Levelized costs of electricity and direct-use heat from Enhanced Geothermal Systems

Abstract

GEOPHIRES (GEOthermal energy for the Production of Heat and Electricity (“IR”) Economically Simulated) is a software tool that combines reservoir, wellbore, and power plant models with capital and operating cost correlations and financial levelized cost models to assess the technical and economic performance of Enhanced Geothermal Systems (EGS). It is an upgrade and expansion of the “MIT-EGS” program used in the 2006 “Future of Geothermal Energy” study. GEOPHIRES includes updated cost correlations for well drilling and completion, resource exploration, and Organic Rankine Cycle (ORC) and flash power plants. It also has new power plant efficiency correlations based on AspenPlus and MATLAB simulations. The structure of GEOPHIRES enables feasibility studies of using geothermal resources not only for electricity generation but also for direct-use heating, and combined heat and power (CHP) applications. Full documentation on GEOPHIRES is provided in the supplementary material. Using GEOPHIRES, the levelized cost of electricity (LCOE) and the levelized cost of heat (LCOH) have been estimated for 3 cases of resource grade (low-, medium-, and high-grade resource corresponding to a geothermal gradient of 30, 50, and 70 °C/km) in combination with 3 levels of technological maturity (today's, mid-term, and commercially mature technology corresponding to a productivity of 30, 50, and 70 kg/s per production well and thermal drawdown rate of 2%, 1.5%, and 1%). The results for the LCOE range from 4.6 to 57 ¢/kWhe and for the LCOH from 3.5 to 14 $/MMBTU (1.2 to 4.8 ¢/kWhth). The results for the base-case scenario (medium-grade resource and mid-term technology) are 11 ¢/kWhe and 5 $/MMBTU (1.7 ¢/kWhth), respectively. To account for parameter uncertainty, a sensitivity analysis has been included. The results for the LCOE and LCOH have been compared with values found in literature for EGS as well as other energy technologies. The key findings suggest that given today's technology maturity, electricity and direct-use heat from EGS are not economically competitive under current market conditions with other energy technologies. However, with moderate technological improvements, electricity from EGS is predicted to become cost-effective with respect to other renewable and non-renewable energy sources for medium- and high-grade geothermal resources. Direct-use heat from EGS is calculated to become cost-effective even for low-grade resources. This emphasizes that EGS for direct-use heat may not be neglected in future EGS development.

The effect of spatial aperture variations on the thermal performance of discretely fractured geothermal reservoirs

“…Although our work did not incorporate fracture slippage and THMC effects it, nonetheless, provides a framework through which to understand how spatial aperture fluctuations affect thermal performance. It shows that fracture surface variations are a reservoir characteristic that researchers should consider in modeling discretely fractured geothermal reservoirs and performing techo-economic analysis (Beckers et al 2014;Held et al 2014). Our systematic approach for generating spatially varying apertures can be used in conjunction with modeling the effects that THMC and fracture slippage have on reservoir thermal performance, by providing a base aperture field that already has a spatially varying aperture field.…”

Project permitting, finance, and economics for geothermal power generation

“…Consequently, levelized unit cost comparisons will usually be developed not only across technologies but also with different sets of financing assumptions (Ayers et al, 2004;Beckers et al, 2014;Johnston et al, 2011;Mines and Nathwani, 2013). A base load unit is typically one that is operated to meet part of the minimum load of a power system and consequently is one that produces electricity both continuously and at a constant rate.…”

A review on heat transfer and energy conversion in the enhanced geothermal systems with water/CO2as working fluid

“…Most of the bottom-hole temperatures in the European EGS projects are lower than 165°C with well depths ranging from 3300 to 4500 m. However, the average EGS bottom-hole temperatures in America, Australia, and Asia range from 160 to 400°C, with well depths similar to those of the European projects. Beckers et al presented the technology development trend as three cases: today's technology, midterm technology, and commercially mature technology, which assumes a well productivity of 30, 50, and 70 kg/s and a 2%, 1.5%, and 1% temperature decrease per year, respectively [15]. It is commonly accepted that for an EGS doublet system to be of commercial size, assuming a depth greater than 3 km and a temperature greater than 150°C, the system should operate at flow rates between 50 and 100 kg/s and produce an electric power of 3 to 10 MWe over a lifespan of at least 25 years [14].…”

“…It is commonly accepted that for an EGS doublet system to be of commercial size, assuming a depth greater than 3 km and a temperature greater than 150°C, the system should operate at flow rates between 50 and 100 kg/s and produce an electric power of 3 to 10 MWe over a lifespan of at least 25 years [14]. Beckers et al presented the technology development trend as three cases: today's technology, midterm technology, and commercially mature technology, which assumes a well productivity of 30, 50, and 70 kg/s and a 2%, 1.5%, and 1% temperature decrease per year, respectively [15]. To obtain both a lower annual temperature decrease and an increase in well flow rate with improving technology requires an increase in the surface area of the fractures (i.e., a larger reservoir).…”

“…The model for a hypothetical EGS project in Europe, consisting of two wells at a depth of 4 km, reservoir temperatures ranging from 125°C to 165°C, flow rates ranging from 33 to 69 kg/s, and a binary power unit of 1.6 MWe running with an annual capacity factor of 86%, estimated LCOE values of 30 to 37 US cents/kWhe [2]. Another model was used by Beckers et al [15] to predict LCOE from EGS. For geothermal gradients of 30°C/km, the LCOE is estimated at approximately 60 US cents/kWhe using current technology, which could decrease to approximately 20 US cents/kWhe in the future with anticipated technology improvements as mentioned in Section 2.1.…”