A new resource classification scheme is described, based on different geothermal potentials: theoretical, technical, economic, sustainable, developable – decreasing successively in size. In converting theoretical to technical potential, the recovery factor (the ratio extractable heat/heat present at depth) is of key importance. The proposed classification of potentials provides a useful template for standardizing the future reporting of geothermal energy resources worldwide.

We revised the concept of convective geothermal plays by analysing four case studies: Larderello and Mt. Amiata (Italy), The Geysers (USA), and Kizildere (Turkey). We suggest a classification based on the age and nature of the heat source and the related hydrothermal circulation, considering that the tectonic setting is not a discriminant parameter suitable for a classification. Finally we propose to distinguish the convective geothermal plays as volcanic, young intrusive and amagmatic.

The present work discusses the utilization of phase change materials for energy storage in geothermal space heating systems. The thermodynamics and thermoeconomics of the combined heating and thermal storing system were studied to show the scope of energy storage and cost savings. A computational model of the combined space heating and thermal storage system was developed and used to perform thermodynamic studies of the heat storage process and heating system efficiency.