Abstract
The United States has not engaged heavily in ocean thermal energy conversion (OTEC) research and development over the past decades. However, with increasing concerns over climate change and a favorable policy landscape, there is renewed interest in OTEC, particularly for remote coastal areas and tropical islands.
OTEC utilizes deep, cold seawater to generate power and offers additional benefits such as seawater air conditioning, desalination, aquaculture enhancement, and other uses. An assessment of the feasibility of small-scale OTEC development (3-10 MW) in US waters was carried out in Hawaii, Puerto Rico, St. Croix, and Guam, funded by the U.S. Department of Energy. PNNL staff, working with OTEC technical experts worldwide, concluded that OTEC is technically mature with manageable environmental effects and potential benefits for local communities.
Building upon this initial assessment, PNNL is working with Makai Ocean Engineering, and Ocean-ERA to assess the feasibility and design requirements for a theoretical multi-use OTEC platform, based on an existing onshore system in Kona, Hawaii, on the site of the Natural Energy Laboratory of Hawaii Authority (NELHA). Key components of this study include examining the year-round OTEC resource around Kona, modeling the cold deep water return to minimize environmental impacts, exploring the use of deep cold water for aquaculture enhancement and other applications, evaluating potential environmental effects for siting and permitting purposes, assessing community acceptance through workshops in collaboration with Hawaii Sea Grant, and conducting a tradeoff analysis among OTEC's ancillary uses. As part of these efforts, PNNL has developed an open-source numerical model to assess the effects of the OTEC cold water return plume to aid in dispersing the water at depth.
Overall, these initiatives demonstrate a commitment to leveraging OTEC as a significant contributor to the global energy transition, offering a sustainable and innovative solution to meet energy needs while addressing environmental and social concerns.