Energy Resources from the Ocean

When we look at the ocean, we often think of waves and water. But underneath this vast blue expanse lies an enormous reservoir of renewable energy — hidden in the tides, thermal layers, and even the heat beneath the ocean floor.

Refer to the following YouTube Video on Ocean Energy: Ocean Energy Systems

Let’s explore how different forms of ocean energy can be tapped:

⚡ Energy from Tides

Imagine the sea behaving like a breathing organism — rising and falling every day due to the gravitational pull of the Moon and the Sun. These tidal movements carry energy, and we can capture it to generate electricity. This is called tidal energy.

Now, how exactly do we extract energy from tides? There are three main technologies:

🔹 Tidal Barrages

Think of a large dam constructed across an estuary or a tidal basin.

• As the tide comes in or goes out, water flows through sluice gates, spinning turbines, which generate electricity.
• La Rance Barrage in France (240 MW) is a classic example — still the world’s largest tidal barrage.

🔹 Tidal Turbines

These are like underwater wind turbines.

• As water flows during tides, it turns the blades, producing electricity.
• Can be individually installed or placed in groups (called arrays) on the seabed.
• This system is scalable and very efficient.

🔹 Tidal Stream Generators

Placed in narrow channels, straits, or coastal areas, where water currents are strong.

• These underwater turbines utilize the kinetic energy of fast-flowing tidal water.

🔍 Current Status (as of 2023):

• Global installed tidal energy capacity has reached 600 MW.
• Major projects:
  • Sihwa Lake in South Korea – 254 MW (largest tidal stream project).
  • La Rance Barrage in France – 240 MW.

🔧 Challenges:

• High installation and maintenance cost
• Environmental impact (especially on marine life and sediment flow)
• Limited number of sites with suitable tidal range

🇮🇳 India’s Case:

• No operational tidal energy projects yet.
• But research shows ~80,000 MW potential, especially along Gujarat coast.
• National Institute of Ocean Technology (NIOT) has launched pilot projects like a 50 kW tidal turbine in the Gulf of Khambhat.

🌡️ Ocean Thermal Energy Conversion (OTEC)

Now let’s move deeper. In tropical seas, surface water is warm (25–30°C), while deep water is cold (around 5°C). This vertical temperature difference — around 25°C — is enough to produce electricity!

OTEC taps into this thermal gradient.

🔁 Types of OTEC Systems:

🔹 Closed-Loop OTEC

• Uses a working fluid like ammonia, which has a low boiling point.
• Warm surface water vaporizes the fluid → vapor drives a turbine → electricity is generated.
• Cold deep water then condenses the vapor back into liquid — a cycle!

🔹 Open-Loop OTEC

• Uses seawater itself (instead of a separate fluid).
• Warm surface water enters a low-pressure chamber, where it boils.
• The resulting steam drives the turbine.
• Cold water is again used to condense the steam.

✅ Advantages:

• Works 24×7 (unlike solar or wind).
• Best suited for tropical/subtropical regions.
• Can desalinate seawater and support aquaculture by using nutrient-rich cold water from below.

🔍 Global Scenario:

• No commercial OTEC plants yet.
• OTEC-1 (USA) worked briefly in Hawaii (1979–1982).
• Yaeyama OTEC (Japan) is a 100 kW plant running since 2013 — mostly for research.

🇮🇳 India’s Story:

• A pilot project was tried in Lakshadweep in the 1990s, but it didn’t succeed commercially.
• However, India has potential of 18,000 MW, especially along South Indian coast.
• A 1 MW experimental plant was set up at Kulasekarapattinam, Tamil Nadu.

🔧 Challenges:

• High cost
• Complex technology
• Need for locations with large and consistent temperature gradients

🔥 Geothermal Energy from Oceans

Now imagine going even deeper — into the ocean floor, where volcanic activity and tectonic movements heat up water and rocks. This creates geothermal reservoirs.

By drilling into these, we can extract steam or hot water, run turbines, and generate electricity.

🔹 Key Sources:

• Hydrothermal Vents: These are cracks on the seafloor that emit superheated water loaded with minerals.
  • Found near mid-ocean ridges or volcanic areas.
• Enhanced Geothermal Systems (EGS):
  • Water is injected into hot rocks, artificially creating fractures.
  • The water heats up, turns into steam, and powers turbines.

✅ Advantages:

• Provides baseload power — consistent and reliable.
• Low carbon emissions.

🔍 Global Research:

• Japan’s DONET Project near Shikoku Island is exploring hydrothermal energy.
• EU’s Horizon 2020 is funding various geothermal studies.

🇮🇳 India:

• No active projects or exploration initiatives as of now.

🔧 Challenges:

• Complex and costly technology
• Risks of disturbing deep-sea ecosystems
• Uncertainty about long-term sustainability

🧠 Conclusion: A Sea of Possibilities… But With Stormy Challenges

Ocean energy — whether from tides, thermal layers, or geothermal heat — holds massive promise as a clean, renewable energy source. But technological, environmental, and economic hurdles remain.

India, with its vast coastline and tropical waters, is well-positioned. But we’re still in the research and pilot phase. If we invest smartly and address these challenges, the ocean may well become one of our biggest allies in the energy transition.