The concept of OTEC is succinctly reviewed, with an emphasis on the specific aspects of the technology that have hampered its development. Although the ocean thermal resource is abundant, widespread and steady, no commercial OTEC system has yet been deployed. Low thermodynamic efficiencies and the need for large systems at sea result in very capital-intensive projects. This traditionally has deterred investors and the resulting lack of operational OTEC power plants has acted as a powerful negative feedback. The location of OTEC resources in tropical areas may have further limited the interest of wealthy, technologically advanced stakeholders. In spite of engineering, economic and possibly geopolitical hurdles, however, prospects for the deployment of OTEC systems seem better today than at any time in the past two decades. In an age of concerns about global warming and energy security, OTEC is a resource which mankind ignores at its peril.
