Engineers at the Tyr drilling rig in Krafla’s snow-covered caldera hope to use a supercritical-water source two miles underground to produce 10 times as much geothermal electricity as a normal well.

It’s spring in Iceland, and three feet of snow covers the ground. The sky is gray and the temperature hovers just below freezing, yet Gudmundur Omar Fridleifsson is wearing only a windbreaker. Icelanders say they can spot the tourists because they wear too many clothes, but Fridleifsson seems particularly impervious. He’s out here every few days to check on the Tyr geothermal drilling rig, the largest in Iceland. The rig’s engines are barely audible over the cold wind, and the sole sign of activity is the slow dance of a crane as it grabs another 30-foot segment of steel pipe, attaches it to the top of the drill shaft, and slides it into the well.

Beneath the calm landscape, though, Fridleifsson and his crew of geologists, engineers and roughnecks are attempting the Manhattan Project of geothermal energy. The two-mile-deep hole they’ve drilled into Krafla, an active volcanic crater, is twice as deep as any geothermal well in the world. It’s the keystone in an effort to extract “supercritical” water, stuff so hot and under so much pressure that it exists somewhere between liquid and steam. If they can tame this fluid — if it doesn’t blow up their drill or dissolve the well’s steel lining — and turn it into electricity, it could yield a tenfold increase in the amount of power Iceland can wrest from the land.

Iceland’s geological evolution makes it especially well suited to harvesting geothermal energy. The island is basically one big volcano, formed over millions of years as molten rock bubbled up from the seafloor. The porous rock under its treeless plains sponges up hundreds of inches of rain every year and heats it belowground. Using this energy is simply a matter of digging a well, drawing the hot fluid to the surface, and sticking a power plant on top. Then, as power plants go, it’s business as usual: Steam spins a turbine that drives a generator, and electricity comes out the other end. More than 50 countries use geothermal power; pretty much anywhere magma and water are within a few miles of the surface is fair game. Iceland ranks 14th in the world for geothermal resources but is the highest per-capita producer of geothermal power. It’s committed to getting clean power out of the ground.

And commitment is what the rocky country needs right now. Last fall, Iceland entered a deep economic recession following a financial meltdown. Now, Iceland’s economy is down to fishing, metals and its clean, limitless supply of geothermal energy. It’s betting heavily on that energy, hoping to someday offload excess electricity to Europe through undersea cables, and Fridleifsson’s project is the all-in wager of the game. Many countries dabble in green energy — a solar plant here, a wind farm there — as they try to wean themselves off oil and coal. Iceland, on the other hand, has been making zero-emissions power a reality since the oil shock of the 1970s, when its progressive inhabitants realized that their dependence on imported energy was an economic vulnerability. Fridleifsson’s project, once just a scientific experiment, is the most recent expression of that ethos. If the gamble pays off, it could not only catapult Iceland out of debt but revolutionize renewable-energy efforts around the world.

From the Ground Up

Paul Wootton

Supercritical water from a 2.5-mile well

[A] transfers its heat energy to clean water [B]. This creates steam, which drives a turbine [C] to generate electricity. A cooling circuit [D] absorbs excess heat and condenses the steam into water to reuse in the heat exchanger. Used supercritical water is pumped back underground [E]

The process has been methodically slow, but after nearly a decade and $22 million, the Iceland Deep Drilling Project should hit supercritical water next month. Fridleifsson has already weathered one failed attempt, in 2005, when a well collapsed during a routine flow test. And so, close as he is, he’s modest about his chances; when pressed, he admits to being “cautiously optimistic” about the current attempt. The project’s risk assessor gives it a 50-50 shot at succeeding. Fridleifsson doesn’t mention that if it works, a plant built around this well could deliver as much power as a small nuclear plant and become the global model for geothermal projects. And he certainly doesn’t mention (as oilmen, solar engineers and wind farmers so often say of their work, but Fridleifsson actually deserves to of his) that it could rearrange the future of energy.

A Modest Proposal
Iceland turns geothermal energy into electricity in two ways: Venting 600°F steam from a mile underground through a turbine, and a more energetic method that pulls 390° water from deep wells and heats surface water, making steam to drive turbines. Harnessing a natural supply of supercritical water — water that’s three times as hot and under enormous pressure — and turning it into electricity would be like switching from diesel to jet fuel. “If we succeed, we expect to increase power output by 5 to 10 times

[above what a typical well can produce]

,” Fridleifsson says.

To appreciate the benefits of free supercritical water, it helps to understand that most coal plants and nuclear power plants make supercritical water before generating electricity. The plants transfer heat energy — produced by burning coal or by the radioactive decay of isotopes — to water in a pressurized tank to bring it to a supercritical state. The process allows the water to maintain the high-energy intermolecular hydrogen bonds of a liquid, yet flow through pipes with near-zero resistance like a gas. It then runs through heat exchangers to create even more steam, which drives turbines to make electricity.

The IDDP well will dip two and a half miles belowground into a pocket of water heated to 1,100° by a bubble of magma. Water normally exists as steam at this temperature, but the immense pressure of the rock above holds the water in a near-liquid state. Once the water squirts to the surface, it will retain nearly all the energy that heated and compressed it. It is virtually certain that engineers will have to redesign existing heat exchangers to handle the water’s heat and potentially corrosive chemistry, but a plant running on naturally occurring supercritical water could churn out up to 500 megawatts, on par with a small nuclear reactor and half of what a large coal plant produces. Unlike these, though, the IDDP’s zero-emissions power source will last as long as the Earth’s core continues to heat rainwater.

Iceland’s geothermal efforts are currently operating at 20 percent capacity. If it exploited the island’s full reserves in only the conventional way, it could produce 20 terawatt-hours of electricity per year — about the same as three nuclear reactors. Tap into other supercritical reserves, or drill deeper into existing wells, and Iceland’s electric output could be five times that of the U.S., the world’s largest producer of geothermal electricity; Iceland is only the size of Kentucky.
In 2000, Fridleifsson recruited Wilfred Elders, a professor emeritus of geology at the University of California at Riverside, from retirement to co-lead the IDDP. Geological studies revealed that supercritical water does indeed flow under Iceland, and the six-mile-wide Krafla caldera was the place to go after it. They realized that all they have to do is tap the stuff — and hope that it doesn’t destroy the drilling equipment in the process.

Iceland has been running on geothermal power since the turn of the 20th century. Geothermal provides four terawatt-hours of electricity to the island a year, fulfilling about 25 percent of the country’s consumption, in addition to nearly 90 percent of its heat and hot water. (The U.S. has an estimated 400 terawatt-hours in geothermal resources but produces just 14.8 terawatt-hours a year, which amounts to only 0.38 percent of its overall electricity consumption.) Iceland’s international expertise on geothermal power, however, came with a steep learning curve. “We know better than anyone else how many things can go wrong,” says Bjarni Palsson, the IDDP’s head drilling engineer.
And with such a volatile fluid, a lot can go wrong. “Worst case, we have a blowout, and an uncontrolled flow of fluid blows the whole rig off,” says engineering geologist Sebastian Homuth, who conducted the risk assessment of the project. This happened on one of Iceland’s drilling projects in 1999, to incredible effect: The blowout left behind a 100-foot-wide crater. That explosion occurred because of a malfunction of the valve used to seal a wellhead in the case of a blowout. The IDDP’s stop valve is strong enough to prevent an explosion from trashing the rig, but a blowout could make reopening the well difficult.

It’s also likely that hydrochloric acid potentially present at these depths will make the water as caustic as battery acid. Engineers plan to strengthen the well with a steel lining, but “there is a good chance that this fluid is so corrosive that it will melt the steel within hours,” Homuth says. As long as the fluid shooting up the well remains in steam form, as the engineers hope it will, the hydrogen and chlorine ions it carries cannot form hydrochloric acid. Unfortunately, no one will know either way until the fluid races to the surface. A more mundane failure is also possible — the drill could simply miss the supercritical water, or hit impenetrable magma, forcing Fridleifsson to abandon this site and drill elsewhere.

The team members have already drilled two miles, but their sensory gear can’t withstand the hellish temperatures of the volcanic rock it will soon encounter, so they will drill the final 3,000 feet blind. The Tyr drilling rig works around the clock, grinding out 300 feet of rock per day, stopping every so often to take uncontaminated samples of the exotic rock. Elders and his team of mudloggers examine these rocks as they emerge from the well, searching for pyroxene-hornfels facies, the distinctive metamorphic rocks that indicate that the drill has hit its target. Regardless of the outcome at Krafla, the group will drill wells into two supercritical reservoirs on the west coast. Then, once they understand the supercritical fluid, they’ll start figuring out how to turn it into electricity. “We’re probably a dozen years away from a pilot plant,” Elders says. “I might not live to see it.”

The Patience to Be Bold
Iceland’s high-pressure geology and volcanic activity make its geothermal plan a model for countries with a similar landscape. Japan and Italy are talking openly about the potential of their own supercritical water. But Iceland is the first country forced to bet everything on green energy, and its combination of desperation and expertise means it could finally make geothermal a viable alternative to oil and gas. As other nations run out of fossil fuels, they will face the same impetus. But you won’t hear that from Fridleifsson. Perhaps it takes his kind of patience and modesty to make geothermal work. Fridleifsson insists that Krafla is just like hundreds of geothermal wells that he has drilled over the years. “There’s no magic in this,” he says. “It’s just a natural process.”