Geothermal Power Plant

Technology Roadmap

Roadmap Overview

Technology Description: Geothermal power plants generate electricity by harnessing geothermal energy through a series of steps. First, geothermal fluid is heated by accessing the geothermal reservoir, either by injecting it directly into the reservoir (Enhanced Geothermal System) or using pipes that pass through the reservoir (Closed Loop). The heated fluid is then brought to the surface and passed through a heat exchanger, transferring its heat to a working fluid. This working fluid, now heated, drives a turbine, which powers a generator to produce electricity. Afterward, the working fluid is cooled and condensed back into a liquid form before being recirculated through the heat exchanger to repeat the process.

Design Structure Matrix (DSM) Allocation

Roadmap Model using OPM

Figures of Merit

Key Publications, Presentations, Patents

Publications

Sandia GeoVision Analysis Report - T. S. Lowry et al., “GeoVision Analysis Supporting Task Force Report: Reservoir Maintenance and Development”

The Sandia GeoVision Analysis report is widely cited as a reference for drilling considerations on all geothermal well development. This report provides a baseline for drilling costs given different borehole diameters and drilling directions. The drilling analysis includes bit design, environmental considerations, non-drilling activities, reservoir stimulation mechanisms and their associated costs, and hydraulic performance. These considerations are oriented on performance and cost, producing well cost curve scenarios for many drilling situations. This provides a significant resource in planning geothermal borehole development without requiring experience in the specific characteristics of the location or development. This report also includes maintenance and management practices to ensure enthalpy production remains within planned bounds. The combination of drilling costs tied to capital expenditure and maintenance and management costs provides a strong resource for estimating the overall costs needed for a levelized cost of electricity assessment.

Numerical Investigation of Closed-loop Geothermal Systems in Deep Geothermal Reservoirs - M. White et al., “Numerical investigation of closed-loop geothermal systems in deep geothermal reservoirs,” Geothermics, vol. 116, p. 102852, Jan. 2024, doi: 10.1016/j.geothermics.2023.102852.

The numerical model presented by White et al., in conjunction with multiple national labs and universities, collects data and processes from many sources and integrates them into a working web-based application. This application, called GeoCluster, provides an estimate for geothermal production and economic viability considering seven input parameters. These parameters are mass flow rate, horizontal extent, vertical drilling depth, rock geothermal gradient, borehole diameter, injection temperature, and rock thermal conductivity. To construct this model, the team integrated multiple computational models developed independently by each laboratory. These models focused on the heat recovery mechanisms of a closed-loop system in deep geothermal reservoirs. The models were integrated to incorporate advantages found in each and then validated using data from the active Utah FORGE geothermal testing site. This subsurface model becomes the Sandia HDR (hot-dry-rock) model. This model was combined with the surface generation model provided by NREL to produce the full GeoCLUSTER application. Overall, this application provides a significant asset to entities entering the geothermal power market by providing accurate cost and benefit estimates for implementing a closed-loop geothermal system considering a range of system and geological constraints.

Patents

The Millimeter-Wave Drilling System patent (US Patent # 8,393,410 B2) is classified as E21B 7/14 in the Cooperative Patent Classification (CPC) system. In this system, E21B refers to technology related to Earth of Rock Drilling; Obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells and 7/14 add the modifier Drilling by use of heat; e.g. flame drilling (CPC: E21B 7/14). We identified this system during our disruptive technology analysis. The classification of this system as using “flame drilling” instead of high energy waves likely identifies the novelty of the technology in the E21B “Earth and Rock Drilling” field. The Millimeter-Wave Drilling System identified in this patent uses millimeter waves generated by a gyrotron and funneled into a borehole by a proprietary waveguide to radically heat the rock at the leading edge of the hole. This rock can be heated to temperatures sufficient to vaporize the rock. This vapor is then exfiltrated out of the borehole using a purge gas system to allow for continuous advancement. If brought into commercial operation, this technology claims to radically decrease the cost of well boring at extreme depths. This would significantly change the cost considerations when considering implementing a geothermal power system.