Current energy

Current energy refers to the kinetic energy of seawater flow, mainly refers to the relatively stable flow in submarine waterways and straits, and the energy generated by regular seawater flow caused by tides. It is another kind of ocean energy that appears in kinetic energy.

The energy of the ocean current is proportional to the square of the flow rate and the flow rate. Relative to waves, the change of ocean current energy is smooth and regular. Trends can change size and direction twice a day with the fluctuations of tides. In general, currents with a maximum flow rate of more than 2m/s have practical development value.

The so-called currents mainly refer to the more stable flows in the submarine waterways and the straits and the regular flow of seawater due to tides. One of them is seawater circulation, which means that a large amount of seawater flows from one sea area to another over a long distance. This seawater circulation is usually caused by two factors: one is seawater circulation, which means that a large amount of seawater flows from one sea area to another in a long distance. This type of seawater circulation is usually caused by two factors: first, the constant wind blowing in the same direction on the surface of the sea, for example, the southeastern side of the equator always blowing the constant southeast wind, while the north side is the same. The wind blows the sea water, making the water surface move, and the water's motility conveys this movement deep into the sea. As the depth increases, the flow velocity of the seawater decreases; sometimes the flow direction also gradually changes with depth, and even the direction of flow of the lower seawater is opposite to that of the surface seawater. In the two halves of the Pacific Ocean and the Atlantic Ocean and the southern half of the Indian Ocean, the predominant wind system created a vast seawater circulation that also rotates in counterclockwise direction. At low latitudes and mid-latitudes, wind is the main driving force for the formation of currents. Secondly, seawater in different sea areas often has different temperature and salinity, and they will affect the density of seawater. The higher the seawater temperature, the lower the salt content and the lower the seawater density. Different seawater densities in these two adjacent sea areas also cause seawater circulation. Seawater flow generates tremendous energy. It is estimated that the global current can reach 5 TW.

Cause factor

This type of seawater circulation is usually caused by two factors: first, the constant wind blowing in the same direction on the surface of the sea, for example, the southeastern side of the equator always blowing the constant southeast wind, while the north side is the same. The wind blows the sea water, making the water surface move, and the water's motility conveys this movement deep into the sea. As the depth increases, the flow velocity of the seawater decreases; sometimes the flow direction also gradually changes with depth, and even the direction of flow of the lower seawater is opposite to that of the surface seawater. In the two halves of the Pacific Ocean and the Atlantic Ocean and the southern half of the Indian Ocean, the predominant wind system created a vast seawater circulation that also rotates in counterclockwise direction. At low latitudes and mid-latitudes, wind is the main driving force for the formation of currents. Secondly, seawater in different sea areas often has different temperature and salinity, and they will affect the density of seawater. The higher the seawater temperature, the lower the salt content and the lower the seawater density. Different seawater densities in these two adjacent sea areas also cause seawater circulation. Seawater flow generates tremendous energy. It is estimated that the global current can reach 5 TW. The energy of the ocean current is proportional to the square of the flow rate and the flow rate. Relative to waves, the change of ocean current energy is smooth and regular. The tide can change in size and direction twice a day with the fluctuations of the tide. In general, currents with a maximum flow rate of more than 2m/s have practical development value.

Cause of flow

The sea is full of water. Why is it forming a current? The reasons for the formation of currents are broadly divided into three types, of which the main ones are:

The reason is that the wind is prevailing. The wind blows up the surface of the sea, pushing the sea water to fluctuate with the wind, and the upper seawater drives the lower seawater to flow. The resulting sea current is called wind current or drifting. However, this current will accelerate and diminish as the depth of seawater increases until it is small enough to be ignored.

The second type of current is the flow of seawater caused by differences in seawater temperature and salinity in different sea areas. Such a current is called density flow. For example, in the Strait of Gibraltar, the Mediterranean has higher salinity than the Atlantic Ocean. Therefore, at a depth of 500m, the Mediterranean seawater flows through the Strait of Gibraltar to the Atlantic Ocean. On the surface of the ocean, the Atlantic Ocean seawater rushes to the Mediterranean Sea, supplementing the lack of Mediterranean seawater.

Other causes of currents include geostrophic flow, compensation flow, river escaping, stricken flow, and shore flow.

Use method

Power generation

The main use of ocean current energy is power generation. Its principle is similar to that of wind power generation.

Any of the wind power generators can be transformed into a marine power plant. However, because the density of seawater is about 1000 times that of air, and it must be placed underwater, there are a series of key technical problems in ocean current power generation, including installation and maintenance, power transmission, corrosion protection, and load and safety performance in the marine environment. In addition, the fixed form and turbine design of the marine power generation device and the wind power generation device are also very different. The current device can be installed and fixed on the sea floor, and can also be installed on the bottom of the floating body, and the floating body is fixed to the sea by the anchor chain. Turbine design in the current is also a key technology. Navigation aid

The traditional use of sea currents by humans is to "shun the water." The ancients used ocean currents to sail. Sailing times,

The use of current navigation aids is often referred to as "swimming." In the 18th century, American politician and scientist Franklin had drawn a map of the Gulf of Mexico. The map plots in detail the flow of the North Atlantic currents for sailboats to and from North America and Western Europe, greatly reducing the time required to cross the North Atlantic. In the East, according to legend, during the Second World War, the Japanese used the Kuroshio to send grain from China and North Korea to the locals with wooden clogs. Modern satellite remote sensing technology can measure the current data of various sea areas at any time to provide the best route navigation service for ships on the ocean.

Current power generation by the ocean has also attracted the attention of many countries. In 1973, the United States tested a giant ocean current power generation device called "Coriolis." The device is a pipeline type hydroelectric generator. The length of the crew is l10 meters. The diameter of the pipeline mouth is 170 meters. It is installed 30 meters below the sea surface. At a flow rate of 2.3 m/s at the sea, the device received 83,000 kilowatts of power. Japan and Canada are also making great efforts to research and test marine power generation technology. China's current research on ocean current power generation has also entered the middle test stage.

In addition to the above-mentioned turbines, which are similar to those of river power stations, the current-generating technology of the ocean currents also includes mechanical devices such as wind turbine blades or anemometers. A type of ocean current power station has a plurality of runners arranged in series between two fixed floating bodies and is opened in a half-circle under the impact of currents, and is called a garland type ocean current power station. In addition, the aforementioned turbine power generation vessels can also be used for ocean current power generation.

Power generator

Current-generating devices for ocean currents mainly include vane type, parachute type, and magnetic flow type. The vane-type current generating device utilizes sea currents to propel the vanes, and the vanes drive the generator to send electric current. The vanes may be propeller type or rotary type. The parachute-type current generating device consists of dozens of "parachutes" connected in series on a ring-shaped hinge rope. The "parachute" in the direction of the ocean currents is propped up by the strength of the currents. The parachute in the direction of the counter current is closed by the force of the current. The "parachutes" are spliced ​​and reciprocated to drive the hinged rope and then the hinged disk on the ship.

The hinged disk drives the generator to generate electricity. The magnetic current type sea current power generation device uses seawater as a working medium, allowing seawater with a large amount of ions to vertically pass through a powerful magnetic field and obtain current. The history of the development of ocean current power generation is not long. The power generation equipment is still in the stage of principle research and small-scale experiment.

The current device can be installed and fixed on the sea floor, and can also be installed on the bottom of the floating body, and the floating body is fixed to the sea by the anchor chain. Turbine design in the current is also a key technology.