Life cycle assessment of geothermal exploration
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Date
2024-07-03
Authors
Σηφάκης, Μιχαήλ
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Abstract
Geothermal energy, as a sustainable alternative to conventional energy sources, has gained significant attention in recent years. However, the exploration and drilling processes involved in harnessing geothermal energy can have considerable environmental impacts. This thesis conducts a comprehensive examination of the environmental implications of geothermal drilling, with a specific focus on the Rate of Penetration (ROP) in granite formations, examined through the methodology of Life Cycle Assessment (LCA) on four real-life cases. The study commences with a thorough review of renewable energy sources, emphasizing their role in fostering environmental sustainability, energy security, and economic growth. Then, the complexity of the drilling process of geothermal wells is described, and the rate of penetration factor is underlined, along with its implications on the various emission factors such as the Global Warming Potential and Fossil Fuel Depletion. Next, the four wells are described, taken from the detailed literature of the Soultz-sous-Forêts and Rittershoffen geothermal sites. Their structural dimensions are described along with the various types of granite formations that were encountered when drilling and the three sets of maximum, average and minimum ROP values that were measured with their respective interval lengths. This data was used to conduct the methodology of LCA, starting from defining the scope and goal of the approach and ending in the interpretation of the results. The inventory analysis part of the LCA includes the emission factors that were used, taken from the SimaPro database. The results show clearly that in order to minimize the emissions produced by the drilling process, higher ROP values are required. This is also present in the analysis that was made with a separate sequence of ROP values for each well, in which the effect of the ROP on the emissions is better described through various individual diagrams. Furthermore, a sensitivity analysis for the fuel consumption of the drill rig was conducted, that yielded a 9% decrease of chlorofluorocarbon production and an 8% decrease of fossil fuel depletion. Another sensitivity analysis on the distance required for the transportation showed a lower than 1% decrease in emissions when using green trucks.
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Keywords
Geothermal energy, Life cycle assessment, Rate of penetration, Geothermal drilling, Enhanced geothermal systems