A vast, untapped source of clean energy lies beneath the western United States – one that could potentially supply around 10 per cent of the country’s electricity, according to a major new assessment by the United States Geological Survey (USGS).
The study, part of a decades-long effort to chart the nation's geothermal potential, focuses on the Great Basin region, spanning Nevada, Utah, California, Idaho, Oregon and Wyoming.
The USGS estimates that these geologically active states could yield up to 135 gigawatts of continuous, reliable geothermal power, provided that emerging technologies can unlock the energy buried deep underground. To put that in perspective, the average US home uses about 1 kilowatt of electricity on a continuous basis – so 135 gigawatts could meet the steady energy needs of around 135 million homes.
“USGS assessments of energy resources are about the future,” said Dr Sarah Ryker, acting director of the USGS. “We focus on undiscovered resources that have yet to be fully explored, let alone developed. We launched this work in the Great Basin because of the area’s history of geothermal activity – and we found even more potential for baseload power than had previously been known.”
Today, geothermal energy supplies less than 1 per cent of America’s electricity. Most of that comes from conventional hydrothermal systems, where naturally heated water rises through permeable rock.
But the USGS report reveals a much larger energy reservoir – one where heat is trapped in dense, impermeable rock layers miles below ground.
To tap these ‘enhanced geothermal systems’ (EGS), engineers would need to drill deep – in some cases, over 6km (3.7 miles) – and fracture the rock to allow water to circulate and absorb heat.
This heated water can then be pumped back to the surface to generate electricity, offering a constant source of power that doesn’t rely on the weather.
To estimate the potential energy available, USGS researchers combined underground temperature maps, heat flow data and advanced techniques that could measure the efficiency of extraction and energy conversion. The collaborated with the US Department of Energy (DOE), state geological surveys and academic researchers across the country.
Ryker emphasised that this kind of work has wider benefits beyond energy production: “Natural resources continue to drive much of the nation’s economy. Over our history, we have reinvented our techniques for mapping and characterising resources, and in fact our newest surveys of the subsurface help identify both geothermal and critical mineral resources, and in some cases, groundwater.”
Still, scaling up EGS technology remains a major challenge. While pilot projects have shown promise across the Great Basin already, no commercial-scale enhanced geothermal plants are yet in operation in the US.
One key obstacle is cost, but the US Department of Energy aims to tackle this through its Enhanced Geothermal Shot™ programme, which is seeking a 90 per cent reduction in the cost of the technology by 2035.
The USGS isn't stopping at the Great Basin. The agency's next focus is the Williston Basin in North Dakota – another region with hidden geothermal promise.
If successfully developed, geothermal energy could become a major pillar of America’s low-carbon future.
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