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OCEAN THERMAL ENERGY CONVERSION

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            CONTENTS

Introduction
Principle and working
 Milestone
Classification
By-products
Advantages of OTEC
Disadvantage
Technical limitations & challenges
Environmental impact
Efficiency of an OTEC plant
Case study
Conclusion
References                           2
            INTRODUCTION
Solar energy is the ultimate source of energy

Oceans cover more than 70% of Earth's surface

Ocean is the largest solar energy collector and
energy storage system.

Man-made solar collectors only work when the
sun shines

 A renewable source of energy.
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SOME CURRENT METHODS OF POWER
         GENERATION

Oil and Natural Gas: Both in relatively short supply. New wells and
extraction methods are costly.

Coal: Less costly than oil but polluting and costly for waste
cleanup. Mercury emissions enter the food chain and affect the
 health of unborn children.

Nuclear Power: Radioactive waste creates an environmental hazard
for thousands of years. Serious malfunction of a nuclear plant or a
terrorist attack could cause a disastrous meltdown.

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Hydro/Dams: Environmentally friendly but most available sites
already utilized.

Wind Power: Environmentally friendly but resource is intermittent,
requiring reliable backup power plants.

Solar Power: Environmentally friendly but needs large areas of
unshaded land and only makes power when sun shines. Needs large
storage systems for night loads and/or backup power plants on cloudy
days and nights.



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    OCEAN THERMAL ENERGY CONVERSION
                [OTEC]

 Converts solar energy to electric power.

 Use ocean’s natural thermal gradient to generate
  electricity.

 Temperature difference between warm surface water
  and cold deep water should be 20°c.

 OTEC can deliver continuous power 24/7, rain or shine,
  day and night.

Stored solar energy could provide 300 times the
world's consumption of electricity.                  6
PRINCIPLE AND WORKING




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                  MILESTONE

1880      - OTEC first proposed by French physicist
            Jacques d’Arsonval.

1920      - A test plant was build in France.

1930      -Builds an open cycle land based plant at The Bay of
           Mantanzas.

Early 1980 -ERDA confirms that OTEC is technologically and
            commercially viable.

Mid 1980 -Mini OTEC floating plant using a refrigerant working
          fluid operates in Hawaii.
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1990   -OTEC heat exchangers can be made from
        inexpensive aluminum alloys and don’t require
        expensive cupronickel or titanium. It also becomes
        clear that bio-fouling of the heat exchanger
        surfaces can be controlled with small amounts of
        chlorination.

2000 -India’s Institute for Energy Studies has been
      working on construction of a small floating plant.




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   CLASSIFICATION
DEPENDING ON LOCATION

  LAND BASED POWER PLANT

  FLOATING POWER PLANT

DEPENDING ON CYCLE USED

  OPEN CYCLE SYSTEM

  CLOSED CYCLE SYSTEM

  HYBRID CYCLE SYSTEM      10
  LAND BASED POWER PLANT




Photograph of 210 kW OC-OTEC Experimental Plant (1993-1998)
      at Keahole on the Kona coast of Hawaii
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OPEN CYCLE SYSTEM




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CLOSED CYCLE SYSTEM




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HYBRID CYCLE SYSTEM




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           BI-PRODUCTS


Seafood

Fresh water

Cold water as a fluid in air conditioning
 system

Ammonia

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           ADVANTAGES OF OTEC

OTEC is a renewable source of energy.

 It causes less impact on environment.

 Rather than electricity it produces seafood and fresh
water.

 The cold water can be used in air conditioner.

 It reduces the dependence on fossil fuels.

 Produce fuel such as hydrogen, ammonia and methanol.

 It gives energy independence and energy security
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                   DISADVANTAGES


 The cost of production of electricity is very high compared to
electricity production from conventional sources.

 Only experimental OTEC plants are established.

 The long pipes and arrangement for anchorage of plant may
 cause damage to reefs and marine plants.

 The temperature difference between surface water and deep
 water will not be always 20°c.



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TECHNICAL LIMITATIONS & CHALLENGES

A portion of the power generated by the turbine-generator is
used in the operation of pumps.

Efficiency is less compared to conventional power plant


Design and installation of cost-effective cold water pipe,
position keeping system and attachment of submarine cable to
floating plant .




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         ENVIRONMENTAL IMPACT


Marine organism entrainment through the water current

Effects of chemicals used to reduce “biofouling”

Upwelling




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    EFFICIENCY OF AN OTEC PLANT
Theoretical efficiency is 7-8%

But practical efficiency is 3%

 To calculate efficiency

          W= [(T-T0)/T]*Q

         W = work/energy
          T = surface water temperature
         T0 = deep water temperature
          Q= thermal value

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               CASE STUDY - INDIA
Low Temperature Thermal Desalination Plant at Kavaratti

   Capacity                           : 1,00,000 LPCD

    Warm Seawater Temperature         :280 C

   Cold Seawater Temperature          : 130 C

   Cold Seawater Intake               : 350 m depth

   Warm Seawater Flow rate            : 145 kg / sec

   Cold Seawater flow rate            : 186 Kg / Sec
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                             The Sump of size 6m diameter and
                             height of 5m was constructed near the
                             jetty.




The Sump was positioned in site and
further construction to raise the wall
was carried out.

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Trestle




          Pipe at Shore



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Flash Chamber Size : 4.5m X 3.0m X 2.5m
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Condenser Size : 1.5m Dia X 6.0m

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                  CONCLUSION

The global importance of a renewable source of energy is
very high.

As long as the sun heats the ocean the fuel for OTEC is
unlimited and free.

For successful implementation of OTEC correct technical
approach and appropriate financial strategy is required.

OTEC offers the opportunity to contribute to the energetic
independence and economic development for the countries and
territories where the technology is found suitable.
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                 REFERENCES

L.A Vega, Ocean Thermal Energy Conversion Primer,
Marine Technology Society Journal, Vol: 6, No: 4
Winter 2002/2003, pg 25-35.

B.Kirke, Enhancing Fish Stock With Wave-powered
Artificial Upwelling, Ocean and Coastal Management,
Vol: 46, 2003, pg 901-915.

G.C Nihous,An Estimate of Atlantic Ocean Thermal
Energy Conversion Resource, Ocean Engineering, Vol: 34,
2007, pg 2210-2221.

R.Balaji,A Technical Paper Presented on Ocean
Thermal Energy Conversion –A Non conventional Energy
Source.                                                   30
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