In Jules Verne’s 1864 classic “Journey to the Center of the Earth,” Professor Lidenbrock and his nephew Axel begin their descent from the slopes of Snæfellsjökull, a volcano on the western tip of Iceland.

Today, scientists and engineers are once again exploring the earth deep beneath Iceland’s surface. But now their goal is not to find remnants of humankind’s lost ancestry but future sources of clean energy.

Iceland is in a unique geological position, sitting astride a rift between two tectonic plates. The region is a hotspot of geological activity, with numerous active volcanoes, geysers and hot springs.

Rising energy demands

As well as boosting Iceland’s tourist industry, this also fulfills many of the island’s energy requirements. Two-thirds of primary energy come from geothermal sources, which provide heat for 90 percent of Iceland’s homes.

However, the country wants to do more with its geothermal resources, particularly geothermal electricity generation. And their efforts could have an impact far beyond the small island on the edge of Europe.

Today, seven geothermal power stations produce around 30 percent of Iceland’s electricity. But demand, especially from the energy-intensive aluminum sector, is rising rapidly.

Large-scale geothermal power production is tricky. The steam and hot water extracted from conventional boreholes to heat buildings are far cooler than steam used in conventional thermal power stations. As a result, the output of geothermal power plants tends to be lower than that of conventional ones.

Iceland’s largest geothermal plant, Hellisheiði, produces 303 megawatts of electricity using steam from 50 wells, each up to 2,200 meters deep.

The search for “supercritical” fluid

In search of greater output, scientists, geologists and engineers are drilling much deeper into the earth. They hope to access water at much higher temperatures and pressures – between 450 and 600 degrees Celsius and 23 to 26 megapascals.

In such extreme conditions, the nature of water changes radically. It becomes a “supercritical” fluid, neither liquid nor gas but with characteristics of both. Supercritical fluids are already widely used in industry and conventional power generation, where they can boost output and thermal efficiency.

There’s a catch, however. To access supercritical water, it is necessary to drill down five kilometers, more than twice the depth of today’s geothermal wells. In 2005, the Iceland Deep Drilling Project set out to do just that. Its first attempt, IDDP-1, had to be aborted in 2009 when the drill unexpectedly reached liquid magma at a depth of just over two kilometers. In 2016, operations shifted to a second site, IDDP-2, at an existing 2,500 meter well on the Reykjanes Peninsula.

Reasons for optimism

In January last year, after 176 days, the IDDP team achieved its objective, reaching a depth of 4,569 meters. Despite challenges along the way, like stuck drills and problems sealing the walls of the well with cement, there are reasons for optimism. Measurements taken indicate favorable conditions for supercritical fluid: a temperature of 426 degrees Celsius, a pressure of 34 megapascals and areas of permeable rock through which it could flow.

The next challenge is power production. Work is already underway to build a flow line and pilot plant. The team is proceeding cautiously – it doesn’t yet know the chemical composition of the fluids that will come up – and flow testing is scheduled to begin in mid-2019.

If all goes to plan, the IDDP won’t just take Iceland one step closer to supercharging its geothermal power production. The work could also have important implications for sustainable power production elsewhere in the world. Geologists believe that supercritical geothermal fluids might be found wherever there are relatively “young” volcanoes. That could include South Pacific islands, parts of Latin America and even the western U.S.

That means that it’s not only Icelanders who could benefit from their ambitious project to harness the geothermal power deep beneath the earth. It could also add another weapon to the world’s arsenal for fighting climate change. —Jonathan Ward

Published: September 2018

Images: Photo4emotion/ddp images