What that work looked like in the early days is almost unimaginable in the age of digital mapping technology. Tasked with producing comprehensive maps of geothermal resources, Wang spent five years developing his method so painstaking it bordered on obsession.

Armed with nothing more than a set square and paper maps, he plotted by hand more than 2,000 hot spring and geothermal well locations across China.

"I'd go through records — province, county, village — then get down on the map with a ruler until I found the exact spot," he said. "I'd mark it, and then I'd imagine the terrain. What did it look like there? Why was the water hot?"

Wang said geothermal exploration is similar to medical diagnosis. First comes the equivalent of a CT scan — geophysical surveys that detect anomalies in electrical signals beneath the surface, hinting at different rock types and structures. Then comes the biopsy — a test well used to measure underground temperatures.

Since 2011, the China Geological Survey has launched a national project to survey and evaluate geothermal resources. Led by Wang, the project has brought together hundreds of technicians from across the country to conduct systematic investigations of geothermal resources in each province.

Among the several types of geothermal resources, the potential of hot dry rock geothermal energy is especially pertinent. Wang and his team estimate that China's hot dry rock resources at depths of between 3 and 10 kilometers contain the heat equivalent of burning 856 trillion metric tons of coal.

"That figure is astronomically large. But it only tells us the heat is there. What we can actually extract is a different question," he said.

"To unlock it, we must artificially fracture the rock, pump cold water down, let it heat up in the cracks, and bring it back up again."

Since 2017, Wang and his team have attempted to answer that question in the Gonghe Basin in Qinghai province. There, they've drilled a well 4,000 meters deep and encountered temperatures exceeding 200 C. Using hydraulic fracturing, they've brought heat to the surface.

The experiment worked, but the amount of energy recovered was still too small to be commercially viable, he said.

"The pathway is open. Now it's about scaling up and bringing down costs. You can't know for certain until you drill. And sometimes, the Earth says no," he said.

Some wells fail because the geology is too complex. But for Wang, failure is simply part of the scientific process.

"We are always moving from the unknown to the known. Every time we add a new method, a new tool, we understand a little more," he said.

When Xiong'an New Area was established in Hebei province in 2017, Wang and his team were tasked with conducting geothermal energy surveys and exploration.

Their work there earned them the first prize of the Hebei Provincial Science and Technology Progress Award.

To Wang, such achievements do not come from individual brilliance alone.

"Geothermal research is deeply interdisciplinary — geophysics, geochemistry, rock mechanics, hydrogeology, even mathematics and chemistry," he said.

"No person can be an expert in all of it. We need a team. And we need to give young people the conditions to settle down and really dig in.

"Working in geothermal exploration also requires the spirit of grinding a sword for 10 years," he said.