Economic assessment of a photovoltaic-gravity storage hybrid system in Spain

Abstract

The economic viability of renewable energy projects with storage depends on market prices as well as on investment costs (CAPEX) and operation and maintenance costs (OPEX). This study evaluates the profitability of a hybrid system composed of a photovoltaic plant with variable capacity (ranging from 0.1 to 15 MWp) and a gravity storage tower constructed from recycled concrete blocks (of 12.99 or 29.23 tons) with variable heights (between 18 and 216 m) over a 30-year horizon. The evaluation is based on hourly prices from the Iberian Energy Market Operator’s daily market during the period 2018–2024 and on discount rates derived from 30 year government bond auctions held in 2024. In addition, three representative locations in Spain (Córdoba, Guadalajara, and Oviedo, corresponding to the 97.5th, 50th, and 2.5th percentiles of solar irradiation, respectively) are analyzed to determine the photovoltaic capacity and tower height in investment decision making. The results identify the optimal configurations that maximize system profitability and offer guidance for designing investment strategies tailored to the heterogeneous conditions of the Spanish electricity market. © 2025, Asociación Española de Dirección e Ingeniería de Proyectos (AEIPRO). All rights reserved.