The electric power production targeted Unconventional Geothermal Systems (UGS), some conceptual designs and their thermodynamics classification

Abstract

The geothermal energy is a renewable and relatively clean energy resource. The amount of geothermal energy stored just in the upper crust of the earth is large enough to meet the world’s energy needs for thousands of years. Unfortunately, only a small portion of this potential can be utilized today by the conventional methods. The rest corresponds to the hot, fluid-poor areas which cannot be utilized by the current technology. The first concrete steps towards the utilization of such high potential areas emerged in the late 1960s and early 1970s. These studies have gradually continued in the following years, and many new terms and conceptual designs have been proposed so far. Unfortunately, no comprehensive definition has been established on this subject yet. This may bring about some difficulties such as the failure to express the intended concept in the right manner, the inability to determine the legal boundaries for the regulations required by the countries to make use of these areas which pose high risks in the commercial point of view. In this paper, some of the major terms and conceptual designs used for the projects targeting the power generation from fluid- poor hot areas are discussed. Furthermore, all of these terms have been gathered under the title of “Unconventional Geothermal Systems-UGS” and these designs are classified according to the types of thermodynamic system for the first time in this study. In addition, some new suggestions that can be used to define the definitional boundaries of these terms are put forward.

Keywords

• geothermal energy
• egs
• ugs
• heat transfer
• hydraulic fracturing