Ocean renewable energy sources are briefly introduced in this review article. Special focus on tidal energy from ocean renewable energy in the Yellow Sea and its practical utilization in South Korea are illustrated with several examples. Among them, the Sihwa Lake tidal power plant, the Garolim Bay tidal power project, the Incheon tidal power project, and the Uldolmok tidal current power station were introduced with more details. A numerical modelling system, Regional Ocean Tide Simulator, is introduced for now- and forecast of tidal regime to evaluate the potential tidal power, to provide operational information for practical purpose of tidal power, and to assess the environmental impacts caused by a change of tidal regime due to large-scale development of tidal barrage.