of recent EGS projects, we estimated an average improvement of 25.1% in the levelized cost of electricity. These findings underscored the pivotal role of flexible operations in enhancing the competitiveness and scalability of EGS as a dispatchable renewable energy source.

Keywords: Enhanced geothermal systems; Flexible; Power; Techno-economics.

Figure 1

Temperature-at-depth heatmap of our model predictions overlain by isotherms based on the predictions by the NREL and SMU models across depth intervals of 1–3 km and 4.5–6.5 km, respectively. This figure was created using Python 3.9.

Figure 2

Difference of temperature-at-depth predictions of the USGS model by Burns et al. minus our STM model across the Great Basin. This figure was created using Python 3.9.

Figure 3

Configuration of an EGS project with a single production-injection doublet, ORC binary power plant, plant bypass line, makeup water source, and power grid connection.

Figure 4

Spatial distribution of average annual generation per unit area across for projects spanning depths of 1–7 km. Grey areas indicate techno-economically infeasible locations, with temperature-at-depth of < 150 °C at a depth of 7 km. This figure was created using Python 3.9.

Figure 5

Optimal LCOE across depths for EGS development across the contiguous United States, under baseload dispatch scenario with (a) baseline and (b) advanced drilling rates. Grey areas indicate techno-economically infeasible locations, with temperature-at-depth of < 150 °C at the deepest reservoir zone of 7 km. This figure was created using Python 3.9.

Figure 6

EGS capacity supply curves versus after-ITC LCOE across different operational and drilling cost scenarios, in comparison to the average LCOE of other renewables.

Figure 7

Sample of annual baseload versus flexible operations in green and red, respectively, of an EGS project simulated at an hourly resolution using FGEM. Brown curves indicate overlapping baseload and flexible profiles.

Figure 8

EGS capacity supply curves versus before-ITC overnight CAPEX across target reservoir depths for the scenario of flexible operations and advanced drilling costs, in comparison to the average CAPEX of other renewables.