Ocean Thermal Energy Conversion (OTEC)

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BETA NUR PRATIWIM0211012)


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What is OTEC ?OTEC ocean thermal energy conversion) :sistem konversi energi panas laut menjadi energi listrik.

FUNDAMENTALS 75% of the Earth Covered by water

Ocean water stores much more heat than theatmosphere

(Jackie Rowley)


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Lockheed Martin


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History 1881: Jacques Arsene d'Arsonval, a French physicist, was the

first to propose tapping the thermal energy of the ocean.

Georges Claude, a student of d'Arsonval's, built anexperimental open-cycle OTEC system at Matanzas Bay, Cuba,in 1930. The system produced 22 kilowatts (kW) of electricityby using a low-pressure turbine. In 1935, Claude constructedanother open-cycle plant, this time aboard a 10,000-ton cargovessel moored off the coast of Brazil. But both plants weredestroyed by weather and waves, and Claude never achievedhis goal of producing net power (the remainder aftersubtracting power needed to run the system) from an open-cycle OTEC system.

1956: French researchers designed a 3-megawatt (electric)(MWe) open-cycle plant for Abidjan on Africa's west coast.But the plant was never completed because of competitionwith inexpensive hydroelectric power.


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History Contd

1979: The first 50-kilowatt ( (kWe)

closed-cycle OTEC demonstrationplant went up at NELHA.

Known as "Mini-OTEC," the plantwas mounted on a converted U.S.Navy barge moored approximately 2kilometers off Keahole Point. The

plant used a cold-water pipe toproduce 52 kWe of gross power and15 kWe net power.


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1993: An open-cycle OTEC plant at Keahole Point, Hawaii,produced 50,000 watts of electricity during a net power-

producing experiment. This broke the record of 40,000 watts set by a Japanese system

in 1982.

Today, scientists are developing new, cost-effective, state-of-the-art turbines for open-cycle OTEC systems, experimentingwith anti corroding Titanium and plastics as rotor material.

The new designs for OTEC are still mostly experimental. Onlysmall-scale versions have been made. The largest so far is nearJapan, and it can create 100 kilowatts of electricity.


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OTEC Description

Oceanic Thermal Energy Conversion

OTEC utilizes the oceans 20C natural thermal gradiebetween the warm surface water and the cold deep sea watto drive a Rankine Cycle

OTEC utilizes the worlds largest solar radiation collectorthe ocean. The ocean contains enough energy power all the worldselectrical needs.

12/18/2009 8OTEC African Deployment


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OTEC System P-Diagram

OTEC

System

ControlsWater Pump

Fluid Pump

OTEC CPU

Turbine

Generator

Heat Exchangers

Pipes

Working fluid

(Noise Factors)

Temperature

Sea state

Weather

Corrosion

(Output Functions)

Power

Water

(Input Signals)

Water

Startup Power

9OTEC African Deployment


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Operational Concept

System Boundary

Power PlanControl

SystemWarm Seawater isExternal Input

Cold Seawater is

External Input

Power

Plant

O

12/18/2009 10OTEC African Deployment


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Open-Cycle

Open-cycle OTEC uses the tropical oceans' warm surfacewater to make electricity. When warm seawater is placed in alow-pressure container, it boils. The expanding steam drives alow-pressure turbine attached to an electrical generator. Thesteam, which has left its salt behind in the low-pressurecontainer, is almost pure fresh water. It is condensed backinto a liquid by exposure to cold temperatures from deep-ocean water.


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Closed-Cycle (Rankine)

Closed-cycle systems use fluid with a low-boiling point, suchammonia, to rotate a turbine to generate electricity. Here's hoit works. Warm surface seawater is pumped through a heexchanger where the low-boiling-point fluid is vaporized. Texpanding vapor turns the turbo-generator. Then, cold, deseawaterpumped through a second heat exchangercondenses the vapor back into a liquid, which is then recyclthrough the system.


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Laju amonia menguap(kg/s)

h:entalphi


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Hybrid SystemHybrid systems combine the features of both the closed-cycleand open-cycle systems. In a hybrid system, warm seawaterenters a vacuum chamber where it is flash-evaporated into

steam, similar to the open-cycle evaporation process. Thesteam vaporizes a low-boiling-point fluid (in a closed-cycleloop) that drives a turbine to produces electricity.

Ammonia is the working flu

Warm sea water is flashed is then used to vaporammonia


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MAIN COMPONENTS OF AN OTEC SYSTEM Evaporators

Condensers

Cold-water pipe

Turbines


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HEAT EXCHANGERS

In an advanced plate-and-fin design,working fluid and seawater flowthrough alternating parallel plates; finsbetween the plates enhance the heattransfer

Original material chosen Titanium -Expensive, so alternative material Aluminium.

Selected Aluminium alloys may last 20years in seawater.

Characterized by low pressure ratios and high mass flow of working fluidsThe turbine is to be designed to have a good isentropic expansion efficover a considerable range of pressure ratio

TURBINES


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Otec production of electricity

Nomi


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ECONOMIC CONSIDERATIONS

OTEC needs high investmentEfficiency only 3% - low energy density large heat transfer equipment

therefore more cost

F b id d hil h i i


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Factors to be considered while choosing a site:

Thermal gradient in the ocean

Topography of the ocean floor

Meteorological conditions hurricanes

Seismic activity Availability of personnel to operate the plant

Infrastructure airports, harbors, etcilabilityof shoreline sites

Offshore

Distance,

km

Capital

Cost, $/kW

10 4200

50 5000

100 6000

200 8100

300 10200

400 12300

Cost Estimates for 100 MW CC-OTEC Plantship(COE for 10 % Fixed Rate, 20 years, Annual Operation & Maintenance 1


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POTENTIALEquatorial, tropical and sub-tropical regions i.e.

20 N to 20 S, have favorable temperature profile Total estimated potential 577000 MW 99 nations and territories have access to the

OTEC thermal resource:

AmericasMainland - 15AmericasIsland - 23AfricaMainland - 18AfricaIsland - 5Indian/Pacific OceanMainland - 11Indian/Pacific OceanIsland - 27

Countries with access to deep ocean water withshore and favorable business climate:

AmericasMainland - 1, Mexico

AmericasIsland - 12

AfricaMainland - 1, Tanzania

AfricaIsland - 1, Madagascar

Indian/Pacific OceanMainland - 1, India

Indian/Pacific OceanIsland

E i t l A t


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Environmental Aspects

Positives:

Environmentally benign - no toxic products are released

Carbon di oxide emission - less than 1% of fossil fuel plant

Nutrient rich coldwaterpromotes mariculture

Chilled soil agriculture promotes growth of temperatecrops in tropical regions.

Cold water for air conditioning

Fresh water production (1 MW plant -> 4500 m3)


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Promotes mariculture


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Environmental Aspects

Negatives:

Fish eggs and larvae entrained, destroyed Sterilization of land by land based plants

Floating plants navigational hazard

Metal pieces entrained affects marine orgs.

Mixing of warm and cold sea water

OTEC is yet untested on large scale over a long period of

time


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Records available from experimental plants demonstrtechnical viability and provide invaluable data on toperation of OTEC plants. The economic evaluation OTEC plants indicates that their commercial future liesfloating plants of approximately 100 MW capacity industrialized nations and smaller plants for small-islandeveloping-states

Small OC-OTEC plants can be sized to produce from 1 Mto 10 MW of electricity, and at least 1700 m3to 3500 m3

desalinated water per day.

The Future

O C &


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210kW OC-OTEC Experimental Plant (1993-1998) in Hawaii

OTEC R&D


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Prospek di IndonesiaUntuk lautan di wilayah Indonesia, potensi termal 2,5 x 1023 joule

dengan efisiensi konversi energi panas laut sebesar tiga persen dapat

menghasilkan daya sekitar 240.000 MW. Potensi energi panas lautyang baik terletak pada daerah antara 6- 9lintang selatan dan 104-

109bujur timur. Di daerah tersebut pada jarak kurang dari 20 km

dari pantai didapatkan suhu rata-rata permukaan laut di atas 28C

dan didapatkan perbedaan suhu permukaan dan kedalaman laut

(1.000 m) sebesar 22,8C. Sedangkan perbedaan suhu rata-rata

tahunan permukaan dan kedalaman lautan (650 m) lebih tinggi dari

20C. Konversi energi panas laut dapat dijadikan alternatif

pemenuhan kebutuhan energi listrik di Indonesia.


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Resources http://www.otecnews.org/

http://www.hawaii.gov/dbedt/ert/otec/index.html

http://www.ocees.com/mainpages/qanda.html#faq3 Pierre Cannon Sumon Nandy Amy Nandy

PRABUDDHA BANSAL ARAVIND G NAVANEETHA KRISHNAN N SHASHANK NARAYAN Finney, Karen Anne.2008.. Guelph Engineering Journal, Ocean Thermal Energy Conversion

(1), 17 - 23. ISSN: 1916-1107. Kadir, Abdul. 2005. Teknologi Konversi Energi Panas Laut:Prinsip, Perkembangan dan

Prospek. L.A.Vega,Ph.D. Marine Technology Society Journal, Ocean Thermal Energy Conversion

PrimerV. 6, No. 4 Winter 2002/2003 pp. 25-35

Mamahit, E.J.Calvin. Pengembangan Konversi Energi Panas Laut. Takahashi and Masutani.2001. Ocean Thermal Energy Conversion OTEC. University of

Hawaii at Manoa, Honolulu, HI, USA.
http://www.otecnews.org/http://www.ocees.com/mainpages/qanda.htmlhttp://www.ocees.com/mainpages/qanda.htmlhttp://www.ocees.com/mainpages/qanda.htmlhttp://www.otecnews.org/http://www.otecnews.org/

Ocean Thermal Energy Conversion (OTEC)

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