Since about two thirds of the Earth is covered by oceans, it's not surprising that oceans may be a lucrative source of renewable energy. In this video, we explore the possibilities of ocean energy, specifically ocean current energy, tidal energy, wave energy, and ocean thermal energy. This data from UNESCO shows the energy potential for motion sources is huge, far exceeding current global energy consumption. But accessing this energy is challenging since the oceans are vast and their energy is largely inaccessible. Accessible ocean energy is much lower than the total, but it's still impressive. Let's start with ocean currents. This map shows the major ocean currents on Earth. Note that many of these currents flow close to continental shores and major population centers, which makes them attractive as sources of renewable kinetic energy. A number of technologies have been proposed to tap energy ocean currents. These include underwater turbines placed in areas with strong tidal flows, fixed underwater turbines placed near shore to capture steady ocean currents, exotic Subsea oscillating generators that wobble on ocean currents, and floating turbines that are anchored to the sea floor with a cable and drift in strong ocean currents. To date, there have been pilot studies and experiments with ocean current turbines, but no large-scale installations. As we know, ocean tides are caused by the gravitational forces of the moon as it orbits the Earth, which causes ocean levels to periodically rise and fall. This map shows the average differences in centimeters between low and high tides around the world. The blue regions have low tidal ranges and the red have high ranges. Note that most of the red regions are in a remote coastlines with relatively low population densities nearby. The notable exception is the west coast of Europe, which uniformly has large tidal ranges so it's understandable that much tidal energy research is centered in Europe. Tidal barrages or dams direct tidal waters through turbines in a dam as water slow in and out with the tide. The oldest and one of the largest tidal barrages in the world is the 240 megawatt Rance River installation in Brittany, France. It was constructed in 1966 with an annual energy output of about 500 gigawatt hours. The only other title barrage of significant size is the 254 megawatt Tsinghua Lake Titled Power Station in South Korea, operating since 2011. Another potential source of renewable energy is from ocean waves. This map shows the average wave energy for ocean regions around the world. Note that most regions with the greatest wave energy are in remote open ocean locations far from land. Again, the exception is the North Atlantic, off the coast of Europe. A variety of technologies to extract energy from waves have been proposed, shown here as a float anchor to the sea floor. As the floor rides up and down with the waves, it drives the stationary linear generator underneath it. Hundreds of these units could be deployed to generate substantial electric power. The operation of the technology is shown here on land or mechanical lift is raising and lowering the float to generate electricity and lighting light bulbs. Another wave energy idea is this Japanese mighty whale technology, who waves are captured within a floating power station. In the station, the waves over top flat turbine blades that power electric generators. Multiples of these units could be combined to generate substantial amounts of electrical energy. Ocean thermal energy conversion or 0 check technologies, make use of ocean thermal gradients for energy. Ocean water temperatures drop rapidly with depth is this graph illustrates. Ocean temperature gradients vary around the world with a greatest variations in equatorial waters. Ocean temperature gradients can be used in two ways. First, cool water can be pumped from ocean depths to cool buildings. This is being done in some island communities around the world with easy access to deep water. Or second, cold seawater can be used to liquefy a working fluid that vaporizes at a low temperature, such as Ammonia or Freon. When heated by warm surface water, the fluid vaporizes and can be used to power turbine generator. Cold seawater then liquefies the vapor exhaust and the process repeats itself. In summary, ocean energy can be an inexhaustible renewable energy resource for nearby locations. Advantages of ocean energy include low visual impact with submerged or low profiles, high predictability of tides, ocean currents, and temperature gradients. You've got high power density of flowing water for ocean turbines, and low noise pollution compared with offshore wind turbines. But ocean energy has significant downsides. Challenges include limited access to ocean resources, high capital construction costs, high maintenance costs, intermittent resources such as wave energy, costly power transmission to the shore, environmental damage to sea beds, degradation of scenic ocean views, and interference with coastal commerce including navigation, fishing, and recreation. Because of these challenges, adoption of ocean energy technologies has been slow, as this graph shows. Despite its significant potential, ocean energy installations have essentially remains level over the past decades. It remains to be seen if adoption of ocean energy technologies accelerates in the years ahead, or if they remain a sidebar to the growth of other renewable technologies. In the next video, we examined geothermal energy, another renewable energy resource that's highly dependent on location. We'll see you there.
