OCEAN THERMAL ENERGY CONVERSION

PRESENTED BYk.Sachin varma

g.Sunkireddyc.h.sairam

INTRODUCTION Oceans cover more than 70% of Earth's surface,

making them the world's largest solar collectors. The sun's heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world.

A heat engine gives greater efficiency when run with a large temperature difference.

OTEC

OTEC utilizes the ocean’s 20ºC natural thermal gradient between the warm surface water and the cold deep sea water to drive a Rankine Cycle

OTEC utilizes the world’s largest solar radiation collector - the ocean. The ocean contains enough energy power all of the world’s electrical needs.

The oceans are thus a vast renewable resource, with the potential to help us produce billions of watts of electric power

Commercial OTEC facilities can be built on

      Land or near the shore

      Platforms attached to the shelf

       Moorings or free-floating facilities in deep ocean water

Ocean Thermal Energy Conversion(OTEC)

ELECTRICITY CONVERSION SYSTEMSElecricity conversion systems are three typesThey are . Closed-cycle system . Open-cycle system . Hybrid sytem (combination of both open &

closed systems)

Closed-cycle

•Closed-cycle systems use the ocean's warm surface water to vaporize a working fluid, which has a low-boiling point, such as ammonia.• The vapor expands and turns a turbine. The turbine then activates a generator to produce electricity.

Open-cycle

• Open-cycle systems actually boil the seawater by operating at low pressures. •This produces steam that passes through a turbine/generator•FOUR STEPS

Flash evaporation,expansion of the vapour,heat transfer,compression of non condensable gases

HYBRID SYSTEM  In a hybrid OTEC system, warm sea water might enter a

vacuum where it would be flash-evaporated into steam, in a similar fashion to the open-cycle evaporation process. 

The steam or the warm water might then pass through an evaporator to vaporize the working fluid of a closed-cycle loop.  The vaporized fluid would then drive a turbine to produce electricity, while the steam would be condensed within the condenser to produced desalinated water

OTEC Process

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1. Power input to pumps to start process

4. Expanding vapor drive the turbine, and electricity is created by a generator

5. Heat extraction from cold-water sink to condense the working fluid in the condenser.

Cycle begins againReturn to step 2

3. Heat addition from the hot-water source used to evaporate the working fluid within the heat exchanger (Evaporator)

2. Fluid pump pressurizes and pushes working fluid to evaporator

Operational Concept

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System Boundary

Power PlantControl SystemWarm Seawater is

External Input

Cold Seawater is External Input

Power to Power Plant is System

Output

Benefits•        Helps produce fuels such as hydrogen, ammonia, and methanol

•        Produces base load electrical energy

•        Produces desalinated water for industrial, agricultural, and residential uses

•        Is a resource for on-shore and near-shore Mari culture operations

•        Provides air-conditioning for buildings

•        Provides moderate-temperature refrigeration

•        Has significant potential to provide clean, cost-effective electricity for the future.

•        Fresh Water-- up to 5 liters for every 1000 liters of cold seawater.

•        Food--Aquaculture products can be cultivated in discharge water

 

Disadvantages

Low thermal efficiency due to small temperature gradient between heat sink and source

Available only in equatorial watersOnly moderate power outputs are availableCurrently this technology is not as monetarily feasible as

conventional power production plantsThe manufacturing and installation of the extremely long

cold water pipes is extremely time consuming and costly.

Sea Water Air Conditioning (SWAC)

Applications Power Plant for Clean Renewable Energy OTEC based

power plants are environmentally safe, efficient, cost effective and delivers 24x7 continuous electric power with a very low PLF.

Desalination Plant for Clean Fresh Water is a complementary extension to the OTEC power plant and is a viable renewable source of unlimited fresh water

Hydrogen Fuel Cells Electricity produced from an OTEC floating vessel power plant is used to separate hydrogen from water which is then compressed and transported to land for use in hydrogen fuel cells.

conclusion OTEC has tremendous potential to supply the

world’s energy. It is estimated that, in an annual basis, the amount solar energy absorbed by the oceans is equivalent to at least 4000 times the amount presently consumed by humans. 

Conventional power plants pollute the environment more than an OTEC plant would and, as long as the sun heats the oceans, the fuel for OTEC is unlimited and free.