Abstracted/indexed

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.

The recent aeromagnetic data over the Bida Basin, Nigeria, have been used to estimate the Curie-point depths (CPDs), geothermal gradients (GGs), and near-surface crustal heat flow (HF) of the basin. The result shows that the CPD varies between 15.57 and 29.62 km, GG varies between 19.58 and 37.25 °C km⁻¹, and HF varies between 48.41 and 93.12 mW m⁻². Regions are observed in the basin with shallow CPDs and corresponding high HFs, thus suggesting anomalous geothermal conditions.

Abandoned mines are usually nothing but problems. The author attempts to show that it is feasible to turn this local problem into an economic benefit by combining other locally available resources such as geothermal heat.

Geothermal potential of southern part of Idaho in the US was recognized in the early 1970s; however, the commercial utilization of geothermal resources in the area is yet to be realized. The composition of hot spring/well water can tell us how hot the water at depth is. In this study, we assembled several existing thermal water compositions to estimate reservoir temperatures with a new tool. Our results show that some areas (e.g., Preston) in southern Idaho have good geothermal potential.

Stored-heat assessment methods for geothermal fields are reviewed against observed field performance. For the method originated by the USGS, and used in the Australian Geothermal Reporting Code, the average recovery factor is shown to be 10%, with an error of ±70%. For enhanced geothermal systems (EGS) the recovery factor in experiments to date has been much less, a few percent at best.

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.