Variability in Diurnal and Seasonal Ambient Conditions on Geothermal Plant Performance and Cost

Research output: Contribution to conferencePaper


Geothermal plant performance is bounded by the second law efficiency, which accounts for the quantity of exergy that can be converted into useful work. This, in turn, is dependent on the geothermal resource temperature and the temperature of the heat sink (i.e., the ambient temperature). In this study, we show that ambient temperature variability on a diurnal and seasonal basis can affect performance and cost estimations for geothermal plants. We have utilized the updated System Advisor Model (SAM) to assess nine geothermal sites with existing resource capacities across three climate zones. Our analysis shows that both evaporatively-cooled flash and air-cooled binary cycle plants are affected by temperature, with a slightly higher effect in enhanced geothermal system binary sites. By assuming an ambient (wet bulb) temperature baseline of 15.6 degrees C (60 degrees F) and comparing baseline results to those from site-specific data, we observe up to 15% underestimation of plant performance and up to 20% overestimation of cost. These results make a case for the inclusion of location-based weather data as inputs to supply curves that are used in capacity expansion models for the prediction of future geothermal deployment scenarios.
Original languageAmerican English
Number of pages14
StatePublished - 2023
EventGeothermal Rising Conference - Reno, Nevada
Duration: 1 Oct 20234 Oct 2023


ConferenceGeothermal Rising Conference
CityReno, Nevada

Bibliographical note

See NREL/CP-5700-86995 for preprint

NREL Publication Number

  • NREL/CP-5700-88692


  • ambient temperature
  • diurnal and seasonal variability
  • geothermal power cycle
  • LCOE


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