Now geoscientists have for the first time produced a realistic simulation of how such reservoirs are created. They predict these natural phenomena are widespread in volcanic areas, such as Japan and New Zealand.
Three ETH Zurich geoscientists decided to simulate this unusual geothermal system using a new computer model—and now they understand how it occurs, under what conditions it can arise, and where to look for other such systems. Their results and the associated modeling have just been published in Nature Communications.
Directly above the magma chamber, the researchers located a unique geothermal reservoir of water: one in which temperatures reached 450 degrees, a state which scientists refer to as supercritical.
Water becomes supercritical when heated above 374 degrees, from which point it starts behaving like a mixture of the gas and liquid phases. The two phases become inseparable and indistinguishable, resulting in a fluid that can be as dense as a liquid but at the same time flow as easily as a gas.
Water that has been heated by the magmatic intrusion to a supercritical temperature contains enough thermal energy for a single borehole to provide 35 megawatts of electrical capacity. In comparison, today’s standard geothermal boreholes have a capacity of 3 to 5 megawatts; a whole series of boreholes must be connected in a circuit to form a power station with a capacity of 50 to 100 megawatts.
Geologic controls on supercritical geothermal resources above magmatic intrusions - Samuel Scott, Thomas Driesner & Philipp Weis, Nature Communications 6, Article number: 7837 doi:10.1038/ncomms8837
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