Unlocking mid-to-long-term flexibility: why seasonal pumped storage outperforms conventional pumped storage in wind-solar dominated grids

Abstract

Global efforts toward Dual Carbon Goals have spurred rapid growth in wind and solar installations worldwide. However, the inherent randomness and intermittency of wind and solar pose critical challenges to long-term flexibility requirements in power systems. While pumped storage remains a crucial regulating power source, the differential effectiveness between seasonal pumped storage (SPS) and conventional pumped storage (CPS) in mitigating medium-to-long-term renewable fluctuations has not been systematically investigated. Therefore, this study provides a comprehensive evaluation of the performance of SPS and CPS in addressing stochastic fluctuations of wind and solar. First, the output characteristics of wind and solar resources were analyzed, and multiple wind and solar scenarios were developed to simulate the regulatory differences between SPS and CPS under varying wind and solar scenarios. Subsequently, this study proposes an integrated evaluation framework combining entropy-weighted and coefficient of variation methods to objectively assess the technical, economic, and stability indicators, using Qinghai Province as a case study to analyze the advantages of both SPS and CPS. The results show that SPS outperforms CPS across many technical indicators. Notably, the carbon emission reduction effect of SPS becomes more pronounced in scenarios with higher wind power capacity. Economically, it has to be admitted that the investment cost of SPS is 1.33 times that of CPS. Although the operating cost is one fifth of CPS, the levelized cost of electricity of SPS is still higher than CPS. Finally, the comprehensive evaluation demonstrates the superiority of SPS, achieving an overall benefit score of 98.03, in stark contrast to 68.6 for CPS. These findings offer critical insights for energy planners and policymakers in optimizing storage solutions to enhance grid flexibility and accelerate decarbonization.This work was supported by the following grants: National Natural Science Foundation of China (Grant No.: 52409120), National Natural Science Foundation of China (Grant No.: 52339006), Free Exploration Basic Research (Grant No.: 2024ZY-JCYJ-02-37), China Postdoctoral Science Foundation, 75th Batch of General Projects (Grant No.: 2024M752626), Postdoctoral Fellowship Program of CPSF (Grant No.: GZC20232157), and Shaanxi Province Postdoctoral Research Project (Grant No.: 2023BSHEDZZ105)