Water cycle driven only by wind energy surplus: Towards 100% renewable energy islands

Abstract

This paper studies how to increase the share of renewable energy by using solely stand-alone renewable energies to drive the water cycle. A case study is undertaken of El Hierro (Canary Islands, Spain), an island already on the path to becoming a 100% renewable energy island thanks principally to a wind-hydro power plant that covered around 60% of the annual electricity demand in 2018. The island's water cycle includes groundwater extraction, seawater desalination and water pumping and distribution, representing altogether around 35% of the annual electricity demand of the island. The idea is to investigate the possibility of driving the entire water cycle solely with the wind energy surplus. For this purpose, two scenarios are considered and developed: one based on the existing decentralised water cycle, and the second on an alternative centralised one, with just one modular reverse osmosis desalination plant and a centralised water storage system. The aim is to establish which model adapts best to an intermittent energy source such as wind energy without conventional backup systems. Results show that both scenarios lead to an increase in the overall renewable energy contribution in the island. Moreover, the centralised water model, specially due to its centralised water storage system, allows a higher contribution from renewable energy sources, increasing their overall annual penetration.