Hybridizing a Geothermal Plant with Solar and Thermal Energy Storage to Enhance Power Generation

McTigue, Joshua D.; Turchi, Craig; Mungas, Greg; Kramer, Nick; King, J. E.; Castro, J. Ramon

doi:10.2172/1452695

Cited by 4 publications

(2 citation statements)

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“…The mass flow rate to the plant is unchanged, but the temperature is increased enough to restore the GBPP to its design point. At Raft River, this approach has high calcite-scaling potential when the brine temperature is raised in the solar heat exchanger, as discussed in [10], [34]. The cost of continuously injecting scale inhibitors to prevent calcite precipitation is not included in the LCOE calculations for this option.…”

Section: Comparison Of Thermal and Generation Performancementioning

confidence: 99%

Solar-Driven Steam Topping Cycle for a Binary Geothermal Power Plant

McTigue

Kincaid

Wendt

et al. 2018

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Executive SummaryGreater deployment of moderate-temperature geothermal binary power plants (GBPPs) and concentrating solar power (CSP) can be limited in some markets by their respective generation characteristics and/or levelized cost of electricity (LCOE). Worldwide, both geothermal power and CSP are under intense pressure from the rapidly dropping cost of solar photovoltaic (PV) and wind energy. In the United States, there is further pressure from the ongoing era of low natural gas prices. CSP can generate high-temperature thermal energy that enables high cycle efficiency and low-cost thermal storage systems, and GBPP can produce baseload power generation. Hybridization may take advantage of technical merits of both technologies to produce energy at a levelized cost of energy (LCOE) competitive in the future energy market. New approaches that can lower the LCOE of both geothermal power and concentrating solar can therefore help to increase adoption of both technologies.In this technical report, we explore several methods of combining heat generated by a concentrating solar field with an existing geothermal binary power plant. The Raft River geothermal power plant in southern Idaho operates below its rated capacity because the reservoir is unable to deliver the design flow and temperature of geothermal energy. The GBPP is a twopressure cycle with independent high-pressure and low-pressure isopentane turbines. Solar heat may be added in several ways to this cycle and we perform a screening study and then more detailed calculations for several configurations, including:1. Geothermal production brine directly heated by solar energy; 2. A fraction of geothermal brine extracted from some part of the binary plant, heated with solar energy, and mixed with the production fluids; and3. The addition of a steam topping cycle, the hot exit flow of which is used to:a. Heat brine, as in points 1 and 2, and b. Vaporize the binary-cycle working fluid after the fluid has been preheated by the geothermal brine.The initial screening study was performed on a large number of different cycle configurations at a single operating condition. Subsequently, a more detailed study investigated annual cost and performance. Both the screening study (using one set of modeling software) and the detailed analysis (using another software package) were calibrated against one or more aspects of the Raft River operating condition. The combined results of the screening and detailed study are shown in Table A (although the results from one model should not be compared to those of the other). vii This report is available at no cost from the National Renewable Energy Laboratory at www.nrel.gov/publications.Table A: Comparison of different hybrid plant configurations from the screening study and detailed study. '-' indicates that the configuration was not studied. Design-Point Cycle EfficiencyAnnual Efficiency Cycle and DescriptionScreening StudyDetailed Study Detailed StudyTwo solar steam turbines: Use high-temperature solar steam in two turbines, which...

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Section: Comparison Of Thermal and Generation Performancementioning

confidence: 99%

Solar-Driven Steam Topping Cycle for a Binary Geothermal Power Plant

McTigue

Kincaid

Wendt

et al. 2018

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“…4. The use of solar thermal energy to heat the subsurface and create a geological thermal energy storage system [8], [9], [10].…”

Section: Recap Of Previous Projectsmentioning

confidence: 99%

Techno-Economic Analysis of Greenfield Geothermal Hybrid Power Plants using a Solar or Natural Gas Steam Topping Cycle

Wendt,

Neupane,

Simpson

et al. 2024

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The relatively low generation costs associated with wind, solar photovoltaic (PV), and natural-gas power plants make it challenging for geothermal power plants to produce and sell the power that has the reliability and sustainability characteristics that are greatly needed in U.S. power markets. This is especially true for geothermal resources with low-to-medium temperatures, which results in relatively low-thermal efficiency and generation costs that are higher than those for wind, solar PV, and natural gas. This analysis evaluates solar thermal-and natural-gas combustion waste heat recovery-based topping cycle hybridization of geothermal binary power plants. This approach provides several benefits that may allow geothermal power plants to generate power at more competitive costs. First, the addition of solar thermal energy or natural-gas combustion waste heat input to a geothermal power plant provides additional heat input that can be converted to electrical power. Second, the temperature level of the heat obtained from concentrating solar collectors or natural-gas combustion exhaust is higher than that of geothermal heat, which provides opportunities for improving the efficiency of the conversion of thermal energy to electrical power. Third, the ease with which solar thermal systems integrate with energy storage and the flexibility of natural gas means power generation can occur during peak demand periods. vi

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