Bridging the Storage Gap in Renewable Power Systems: A Systematic Meta-Analysis

Abstract

The rapid expansion of wind and solar power has exposed a fundamental challenge in electricity systems: aligning variable generation with continuous demand. This study addresses this temporal imbalance through a systematic meta-analysis of 112 techno-economic studies published between 2018 and 2025, with all cost data harmonized to 2024 conditions under consistent financial and operational assumptions. The novelty of this study lies in the joint application of: (1) a harmonized analytical framework that combines updated cost benchmarks with learning-based projections to reduce bias from publication lag; (2) climate-zone stratification that directly tests the structural “latitude bias” in the literature; (3) life-cycle critical-mineral-intensity indicators; and (4) an explicit distinction between storage-level and system-level costs. The results show that lithium-ion batteries remain cost-effective for short-duration applications. However, recent cost declines extend their competitiveness beyond earlier estimates, with the economic duration threshold now more fluid than previously assumed. For mid-duration storage, flow batteries and metal-air systems exhibit more stable cost scaling, with iron-air technologies emerging as a low-cost option with projected capital costs of approximately $22/kWh. For long-duration and seasonal storage, hydrogen becomes economically relevant in regions with pronounced seasonal variability. In contrast, in tropical systems, solar overbuilding combined with moderate-duration storage achieves comparable reliability under the modeled tropical-system assumptions at approximately 30% lower system cost than the hydrogen-based seasonal storage benchmark. Cost outcomes are highly sensitive to assumptions such as charging prices, discount rates, and reliability criteria. Distinguishing between storage-level and system-level costs reveals that optimal solutions depend on both technology characteristics and regional resource patterns. Overall, no single technology dominates across all durations; cost-effective decarbonization requires a portfolio of storage solutions supported by market frameworks that value reliability and flexibility.