Ocean Thermal Energy Conversion (OTEC) is a renewable energy technology that utilizes the temperature difference between warm surface water and cold deep ocean water to generate electricity through turbines. The document discusses various OTEC systems, including closed, open, and hybrid cycles, along with their advantages and disadvantages, such as carbon neutrality and high costs compared to fossil fuels. It also highlights site selection for OTEC plants, their potential applications, current operating OTEC facilities, and prospects for implementation in India.

1. Ocean Thermal Energy Conversion
(OTEC)
By
Prof. Ashish Bandewar

2. Unit 4 - Energy from Ocean
1. OTEC (Ocean thermal energy conversion)
2. Tidal Energy
Introduction
• Oceans cover more than 70% of Earth's surface,
making them the world's largest solar collectors.
• OTEC is a renewable energy technology that
converts solar radiation into electric power by use of
world oceans.
• OTEC Process uses temperature difference between
cold deep water (5 ℃) & warm surface water (27 ℃)
to power a turbine to generate electricity.

3. Solar energy absorption by water takes place
according to -

4. OTEC Working Principle
• This plant works on the principle of a closed Rankine
Cycle.
• Warm Water is used to evaporate working fluid like
Ammonia or halocarbon Refrigerant.
• Evaporated Fluid expands in a low pressure turbine,
which is coupled with a turbo alternator to produce
electricity

5. OTEC Systems
• There are three types of electricity conversion
systems:
I. The Closed or Anderson, OTEC Cycle Power Plant
II. The Open or Claude OTEC Cycle Power Plant
III. Hybrid Cycle OTEC Power Plant

6. Closed-loop OTEC
• Closed cycle system use fluid with a low boiling
point, such as ammonia, Propane or Freon to power a
turbine to generate electricity.
The schematic diagram for Closed cycle OTEC

7. CLOESD LOOP OTEC
Closed cycle was designed by Anderson, so its is
also Called Anderson Cycle

8. Open-loop OTEC cycle
• Georges Claude Constructed first OTEC plant in 1929
in Cuba.
• The Claude Plant used an open cycle in which
seawater itself plays the multiple role of heat source,
working fluid, coolant, & heat sink

9. Hybrid OTEC cycle
•A Hybrid cycle combines the features of both the
closed & Open Cycle System.

10. Heat Exchanger( Evaporator)
• Efficiency for conversion of heat into mechanical work
depend on drop in temp inside turbine and turbine inlet
temp
• ɳ Thermal =
𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 𝑖𝑛 𝑇𝑢𝑟𝑏𝑖𝑛𝑒
𝑇𝑢𝑟𝑏𝑖𝑛𝑒 𝐼𝑛𝑙𝑒𝑡 𝑡𝑒𝑚𝑝.
• Temperature at inlet of turbine should be high and leaving
from turbine should be low form max ɳ thermal.
• Primary materials considered for this – Titanium,
Aluminium, Alloy of copper and nickel.

11. Bio-fouling in Heat Exchangers
• Deposition and growth of micro-organism on
cooling water side of condenser heat exchanger
• Less if copper is used
• Can be dealt with by using chlorination or using
mechanical brushes
• Increasing flow rate of water can be advantageous
(organisms will not attached with HE)

12. Site Selection and Energy Generation for OTEC
• Temperature difference between surface and deep
ocean water
• Best sites are in tropical belt between about 20oN
and 20oS latitude.
• Locations where less bio-fouling.
• OTEC plant would be located offshore in order to
access to deep water.
• Plant should be less than 30 km from shore.
• Electricity generated could be transmitted
inexpensively to land by submarines

13. An OTEC system application
• Hydrogen can be produced via electrolysis using
electricity generated by the OTEC process.
• Desalination It’s produced in open & Hybrid cycle.
System analysis indicates that a 2 MW plant can produce
4300 cubic meter desalination water each day.
• Aquaculture
It reduces the financial & energy costs of pumping large
volumes of water from deep ocean.
Deep ocean water contains high concentration of
essential nutrients that are depleted in surface water due
to biological consumption.

14. • Mineral Extraction
The ocean contains 57 trace elements in salt dissolved
in solution.
The Japanese investigated the possibility of extracting
Uranium.

15. Advantages of OTEC
• Warm surface sea water and cold water from the
ocean from the ocean depths replace fossil fuels to
produce electricity.
• OTEC plants will produce little or no carbon dioxide
or other polluting chemicals.
• OTEC systems can produce fresh water as well as
electricity. A lot of fish & other nutritious sea-food
will be collected in outlet flow.
• OTEC can also be used to produce ammonia,
hydrogen, aluminium, chlorine and other
chemicals.

16. Disadvantages of OTEC
• OTEC produced electricity at present would cost
more than electricity generated from fossils fuels at
their current costs.
• No energy company put money in this project
because it only had been tested in a very small
scale.
• Construction of OTEC plants and lying of pipes in
coastal waters may cause localized damage to reefs
and near-shore marine ecosystem.

17. Current operating Plants of OTEC
• In March 2013, Makai installed and operate a 100 kilowatt
turbine on the OTEC Heat Exchanger Test Facility, and connect
OTEC power to the grid.
•Okinawa Prefecture announced the start of the OTEC operation
testing at Kume Island on April 15, 2013. The plant consists of
two units; one includes the 50 kW generator while the second
unit is used for component testing and optimization.
•In July 2014, DCNS group partnered with Akuo Energy
announced their NEMO project. If successful, the 16MW gross
10MW net offshore plant will be the largest OTEC facility to
date.

18. Prospects of OTEC in India
• OTEC project cell established in IIT, Chennai
• Completed preliminary study for establishing 1
MW OTEC in Lakshadweep Island.
• Hydrographic survey of proposed site was
undertaken by National Hydrographic Office,
Dehradun.
• Assessment of survey indicates suitable condition
to establish OTEC