Ocean Energy Questions and Answers – Ocean Thermal Energy – 1

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This set of Ocean Energy Multiple Choice Questions & Answers (MCQs) focuses on “Ocean Thermal Energy – 1”.

1. What is ocean thermal energy conversion?
a) Harnessing the temperature differences between surface waters and deep ocean waters
b) Harnessing the temperature differences between the coastal waters and deep ocean waters
c) Harnessing the heat energy from the underwater volcanoes
d) Harnessing the heat energy between surface water vapour and atmospheric gases
View Answer

Answer: a
Explanation: The process of generating energy by using temperature difference (or gradient) varying with depth of seawater is called Ocean thermal energy conversion (OTEC). A temperature gradient exists between the surface waters and deep sea waters due to various physical phenomenon.
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2. What is the temperature difference used in ocean thermal energy conversion? Note that F denotes Fahrenheit
a) 10 degree F
b) A minimum of 77 degree F
c) Between 50 and 60 degree F
d) A minimum of 100 degree F
View Answer

Answer: b
Explanation: The temperature difference is at least 77 degree F (or 25 degree C). Ocean thermal energy conversion systems use this temperature difference between the surface and the bed (or deep sea waters) to generate electricity.

3. What is thermohaline circulation?
a) Circulation of halogens throughout the ocean
b) Circulation of halogens due to temperature differences throughout the ocean
c) Large scale ocean circulation driven by global density gradients
d) Large scale halogens circulation due to global density gradients
View Answer

Answer: c
Explanation: Thermohaline circulation is a constituent of large scale ocean water movement and circulation caused due to global density gradients. The cause for this gradient is heat of the surface and freshwater fluxes. Halogens are group 17 elements in the periodic table and are not related to thermohaline circulation.
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4. What is the maximum estimated potential of ocean thermal energy conversion per year?
a) 80 GWh
b) 900 MWh
c) 10000 TWh
d) 88000 TWh
View Answer

Answer: d
Explanation: Ocean thermal energy conversion is one of the continuously available renewable energy resource. The maximum estimated potential is 880000 TWh per year. In fact, it is strongly believed that this resource could contribute to base-load power supply.

5. How does the cold and denser water masses sink to the depths of ocean?
a) Thermohaline circulation
b) Temperature gradient
c) Density gradient
d) Freshwater fluxes
View Answer

Answer: a
Explanation: The cold and denser water masses formed by surface water sink to the depths of the ocean by thermohaline circulation. It is circulation of ocean water due to density gradient.
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6. Why is ocean thermal energy conversion a renewable resource?
a) Because the temperature gradient lasts for a short period of time
b) Because the upwelling of cold water from the deep ocean is replaced by downwelling of surface waters
c) Because ocean water is available in plenty
d) Because of sun’s heat
View Answer

Answer: b
Explanation: Ocean thermal energy conversion is a renewable resource because the temperature gradient is continuously restored. This occurs because the upwelling of cold water from the deep ocean is replaced by downwelling of surface waters.

7. Which of the following are types of systems used in ocean thermal energy conversion?
a) Horizontal and vertical
b) Vertical and open cycle
c) Open cycle and closed cycle
d) Horizontal and closed cycle
View Answer

Answer: c
Explanation: The types of systems used in ocean thermal energy conversion are closed cycle and open cycle systems. Horizontal and vertical are related to turbines used in harnessing tidal and wind energy.
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8. Which of the following is used as working fluid in closed cycle oceanic thermal energy conversion systems?
a) Thermohaline circulation
b) Temperature gradient
c) Greenhouse gases
d) Refrigerants
View Answer

Answer: d
Explanation: Closed cycle oceanic thermal energy conversion systems use refrigerants like ammonia as working fluids. These fluids have low boiling points and are suitable to power the generator thereby producing electricity.

9. Rankine Cycle is the most commonly used heat cycle for ocean thermal energy conversion.
a) True
b) False
View Answer

Answer: a
Explanation: Rankine Cycle is the most commonly used heat cycle for ocean thermal energy conversion. It is a model used to predict the performance of a steam turbine and was also used to study reciprocating steam engines.
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10. _______ turbine is used in closed cycle ocean thermal energy conversion.
a) Horizontal
b) Low-pressure
c) High-pressure
d) Vertical
View Answer

Answer: b
Explanation: Low-pressure turbines are used in closed cycle ocean thermal energy conversion. These systems use the Rankine heat cycle to generate electricity.

11. Open cycle ocean thermal energy conversion systems use _____ as the working fluid.
a) vapour from rivers
b) water from rivers
c) vapour from seawater
d) seawater
View Answer

Answer: c
Explanation: Open cycle ocean thermal energy conversion systems use vapour from seawater as the working fluid. Unlike the closed cycle ocean thermal conversion systems, the working fluids are not thought as refrigerants.

12. What is the byproduct of an ocean thermal energy conversion system?
a) Electricity
b) Clean water
c) Water vapour
d) Cold water
View Answer

Answer: d
Explanation: Ocean thermal energy conversion systems supply cold water as their by-product. These can be used for air conditioning and refrigeration. Electricity is the primary product.

13. Where is the world’s only operating ocean thermal energy conversion plant located?
a) Japan
b) United States
c) China
d) Korea
View Answer

Answer: a
Explanation: Ocean thermal energy conversion was first developed in the 1880s. The world’s only operating ocean thermal energy conversion plant is located in Japan. The plant is overseen by Saga University.

14. Which of the following best describes the working of an ocean thermal energy conversion plant?
a) Oceanic water → evaporator → turbine/generator → electricity
b) Warm surface oceanic water → evaporator containing working fluid → turbine/generator → electricity
c) Cold surface oceanic water → electricity → evaporator containing working fluid → turbine/generator
d) Cold deep oceanic water → electricity → evaporator containing working fluid → turbine/generator
View Answer

Answer: b
Explanation: Warm surface oceanic water is passed through an evaporator containing the working fluid. The vapourized fluid drives the turbine/generator thereby generating electricity. Deep oceanic water is not used as it’s cold.

15. The vapourized fluid in an ocean thermal energy conversion system is converted back into working liquid.
a) True
b) False
View Answer

Answer: a
Explanation: The vapourized fluid in an ocean thermal energy conversion system is converted back into working liquid by passing it through a condenser. By using the deep oceanic cold water, the temperature of the condenser is maintained so as to cool the vapourized fluid.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter