An extended methodology for multi-criteria decision-making process focused on enhanced geothermal systems

Abstract

When considering geothermal project development, the complex assignment of aggregating and quantifying the influencing factors and their interactions is an inevitable task that enables comprehensive assessment of the geothermal energy utilization from many different aspects. The main purpose of the scientific work is a revised set of criteria for comprehensive evaluation of geothermal project focusing on Enhanced Geothermal Systems (EGS) and considering the geological settings, technology, economic and financial aspects of project development, and societal and environmental parameters. The newly presented work is conceived as an addition to the previous work, defining and thoroughly describing twenty-eight influencing factors for evaluation of deep geothermal energy. The mentioned factors consist of 18 newly introduced criteria, 6 replaced criteria, and 4 modified criteria which are based on the extensive literature review and expertise integrating all aspects of EGS project development. One of the key findings of the presented methodology is that it provides broad assessment of an EGS project, applicable to different end-uses including only electricity generation, only heat production and combined heat and power production. The proposed methodology could serve as a preparatory guideline for more detailed analysis and calculations for a future project development, either greenfield or brownfield, encompassing technological, geological, economic, and environmental aspects. The methodology was tested in case study where two different geothermal sites were assessed for heat production and electricity production scenarios. Both sites, with their main geological parameters, resulted in production of electricity, from 263.51 GWh up to 927.69 GWh, and heat production from 334.25 GWh up to 5,207.68 GWh. Such increase of renewable energy production from geothermal source derived the avoidance of CO2 emissions ranging from 79,686 tonnes of CO2-eq up to 1,241,542 tonnes of CO2-eq. The final grades of each criterion for the heat and electricity production scenarios resulted in favor of Site 2, where better reservoir and economic performance values derived the higher final grade of site’s overall performance. The summarized results lead to a conclusion that the proposed methodology is applicable for assessment of different end-usage options for one geothermal site and for comparison of projects at different geothermal sites.