New technologies could unlock geothermal almost anywhere
Traditional geothermal plants require naturally occurring hot water and permeable rock. Next-generation approaches aim to remove these constraints.
The basic idea is simple: hot rock exists almost everywhere, but naturally occurring hot water and permeable reservoirs do not. Traditional geothermal systems only work where both are present. New technologies aim to overcome this limitation.
1. Conventional hydrothermal: This is the approach used today in places like California and Nevada. Natural hot water and fractures already exist underground. Wells bring the hot water to the surface, where it drives turbines to generate electricity.
Today, in places like California and Nevada:
Surface
↓
Well ↓ ↑ Well
========================
Natural hot water
========================
2. Enhanced geothermal systems (EGS): If natural water is absent or fractures are limited, engineered solutions can create a reservoir.
Using techniques adapted from the oil and gas industry, including horizontal drilling and hydraulic fracturing, water is circulated through hot rock. This allows previously inaccessible heat resources to be turned into electricity.
Surface
↓ Water injection
Well ↓
========================
Hot rock
Engineered fractures
========================
Well ↑ Hot water
Using horizontal drilling and hydraulic fracturing techniques borrowed from the oil and gas industry, water is circulated through hot rock, turning previously inaccessible heat into a source of electricity.
3. Closed-loop systems: In closed-loop systems, the fluid never comes into contact with underground rock formations or groundwater. Instead, fluid circulates inside sealed pipes, absorbs heat from surrounding rock, and returns to the surface. These systems require little or no natural reservoir.
The fluid never comes into contact with groundwater or rock formations:
Surface
↓ ↑
│ │
│ │
│________________│
Hot rock
Fluid circulates inside a sealed pipe, absorbs heat from surrounding rock, and returns to the surface. Little or no natural reservoir is required.
4. Superhot geothermal: By drilling deeper, temperatures above 400°C can be reached. At such temperatures, a single well could potentially produce several times more energy than conventional geothermal wells.
By drilling much deeper:
Surface
↓
│
│
│
========================
>400°C superhot rock
========================
↑ Steam
Temperatures above 400°C can be reached, potentially allowing each well to produce several times more energy than conventional geothermal wells.
Why does this matter for the eastern United States?
Unlike California and Nevada, the eastern U.S. has relatively few shallow hydrothermal resources. However, hot rock exists several kilometers underground.
This means:
Today: geothermal electricity is concentrated mainly in California and Nevada.
If EGS succeeds: states such as Texas, Colorado, Utah, and even parts of Pennsylvania, Ohio, and Appalachia could generate geothermal power.
If closed-loop technologies mature: geographic limitations could be reduced even further.
This is why some experts describe geothermal as "underground nuclear energy" — a vast resource capable of providing reliable 24/7 power, unlike wind and solar, but one that remains largely untapped today.