A novel interval type-2 fuzzy consensus reaching process model and group decision-making method for renewable energy investment

Renewable Energy Investment (REI) is a critical challenge for both governments and investors, often complicated by conflicting criteria and uncertainties that must be managed to obtain reliable and useful decisions. To address the REI problems, a novel group decision -making approach under uncertainty is proposed. Our approach introduces the Interval Type -2 Fuzzy Sets (IT2FS) to construct linguistic terms that reflect their uncertainty and personalized semantics. Subsequently, we develop a novel automatic interval type -2 fuzzy Consensus Reaching Process (CRP) model to detect disagreements among experts and generate personalized recommendations to improve the consensus level. The proposed CRP model conducts interval analysis to facilitate consensus adjustments, thereby enhancing its capacity to describe uncertainty. Once the CRP is finished, the prospect theory is extended to the IT2FS to calculate the overall values for each alternative, which can capture the decision makers' attitudes towards risk and uncertainty. Given that prospect values are characterized by interval values, we propose a two -stage interval -valued ranking approach to compare and rank them. Finally, an illustrative case study is provided to demonstrate the feasibility of our approach, along with comparative analysis to highlight its advantages and sensitivity analysis to show the robustness of parameters on decision results.