OTEC, or Ocean Thermal Energy Conversion, is a technology that generates electricity by exploiting the temperature differences between warm surface waters and colder deep waters in tropical oceans. There are three main types of OTEC systems - floating, land-based, and self-mounted. OTEC plants use the ocean's thermal gradient to evaporate a working fluid like ammonia in a heat exchanger, which then drives a turbine that generates electricity. While OTEC is not yet economically viable at scale, it has advantages of being renewable, low maintenance, and producing fresh water and minerals as byproducts while emitting very little carbon. Further development is needed to minimize environmental impacts and reduce costs to compete with other power sources.

1. Ocean Power
Presented By
Nitish Kulkarni
MESCOE PUNE -01

3. OTEC
Ocean Thermal Energy
Conversion :–
The technology that converts
solar radiation into electric power.

4. In detail - OTEC
Hydro energy conversion system which uses ocean's natural thermal
gradient—the fact that the ocean's layers of water have different
temperatures, similar to run a heat engine.
OTEC plants are of 3 types
* Floating ( Placed in cargo ship)
* Land Based
* Self Mounted

5. Contd.
1. Based on Rankine cycle - Thermodynamic cycle which converts
heat into work through a heat engine
2 . Uses the vertical temperature gradient in the ocean as a heat
source/sink.
3. Temperature differences generally increases with decreasing
latitude , in the tropics, thereby mainly used in equatorial waters
where temperature difference is greatest
4. OTEC can produce electric energy 10 to 100 times greater than
Wave power ( Tidal Energy) and it can produce energy constantly.

6. History
• 1881: Jacques Arsene d'Arsonval, a French physicist, was the first to
propose tapping the thermal energy of the ocean. Georges Claude, a
student of d'Arsonval's, built an experimental open-cycle OTEC
system at Matanzas Bay, Cuba, in 1930. The system produced 22
kilowatts (kW) of electricity by using a low-pressure turbine. In 1935,
Claude constructed another open-cycle plant, this time aboard a
10,000-ton cargo vessel moored off the coast of Brazil. But both plants
were destroyed by weather and waves, and Claude never achieved his
goal of producing net power (the remainder after subtracting power
needed to run the system) from an open-cycle OTEC system.
• 1956: French researchers designed a 3-megawatt (electric) (MWe)
open-cycle plant for Abidjan on Africa's west coast. But the plant was
never completed because of competition with inexpensive
hydroelectric power.

7. History- Contd
• 1979: The first 50-kilowatt
(kWe) closed-cycle OTEC
demonstration plant went up
at NELHA.(Natural Energy Lab of
Hawaii Authority)
• Known as "Mini-OTEC," the plant was
mounted on a converted U.S. Navy
barge moored approximately 2 kilometers
off Keahole Point. The plant used a cold-water
pipe to produce 52 kWe of gross power and
15 kWe net power.

8. Need Of OTEC
• Fossil fuels in near future will be
consumed,we have to find alternative
source.
• OTEC uses Renewable Solar collector
instead of artificial collector.
• It Can be Used To produce Desalined
Water.(Salt Free Water)

9. Process
• Carnot Efficiency (T1-T2)/T1:
in transferring heat to do work,
the greater the spread in
temperature between the
heat source and the heat sink,
the greater the efficiency
of the energy conversion
T1- Temp at surface level
T2- Temp at bottom level
• 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 a maximum Carnot
Efficiency of about 6.7%

10. 2. Fluid pump pressurizes and
pushes working fluid to evaporator
1. Power input to
pumps to start
process
3. Heat addition from
the hot-water source
used to evaporate the
working fluid within
the heat exchanger
(Evaporator)
EVAPORATOR
CONDENSER
WARM SURFACE
WATER 28 C
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.
TURBINE
GENERATOR
COLD DEEP
WATER
5 C
WORKING FLUID
(LIKE AMMONIA)

13. OPEN CYCLE SYSTEM
OPEN CYCLE SYSTEM SYSTEM
Open-cycle OTEC uses the
tropical oceans' warm
surface water to make
electricity. When warm
seawater is placed in a
low-pressure container, it
boils. The expanding
steam drives a low-
pressure turbine attached
to an electrical generator.
The steam, which has left
its salt behind in the low-
pressure container, is
almost pure fresh water. It
is condensed back into a
liquid by exposure to cold
temperatures from deep-
ocean water.

14. CLOSED CYCLE SYSYTEM
CLOSED CYCLE SYSTEM SYSTEM
Closed-cycle systems( Rankine )
use fluid with a low-boiling point,
such as ammonia, to rotate a
turbine to generate electricity.
Here's how it works. Warm
surface seawater is pumped
through a heat exchanger where
the low-boiling-point fluid is
vaporized. The expanding vapor
turns the turbo-generator. Then,
cold, deep seawater—pumped
through a second heat
exchanger—condenses the
vapor back into a liquid, which is
then recycled through the
system.

15. Hybrid systems
Hybrid systems combine the features of both the closed-
cycle and open-cycle systems.
In a hybrid system, warm seawater enters a vacuum
chamber where it is flash-evaporated into steam, similar
to the open-cycle evaporation process.
The steam vaporizes a low-boiling-point fluid (in a
closed-cycle loop) that drives a turbine to produces
electricity.

17. Advantages
• Eco- friendly
• Minimal maintenance costs compared to other power production
plants.
• Provide air conditioning to buildings within the OTEC plant.
• Fresh water - first by-product is fresh water. A small 1 MW OTEC is
capable of producing some 4,500 cubic meters of fresh water per
day, enough to supply a population of 20,000 with fresh water
• Open cycle OTEC systems can produce desalinated water which is
very important in middleast countries.
• Chilled soil agriculture- cold seawater flowing through underground pipes,
chills the surrounding soil. Thereby allowing many plants evolved in
temperate to be grown in subtropics due to temp. difference in the plant
roots in cool soil and plant leaves in warm air

18. Advantages- Continued
• Mineral Extraction – OTEC helps in mining
ocean water for 57 trace elements.
Most economic analyses have suggested that mining the
ocean for trace elements would be unprofitable as so much energy
is required to pump the large volume of water needed and because
of the expense involved in separating the minerals from seawater.
But in OTEC plants already pumping the water, the only
remaining economic challenge is to minimize the cost of the
extraction process.

19. Environmental Impact
• Mixing of deep ocean water and shallower water brings up nutrients
and makes them available to shallow water life.
• This may be advantage for aquaculture, but it may unbalance
ecological system around powerplant .
• Catastropic failure ( Working fluid escape) has only local effects, but
doesn’t make major disaster, it can be overcome by Correct design.
• To much of extraction of water may damage aquatic life cycle of
aquatic plants & animals.
• OTEC Plant Produce nearly zero carbon emissions, also no solid
wastes.

21. Floating Plant for OTEC

22. Conclusion
• Amount of solar energy absorbed by oceans is 4000 times presently
consumed by humans. We would need less than 1% of that
renewable energy to satisfy our desires.
• Conventional power plants pollute environment more than OTEC
plant.
• As no emissions of hazardous substance hence it is harmless.
• “As long as the Sun heats oceans, fuel for OTEC is unlimited & free”