Subject: Comments to Draft Specifications for Application of UNFC-2009 to Renewable Energy Resources: from Chris Bromley, Chairman, IEA-GIA (Geothermal Implementing Agreement)
12 September 2014
Comments from Chris Bromley, Chairman, IEA-Geothermal Implementing Agreement, to Draft Specifications for Application of UNFC-2009 to Renewable Energy Resources.
12 September 2014
- Check consistency with existing country-specific geothermal resource assessment codes (e.g. Austalia and Canada).
- The main issue is really fundamental to all renewable energy resource assessments, that is, they are very difficult to quantify. If, as suggested in the draft specifications, one uses project economic design life as a limit to resource potential, there are wide ranges. For example turbines might have a design life of 25 years, but some Wairakei geothermal turbines have lasted 56 years and are not expected to be de-commissioned for another 10 years, Some wells corrode and fail in a few months or years, others (such as a bore drilled in 1928 in Kamojang, Indonesia) might have a discharge or injection lifetime of 100 years or more.
- The report uses the term 'geology' in a generic sense with respect to information required to constrain geothermal resource assessments. In fact, what is really needed for an economic and sustainable development strategy is a site-specific, mathematical reservoir simulation model, populated by rock properties (such as permeability and porosity), boundary conditions, and heat sources, that predicts energy extraction performance under different scenarios, and recharge/recovery rates from adjacent or deeper heat/fluid resources outside of the drilled volume. With development history, the models get better (through performance calibration), the rock properties change, and the sustainable energy extraction estimates get better. This, in a way, sets geothermal apart from the other renewables, as well as from hydrocarbon resource assessments. From a resource management point of view, geothermal is probably somewhere in between.
Comments from Chris Bromley, Chairman, IEA-Geothermal Implementing Agreement, to Draft Specifications for Application of UNFC-2009 to Renewable Energy Resources.