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Ocean Energy

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Fast Facts About
Ocean Energy

Principal Energy Use: Electricity
Forms of Energy: Kinetic/Thermal

Ocean energy, also known as marine energy or hydrokinetic energy, is an abundant renewable energy resource that uses ocean water to generate electricity. The majority of ocean energy technologies are still in research and development. While the potential of ocean energy is great, it faces significant technological, environmental, and financial challenges and has low levels of investment.

There are four main types of ocean energy systems:

  1. Tidal Barrage Systems are dam-like structures built across ocean inlets to form a tidal basin. Installed turbines inside the tidal barrage let water in to fill up the basin during times of high tide, and let the water flow out during times of low tide, generating electricity in both directions.
  2. Tidal Stream (or Tidal Current) Systems use electrical generators installed directly into the stream of water, similar to placing wind turbines underwater. As water flows through the generators, they harness kinetic energy of the water and convert it into electricity.
  3. Wave Energy Systems use the motion of waves to run a system that converts the mechanical energy of wave motion into electrical energy.
  4. Ocean Thermal Energy Conversion (OTEC) takes advantage of the temperature difference between warm surface water and much colder water at depth to power a turbine in a closed-loop system that can generate electricity

The statistics in this Fast Facts only include data for countries that participate in the Ocean Energy Systems (OES) organization under the IEA. Here is a complete list of member countries.


Energy Mix

<0.01% of world 🌎
0% of US* 🇺🇸

Electricity Generation

<0.02% of world 🌎
0% of US* 🇺🇸

Global Demand

Moderate increase:
⬆ 26%

* The US does not have any operational ocean energy capacity. All US marine energy projects are installed in river inlets and are accounted for on our Hydropower page.


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Capacity of Largest Operational Ocean Energy Projects

Sihwa Lake Tidal Barrage (Korea)
254 MW

La Rance Tidal Barrage (France)
240 MW

MeyGen Tidal Current (Scotland)
6 MW

The two tidal barrage plants represent 96% of the 516 MW of 2021 installed capacity.


  • Abundant, renewable energy source
  • No air or greenhouse gas emissions
  • Water is 830x more dense than air, so smaller ocean energy systems are able to capture the same amount of energy as larger wind turbines
  • Tidal energy is predictable
  • Many large cities (high demand centers) are coastal
  • Local renewable resource for islands
  • Potential to produce fresh water through OTEC open cycle technologies


  • Local opposition (NIMBY/BANANA*)
  • Site-specific resource
  • Harsh environment (salt water, biofouling, storms) can corrode materials and slash useful lifetime of energy systems
  • Wave energy depends on weather patterns
  • Technologies are still in the research and development phase
  • Not cost-competitive with other renewable energy sources like solar, wind, hydro
  • Inconsistent policy support and relatively low investment
  • Environmental concerns (marine life)
  • Competing uses (recreation, fishing, marine navigation)

*NIMBY - not in my backyard; BANANA - build absolutely nothing anywhere near anything

Climate Impact: Low

Low gradient
  • Near zero emissions

Environmental Impact: Medium

medium on a scale from low to high
  • No air pollution, but potential for significant impact to marine species and their habitats
  • Collision of marine life with underwater turbines
  • Creation of underwater noise pollution
  • Habitat changes

Before You Watch Our Lecture on
Ocean Energy

We assign videos and readings to our Stanford students as pre-work for each lecture to help contextualize the lecture content. We strongly encourage you to review the Essential videos and readings before watching our lecture on Ocean Energy. Include selections from the Optional and Useful list based on your interests and available time. 


Optional and Useful

Our Lecture on
Ocean Energy

This is our Stanford University Understand Energy course lecture on ocean energy. We strongly encourage you to watch the full lecture to understand ocean energy as an energy system and to be able to put this complex topic into context. For a complete learning experience, we also encourage you to watch / read the Essential videos and readings we assign to our students before watching the lecture.

Diana Gragg

Presented by: Diana Gragg, PhD; Core Lecturer, Civil and Environmental Engineering, Stanford University; Explore Energy Managing Director, Precourt Institute for Energy
Recorded on: May 26, 2023   Duration: 37 minutes

Table of Contents

(Clicking on a timestamp will take you to YouTube.)
00:00 Introduction
06:06 Potential, History, and Environment
09:48 Kinetic
26:25 Thermal
32:56 Chemical
34:16 Future of Ocean Energy

Lecture slides available upon request.

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Additional Resources About
Ocean Energy

Stanford University

Government and International Organizations

Fast Facts Sources
Energy Mix: World 2021 (OES 2021 Annual Report pp 207-213, BP Statistical Review of World Energy 2022, p 8), U.S. 2021 (OES 2021 Annual Report p 213)
Electricity Mix: World 2021 (OES 2021 Annual Report pp 207-213, BP Statistical Review of World Energy 2022, p 50), U.S. 2021 (OES 2021 Annual Report p 213)
Global Demand Growth: 2016-2021 (OES 2016 Annual Report pp 174-180, OES 2021 Annual Report pp 207-213)
Operational Capacity by Country: 2021 (OES 2021 Annual Report pp 207-213)
Operational Capacity by Technology: 2020 (IRENA Offshore Renewable Energy, p 12, OES 2021 Annual Report pp 207-213)
Capacity of Largest Operational Projects: 2021 (OES 2021 Annual Report pp 207-213)
More details available on request.
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