OTEC originates from the conversion of thermal energy generated by the temperature gradient in the vertical direction in the ocean. Despite the presence of major shortcomings (limited temperature difference, high initial investment cost and maintenance costs, etc., as one of the sources of green and renewable energy, OTEC is superior to wind and solar energy in stability, given that the temperature difference and temperature, especially in deep cold seawater (DCS), remain constant except for ocean currents and seasonal variations. Global net electricity production from OTEC is approximately 30 TW, according to a fully three-dimensional ocean general circulation model. The regions with high OTEC potential are mainly small islands and coastal areas in the tropics (between 20° north and 20° south); in these areas, the steep seabed or no-continental shelf is accessible, meaning that deep seawater (at depths exceeding 1000 m) can be accessed within 10 km of the coastline in the former case and near the coastline in the latter. Furthermore, a suitable marine environment is another advantage of these regions; for example, the equatorial waters of the Pacific Ocean are not substantially affected by adverse events in the external environment, such as typhoons and waves. Against this backdrop, this opinion article mainly sheds light on improvements to OTEC power cycles, with a partial focus on future prospects.