Application of Variable Weight Theory in the Suitability Evaluation of Regional Shallow Geothermal Energy Development

Blindly developing shallow geothermal energy (SGE) may lead to difficulties in reinjection, a low coefficient of performance (COP), and the waste of funds. In order to avoid these problems and improve development efficiency, it is necessary to scientifically conduct a development suitability evaluation and classify the suitability levels before development. This article takes Chengde City, Hebei Province, China as an example and constructs an evaluation index system based on the analysis of regional basic conditions. The Analytic Hierarchy Process (AHP) was used to calculate the constant weight. A Fuzzy C-means Clustering (FCM) analysis was used to determine the critical value of evaluation index classification and the interval threshold of variable weights. The parameters of the variable-weight model were calculated using the method of model backcalculation. Based on the constructed variable-weight model, the suitability of SGE development for groundwater sources in the study area was evaluated, and it was divided into five levels: most suitable area, suitable area, relatively suitable area, less suitable area, and unsuitable area. Through a verification analysis of engineering examples and a comparison with the evaluation results under traditional constant-weight models, it was found that the evaluation results based on variable weight theory have better data discreteness and a higher accuracy. Research has shown that variable-weight models can adjust the weight of each index based on its state value. Through this study, the accuracy of the suitability evaluation for regional SGE development can be improved. This can provide a certain reference for the suitability evaluation of SGE development in other regions.