One of the “ordinary” geothermal power plants
Can enormous heat deep in the earth be harnessed to provide energy for us on the surface? A promising report from a geothermal borehole project that accidentally struck magma – the same fiery, molten rock that spews from volcanoes – suggests it could.
The Icelandic Deep Drilling Project, IDDP, has been drilling shafts up to 5km deep in an attempt to harness the heat in the volcanic bedrock far below the surface of Iceland.
But in 2009 their borehole at Krafla, northeast Iceland, reached only 2,100m deep before unexpectedly striking a pocket of magma intruding into the Earth’s upper crust from below, at searing temperatures of 900-1000°C.
This borehole, IDDP-1, was the first in a series of wells drilled by the IDDP in Iceland looking for usable geothermal resources. The special report in this month’s Geothermics journal details the engineering feats and scientific results that came from the decision not to the plug the hole with concrete, as in a previous case in Hawaii in 2007, but instead attempt to harness the incredible geothermal heat…
…cementing a steel casing into the well, leaving a perforated section at the bottom closest to the magma. Heat was allowed to slowly build in the borehole, and eventually superheated steam flowed up through the well for the next two years…
The well funnelled superheated, high-pressure steam for months at temperatures of over 450°C – a world record. In comparison, geothermal resources in the UK rarely reach higher than around 60-80°C.
The magma-heated steam was measured to be capable of generating 36MW of electrical power. While relatively modest compared to a typical 660MW coal-fired power station, this is considerably more than the 1-3MW of an average wind turbine, and more than half of the Krafla plant’s current 60MW output.
Most importantly it demonstrated that it could be done. “Essentially, IDDP-1 is the world’s first magma-enhanced geothermal system, the first to supply heat directly from molten magma,” Elders said. The borehole was being set up to deliver steam directly into the Krafla power plant when a valve failed which required the borehole to be stoppered. Elders added that although the borehole had to plugged, the aim is to repair it or drill another well nearby.
Bravo! None of this response was as placid as it may sound written up for scientific journals. The facility faced the danger of eruption and fire throughout the experiment. Staff and scientists demonstrated their resourcefulness, resolving questions on the fly.