Complementary value of wave and tidal current energy in the power grid and their impact on balanced energy demand

This study, based on wave-current interaction simulation data from 1996 to 2022, systematically evaluates the energy density, stability, and availability of wave and tidal current energy in the China's Eastern Adjacent Seas. The threshold method is used to explore wave-current synergy, and an improved co-location feasibility index is proposed to identify four combined hotspots: Zhoushan, Taizhou, Penghu, and New Taipei. By constructing resource availability, sustainability, and complementarity indices, the wave-current complementarity characteristics of these hotspots are further analyzed. The performance of wave-current combined power systems under actual power load scenarios is also investigated, examining the impact of renewable energy penetration and wave energy capacity configuration on grid-balanced energy demand. The results show that the wave energy availability in representative sea areas is 38.0 %–40.7 %, and the complementarity score is 12.9 %–22.4 %. The combined system (50 % wave energy installed capacity) can reduce the monthly coefficient of variation by 20 %–50 %, significantly smoothing power output fluctuations and reducing annual balanced energy demand (e.g., in Taizhou, with α = 1.0 and βM = 0.5, the annual normalized balanced energy demand decreased from 5300 to 4000, a reduction of 24.5 %). The combined system can also reduce the peak-to-valley ratio of balanced energy demand, alleviating the burden of rapid grid regulation.