Geologists tap magma as high-grade energy source

Posted by Kate Taylor

Geologists have been testing a technique to generate energy from magma, after molten rock unexpectedly flowed into an exploratory well they'd been drilling in Iceland.

The magma appeared at a depth of 6,900 feet, forcing the researchers to terminate the drilling.

"We were drilling a well that was designed to search for very deep – 15,000 feet – geothermal resources in the volcano," says said Wilfred Elders of the University of California. "While the magma flow interrupted our project, it gave us a unique opportunity to study the magma and test a very hot geothermal system as an energy source."

Currently, a third of Iceland's electric power and 95 percent of its home heating is produced from the steam and hot water that occur naturally in volcanic rocks.

"The economics of generating electric power from such geothermal steam improves, the higher its temperature and pressure. As you drill deeper into a hot zone the temperature and pressure rise, so it should be possible to reach an environment where a denser fluid with very high heat content, but also with unusually low viscosity occurs, so-called 'supercritical water'," says Elders.

"Although such supercritical water is used in large coal-fired electric power plants, no one had tried to use supercritical water that should occur naturally in the deeper zones of geothermal areas."
               
After the influx of magma, the team terminated drilling and completed the hole as a production well.

"When the well was tested, high pressure dry steam flowed to the surface with a temperature of 400 Celsius or 750 Fahrenheit, coming from a depth shallower than the magma," Elders said. "We estimated that this steam could generate 25 megawatts of electricity if passed through a suitable turbine, which is enough electricity to power 25,000 to 30,000 homes."

The well is a particularly attractive source of energy, he says,  as typical high-temperature geothermal wells produce only five to eight megawatts of electricity from 300 Celsius or 570 Fahrenheit wet steam.

Elders believes it should be possible to find reasonably shallow bodies of magma, elsewhere in Iceland and the world, wherever young volcanic rocks occur.

"In the future these could become attractive sources of high-grade energy," he says.