Serge van Gessel-EuroGeoSurveys

Subject: Comments to Draft Specifications for Application of UNFC-2009 to Renewable Energy Resources: from Serge van Gessel, Vice-Chair of the Geo-Energy Expert Group, EuroGeoSurveys
12 September 2014

I would like to thank you for the invitation to review and comment the draft specifications for Application of UNFC to Renewables.
 
In general the UNFC specifications for renewable energy are well implemented and documented within the existing framework. Most aspects are to my knowledge sufficiently covered. The following comments are intended for further clarification.

• In theory most renewable primary energy sources represent an infinite “in-place” (or “in-situ”) quantity whereas fossil/mineral resources are finite and physically constrained to accumulations and rock volumes. This has the following implications for production strategy:
  • Production development of fossil/mineral resources is typically limited by the outlines of an accumulation or a rock volume and strives for an optimal recovery of “in-place” resources.
  • Production development of renewable energy is less influenced by geographical occurrence (i.e. the required primary conditions such as sun and wind are less strictly limited to specific locations) and strives for an optimal and cost-effective capturing of power/energy generated at a location.
• Although geothermal energy is considered to be a renewable resource, it actually represents a finite resource at the timescale of the project. The rate of subsurface reheating of cold injected water is generally much slower than the production rate the hot water.

Part II, Section C, Page 4, Second paragraph:

• An economic limit will be appropriate for geothermal doublets as the cooled injected water will eventually reach the hot water production well which will result in a decrease of performance.

Part II, Section E, Page 4 and Table for F-classes, Page 7:

• Class F4 raises the question “how to provide a reasonable resource estimation for undeveloped renewables?”. Renewable resources typically represent an infinite quantity. What methodology and further assumptions can be used best for objectively quantifying these classes (e.g. a single notional development plan, an estimate of energy that can be recovered over a fixed period of time)? How to define the recovery factor?

Table for F-classes, page 7:

• The term “renewable project” has been used in the “grey” text but this is not consistently done throughout the table. It seems that this adjustment should belong to the right column.

Part IV, Section C, Page 10:

• What assumptions/criteria are used to estimate/determine remaining quantities that could potentially be produced by future projects? (e.g. re-investments for replacing infrastructure in order to extend production, etc.).

Comments from Serge van Gessel, Vice-Chair of the Geo-Energy Expert Group, EuroGeoSurveys, to Draft Specifications for Application of UNFC-2009 to Renewable Energy Resources.