Mitigating curtailments in offshore wind energy: a comparative analysis of new and second-life battery storage solutions

Challenging goals set for the energy transition by 2030 are prompting Mediterranean countries to plan significant offshore wind production. However, with the growth of intermittent renewable power fed into the grid, operators may be forced to introduce energy curtailments in the short term, since grid revamping could require more time than new installations. This study aims to evaluate possible management strategies for curtailed energy to assess its impact on the revenues of an offshore wind farm. Li-ion batteries are considered as energy storage systems (BESS) to reduce energy waste. A comparison between brand-new (NBESS) and second-life (SBESS) batteries has been performed to assess the economic and environmental benefits related to the adoption of past vehicle batteries. The first step of the analysis involves the optimization, by means of the levelized cost of energy (LCOE) minimization, of the layout of a floating offshore wind farm located in Sicily. Optimal inter-turbine distances of 14 and 7.5 diameters have been estimated in wind and cross-wind directions, respectively, corresponding to LCOEs ranging between 106 and 135 €/MWh. Then, a sensitivity analysis is carried out by varying the assumptions on curtailed energy remuneration and the daily and monthly distribution of curtailments. The second step of the study focuses on the management of curtailed power in order to evaluate the cost-effectiveness of NBESS and SBESS. Different BESS costs and curtailment scenarios are considered to account for the uncertainties in the energy market and component costs. Across all evaluated scenarios, results show that batteries, if correctly sized, enhance the revenues of the considered 1 GW wind farm up to 450 M€, corresponding to financial gains of 10 % with respect to the Net Present Value of the base plant. Regarding SBESS, although they can reach economic benefits comparable to NBESS only with capital costs of 50 €/kWh, savings of lithium coupled with carbon emission reduction up to 2400 t CO2-eq can represent a game-changer for a more sustainable diffusion of offshore energy.