A renewable energy storage system that stores renewable energy, includes: an electrical power generator that converts renewable energy into electrical power; an electrical storage device that stores the electrical power; a hydrogen production device that produces hydrogen using the electrical power from the electrical power generator and/or the electrical power stored in the electrical storage device; a hydrogenation device that adds the hydrogen produced by the hydrogen production device to the unsaturated hydrocarbon; a saturated hydrocarbon storage device that stores the saturated hydrocarbon produced by the addition of the hydrogen to the unsaturated hydrocarbon; an unsaturated hydrocarbon storage device that stores the unsaturated hydrocarbon; and an unsaturated hydrocarbon supply controller that controls the supply of unsaturated hydrocarbon stored in the unsaturated hydrocarbon storage device to the hydrogenation device.