Searching for power from underground



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If geothermal power was a company, it would have what marketers call a branding problem.“Geothermal,” confusingly, means different things in different locations.In hot spots like Iceland or Yellowstone, it means tapping high underground heat, the sort associated with volcanoes or steam vents, usually to create electricity.In volcano-free New Hampshire, however, it really means “geo heat exchange,” in which water piped past the cool but predictable temperature of underground rock is used to reduce the cost of cooling or heating buildings.That type of geothermal is a small but growing part of the state’s attempts to reduce energy use. But maybe, just maybe, real geothermal is also possible here, and now it’s time to find out.“We’re looking to collect some more data and put it all together and create a database that a company could use (if it) wants to come and explore for geothermal heat,” said David Wunsch, New Hampshire state geologist.That data collection will come about as part of a new National Geothermal Data System, being put together by 40 state geological surveys, including New Hampshire’s. The New Hampshire Geological Survey will get a $297,665 grant from the U.S. Department of Energy as part of the $17.79 million geothermal data project. What kind of data do they want? Partly, it’s basic geological information, such as type and depth of bedrock. But it also includes temperatures at the bottom of some of the roughly 115,000 wells throughout New Hampshire or other deep holes to get a sense of where anomalous heat might be lurking.Wunsch said the deepest hole in state history was drilled three decades ago – it went down about one kilometer – as part of early geothermal exploration, but funding ran out and nothing was done about it. A flurry of geothermal excitement happened two years ago, when an MIT-led study designed to encourage geothermal energy mentioned the Conway region as the most likely location for it in the Northeast.Wunsch says this is due to high levels of uranium in Conway granite, which releases a sort of background energy that can heat water.The MIT study urged more research into using water or other liquids to enlarge cracks in granite and thus increase their ability to release heat. Such “fracking” is done to increase the flow from drilled water wells, although at much shallower depths than needed for geothermal power.Since the 2007 report, problems have come up with geothermal fracking, which may have contributed to small earthquakes in Switzerland and California. But it still seems the likeliest route to real geothermal.Even if New Hampshire never gets an electric plant powered by the Earth’s heat, the Geothermal Data System could help homes and businesses decide on geothermal heat exchange, Wunsch says.“We want to create some maps that show the thickness of the glacial deposits, sand and gravel, because that makes a big difference if you’re thinking of putting in a (heat) pump for your house.“If you’re sitting on 200 feet of gravel and sand, that doesn’t have enough heat capacity that granite would. The map would make a good planning tool for homeowners,” he said.This isn’t a project for the impatient, since the data gathering is expected to last three years, and then comes planning and construction. Still, you’ve got to start somewhere. – DAVID BROOKS/THE TELEGRAPHDavid Brooks’ GraniteGeek column runs Wednesdays in The Telegraph and online at granitegeek.org. He can be reached at 594-5831 or dbrooks@nashuatelegraph.com.

 

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