Improved techno-economic optimization of an off-grid hybrid solar/wind/gravity energy storage system based on performance indicators

Abstract

High proportions of energy from solar and wind should be used to transform the electricity system to a renewable energy (RE) system. The intermittency of wind and photovoltaic power production adds a new level of complexity. To balance power demand and supply, energy storage technologies are required to store surplus electricity and generate energy when needed. In this study, a new emerging energy storage system named gravity energy storage (GES) is integrated into large-scale renewable energy plant with an aim to investigate its optimal design and operation while prove its competitiveness compared to battery storage. The novelty of the proposed approach consists of combining energy management strategy and Fmincon interior point method as an optimization algorithm. The proposed model aims to determine a suitable design of a hybrid renewable-gravity energy storage system (RE-GES) and a hybrid renewable-battery energy storage (RE-Battery) considering techno-economic performance indicators; such as loss of power supply probability, life-cycle cost, and levelized cost of energy. The optimal solution with full satisfaction of load demand was employed to illustrate the operation of four scenarios in order to analyze the effect of solar and wind energy proportion on the system cost, storage capacity, and oversupply. Finally, a sensitivity analysis was performed to identify the variables which have the highest impact on the model objective functions. The study demonstrates that the incorporation of hybrid Solar and wind technologies decrease the required energy storage capacity of up to 34.7% and 30% for GES and Battery system, respectively. The results show that, the hybrid PV-wind-GES is the best option in terms of reliability and economic benefits for the considered case study. The optimal solution comprises 418 PV modules, 477 wind turbines with a GES capacity of 15 MWh. The obtained results show that the cost of energy of RE-GES ranges between 0.3 €/kWh and 0.018 €/kWh while it is between 0.25 €/kWh and 0.05€/kWh for RE-Battery.