With pumped water storage for when there's no wind...El Hierro, the smallest of the Canary Islands, which are owned by Spain and located off the coast of Africa (see the maps below), is jumping with both feet into renewable energy. 5 wind turbines have been built on the northeastern tip of the island (you can see one in the photo above), for a total capacity of 11.5 megawatts, which is more than enough for the 10,000 people who live there.
But what happens when the wind doesn't blow?
Backup power will come from pumped water storage. Surplus power from the wind turbines will be used to pump water from a reservoir near the harbor to another larger reservoir near a volcanic crater about 2,300 feet (700 meters) above. This means that when there's not enough wind to generate the power needed by the island, they can simple open the valves on the top reservoir and gravity does the rest, bringing the water back down, and in between turbines capture some of that kinetic energy and turn it into electricity. No need for batteries, just good ol' gravity!
The wind farm + pumped water storage project will cut CO2 emissions by about 18,700 tonnes per year and eliminate the island's annual consumption of 40,000 barrels of oil, though El Hierro will maintain its fuel oil power station as a back up, just in case.
Hopefully all goes well this summer when the wind farm is fully operational and other island nations take inspiration from El Hierro. Many islands burn oil to produce electricity, but wind, pumped hydro, and solar are cleaner and potentially much cheaper alternatives over the long term (it costs something at first, but after that 'fuel' is free!).
Above is a pumped-hydro station. The drawing isn't based on the El Hierro setup, but it should give you an idea of how it works.