Hawaii National Marine Renewable Energy Center

World-Wide OTEC Thermal Resource

P.I.: Assoc. Prof. Gerard Nihous, Department of Ocean and Resources Engineering

Objective:  (i) Document the ocean thermal resource; and (ii) Analyze potential OTEC worldwide sustainable energy production.

One might ask: is OTEC renewable energy?  The simple answer is that as long as the sun shines and, if and only if, deep-ocean cold water is provided by the thermohaline circulation the ocean thermal resource is renewable.  A pertinent question, however, is: what is the worldwide power resource that could be extracted with OTEC plants without affecting the thermohaline ocean circulation? Our estimate is that the maximum steady-state OTEC electrical power is about 14 TW (Terawatts) corresponding to 250,000 plants  of the kind described in the “OTEC Power Production” link below. These would be deployed throughout the OTEC region in the exclusive economic zone (EEZ) of ninety-eight nations.  This power rating corresponds to 77% of the current worldwide annual energy consumption (Global OTEC Resources_2013).

Please use Google Chrome or Safari to view the links given below because Internet Explorer does not provide the display we intended.

Ocean Thermal Resource.- The temperature difference between 20 m and 1000 m water depths gives a good indication of available OTEC resources across tropical oceans.  For example, values less than 18°C may not be economically viable for OTEC power generation.  The NOAA National Ocean Data Center’s World Ocean Atlas (WOA) database (2005 version) was used to construct the link given below which shows the annual and monthly averages of the temperature difference (between 20 m and 1000 m depths) across the world oceans on a quarter-degree horizontal grid. The link  TemperatureDifferentialWOA2005  provides the user with a color coded world map of the annual average temperature difference. The user can choose any region of interest defined by specific latitude and longitude ranges to view color-coded data of the annual average temperature difference as a function of latitude and longitude. Further, clicking on any location gives a plot of monthly averages of the temperature difference there.

OTEC Power Production.- An estimate of OTEC power production capabilities can be made with the temperature difference data available from the WOA database.  The link PowerMaps gives annual and monthly averages of the power that would be produced by a single generic OTEC plant rated at 100 MW in standard conditions (seawater temperature difference of 20°C between 20 m and 1000 m depths, and seawater temperature of 300 K at 20 m depth).  The standard conditions, along with other realistic assumptions are found in:  OTEC Summary Aug 2012.  The display is limited to a latitude band between 30°S and 30°N.  The link provides the user with a color-coded distribution of OTEC power production from the generic 100 MW plant, in GWh per year.  The user can choose any region of interest between 30°S and 30°N to view detailed values of annual average power. Further, clicking on any location provides the user with a plot of the monthly averages of net power there, in GWh per month.

4 thoughts on “World-Wide OTEC Thermal Resource

  1. Luis A. Vega Post author

    Aloha Energy Island, if you click on the Figure (photo) to enlarge display you will see temperature color scale

  2. Jim Anderson

    Great presentation. Interesting how the thermocline shifts Northward in Summer months so that the Northern Kauai has a higher temperature potential than does Hawaii! Thanks Luis.

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