# Multicriteria Decision Making and Its Application in Geothermal Power Project
## 1 Introduction  
The overall demand for electricity in Vietnam is forecasted to grow up to 8-10% per year from 2021, based on the data from Vietnam Ministry of Industry and Trade. In the meantime, the current sources of energy that businesses still rely on are mainly imported fossil fuel energy sources, such as gas, coal, and petroleum. Therefore, the development of renewable energy is said to be the solution to the problem of national energy security in the future. Along with energy from wind, the sun, and ocean waves, geothermal is a clean, environmentally friendly energy source that is being used by 50 countries around the world to produce electricity [1]. The origin of geothermal energy comes from the core of the Earth where natural elements are currently decaying radioactively, such as potassium, thorium, and uranium. Due to the change of entropy generating heat, potential electrical energy of 42 million megawatts can be generated from the Earth's average heat flow of 82 mW/m\({}^{2}\)[2]. Overall, the estimated heat coverage on Earth is around 12.6 \(\times\) 10\({}^{24}\) MJ, and the crust of the Earthalone is only 0.0004% of the coverage (approximately 5.4 \(\times\) 10\({}^{21}\) MJ) [3]. The heat energy of the crust alone would provide more than enough energy, compared with the current overall electricity generation of 7.1 \(\times\) 10\({}^{13}\) MJ [4]. Such an immense source of energy exists, yet only a small portion is currently being developed. The utilization of geothermal energy is restricted to areas with a carrier that could transport sufficient equipment to trigger geothermal energy sources. The classification of the geothermal energy types is shown in Table 1; types over 150 \({}^{\circ}\)C are sufficient for energy generation. A location selection problem is modelized to determine the optimal site for a geothermal power plant. In this decision-making process, the problem considers the selection of site and ranking of alternatives. A Multicriteria Decision-Making Model (MCDM) is a section of operations research dealing with decision making that often involves unclarity, which is effectively solved using fuzzy sets with decision-making techniques. Therefore, to support researchers and decision makers, the objective of this article is to present an MCDM for determining the optimum site for a geothermal power plant. The MCDM's process is performed through six steps, as shown in Figure 1.  
A Multicriteria Decision-Making Model (MCDM), such as the Brown-Gibson model, Aggregated Indices Randomization Method (AIRM), Best Worst Method (BWM), etc., can be used to help decision-making processes. The decision maker must frequently take both qualitative and quantitative elements into account. In these situations, the MCDM technique is combined with fuzzy theory to develop a fuzzy MCDM strategy to support the decision-making processes. Although several MCDM models have been put forth to support the location evaluation and selection processes in renewable energy, very few hybrid MCDM models have been created to address the location selection for Geothermal Power Plants, particularly in a fuzzy decision-making environment. In this research work, the author has proposed a fuzzy MCDM model for the location selection \begin{table}
\begin{tabular}{c c} \hline \hline
**Resource Type** & **Temperature Range \({}^{\circ}\)C** \\ \hline \multicolumn{3}{c}{Convective hydrothermal resources} \\ Vapor dominated & 240 \\ Hot water dominated & 20 to 350+ \\ \multicolumn{3}{c}{Other hydrothermal resources} \\ Sedimentary basin & 20 to 150 \\ Geo-pressured & 90 to 200 \\ \multicolumn{3}{c}{Radiogenic} & 30 to 150 \\ \multicolumn{3}{c}{Hot rock resources} \\ Solidified & 90 to 650 \\ Part still molten & \textgreater{}600 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Types of Geothermal Resources [5; 6]. Figure 1: General procedures of MCDM model. of geothermal power plants. The FAHP was used to determine the weights for each criterion to rank numerous alternatives.