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News

Changed methodology for assessing geothermal primary energy production for electricity generation and heating

7.12.2010

The National Energy Authority (NEA) has revised its methodology for assessing geothermal primary energy production for electricity generation and heating

Earlier assessments assumed 10% efficiency in the electricity generation conversion process, while the cutoff temperature for determining the energy content of fluids utilized for heating was taken as 15°C.  Geothermal primary energy is now defined as the energy released from geothermal fluid as it passes from an initial thermodynamic state to a reference state, which is taken to be 15°C at 1 bara.  Geothermal primary energy use over a given period is the difference between the primary energy production and the primary energy content of reinjected fluid over the period.  NEA will use this single definition for assessing geothermal primary energy production and use for energy statistics purposes, irrespective of the mode of usage (electricity generation or heating).  Primary energy assessments will thus from now on require reliable and detailed information on the enthalpy and mass production of geothermal fluids in high-temperature areas as well as low-temperature areas.

Geothermal primary energy production has been reassessed on the basis of the revised methodology back to 2001, as the utilizitation ratio of produced primary energy for electricity generation has risen steadily over the past decade.  Previously published assessments that were based on the assumed 10% conversion efficiency for electricity generation have thus changed slightly.

The methodology and its basis is discussed in detail in a report recently published by the NEA:  Primary energy use of geothermal power plants and district heating utilities in Iceland until 2009.  The report is only available in Icelandic