Tap Into a Volcano: Geothermal Energy From Supercritical Fluids
In Iceland, water comes in beautiful shapes and forms. The island, famous for its volcanic activity, containing geysers, hot pools, and a generally beautiful landscape might be the perfect place for geothermal energy innovation.
In 2000, scientists at the Energy Department of Iceland coined the question: Is it economically feasible to produce energy and chemicals from geothermal systems at supercritical conditions?
In order to answer this question, a potential industry-transforming geothermal operation has been initiated. The ambitious goal of the entire operation is to generate 40 MW of energy output from a single geothermal well, which is 36MW more than energy from a conventional geothermal well.This would result in an unprecedented advancement in the field of geothermal energy.
Conventional Geothermal Energy
The concept of geothermal energy is rather simple: drill a hole and feed steam originating from groundwater into power turbines. However, putting the theory of creating a geothermal energy resource into practice is a rather different story.
The technical challenges that have to be overcome are complicated and can best be referred to by using the appropriate jargon like logging, milling, reaming, rinsing, cementing, circulating, and casing a well. Proper execution of these proceedings usually result in creating a geothermal well that is around 2.5km deep and can produce steam at about 300 °C, resulting in 4 to 7 MW of electricity generation.
Increasing Geothermal Energy Output By 10 Times
If you squeeze water to an enormous pressure and try boiling it, you would no longer see any bubbles. Instead, the molecules full of energy are still, this phase is called supercritical. The groundwater in Iceland’s Reykjanes area consist of seawater that has seeped through tectonic plates. Like the ocean, pressure increases while you dig deeper into the earth’s crust.
To understand how pressure and temperature relate to normal conditions, imagine a liquid petroleum gas (LPG) fuel cell that has an approximate pressure of 7 bars at an ambient temperature of 16 °C. The temperature that is needed for sea water to become a supercritical fluid has to be at least 390 °C, and must be under 220 bars of pressure. Iceland, the country which is situated on top of the Mid Atlantic Rift, understands the potential of such geological resources and is trying to innovate the geothermal energy industry by developing a sustainable wellhead that taps into the source of volcanoes.
Iceland’s Journey Capturing Supercritical Fluid
IDDP-1, The First Well For Energy From Supercritical Fluid
The Iceland Deep Drilling Project was founded by a consortium of three Icelandic energy companies. Their collaboration has resulted in the creation of the IDDP-1 well. During the drilling operation they encountered unexpected challenges. They expected that drilling to 3.5 km depth would lead to finding an environment suitable for generating energy from supercritical fluids. However astonishingly, during their attempt, they encountered a chamber of molten magma at only 2.1 km below the surface and managed to control the hotspot without the explosive magma bursting the well. IDDP immediately saw the potential that this situation offered, as it might enable for serious testing of so-called engineered geothermal systems (EGS).
EGS employ a technique called hydrofracking, where cold water is pumped under enormous pressures into a neighbouring well with the attempt to split the rock and retrieve the resulting supercritical fluid in the IDDP-1 structure. To their relief, they succeeded in their efforts and installed steel casing at the bottom of the hole, thus constructing a well that delivered a transparent superheated steam flow of 410 °C. Incredibly, they demonstrated their capability of coping with the difficult chemical composition of steam and were able to transport the steam directly into an existing power plant, resulting in a power output of 36MWe.
IDDP-2, The Second Well Destined For Energy From Supercritical Fluid
On the 25th of January 2017, IDDP-2 officially became the deepest geothermal well in the world with a depth of 4,659 metres. Consequently the bottom of the well reached fluids at supercritical conditions. The Iceland Deep Digging Project is still investigating whether there is potential utilisation of the well, and it is expected that they will share the result from their investigation early 2019. If utilising supercritical wells in Iceland and elsewhere in the world proves to be successful, fewer wells would be needed to produce the same power output, leading to less environmental impact and improved economics.
