Ocean thermal energy conversion (OTEC) offers a conceptually simple way to generate power in tropical oceans. Surface water sits around 25°C, while water roughly a kilometer down is near 4–5°C. A heat engine placed between these two reservoirs can use the warm water to vaporize a working fluid and drive a turbine.
The appeal is clear: the ocean itself acts as a vast solar collector, providing a steady temperature difference without fuel or batteries. But according to CleanTechnica, the practical hurdle is not the thermodynamics — it is the seawater flow. Moving enough warm and cold water through the system to sustain power generation is the real problem.
In other words, the concept works, but the plumbing is the limiting factor. The source focuses on this flow challenge as the central issue for OTEC's viability, rather than questioning the underlying physics.