Geothermal systems making use of advanced drilling and well stimulation techniques have the potential to provide tens to hundreds of gigawatts of clean electricity generation in the United States by 2050. With near-zero variable costs, geothermal plants have traditionally been envisioned as providing “baseload” power, generating at their maximum rated output at all times. However, as variable renewable energy sources (VREs) see greater d. Geothermal systems making use of advanced drilling and well stimulation techniques have the potential to provide tens to hundreds of gigawatts of clean electricity generation in the United States by 2050. With near-zero variable costs, geothermal plants have traditionally been envisioned as providing “baseload” power, generating at their maximum rated output at all times. However, as variable renewable energy sources (VREs) see greater deployment in energy markets, baseload power is becoming increasingly less competitive relative to flexible, dispatchable generation and energy storage. Herein we conduct an analysis of the potential for future geothermal plants to provide both of these services, taking advantage of the natural properties of confined, engineered geothermal reservoirs to store energy in the form of accumulated, pressurized geofluid and provide flexible load-following generation. We develop a linear optimization model based on multi-physics reservoir simulations that captures the transient pressure and flow behaviors within a confined, engineered geothermal reservoir. We then optimize the investment decisions and hourly operations of a power plant exploiting such a reservoir against a set of historical and modeled future electricity price series. We find that operational flexibility and in-reservoir energy storage can significantly enhance the value of geothermal plants in markets with high VRE penetration, with energy value improvements of up to 60% relative to conventi. ••Enhanced geothermal power plants are capable of time-shifting generation via modulation of injection and production rates.••Hydraulically confined reservoirs enable accumulation and discharge of pressurized geofluid.••In-reservoir energy storage can achieve durations ¿100 hours.••Energy storage is more valuable in systems with high wind and solar penetration.••Firm, low-carbon resources have been identified as critical for cost-effective deep decarbonization of electricity systems,. Geothermal power is one such resource, with added benefits of full renewability and minimal land and resource use relative to other sources of electricity. Despite these advantages, geothermal deployment has historically been constrained to a very select set of sites where naturally-occurring hydrothermal reservoirs can be exploited for electricity generation. Due in large part to this lack of resource availability, geothermal power currently supplies only 0.4% of annual electricity demand in the United States, with a total installed generating capacity of under 4 GW.Through technology innovation, drilling cost reductions, and improved exploration techniques, it may be possible to significantly increase the economically viable resource base for geothermal energy. For example, studies by the USGS have indicated that up to 30 GW of undiscovered hydrothermal resources may exist in the US,, which could be identified using novel geophysical exploration techniques. In addition, recent innovations in horizontal drilling, reservoir stimulation techniques, and other Enhanced Geothermal System (EGS) technologies can enable geothermal development in formations that would otherwise be unsuitable or uneconomic. Relatively shallow EG. 2.1. Representative plant designEGS is an emerging technology, and most proposed plans for its commercialization hinge on using early “near-field” projects to accelerate technological learning. These projects would target the hot but low-permeability formations surrounding known hydrothermal sites, where minimal exploration and drilling is necessary for development. Sufficient cost reductions in these early phases could enable the economical development of “deep EGS” resources, those at depths of 3 km or more located in low-permeability basement rock. It is this deep resource that represents the vast majority of geothermal potential worldwide. In this paper we focus on the transitional point in this approach, considering an EGS plant mining a 218 °C low-permeability geothermal resource at a depth of 3 km. We use this representative case to analyze the impact of flexibility and energy storage on the economics of early EGS projects.In our analysis we consider a triplet well design similar to those discussed in Gringarten et al., Olson et al., Li et al., and others. An injection well is drilled to the target depth and deviated to produce a 1.5 km horizontal section. Hydraulic stimulation is used to create regularly-spaced vertical fractures along this interval, and two production wells are drilled in parallel and at opposite orientation to the injection well, intersecti. 3.1. Base case resultsOptimization results under baseline reservoir performance and plant costing assumptions for historical price series are given in Table 2, and results for modeled 2030 price series are given in Table 3. All energy value and component-sizing results are presented with respect to the corresponding values for a baseload geothermal plant. The average hourly energy value per MW of net generating capacity for such a plant is equal to the average hourly price of electricity for each series. Relative improvement over this “baseload” average energy value from a curtailment-only operating strategy similar to that discussed in Millstein et al. is given for both sets of price series. This number represents the degree to which value could be improved if the plant curtailed generation during negative pricing episodes but did not store the lost energy. Value improvement from full flexibility represents the average energy value of the same plant under flexible operations with IRES, after subtracting the annuitized cost of any oversizing of surface facilities. For all flexible cases, energy value is given with respect to the total annual generation of a baseload plant. This allows for meaningful comparison of results in cases where annual flexible generation is less than baseload (e.g. due to increased pumping loads). The optimal degree of plant, interconnection, and injection pump oversizing fo.
