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Tapping A Volcano, One Caribbean Island Prepares To Make Power For Many

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by Lina Zeldovich

Sitting on top of a volcano may be just what Nevis, a small sombrero-shaped Caribbean Island, needs to become one of the greenest nations on Earth. Frequented by many celebrities including Oprah Winfrey, Dustin Hoffman, Michael Douglas and Beyoncé, this former British colony is about to tap into the geothermal power that lies beneath its pristine surface.

“Nevis is on the cusp of something truly revolutionary,” says Hon. Mark Brantley, Nevis’s deputy premier. “We in Nevis care deeply about the environment—and weaning ourselves off fossil fuels for our energy needs reduces our carbon footprint.”

Geothermal energy, which converts the heat of magma into electricity, is the island’s new frontier. Magma is naturally hot from decaying radioactive uranium and potassium. Typically, it is contained around six miles below the Earth’s crust, but there are “hot spots” where the heat is easier to access—often near volcanos, boundaries of tectonic plates or places where the crust is thin. Underground water sitting in rock fractures above the molten rock is heated and becomes pressurized. This surges up to the surface, where it turns into steam that geothermal plants use to spin electricity-producing turbines. A green energy source, geothermal doesn’t produce carbon dioxide like fossil fuels, presents less danger than nuclear plants and is renewable because it’s essentially inexhaustible.

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(Diagram of a geothermal power plant. Courtesy University of Texas Bureau of Economic Geology.)

But finding a workable hot spot can be tricky. The right site requires a combination of factors, says Thomas Drolet, president and CEO of Nevis Renewable Energy International (NREI), the company that will be developing the plant once a concession agreement is signed. “We are after that magma-heated rock that represents the reservoir of heat, but we also have to have the method of carrying this heat to the surface,” he says, explaining that the presence of interstitial water in the rocks’ fractures is crucial. “If there’s no water and fractures in that rock, then I can’t bring it up to the surface.”

Paradise for celebrities and geothermal energy

Every geothermal project starts with site exploration.  A few years ago, Mark Lambrides, the energy and climate change division chief for the Organization of American States’ Department of Sustainable Development, led a crew of scientists up to Nevis Peak, the extinct volcano that stopped erupting about 100,000 years ago. Geologists looked at local plates and fault lines, geochemists measured the water’s temperature and chemical make-up, and geophysicists assessed the depth of the underground reservoir. “We did surface-based studies,” Lambrides says. “It was clear that this was an attractive opportunity.”

Drolet describes the target area in Nevis as particularly well fractured. The question iswhere and how deep they’ll have to drill the wells.

Drilling wells is the hardest part of the project, says Bruce Cutright, NREI’s Chief Technology Officer. The team needs to hit a spot with sufficient water volume and temperatures above 300 degrees Fahrenheit; the hotter the better, in fact. “If we don’t end up with the well that produces enough steam, then we need to drill another well,” Cutright says.

Water chemistry is also important—the fewer dissolved minerals the better to keep steam from leaving unwanted deposits on the pipes. Other chemicals such as hydrogen sulfate, a dissolved gas compound, can be corrosive and dangerous. “There are simple engineering techniques to deal with it,” says Cutright, “but you need to know this in advance so you take proper precautions when building the production generator.” 

Cutright expects to drill up to four production wells that will supply steam to the generator. Once the wells are secured, erecting the actual plant will be easy. “That is relatively straightforward,” Drolet says. “Drilling is where the risk is, where the nail biting is.”

Nevis’s first attempt at building a geothermal plant foundered—the prior developer, West Indies Power Company, had trouble securing financing. NREI has secured partnerships with sustainable development veterans Tetra Tech and AltaRock Energy. “Our partners are our strength,” says Drolet, who estimates the entire project taking around four years.  

A regional power supplier?

Depending on how much steam the team will uncover, Nevis may be able to export energy to the nearby islands of St. Kitts, St. Lucia and Dominica via subsea cables. To sustain itself, Nevis needs to produce 10 to 15 megawatts (MW) of power. But its geothermal energy production potential is greater, although it’s not yet clear by how much. Preliminary assessments range from 40 to 400 MW of recoverable power. The drilling will answer that question.

Cutright, whose previous work involved running subsea cables across Alaskan bays, says that the project could open the region to an interconnected power supply. “If we find steam that’s really coming out of our ears,” he says, “we can afford to transport the power.”   

That may transform the economics of the entire Eastern Caribbean. “Little islands and small economies like Nevis are constantly buffeted by escalating oil prices,” says Brantley. The island is now almost entirely powered by expensive, environmentally dangerous diesel that has to be imported on tankers. “Geothermal changes that,” he says.

Brantley hopes Nevis can stop using fossil fuels entirely, which would appeal to eco-conscious travelers, and envisions tourists renting electric scooters and cars in about five years. “We stand on the threshold of being the paradigm of sustainable development,” he says. “Especially if we can export power to our neighbors.”

But is constructing a plant on top of a volcano safe? Can drilling wake it up again?

“Volcanoes are historically irritable characters, but we’ve got a pretty good handle on the Caribbean geology,” Cutright says, affirming that there’s no danger of Nevis Peak erupting. “The geological survey and the whole Caribbean volcanic history give us that confidence.” 

Neither can the plant’s construction cause volcanoes to flare up, he adds. “A geothermal plant will actually be cooling the rock below the land surface—although over time scales of many years—and, if anything, this would serve to make the area more stable, rather than more prone to an eruption.”

Top Image: Nevis.

Lina Zeldovich grew up in a family of Russian scientists listening to bedtime stories about the inner workings of volcanos and black holes. Now she writes about science, medicine, health, environment and technology. Her work has appeared in Nautilus, Scientific American and Psychology Today.

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