Castro-Santos, LauraFilgueira-Vizoso, AlmudenaSeijo García, María AntoniaMuñoz Camacho, Eugenio2026-07-032026-07-032011-03-30A. FILGUEIRA VIZOSO, L. PIEGARI, and P. TRICOLI, 2024. A photovoltaic power unit providing ancillary services for smart distribution networks. RE&PQJ. Online. 17 January 2024. Vol. 9, no. 1. DOI 10.24084/repqj09.356. [Accessed 26 June 2026]2172-038Xhttps://hdl.handle.net/2183/48762[Abstract]: Protecting the environment is becoming a major concern; people are beginning to realise that their living conditions may worsen if they do not rationalise energy use and habits. Environmental pollution and emissions from greenhouse gases caused by fossil fuel use are a threat to sustainable development. With renewable energy sources, no polluting emissions are released into the atmosphere. Therefore, using these sources on a large-scale is a key to reducing emissions and meeting the commitments established by the Kyoto Protocol. At the same time, renewable energy contributes to sustainable development. This study describes economic aspects of the repowering process for the wind farms. This process was the result of a growing demand for renewable energies, facilitated by the great potential of wind energy in the north of Spain. The wind farms studied in this work were set up before 1998 and they have obsolete machinery with low power.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/RepoweringViability studyWind farmsSensibility analysisjournal articleopen access10.24084/repqj09.603