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					   ASN WOMEN’S ENGENEERING COLLEGE TENALI


   OCEAN THERMAL ENERGY CONVERSION




SUBMITTED BY
G.CHIDRUPI
K.SRI LAKSHIMI
CONTENTS:


   INTRODUCTION


   TYPES OF OCEAN THERMAL ENERGY CONVERSION


  1. CLOSED CYCLE O.T.E.C. PLANT


  2. OPEN CYCLE O.T.E.C.PLANT


  3. HYBRID CYCLE O.T.E.C.PLANT


  4. POTENTIAL FOR O.T.E.C . PLANT


   APPLICATIONS


   ADVANTAGES


   DISADVANTAGES


   CONCLUSION
ABSTRACT:


          Ocean Thermal Energy Conversion (OTEC) is
    the concept for a system which will extract energy
    from the ocean by taking advantage of the sizable
    temperature difference between surface and bottom
    water in a tropical ocean. A fundamental part of an
    OTEC system is a large section of heat exchangers
    through which the energy transfer is made.
INTRODUCTION:

 The oceans collect and store large quantities of solar radiation as heat energy. A heat engine that uses the warm

surface water as a heat source and the cold subsurface water as a heat sink is capable of converting significant

amounts of this thermal energy to mechanical and thence to electrical energy. Because the temperature difference

between the heat source and heat sink is relatively small, the conversion efficiency will be low compared to the more

familiar power -conversion cycles. However, since no fuel is required, the net cost of the energy can be made

economically competitive. The challenge is to develop a conversion system that is low in cost and reliable and is

acceptable politically, socially, and environmentally
The ocean as a heat source for power generation:




              The Sun warms the surface of the ocean in the Tropics to a consistent 20-25°C,

compared to the temperature of 5²C in the ocean depths (below 1000m). A heat engine can be to

harness this temperature differential to generate electricity. The temperature differences are small
and plant efficiency is low but the resource is available 24/7 and therefore capable of providing

continuous base load electricity without the logistical nightmare that providing power to remote

tropical communities can entail. The technology is currently only viable in the Tropics but potentially

could




Closed-cycle OTEC plants




                                  Diagram of a closed cycle OTEC plant


In a closed-cycle system, a low boiling point fluid, such as ammonia, is vaporized to power a low-

pressure turbine to generate electricity. The fluid is vaporized using warm surface seawater pumped

through an ex-changer (the evaporator – 2). This expanding fluid turns the turbo-generator. This is

then re-condensed to a liquid in a second exchanger (the condenser – 8) fed with cold deep

seawater. The condensed fluid is then circulated back to the evaporator (2) to start a new cycle.
            This is a classic heat transfer cycle, similar to that used in air conditioning or a

domestic refrigerator, except that water take the place of air as the heating and cooling medium.

Some savings on costs can be achieved by having the fluid re-condense naturally as it plunges into

colder water before being re-circulated. This removes the necessity for a cold water pump. Other

fluids can be used instead of ammonia, such as CFCs and hydrocarbons, but these create greater

environmental problems in the event of a leak and hydrocarbons are extremely flammable.




Open-cycle OTEC plants:
                                 Diagram of an open cycle OTEC plant


In an open-cycle OTEC plant, the warm surface water is used directly to make electricity. Surface

seawater is forced to vaporize in a near vacuum created in a special pressure vessel. The (steam)

drives a low-pressure turbine generator to produce electricity in the same way as a closed-cycle

OTEC plant. This steam is then condensed back into pure fresh water by passing the steam through

an ex-changer fed with cold water from the ocean deeps or by pumping it.
Hybrid cycle OTEC plants




           A hybrid OTEC plant combines the main elements of the open and closed-cycle systems.

Warm seawater is evaporated in a near vacuum as in the open cycle but the steam created is then

used to vaporize the working fluid (ammonia, refrigerant, etc.) in a closed-cycle loop via an

exchanger. It is the vaporized working fluid that drives the turbo-generator. The steam condenses

back to desalinated water in the exchanger and can then be used in the same way as the freshwater

from an open-cycle plant.




The potential for OTEC plants
                                   Floating OTEC plant off the Indian coast


        OTEC technology has the potential to produce vast amounts of zero-carbon electrical

power. The potential hydrogen production could completely replace all fossil fuel consumption with

the exception of lubricants. The technology even makes it feasible to mine the sea for minerals and

metals. Reduction of costs is still a concern but the technology is effectively still in its infancy and, as

with all currently used technologies, ongoing research and experience will produce advances that

will reduce costs considerably. The advantages of OTEC technology are that the power source is

constantly available, essentially inexhaustible, creates no significant pollution, provides significant

useful by-products, is relatively easy to maintain and has a long service life with no inconvenient
APPLICATION:

Ocean thermal energy conversion (OTEC) systems have many applications or uses. OTEC can
be used to generate electricity, desalinate water, support deep-water mariculture, and provide
refrigeration and air-conditioning as well as aid in crop growth and mineral extraction. These
complementary products make OTEC systems attractive to industry and island communities
even if the price of oil remains low.
ADVANTAGES:




DISADVANTAGES:
     Net effect of OTEC operation on aquatic life.

     Electrical hazards.

     Rotating machinery.

     OTEC plant construction and operation is difficult.
CONCLUSION:

				
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