The Ocean Energy
Shaharior Anik, Treasurer
The subject area Ocean Energy provides information about the use of resources of the world's oceans as an energy source. This may be in the form of mechanical energy from waves, tides, or currents, or in the form of thermal energy from the Sun's heat.
The ocean can produce two types of energy-
1.Thermal energy from the sun's heat
2.Mechanical energy from the tides and waves.
Oceans cover more than 70% of the Earth's surface, making them the world's largest solar collectors. The sun's heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world.
Ocean thermal energy is used for many applications, including electricity generation. There are three types of electricity conversion systems:
1.Closed-cycle,
2.Open-cycle,
3.Hybrid.
1. Closed-cycle systems use the ocean's warm surface water to vaporize a working fluid, which has a low-boiling point, such as ammonia. The vapor expands and turns a turbine. The turbine then activates a generator to produce electricity.
2. Open-cycle systems actually boil the seawater by operating at low pressures. This produces steam that passes through a turbine/generator.
3.Hybrid systems combine both closed-cycle and open-cycle systems.
Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. As a result, tides and waves are intermittent sources of energy, while ocean thermal energy is fairly constant.
Before they break onshore, ocean waves pack immense energy. The energy of a single wave, for instance, could power an electric car for hundreds of miles. Researchers are working to harvest and convert that energy into cost-effective and reliable electricity.
But how are ocean waves converted to electricity, exactly? It's a process that begins with the sun:
1. The wind blows across the ocean, creating waves
The sun heats up air at different places around the globe, which creates wind that blows over ocean surfaces. The wind creates surface waves, like those that crash on a beach. The waves range in sizes (from ripples to nearly 100 feet tall) and can travel thousands of miles before they reach land with almost no energy loss.
2. Waves approach land
Regular waves, like radio or light waves, have a constant frequency and amplitude (see picture below). Ocean waves, on the other hand, interact with each other, the environment, and the weather. By the time a wave approaches land, it's unlike any other. This is where researchers aim to extract the energy.
3. Waves Encounter Machines
Ocean waves are converted to electricity with wave energy converter, or WEC, devices. Researchers expect typical full-scale WEC devices to be anchored miles offshore in deep water where wave energy is strongest. Because WECs extract energy from waves of all sizes that move in multiple directions, identifying the type of machine that can most-effectively do this work is a key goal of the U.S. Department of Energy.
4. Machines convert waves into electricity
In short, ocean waves will move a WEC and that motion drives a generator that creates electricity. How machines take this motion of low-speed ocean waves with high energy content and convert them into the high-speed motion required for generators is not fully understood. Neither is how to do this economically and reliably, while also surviving harsh ocean conditions.
5. Electricity is applied to the grid or other needs
Wave energy could power the swaths of coastal homes and businesses. In fact, developing just a third of the available wave energy near Pacific states.
Wave energy is highly predictable and can be developed close to load centers to reduce transmission needs and ease integration onto the grid.
