1. OCEAN THERMAL ENERGY CONVERSION
PRESNTED BY
G.MANI,
SIDDARTHA INSTITUTE OF SCIENCE AND TECHNOLOGY
PUTTUR
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2. ABSTRACT
OTEC, or Ocean Thermal Energy Conversion, is an energy technology that
converts solar radiation to electric power. OTEC systems use the ocean's natural
thermal gradient—the fact that the ocean's layers of water have different temperatures to
drive a power-producing cycle. As long as the temperature between the warm surface
water and the cold deep water differs by about 20°C (36°F), an OTEC system can
produce a significant amount of power, with little impact on the surrounding
environment.
The distinctive feature of OTEC energy systems is that the end products include
not only energy in the form of electricity, but several other synergistic products. The
principle design objective was to minimize plan cost by minimizing plant mass, and
taking maximum advantage of minimal warm and cold water flows. Power is converted
to high voltage DC, and is cabled to shore for conversion to AC and integration into the
local power distribution network.
The oceans are thus a vast renewable resource, with the potential to help us
produce billions of watts of electric power.
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3. OCEAN THERMAL ENERGY CONVERSION
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.
I. INTRODUCTION TO OCEAN ENERGY:
Most people have been witness to the awesome power of the world's oceans. For
least a thousand years, scientists and inventors have watched ocean waves explode
against coastal shores, felt the pull of ocean tides, and dreamed of harnessing these
forces. But it's only been in the last century that scientists and engineers have begun to
look at capturing ocean energy to make electricity.
The ocean can produce two types of energy: thermal energy from the sun's heat,
and mechanical energy from the tides and waves. Ocean thermal energy is used for many
applications, including electricity generation. Ocean mechanical energy is quite different
from ocean thermal energy. Even though the sun affects all ocean activity, tides are
driven primarily by the gravitational pull of the moon, and waves are driven primarily by
the winds. As a result, tides and waves are sporadic sources of energy, while ocean
thermal energy is fairly constant. Also, unlike thermal energy, the electricity conversion
of both tidal and wave energy usually involves mechanical devices.
II. OCEAN THERMAL ENERGY CONVERSION:
OTEC or Ocean Thermal Energy Conversion (OTEC) is a process which utilizes
the heat energy stored in the tropical ocean. The world's oceans serve as a huge collector
of heat energy. OTEC plants utilize the difference in temperature between warm surface
sea water and cold deep sea water to produce electricity.
Thermal energy conversion is an energy technology that converts solar radiation
to electric power. OTEC systems use the ocean's natural thermal gradient—the fact that
the ocean's layers of water have different temperatures—to drive a power-producing
cycle. As long as the temperature between the warm surface water and the cold deep
water differs by about 20°C, an OTEC system can produce a significant amount of
power. The oceans are thus a vast renewable resource, with the potential to help us
produce billions of watts of electric power. This potential is estimated to be about 10 13
watts of base load power generation, according to some experts. The cold, deep seawater
used in the OTEC process is also rich in nutrients, and it can be used to culture both
marine organisms and plant life near the shore or on land. OTEC produce steady, base-
load electricity, fresh water, and air-conditioning options.
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4. OTEC requires a temperature difference of about 36 deg F (20 deg C). This
temperature difference exists between the surface and deep seawater year round
throughout the tropical regions of the world. To produce electricity, we either use a
working fluid with a low boiling point (e.g. ammonia) or warm surface sea water, or turn
it to vapor by heating it up with warm sea water (ammonia) or de-pressurizing warm
seawater. The pressure of the expanding vapor turns a turbine and produces electricity.
Plant Design and Location
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
Land-based and near-shore are more advantageous than the other two. OTEC plants
can be mounted to the continental shelf at depths up to 100 meters, however may make
shelf-mounted facilities less desirable and more expensive than their land-based
counterparts. Floating OTEC facilities with a large power capacity, but has the difficulty
of stabilizing and of mooring it in very deep water may create problems with power
delivery.
Commercial ocean thermal energy conversion (OTEC) plants must be located in an
environment that is stable enough for efficient system operation. The temperature of the
warm surface seawater must differ about 20°C (36°F) from that of the cold deep water
that is no more than about 1000 meters (3280 feet) below the surface. The natural ocean
thermal gradient necessary for OTEC operation is generally found between latitudes 20
deg N and 20 deg S.
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