Hybrid gravity energy storage and fast hydraulic accumulator for reliability-constrained industrial renewable systems: Multi-timescale design and dispatch framework

Abstract

High-power industrial electrification requires hybrid renewable energy systems (HRES) that simultaneously minimize cost, satisfy stringent adequacy targets, and withstand fast power ramps that conventional long-duration energy storage cannot efficiently absorb. This paper proposes a novel reliability-constrained HRES design and operational framework integrating long-, medium-, and fast-response energy storage technologies. The system integrates photovoltaic (PV) system, wind turbines (WT), a battery energy storage system (BESS), a liquid gravity energy storage (GES) unit, and a fast hydraulic accumulator (ACC). A three-layer multi-timescale dispatch strategy is introduced to decompose the net power imbalance into slow, mid, and fast components using causal filtering, enabling GES to serve energy-shifting needs, BESS to mitigate intra-hour variability, and the accumulator to handle high-frequency ramps and spikes. System sizing is solved using differential evolution under a minimum reliability requirement of R greater than or equal to 95%, with the accumulator included in the dispatch model to reflect its operational value. A full-year simulation at 15-min resolution is performed using an industrial load dataset (kWh per 15 min) and hourly meteorological inputs resampled to the dispatch grid. The results show that the accumulator-assisted design reshapes the optimal capacity mix by reducing battery capacity from 141.9 to 105.9 kWh and the number of wind turbines from 7 to 5, while increasing PV capacity from 551.73 to 646.60 kW and GES capacity from 451.8 to 700.2 kWh. The proposed configuration reduces the LCOE from 0.1240 to 0.1171 $/kWh, corresponding to a 5.6% reduction, while maintaining the 95% reliability target. Over the 25-year project horizon, the accumulator-assisted design reduces battery-related costs by approximately $92 k and total system cost by about $150 k.The proposed framework demonstrates that integrating fast hydraulic buffering alongside mid- and long-duration energy storage can reduce overinvestment in converter-limited storage power, improve operational flexibility, and deliver lower-cost renewable supply for industrial demand under explicit adequacy constraints.