OTEC

Capturing energy using temperature gradients across water depths.

Ocean thermal energy conversion (OTEC) technology converts solar energy stored in the layers of the tropical and subtropical oceans. Thermal heat engines use the temperature difference between the sun-warmed surface water and cold water in the deep ocean. The temperature difference between surface waters and deeper water can reach over 25 oC in summer months, although usually this temperature difference exists only over water with depths of 1,000 m or greater. Many different OTEC archetypes have been investigated, some on floating offshore platforms and some built onshore with pipelines to transport the water to and from the ocean. Each system uses one or a combination of thermodynamic processes to turn the temperature difference into mechanical energy.

  • Closed-cycle: A working fluid with a low-boiling point, such as ammonia or propane, is circulated. Warm, surface seawater is pumped through a heat exchanger where the working fluid is vaporized and driven through a turbine, which then generates electricity. Cold, deep seawater is then pumped through a second heat exchanger where the working fluid vapor condenses back into a liquid and is recycled through the system.
  • Open-cycle: Warm, surface seawater is placed in a low-pressure container that causes the water to boil, turning a turbine as the steam expands. The steam is then exposed to cold, deep seawater and condenses into freshwater.
  • Hybrid-cycle: Warm, surface seawater enters a vacuum chamber where it is flash-evaporated into steam. The steam is used to vaporize a working fluid with a low-boiling point, which then turns a turbine to generate electricity. Hybrid configurations also produce freshwater, which can have other uses such as agriculture and potable drinking water.

The primary environmental concerns associated with OTEC technologies typically encompass changes in water quality. A major environmental concern arises as cool, nutrient rich water is withdrawn from the deep ocean and discharged higher in the water column. The effects of this cooler water and transport of nutrients on ecosystem processes could vary but may affect nearby habitats through temperature changes or increased biological growth. Screens will cover the intake tubes, but there is still a chance that marine organisms could be fatally entrapped. In order to maintain the efficiency of the heat exchangers, the warm water will need to be treated with chlorine, which will cause changes to water quality.

Photo Credit: Okinawa Prefecture Industrial Policy Division

Marine and Wind Energy Environmental Documents

Tethys is a knowledge hub that contains documents on the environmental effects of wind and marine energy. The table below contains all of the documents in the Tethys Knowledge Base associated with OTEC.

Total: 123

Searches title and abstract.
Title Author Date Content Type Technology Stressor Receptor
Modeling the Physical and Biochemical Influence of Ocean Thermal Energy Conversion Plant Discharges into their Adjacent Waters Grandelli, P., Rocheleau, G., Hamrick, J. Report Marine Energy, OTEC
Modeling the Physical and Biochemical Influence of Ocean Thermal Energy Conversion Plant Grandelli, P., Rocheleau, G., Hamrick, J. Report Marine Energy, OTEC Habitat Change Ecosystem Processes, Physical Environment, Water Quality
Revisiting ocean thermal energy conversion Fujita, R., Markham, A., Diaz, J. Journal Article Marine Energy, OTEC Changes in Flow, Entanglement Invertebrates, Physical Environment, Water Quality
Assessment of Ocean Thermal Energy Conversion Muralidharan, S. Thesis OTEC, Marine Energy
Environmental assessment for ocean thermal energy conversion in Hawaii: Available data and a protocol for baseline monitoring Comfort, C., Vega, L. Conference Paper Marine Energy, OTEC
Electricity Generation by the Ocean Thermal Energy Etemadi, A., Emdadi, A., AsefAfshar, O. Journal Article OTEC, Marine Energy Habitat Change Physical Environment
Physical and Biological Modeling of a 100 Megawatt Ocean Thermal Energy Conversion Discharge Plume Rocheleau, G., Grandelli, P. Conference Paper Marine Energy, OTEC Habitat Change Ecosystem Processes, Physical Environment
Environmental Assessment for Ocean Thermal Energy Conversion in Hawaii Comfort, C., Vega, L. Conference Paper Marine Energy, OTEC Physical Environment, Human Dimensions, Environmental Impact Assessment
Research and Developments on Ocean Thermal Energy Conversion Wang, C., Yee, A., Krock, H. Journal Article OTEC, Marine Energy
Status of Hawaii's ocean energy projects and permitting regime Gill, A., Black, C. Conference Paper Marine Energy, OTEC, Wave Human Dimensions, Environmental Impact Assessment, Legal & Policy
Ocean Thermal Energy Conversion (OTEC) Power Plant and it's By Products Yield for Small Islands in Indonesia Sea Water Siahaya, Y., Salam, L. Conference Paper Marine Energy, OTEC Human Dimensions
Bringing OTEC Environmental Assessments of the 1980s Up To 21st Century Oceanographic Standards Sansone, F., Comfort, C., Weng, K. Conference Paper Marine Energy, OTEC
Ocean Thermal Energy Conversion: Assessing Potential Physical, Chemical and Biological Impacts and Risks Cunningham, J., Magdol, Z., Kinner, N. Report Marine Energy, OTEC
An Overview Of Ocean Renewable Energy Technologies Bedard, R., Jacobson, P., Previsic, M. Magazine Article Wind Energy, Wave, Tidal, OTEC, Fixed Offshore Wind, Marine Energy
Potential Environmental Effects of Ocean Thermal Energy Conversion Sound and Sea Technologies Presentation Marine Energy, OTEC
Potential OTEC Impacts in the Hawaiian Marine Environment Parke, M. Presentation OTEC, Marine Energy
Ocean Thermal Energy Conversion (OTEC) Environmental Impacts NOAA Office of Ocean & Coastal Resource Management Report Marine Energy, OTEC
Ammonia Energy Storage, Transmission and Usage Development for Offshore Wind and Applicability to OTEC Hart, G., Holbrook, J. Conference Paper Marine Energy, OTEC, Wind Energy, Fixed Offshore Wind, Floating Offshore Wind Physical Environment
PLOCAN Marine Test Site for Ocean Energy Converters Oceanic Platform of the Canary Islands (PLOCAN) Project Site Marine Energy, OTEC, Wave, Wind Energy, Fixed Offshore Wind, Floating Offshore Wind
Worldwide Synthesis and Analysis of Existing Information Regarding Environmental Effects of Alternative Energy Uses on the Outer Continental Shelf Michel, J., Dunagan, H., Boring, C. Report Wind Energy, Wave, OTEC, Fixed Offshore Wind, Ocean Current, Marine Energy Habitat Change
Overview of Environmental Effects: OTEC vs Other Power Generation Methods Martí, J. Presentation OTEC, Marine Energy
Review and Analysis of Ocean Energy Systems Development and Supporting Policies AEA Energy & Environment Report Marine Energy, OTEC, Tidal, Wave Human Dimensions, Legal & Policy
Environmental Issues of Natural Temperature Differences Utilization Gauthier, M. Book Chapter OTEC, Marine Energy Changes in Flow Water Quality, Physical Environment
Potential and Future Prospects for Ocean Thermal Energy Conversion (OTEC) In Small Islands Developing States (SIDS) Binger, A. Report Marine Energy, OTEC Human Dimensions, Social & Economic Data
Design considerations for ocean energy resource systems Bregman, R., Knapp, R., Takahashi, P. Conference Paper Marine Energy, Ocean Current, OTEC, Tidal, Wave Human Dimensions, Social & Economic Data
Renewable Energy From the Ocean: A Guide to OTEC Avery, W., Wu, C. Book OTEC, Marine Energy
Carbon Dioxide Release from OTEC Cycles Green, H., Guenther, P. Report Marine Energy, OTEC
Effects of cold shock on egg, larval, and juvenile stages of tropical fishes: Potential impacts of ocean thermal energy conversion Lamadrid-Rose, Y., Boehlert, G. Journal Article Marine Energy, OTEC Fish, Pelagic Fish
Potential Environmental Impacts of Closed-Cycle Ocean Thermal Energy Conversion Quinby-Hunt, M., Sloan, D., Wilde, P. Journal Article OTEC, Marine Energy Chemicals, Changes in Flow
The 40 MWe OTEC Plant at Kahe Point, Oahu, Hawaii: A Case Study of Potential Biological Impacts Harrison, J. Report Marine Energy, OTEC
The Potential Impact of Ocean Thermal Energy Conversion (OTEC) on Fisheries Myers, E., Hoss, D., Matsumoto, W. Report OTEC, Marine Energy Human Dimensions, Fisheries
Potential Environmental Impacts of Open-Cycle Thermal Energy Conversion Quinby-Hunt, M., Wilde, P., Dengler, A. Journal Article Marine Energy, OTEC
Potential Impacts from OTEC-Generated Underwater Sounds Rucker, J., Friedl, W. Conference Paper Marine Energy, OTEC Noise
Tropical Island Applications for Ocean Thermal Energy Conversion (OTEC) Ford, J., Toms, A. Conference Paper Marine Energy, OTEC Human Dimensions
Waterborne Noise Due to Ocean Thermal Energy Conversion Plants Janota, C., Thompson, D. Journal Article OTEC, Marine Energy Noise
Ocean Thermal Energy Conversion: Environmental Effects Assessment Program Plan, 1981-85 NOAA Office of Ocean Minerals and Energy Report OTEC, Marine Energy
Ocean Thermal Energy Conversion Final Environmental Impact Statement National Oceanic and Atmospheric Administration (NOAA) Report Marine Energy, OTEC Chemicals, Habitat Change, Noise Human Dimensions, Environmental Impact Assessment
The Potential Environmental Consequences of Ocean Thermal Energy Conversion (OTEC) Plants Walsh, J. Workshop Article Marine Energy, OTEC Chemicals, Habitat Change Physical Environment, Water Quality
Ocean thermal energy conversion (OTEC): Social and environmental issues Lavi, A., Lavi, G. Journal Article Marine Energy, OTEC Chemicals Physical Environment, Water Quality
Environmental Impact Assessment for Operational OTEC Platforms Sands, M. Conference Paper Marine Energy, OTEC Human Dimensions, Environmental Impact Assessment
Displaying 81 - 120 of 123 results