Battery-hydrogen vs. flywheel-battery hybrid storage systems for renewable energy integration in mini-grid: A techno-economic comparison

摘要

Decentralized renewables power production is rapidly growing because of environmental concerns. With the purpose of maximizing renewable exploitation, energy storage systems integration in Mini-Grids (MGs) is needed. Hybrid energy storage systems (HESSs) are promising to obtain enhanced performances in terms of both capacity and responsiveness, yet their feasibility may be hindered by design and management choices impacting the economic competitiveness. In this paper, two HESSs are analysed and compared in a real case-study, namely reversible solid oxide cell (rSOC)/Li-ion battery and flywheel/Li-ion battery systems. The analysis here devel-oped handles annual photovoltaic generation and electric load actual dataset and includes: i) a statistical analysis to obtain the most representative days, ii) dynamic modeling of the HESSs, iii) simulations to define components sizing and to extrapolate the evolution of annual battery state-of-charge, iv) battery lifespan assessment through application of the rainflow cycle counting algorithm, and v) a detailed economic evaluation (Levelized Cost of energy LCOE, Levelized cost of Storage LCOS and their sensitivity to electricity market price) including subsidies for self-consumption. For both HESSs, performance indexes of reduction of energy withdrawal from the grid and self-consumption increase are fixed at about 30 and 70 respectively, with reference to the features of the investigated MG. As main outcomes for this integrated methodology, it appears that self-consumption rewards (i. e.110 euro/MWh) let the flywheel/Li-ion battery HESS reach a LCOS agreeing with 2021 average market parity. On the contrary, LCOS is more than two-fold for the rSOC/Li-ion battery HESS, being equal the impact on the MG management and its energy independence from the main power grid. The integrated methodology is adequate for critically reviewing design and management choices and understanding the impact of the market on the prof-itability of a sub-system, with insight on energy storage units.