Valverde (Capital) Upper Reservoir Valves Wind Farm Pipelines Downhill Reservoir Pumps and Stored Energy Hydro Turbines Port Area Conventional Power Plant (a) Annual Electricity Supplied to El Hierro (%) 70 60 56.5 50 46.5 40.68 40 30 19.39 20 10 2.32 0 2014 2015 2016 2017 2018 Year (b) figure 7. (a) The Gorona del Viento power plant at El Hierro. (b) The percentage of electricity produced by Gorona del Viento per year. (Source: Gorona del Viento.) 72 ieee power & energy magazine november/december 2020