Subject: Comments to Draft Specifications for Application of UNFC-2009 to Geothermal Energy Resources: from Christopher Rochelle, British Geological Survey, United Kingdom
20 July 2016
This is a useful document as it aims to provide a set of common reference points with which to compare geothermal assessments. I like the use of the case studies to show how this might be implemented.
Some of the areas covered are outside my area of expertise, so I have only a few comments. These are listed below. I realise that they may be slightly to one side of the aims of the report, but I raise them as I think they have a bearing on the subject.
(1) In terms of ‘other geothermal products’ (Section A). I note that these have the potential to make an important difference in terms of whether a geothermal project goes ahead, as they may make the difference between a project being sub-economic or economic. So though they may have little direct relevance in terms of power output, they may play a very important role in terms of being able to increase overall geothermal power development. This has been recognised by the European Commission by the recently funded CHPM2030 project which is considering production of combined heat, power and metals (http://www.chpm2030.eu).
(2) In terms of ‘other geothermal products’ (Section A) and/or ‘Multiple Energy Products’ (Section H). These address producing heat, energy or physical products. But a concept exists (though not demonstrated yet) for using CO2 as a working fluid instead of water. One consequence of this, is reaction of CO2 with rocks and the trapping of the CO2 underground. Essentially, this represents one type of CO2 sequestration technology, and disposal of a waste product from another energy sector. The ‘product’ in this case would be a service, using up waste CO2. This could also have economic (and environmental) benefits, if linked to carbon credits or other such revenue stream for disposal of CO2. I suggest the wording of the text be checked to be flexible enough to include this concept should it become more developed.
(3) I could see no mention of ‘heat storage’ in the document. It appears to concentrate on natural thermal resources already in place. However, there is potential to use the geosphere for the (probably seasonal timescale) storage of waste heat – essentially creating an artificial geothermal resource. This could cover waste heat from conventional power plant, or excess heat at times of low demand (some types of conventional and nuclear power plant are slow to shut down, so disposal of waste heat could be necessary). Again, this concept is in its infancy, but it might be useful for the document to either include it specifically, or allow the text to be flexible enough to include it should it be developed.
(4) In terms of case studies. I like the range of different systems that these cover, though I wonder if it might have been useful to include one or two examples of the larger, perhaps better known high enthalpy systems.
Comments from Christopher Rochelle, British Geological Survey, to Draft Specifications for Application of UNFC-2009 to Geothermal Energy Resources.
20 July 2016
This is a useful document as it aims to provide a set of common reference points with which to compare geothermal assessments. I like the use of the case studies to show how this might be implemented.
Some of the areas covered are outside my area of expertise, so I have only a few comments. These are listed below. I realise that they may be slightly to one side of the aims of the report, but I raise them as I think they have a bearing on the subject.
(1) In terms of ‘other geothermal products’ (Section A). I note that these have the potential to make an important difference in terms of whether a geothermal project goes ahead, as they may make the difference between a project being sub-economic or economic. So though they may have little direct relevance in terms of power output, they may play a very important role in terms of being able to increase overall geothermal power development. This has been recognised by the European Commission by the recently funded CHPM2030 project which is considering production of combined heat, power and metals (http://www.chpm2030.eu).
(2) In terms of ‘other geothermal products’ (Section A) and/or ‘Multiple Energy Products’ (Section H). These address producing heat, energy or physical products. But a concept exists (though not demonstrated yet) for using CO2 as a working fluid instead of water. One consequence of this, is reaction of CO2 with rocks and the trapping of the CO2 underground. Essentially, this represents one type of CO2 sequestration technology, and disposal of a waste product from another energy sector. The ‘product’ in this case would be a service, using up waste CO2. This could also have economic (and environmental) benefits, if linked to carbon credits or other such revenue stream for disposal of CO2. I suggest the wording of the text be checked to be flexible enough to include this concept should it become more developed.
(3) I could see no mention of ‘heat storage’ in the document. It appears to concentrate on natural thermal resources already in place. However, there is potential to use the geosphere for the (probably seasonal timescale) storage of waste heat – essentially creating an artificial geothermal resource. This could cover waste heat from conventional power plant, or excess heat at times of low demand (some types of conventional and nuclear power plant are slow to shut down, so disposal of waste heat could be necessary). Again, this concept is in its infancy, but it might be useful for the document to either include it specifically, or allow the text to be flexible enough to include it should it be developed.
(4) In terms of case studies. I like the range of different systems that these cover, though I wonder if it might have been useful to include one or two examples of the larger, perhaps better known high enthalpy systems.
Comments from Christopher Rochelle, British Geological Survey, to Draft Specifications for Application of UNFC-2009 to Geothermal Energy Resources.