The oceans and seas retain a significant amount of solar energy. The tropical waters absorb solar energy equivalent to the heat content of 245 billion barrels of oil on an average of 60 million square kilometers. Ocean Thermal Energy Conversion (OTEC) is the method by which this energy is captured. It operates a heat engine that generates electricity by using the temperature difference between the ocean's surface and the depths of roughly 1000 meters. Ocean Thermal Energy Conversion is estimated to have a substantially higher resource potential than other ocean energy types. Ocean Thermal Energy Conversion could create up to 88,000 TWh/yr of power without changing the ocean's thermal structure. This article will explain to you Ocean Thermal Energy which will be helpful in preparing the Environment syllabus for the UPSC Civil Service exam.

What is Ocean Thermal Energy Conversion (OTEC)?

• Ocean Thermal Energy Conversion (OTEC) is a marine renewable energy system that generates electricity by harnessing the solar energy collected by the oceans.
• The sun's heat warms the surface water much more than the deep ocean water, creating a natural temperature gradient, or thermal energy, in the ocean.
• OTEC vaporizes a working fluid with a low boiling point, such as ammonia, using the ocean's warm surface water with a temperature of around 25°C (77°F).
• To generate energy, the vapor expands and turns a turbine connected to a generator.
• Seawater pushed from the deeper ocean layer, where the temperature is around 5°C (41°F), subsequently cools the vapor.
• The working fluid is then condensed back into a liquid, ready to be reused. This is a continuous cycle for generating power.
• The temperature differential has a significant impact on the cycle's efficiency.
• The higher the temperature difference, the more efficient the system is.
• As a result, the technology is only viable in tropical regions with a year-round temperature difference of at least 20 degrees Celsius (36 degrees Fahrenheit).

Ocean Thermal Energy Conversion - History

• Jacques-Arsène d'Arsonval, a French engineer, was the first to propose the OTEC concept in the early 1880s.
• His concept called for a closed-cycle system, which has since been adopted by most modern OTEC pilot plants.
• A secondary working fluid (a refrigerant) like ammonia is used in such a system.
• During the 1970s and 1980s, the US, Japan, and a number of other countries began experimenting with OTEC systems in an attempt to establish a sustainable renewable energy source.
• The first OTEC plant capable of generating practical amounts of electric power—roughly 15 kilowatts of net power—was put into operation in 1979 by American researchers.
• This closed-cycle system, known as Mini-OTEC, was erected aboard a US Navy barge a few kilometers off the coast of Hawaii.

Types of Ocean Thermal Energy Conversion Systems

Closed System

• Ocean Thermal Energy Conversion systems use a low-boiling-point working fluid, such as ammonia, to power a turbine that generates electricity.
• At 5 degrees, warm seawater is drawn from the surface of the oceans, while cold water is drawn from the depths.
• Warm seawater evaporates the fluid in the heat exchanger, spinning the turbines in the generator. When the fluid in the vapor state comes into touch with cold water, it returns to a liquid condition.
• Because the fluid is recycled in the system, it is referred to as a closed system.

Open System

• Open Cycle OTEC generates power directly from the surface's warm water.
• The heated saltwater is initially poured into a low-pressure chamber, where the pressure causes a reduction in boiling point.
• The water begins to boil as a result of this. This steam powers a low-pressure turbine that feeds an electric generator.
• The open cycle has an advantage over a closed system in that desalinated water is obtained in the form of steam.
• It is free of any contaminants since it is steam. This water can be used in a variety of ways, including for domestic, industrial, and agricultural purposes.

Types of Ocean Energy

A.Wave Energy

• The total wave resource of the world has been estimated to be as high as 2 terawatts (TW) of energy, which is the equivalent of the world's electricity consumption.
• If the wave energy is properly harnessed, it could provide over 40% of the world's energy demands which is equivalent to the output of over 800 nuclear power plants.
• The transmission and collection of energy by ocean surface waves are known as wave energy (or wave power).
• The captured energy is subsequently used for a variety of tasks, including electricity generation, water desalination, and water pumping.
• Wave energy is a type of renewable energy that is considered to be the world's largest ocean energy resource.
• Wind contributes energy to the waves when it blows across the water surface. They are extremely potent energy sources.
• Wave speed, wave height, wavelength, and water density are used to calculate the energy output.
• The more powerful the waves, the more electricity they can generate.
• The wave generating plants are difficult to harness, which is why there are so few of them around the world.

Wave Energy Potential in India

• India's 7517-kilometer coastline is studded by several estuaries and gulfs, making it ideal for the development of marine energy projects.
• India's wave energy potential is estimated to be between 40 and 60 GW.
• Ocean energy methods such as wave and tidal, on the other hand, are still in their early phases of development in India when compared to other renewable energy sources.
• According to a study conducted by IIT Madras and Credit Rating Information Services of India Ltd (CRISIL), the western coast has a stronger wind potential than the eastern coast.
• They've identified possible wave power development sites in Maharashtra, Goa, Karnataka, and Kerala on India's west coast.
• Due to the effects of refraction and strong winds, Kanyakumari, located near the southern tip of the Indian peninsula, has the most power.
• The quantity of power that can be created from wave energy with currently available technologies is substantially less than the theoretical predicted potential.
• In India, the capacity utilization factor for wave energy is in the range of 15-20%.

*To know more about the topic, click this link Wave Energy

B.Tidal Energy

• Although estimates of global tidal energy-generating potential vary, tides have a total energy of 3,000 gigawatts.
• However, the analysis of how much of that energy is available for power generation by tidal barrages ranges from 120 to 400 GW, depending on location and conversion potential.
• Tidal energy is generated by the gravitational interaction between the Earth, the sun, and the moon, which causes the natural rise and fall of tides.
• The tides can be used to generate electricity by creating a reservoir or basin behind a barrage and then passing tidal water through turbines in the barrage.
• The intensity of the water from the rise and fall of tides is a form of kinetic energy, and tidal energy is created using the movement of tides and oceans.
• The energy of tidal flows is converted into power by a tidal generator.
• It is a type of gravitational hydropower that generates electricity by using the movement of water to push a turbine.
• Greater tidal variation and higher tidal current velocities can significantly boost a site's tidal electricity generation potential.

Tidal Energy Potential in India

• The moon's gravitational force causes the tidal cycle to occur every 12 hours.
• Potential energy is the difference in water height between low and high tide.
• The height of high tide must be at least five meters (16 feet) higher than low tide to capture enough power from the tidal energy potential.
• There are only about 20 places on the planet where the tides are this high, and India is one of them.
• The Gulf of Cambay and the Gulf of Kutch on the west coast of Gujarat have maximum tidal ranges of 11m and 8m, respectively, with average tidal ranges of 6.77m and 5.23m.

*To know more about the topic, click this link Tidal Energy

Advantages

• Predictable and Reliable: Ocean energy sources are more predictable and reliable than wind energy. The never-ending flows provide a steady supply of goods in the future.
• Global Presence: Tidal streams and ocean currents can be found practically anywhere on the planet.
• Renewable Source: It's a renewable resource, which means it's limitless. It does not require human intervention to survive. Humans will continue to harness it till the end of time. As a result, ocean energy is a dependable and efficient energy source.
• Employment Generation: The ocean energy sector has the potential to provide several green opportunities to both remote and urban people, because wave power may reach places that are not serviced by traditional electricity.
• Energy-rich: Moving water is more than 800 times denser than moving air, which doubles kinetic energy by the same figure and allows massive amounts of energy to be released.

Drawbacks

• In our country, deployment is currently limited, and already deployed technologies are underutilized.
• Either little study has been done on the technologies, or they are still in the early stages of R&D, demonstration, and commercialization.
• Uncertainty in the marine environment and commercial-scale risks such as corrosion of materials due to seawater salinity, offshore maintenance challenges, environmental impact on landscapes and the marine ecosystem, and rivalry from other marine industries such as fishing.

Conclusion

The future of Ocean Thermal Energy Conversion technology in commercial applications appears bright, especially on islands and in developing countries in tropical regions where circumstances are ideal for Ocean Thermal Energy Conversion plant operation. Each day, tropical ocean waters are expected to absorb solar energy equivalent to around 250 billion barrels of oil in terms of heat content. The removal of this much heat from the ocean would have no effect on its temperature, but it would allow the continual generation of tens of millions of megawatts of power.

FAQs

MCQs

1. Which of the following is the primary source of energy in Ocean Thermal Energy Conversion (OTEC)?

A) Wind energy
B) Ocean temperature gradient
C) Solar energy
D) Geothermal energy

2. What type of fluid is typically used in Closed-Cycle OTEC systems?

A) Water
B) Ammonia
C) Chlorine
D) Carbon dioxide

3. What is the primary advantage of Ocean Thermal Energy over other renewable energy sources?

A) It is available worldwide
B) It does not depend on weather conditions
C) It generates more electricity than solar power
D) It is cheaper to install than wind energy systems

4. Which of the following regions is most suitable for Ocean Thermal Energy generation?

A) Polar regions
B) Equatorial regions
C) Temperate regions
D) Desert regions

5. Which of the following is NOT a type of Ocean Thermal Energy Conversion system?

A) Closed-Cycle OTEC
B) Open-Cycle OTEC
C) Hybrid OTEC
D) Solar OTEC

GS Mains Questions and Model Answers

Q1: Discuss the potential and challenges of implementing Ocean Thermal Energy Conversion (OTEC) as a renewable energy source in India.

Answer: Ocean Thermal Energy Conversion (OTEC) offers great potential as a renewable energy source in India, particularly along its long coastline. The country’s tropical location provides an ideal temperature gradient for efficient OTEC operations. However, challenges include the high initial costs of building OTEC plants, technical complexities, and the environmental impact of installing such systems in marine environments. Despite these challenges, India’s focus on diversifying its renewable energy sources and improving marine infrastructure could enable successful OTEC implementation in the future.

Q2: Evaluate the environmental and socio-economic benefits of Ocean Thermal Energy Conversion (OTEC) systems.

Answer: OTEC systems provide significant environmental benefits by offering a clean, renewable energy source with minimal carbon emissions. They also help mitigate the effects of climate change by reducing reliance on fossil fuels. Socio-economically, OTEC can improve energy security, create jobs in coastal regions, and promote sustainable development. Additionally, it can provide a stable source of electricity to remote islands and coastal communities, thus enhancing regional development.

Q3: How does the Ocean Thermal Energy Conversion (OTEC) system contribute to India’s efforts in achieving renewable energy targets?

Answer: OTEC can play a crucial role in India’s renewable energy transition by diversifying its energy mix. As part of India’s commitment to achieving its renewable energy targets, OTEC provides a sustainable and consistent source of power that can supplement other renewable sources like solar and wind energy. By harnessing the energy from the ocean, OTEC can contribute to India’s energy security, reduce dependence on coal, and help meet the nation’s climate goals.

Previous Year Questions on Ocean Thermal Energy

1. UPSC CSE Prelims 2020:

Question: Which of the following is a major advantage of Ocean Thermal Energy Conversion (OTEC)?

A) It can generate electricity during the night
B) It depends on seasonal variations
C) It only works in colder climates
D) It is cheap to install

Answer: (A)

Explanation: OTEC can generate electricity 24/7, as it relies on the temperature gradient in the ocean, which remains relatively constant year-round.

2. UPSC CSE Mains 2018 (GS Paper 3):

Question: "Examine the role of Ocean Thermal Energy in India’s renewable energy strategy and its potential to contribute to sustainable energy development."

Answer: Ocean Thermal Energy has immense potential as a renewable energy source, especially for tropical countries like India. It can contribute significantly to India’s renewable energy strategy by providing a continuous and sustainable source of power, which complements solar and wind energy. The ability of OTEC to provide electricity without depending on weather conditions offers a unique advantage in maintaining a stable energy supply. By focusing on ocean-based renewable energy technologies, India can reduce its carbon footprint and move towards sustainable energy development.