Courtesy of The Conversation:
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.
Wilfred Elders, professor emeritus of geology at the University of California, Riverside, co-authored three of the research papers in the Geothermics special issue with Icelandic colleagues.
“Drilling into magma is a very rare occurrence, and this is only the second known instance anywhere in the world,“ Elders said. The IDDP and Iceland’s National Power Company, which operates the Krafla geothermal power plant nearby, decided to make a substantial investment to investigate the hole further.
This meant 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.
Elders said that the success of the drilling was “amazing, to say the least”, adding: “This could lead to a revolution in the energy efficiency of high-temperature geothermal projects in the future.”
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.
Gillian Foulger, professor of geophysics at Durham University, worked at the Kravla site in the 1980s during a period of volcanic activity. “A well at this depth can’t have been expected to hit magma, but at the same time it can’t have been that surprising,” she said. “At one point when I was there we had magma gushing out of one of the boreholes,” she recalled.
Volcanic regions such as Iceland are not active most of the time, but can suddenly be activated by movement in the earth tens of kilometres below that fill chambers above with magma. “They can become very dynamic, raised in pressure, and even force magma to the surface. But if it’s not activated, then there’s no reason to expect a violent eruption, even if you drill into it,” she said.
“Having said that, with only one experimental account to go on, it wouldn’t be a good idea to drill like this in a volcanic region anywhere near a city,” she added.
The team, she said, deserved credit for using the opportunity to do research. “Most people faced with tapping into a magma chamber would pack their bags and leave,” she said. “But when life gives you lemons, you make lemonade.”
Water and heat = power. nea.is
In Iceland, around 90% of homes are heated from geothermal sources. According to the International Geothermal Association, 10,700MW of geothermal electricity was generated worldwide in 2010. Typically, these enhanced or engineered geothermal systems are created by pumping cold water into hot, dry rocks at depths of between 4-5km. The heated water is pumped up again as hot water or steam from production wells. The trend in recent decades has been steady growth in geothermal power, with Iceland, the Philippines and El Salvador leading the way, producing between 25-30% of their power from geothermal sources. Considerable effort invested in elsewher including Europe, Australia, the US, and Japan, has typically had uneven results, and the cost is high.
With the deeper boreholes, the IDDP are looking for a further prize: supercritical water; at high temperature and under high pressure deep underground, the water enters a supercritical state, when it is neither gas nor liquid. In this state it carries far more energy and, harnessed correctly, this can increase the power output above ground tenfold, from 5MW to 50MW.
Elders said: “While the experiment at Krafla suffered various setbacks that pushed personnel and equipment to their limits, the process itself was very instructive. As well as the published scientific articles we’ve prepared comprehensive reports on the practical lessons learned.“ The Icelandic National Power Company will put these towards improving their next drilling operations.
The IDDP is a collaboration of three energy companies, HS Energy Ltd, National Power Company and Reykjavik Energy, and the National Energy Authority of Iceland, with a consortium of international scientists led by Elders. The next IDDP-2 borehole will be sunk in southwest Iceland at Reykjanes later this year.