Man-Made Geothermal Power: Wresting Energy from Hot Rocks--One Kilowatt at a Time [Slide Show]
The enhanced system at Soultz in France is the first such artificial geothermal power plant
Credits: © EITAN HADDOKROCKY ECONOMICS?: All told, the 1.5 megawatts of electricity cost $64.5 million (50 million euros) for research and construction, but the system could potentially produce as much as three megawatts. Electricity could be delivered to the grid for 31 cents (0.24 euro) per kilowatt-hour, according to Graff, though the project is designed to remain simply an experimental prototype... © EITAN HADDOK
SUSTAINABLE SOURCE?: Engineer Jean-Jacques Graff, director of the site, and geologist Albert Genter, under the drilling derrick GPK2, discuss how long Soultz-sous-Forêts might produce energy. Eventually, the action of the water will cool the rock to the temperature where there will not be enough heat energy to spin turbines... © EITAN HADDOK
CLEANING HOUSE: Nevertheless, the heat exchangers require periodic cleaning to remove fragments of rocks brought up with the fluid. And hydrochloric acid or other chemical "cocktails" can be added to prevent dissolved sediments from clogging the injection well... © EITAN HADDOK
HARSH BREW: Because the briny water is three times as concentrated as the ocean—13 ounces of salt per gallon (100 grams per liter)—and carries dissolved metals and minerals, as well, it can quickly plug the piping... © EITAN HADDOK
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LAYING PIPE: At a depth of 14,763 feet (4,500 meters), the fluid—briny water found at that depth—flows through an eight-inch- (20-centimeter-) wide pipe before being released into the rock and migrating another 1,640 feet (5,000 meters) deeper... © EITAN HADDOK
GRANITE FLOOR: The granite 16,400 feet (5,000 meters) down is roughly 392 degrees Fahrenheit (200 degrees Celsius), and has been transformed by faulting and deep hydrothermal fluids into a softer, crumbly rock susceptible to fracturing... © EITAN HADDOK
DRILL BIT: Such triple-head drills, known as Tricone bits, are used to drive boreholes some 16,400 feet (5,000 meters) deep beneath the surface, opening the way for an eight-inch- (20-centimeter-) wide pipe... © EITAN HADDOK
HOT ROCKS: Soultz-sous-Forêts is located in France's northern Alsace region, an area known geologically as the Rhine Graben, which contains the perfect rock for human-engineered geothermal energy... © EITAN HADDOK
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TERRA WATTS: Soultz-sous-Forêts's enhanced geothermal power plant involved drilling two pairs of boreholes down to deep, fractured rock—one from each pair in which hot fluid is extracted to deliver its calories and the others into which the cooled fluid is injected after it is used to make electricity... © EITAN HADDOK
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