MHK Technologies/OTEC

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Technology Profile
Primary Organization Makai Ocean Engineering Inc
Project(s) where this technology is utilized MHK Projects/Makai Ocean Energy Research Center
Technology Resource
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Ocean Thermal Energy Conversion (OTEC)
Technology Type
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Technology Readiness Level
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TRL 5/6: System Integration and Technology Laboratory Demonstration
Technology Description Closed-cycle OTEC uses deep cold seawater and warm surface seawater as the cold and warm sources for a 4-stage rankine cycle. A refrigerant, such as ammonia, is the working fluid.

Warm surface water (typically about 25 deg C) is passed through a heat exchanger that is used to boil the working fluid. This high pressure vapor then expands as it passes through a turbine (generating electricity). Then the vapor is condensed back to a liquid in a cold seawater heat exchanger, and then is pumped back around to complete the closed loop. The working fluid never leaves the system.

OTEC is currently being demonstrated in Hawaii. See here:

Designed to Operate with Shore Connection? Yes
Power Transfer Method Current facility is land-based (offshore pipelines draw the deep and surface seawater required). Electrical connection to the grid is accomplished on land.

Future plants will be house on an offshore platform and require a dynamic power cable to shore.

Water Column Location Tropical oceans with a 20 deg C temperature difference between seawater that is at the surface vs ~3,000 ft deep. Demo plant is using water offshore Kailua-Kona, Hawaii.
Mooring Configuration Offshore pipelines are secured using concrete weights, pendant weights, bridles, and anchor chains.
Optimum Marine/Riverline Conditions Tropical oceans with a 20 deg C temperature difference between seawater that is at the surface vs ~3,000 ft deep.
Distance from Shore (m) Land-based or offshore
Technology Dimensions
Device Testing
Have Key Components Been Fabricated and Tested in the Lab? Yes
If Yes, Please Explain OTEC heat exchangers are being designed and test for thermodynamic performance, and corrosion resistance.
Scale Test •Multiple 2 megawatt thermal duty HXs are being tested at the facility. The facility is a 1:100 scale test of a commercial scale plant.
Lab Test •Corrosion samples of the HX material are being tested in the laboratory.

Do Records of Operation of System Prove Reliable Performance? Yes
If Yes, Please Explain Simulated power production currently shows a stable, 24/7 baseload power output from the facility. Actual power production will be measured and studied in late 2014 after installation of the 100kW turbine
Number of Devices Sold 0

Was This Project DOE Funded? No

Date Submitted 2014/02/26

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