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RESEARCH PAPERS

A Preliminary Assessment of Ocean Thermal Energy Conversion Resources

[+] Author and Article Information
Gérard C. Nihous

Hawaii Natural Energy Institute, University of Hawaii, 1680 East-West Road, POST 109, Honolulu, HI 96822nihous@hawaii.edu

http:∕∕www.eia.doe.gov∕aer∕txt∕ptb1117.html

The polar regions receive an advective heat flux wT from the mixed layer; this water cools, downwells and spreads over the ocean floor, inducing an upward advective heat flux wTp in the one-dimensional model.

J. Energy Resour. Technol 129(1), 10-17 (Jul 07, 2006) (8 pages) doi:10.1115/1.2424965 History: Received November 23, 2005; Revised July 07, 2006

Worldwide power resources that could be extracted from Ocean Thermal Energy Conversion (OTEC) plants are estimated with a simple one-dimensional time-domain model of the thermal structure of the ocean. Recently published steady-state results are extended by partitioning the potential OTEC production region in one-degree-by-one-degree “squares” and by allowing the operational adjustment of OTEC operations. This raises the estimated maximum steady-state OTEC electrical power from about 3TW(109kW) to 5TW. The time-domain code allows a more realistic assessment of scenarios that could reflect the gradual implementation of large-scale OTEC operations. Results confirm that OTEC could supply power of the order of a few terawatts. They also reveal the scale of the perturbation that could be caused by massive OTEC seawater flow rates: a small transient cooling of the tropical mixed layer would temporarily allow heat flow into the oceanic water column. This would generate a long-term steady-state warming of deep tropical waters, and the corresponding degradation of OTEC resources at deep cold seawater flow rates per unit area of the order of the average abyssal upwelling. More importantly, such profound effects point to the need for a fully three-dimensional modeling evaluation to better understand potential modifications of the oceanic thermohaline circulation.

FIGURES IN THIS ARTICLE
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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A map of the OTEC resource: temperature difference ΔTdesign between a 75m surface mixed layer and 1000m deep water; 1°C contours are plotted for ΔTdesign>18°C (data from 13)

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Figure 2

Illustration of the OTEC temperature ladder

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Figure 3

Steady-state OTEC net power (at standard conditions) as a function of deep seawater flow rate per unit area

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Figure 4

Steady-state oceanic temperature profiles: base line, or with large-scale OTEC operations (standard conditions and deep seawater flow rate per unit area of 3.75m∕yr)

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Figure 5

Time history of mixed layer temperature with large-scale OTEC operations initiated at t=0 (standard conditions and deep seawater flow rate per unit area of 3.75m∕yr)

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Figure 6

Time history of OTEC cold seawater temperature (1000m depth) with large-scale OTEC operations initiated at t=0 (standard conditions and deep seawater flow rate per unit area of 3.75m∕yr)

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Figure 7

Time histories of OTEC net power (at standard conditions) for selected cases of large-scale OTEC operations initiated at t=0

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Figure 8

Time histories of OTEC net power (at standard conditions) for selected cases of gradually implemented large-scale OTEC operations

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