This part of the article really kind of gets to the "meat and potatoes" of the issue:
For geothermal power developers looking to invest in Wyoming, a 2022 assessment of underground hot water resources might help point the way.
Produced by Petrolern (now known as Teverra) for the Wyoming Energy Authority, the 2022 report painted a modest picture of the state's immediate geothermal electricity potential.
Emilie Gentry, geothermal lead with Teverra, said the research used existing public data to map the state's geothermal resources.
"What came out of that report was really, kind of a very regional general mapping of the resource and then an understanding from there based on those temperatures at depth, can you produce electricity?" she explained.
The Wyoming-specific study found that the state's geothermal resources are moderate to low temperatures and situated in localized regions throughout the state.
Many of the geothermal resources are below 200 degrees Fahrenheit and not ideal for generating electricity.
"Most of the state is better suited for direct use, meaning using that thermal water for heating,” Gentry explained. “And that can be homes, it can be town main streets, it can be manufacturers that use higher temperatures."
However, the study did identify some promising areas for geothermal electricity generation.
The 2022 study identified 1,284 wells within the state that are above 200degrees bottom-hole temperature that are not plugged and abandoned.
The Powder River Basin, particularly the southeastern portion near Casper, emerged as one of the most promising regions.
The Salt Creek-Meadow Creek area, located about 4 miles north of Casper, shows exceptional geothermal potential with higher heat flow, numerous faults, and documented flowing water wells with temperatures reaching 183°F at the surface.
Southwestern Wyoming around Rock Springs offers substantial opportunities with 863 wells above 200°F — the highest number among all Wyoming basins.
To generate electricity, the higher the temperature the better. A nuclear plant produces "moderate" temperature steam; steam that is cooler than what is used at a fossil plant, which is why they are less efficient in terms of turning those MWth into MWe. A nuclear plant that uses steam generators has a boiler outlet temperature of about 528F, which yields an efficiency of about 31-32%.
So, setting the bar at "above 200F" for a limited cross-section of these wells isn't putting it very high. You need much higher temperatures to make it worthwhile to try and harness it using the Rankine Cycle.
The article mentions the Gysers facility in California, which has a fantastic Wiki:
https://en.wikipedia.org/wiki/The_Geysers
There is currently 1,590MWe of installed capacity at Gysers, covering an area of 29,000 acres (120 square kilometers). None of the units are "large", which the biggest being 119MW. Production is about 6.5TWh.
As of the end of 2024, California had an impressive 2.04GW of installed Geothermal, which produced 6.69TWh or about 2.81% of the state's electricity.
In comparison, California's only operating nuclear plant, Diablo Canyon, at 2.27GW, produced 18.4TWh over the same period, or about 7.72% of the state's electricity and its grounds are probably a couple hundred acres.
So, to me, this sounds a lot like the "Geologic Hydrogen" hype. Yes, these geothermal resources "exist", but are most of them worth exploiting? Probably not. That doesn't mean we shouldn't exploit the ones that ARE worth exploiting however. Geothermal is another tool in the toolbox for displacing FF's in powergen.
