The World’s Oceans Are Much More Than Vast Bodies of Water
How can we use the enormous energy stored in tides, waves, currents and ocean temperature differences?
The world’s oceans are constantly moving. Waves rise and fall, tides flow in and out, currents travel across enormous distances, and differences in water temperature create opportunities for energy conversion. These natural processes could provide useful renewable energy for coastal communities and electricity grids.
Why Is the Ocean an Energy Resource?
Water is extremely dense compared with air. This means that moving seawater can carry a substantial amount of kinetic energy. The Moon’s gravity drives tides, winds create waves, and solar heating contributes to temperature differences in the ocean.
Instead of burning coal, oil or natural gas, engineers can design technologies that capture some of this naturally occurring energy and convert it into electricity.
4 Major Ways We Can Use Ocean Energy
1. Wave Energy
Waves contain mechanical energy created mainly by wind blowing across the surface of the ocean. Special devices can move with waves and use that motion to drive generators.
Wave-energy systems may use floating structures, oscillating devices or chambers that convert wave motion into electricity.
2. Tidal Energy
Tides are the regular rise and fall of sea levels caused mainly by the gravitational interaction of the Earth, Moon and Sun.
Tidal turbines can be placed in areas where water moves rapidly during incoming and outgoing tides. The flowing water spins the turbine and helps generate electricity.
3. Ocean Current Energy
Large-scale ocean currents continuously move water around the planet. Underwater turbines can potentially capture some of the kinetic energy in these currents.
Because seawater is dense, even relatively slow-moving water can exert considerable force on appropriately designed turbines.
4. Ocean Thermal Energy
Tropical oceans can have warm surface water and much colder water at greater depths. This temperature difference can be used in ocean thermal energy conversion systems.
A heat engine can use the temperature difference to produce mechanical energy and, ultimately, electricity.
How Does Tidal Electricity Work?
One approach uses underwater tidal turbines. These turbines work somewhat like underwater wind turbines, except they are driven by moving seawater rather than air.
- Water begins to move: During changing tides, large quantities of seawater flow through suitable coastal channels.
- Turbine blades rotate: The moving water pushes against turbine blades and causes the rotor to spin.
- The generator produces electricity: Mechanical rotation is transferred to an electrical generator.
- Electricity is transmitted: Power-conditioning equipment and cables can transfer electricity toward a local network or larger electricity grid.
How Does Wave Energy Work?
Wave-energy converters are designed to extract energy from the repetitive movement of ocean waves. Different technologies use different types of motion.
For example, a floating device may move up and down as waves pass underneath it. That movement can be converted into mechanical motion and then electricity.
Another approach uses an enclosed chamber. As waves enter and leave the chamber, they can compress and decompress air. The moving air can pass through a turbine connected to a generator.
What About Ocean Currents?
Ocean currents are enormous streams of moving seawater. Some are relatively slow, while others can be powerful and persistent. Engineers can investigate suitable locations for underwater turbines where currents are strong enough to make electricity generation practical.
Comparing Ocean Energy Technologies
| Technology | Main Energy Source | Typical Device | Main Challenge |
|---|---|---|---|
| Wave energy | Wave motion | Wave-energy converter | Storms and harsh marine conditions |
| Tidal energy | Tidal currents | Underwater turbine | Suitable locations and installation costs |
| Ocean current energy | Moving seawater | Subsea turbine | Maintenance and marine environment |
| Ocean thermal energy | Temperature difference | Heat-engine system | Efficiency and infrastructure |
Advantages of Ocean Energy
Ocean energy has several attractive characteristics. Tidal cycles are highly predictable, while waves and currents can provide energy without directly consuming fuel.
- 🌊 Uses naturally occurring ocean processes.
- ⚡ Can generate electricity without burning fossil fuels during operation.
- 🌙 Tidal energy can be highly predictable.
- 🏝️ May be valuable for some coastal and island communities.
- 🔋 Can complement other renewable energy sources.
- 🌱 Has potential to contribute to a lower-carbon electricity system.
What Are the Challenges?
Capturing energy from the ocean is not as simple as installing a turbine in water. Saltwater is corrosive, waves can be extremely powerful, and equipment must survive storms and continuous mechanical stress.
Installation and maintenance can also be expensive because equipment may be located offshore or underwater. Engineers must additionally consider fishing, shipping, marine ecosystems, underwater noise and other environmental factors.
Can Ocean Energy Power the Future?
Ocean energy is unlikely to come from one single technology. Instead, different approaches may be useful in different locations. A coastal region with strong tidal currents may benefit from tidal turbines, while another location may have better wave-energy resources.
Ocean energy can therefore become one part of a broader renewable energy system alongside solar, wind, hydropower, geothermal energy and energy storage.
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