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As a world leader in geothermal energy Iceland has developed expertise in different types of wells or fields. These are divided into high temperature and medium temperature fields, where water of hot water of varying temperatures (from 120 to 350 deg C) is used to power turbine generators. Beyond these conventional systems, there are two more advanced geothermal fields being researched; enhanced and supercritical systems. Enhanced geothermal systems (EGS) involve injection of cold water into the hot rock layer. As well as Iceland, experiments with EGS are ongoing in various places around the globe, including central Europe and Australia. If successful, this EGS research could create major opportunities for distributed small scale geothermal energy production (and by extension hydrogen production) in many countries. Globally, the potential for geothermal energy is tremendous, says Bjarnason. “Heat is constantly being produced within the core of the planet from the decay of radioactive material,” he explains. “The total amount of heat stored in the earth’s crust is of the order of 5.4 billion EJ.” (For comparison the US consumes about 14 EJs - Exajoules - of electrical energy per year). According to Bjarnason, only 0.1 percent of this stored energy would satisfy the world’s energy consumption for the next 13,500 years. “The only problem is how to get to it.” One answer is deep drilling. As well as EGS projects, Iceland’s drilling experts are investigating supercritical geothermal systems (SGS), wherein wells are sunk five kms deep (twice the depth of conventional boreholes) to access supercritical steam. Compared to the 235 deg C temperature and 30 bar pressure of a conventional steam well, a supercritical field could produce steam at 430-550 deg C and 230-260 bar, resulting in a tenfold increase in energy output.
Deep well drilling to access supercritical steam in new technological frontier in geothermal industry. Deep drilling is a very complex and costly challenge, but Iceland is pushing ahead with three planned wells, one of which is government funded and expected to be started this year or next. |
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