Comprehensive Overview of Ocean-Based Renewable Energy Technologies: Tidal, Wave, and OTEC

Tidal energy is primarily captured through two types of systems: tidal range and tidal stream devices. Tidal range technologies, such as barrages and lagoons, make use of the difference in water levels between high and low tides, while tidal stream devices capture kinetic energy from water currents using horizontal or vertical axis turbines. Hybrid systems like dynamic tidal power combine both approaches to improve efficiency in energy conversion^[5]. In contrast, wave energy converters employ different technologies to transform the energy from ocean swells into electricity, as exemplified by systems proven in locations like northern Portugal. Meanwhile, OTEC systems use the temperature difference between surface and deep ocean water to generate power, although this technology remains at an earlier stage of commercial development compared to tidal and wave devices^[10].

Tidal energy offers significant advantages in terms of predictability and reliability. Unlike wind and solar, the tidal cycle is highly predictable extending years into the future, which facilitates long-term planning and grid integration^[5]. However, high initial capital costs and maintenance challenges, such as resisting the corrosive nature of seawater, contribute to a higher levelized cost of tidal energy compared to other renewables. For instance, studies have estimated tidal energy costs at around US$280 per megawatt hour, while wind energy costs are substantially lower, around US$20 per megawatt hour^[5].

Environmental impacts are a key area of study. On the positive side, tidal and wave energy systems produce minimal greenhouse gas emissions and have a smaller spatial footprint compared to wind and solar installations. Nonetheless, underwater noise, electromagnetic fields from cables and turbines, and potential collision risks for marine wildlife are important concerns. Detailed monitoring at sites like Sihwa Lake and La Rance has shown both potential benefits, such as improved water quality due to increased circulation, and drawbacks, for example, disturbances in marine habitats that could affect aquatic life patterns^[11].

The pace of commercializing tidal and wave energy technologies has improved with increased governmental and private funding. In the United States, for example, new legislation such as that passed in New Jersey provides financial incentives and regulatory support to drive tidal power projects forward^[4]. Concurrently, industry reports have set ambitious deployment targets; the marine energy sector has outlined goals of 50 MW by 2025, 500 MW by 2030, and 1 GW by 2035, urging further financial support to overcome market barriers^[2].

European markets are also experiencing significant momentum in ocean energy development. According to recent statistics, EU funding combined with national revenue supports is enabling roughly 137 MW of tidal and wave energy projects to be deployed over the next five years, with private investments rising by 75% in 2023 alone^[8].

A number of pioneering projects highlight the global momentum in ocean energy. In the United Kingdom, tidal power developments such as the Centre Port project in the Wash, with an estimated investment of $2.4 billion, aim to generate enough power for 600,000 homes. Additional tidal ventures in Scotland and Wales have secured significant funding and are progressing toward higher capacities^[4].

In the wave energy sector, breakthroughs include commercially scaled devices operating off the coast of northern Portugal by companies such as CorPower Ocean. Research from institutions in Finland points toward a future scenario in which 27 GW of wave energy capacity could play a critical role in a cost-effective net zero system, emphasizing the importance of integrating multiple renewable resources to meet future energy demands^[7].

Project portfolios also extend to OTEC initiatives, which, although at a nascent stage of commercial deployment, have demonstrated the potential to complement other ocean energy technologies. The overall outlook for ocean energy is one of growing industrialization and scaling, supported by both public policy and private investment initiatives worldwide^[10].

Ocean-based renewable energy technologies, including tidal, wave, and OTEC, are advancing toward commercialization with significant progress in efficiency improvements and capacity expansion. Although challenges remain – particularly with respect to environmental impacts and high initial costs – the predictability and stable operation of tidal systems, the low greenhouse gas emissions of all these technologies, and steady government as well as private sector support provide robust promise for a cleaner energy future. With detailed research and proactive environmental safeguards being implemented alongside innovative projects globally, these technologies are positioned to contribute substantially to achieving net zero emissions in the coming decades^[7].