Ocean Thermal Energy Conversion Energy From the Sea Dr Peter Ridd Physics Department James Cook Univ

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Ocean Thermal Energy ConversionEnergy From the
SeaDr Peter RiddPhysics Department James
Cook University
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Alternative Energy

• Solar Power
• Wind Power
• Wave Power
• Tidal Power
• Bio-fuels
• Nuclear Energy
• OTEC

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Heat Engines

• Petrol Engines
• Diesel Engines
• Steam Engines
• Gas Turbines (e.g. jet engines)

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Rolls Royce V12 Aero Engine27 litres 1600 HP
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MarineDieselNote the size of the people
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Jet Engines
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• All heat engines have a hot end and a cold end
• Gas is heated (Hot end) and allowed to expand.
• Expanding gases cool
• Much of the heat in the gas is wasted in the
  exhaust gas (cold end)

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Rankine Cycle
Heating Required HOT WATER
Cooling required COLD WATER
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• Require a gas that boils at about 20 degrees

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The Queensland coast is a possible location for
OTEC
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• Surface Seawater around 25 degrees
• Bottom seawater around 4 degrees

Coral Sea
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1000 m
Cairns
Townsville
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Carnot efficeincy
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• Problem
• As the temperature difference between the hot end
  and cold end gets smaller, the efficiency
  decreases
• Diesel engine DT 500 degrees
• OTEC DT 20 degrees
• Diesel Engine Efficiency is about 25
• OTEC Efficiency is at most 7

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Other Problems

• Submarine Cable
• Moorings
• Extreme environment (Salt Water)

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Consider 1000 MWatt plant

• Assume 3 efficiency
• Require 1000 cubic meters/sec flow rate
• Pipe of radius of 10 m with flow rate of 3
  m/s
• Approximately the same flow rate as the Tully
  River in moderate flood
• Energy loss is relatively small as pumping head
  is equivalent about 6 m. Perhaps 60 MW

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Waste Water Plume

• High in Nutrients (orders of magnitude higher
  than shelf water)
• Plume must be discharged on slope below
  thermocline

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