New Wind Power Technology: Three Kites Power Generation Methods

What is a kite? The simplest kite, is made of small string of colored paper tied into the colorful children's toys.

About 20 years ago, more and more surfers began to skateboarding with large kites instead of motorboats. The 20-square-meter kite and high-tech ropes of 15 times the strength of steel cables allowed surfers to surpass 100 Km away from the speed, or fly to 15 meters above the air and then gently slide back to the water.

Right now, researchers from all over the world are trying to give the kite a new feature - making it a platform for high-altitude wind power generation. For the foreseeable future, "wind kites" will fly into the sky and "capture" the winds that are stronger and more stable there.

Three methods of generating electricity with kites

According to records, a large kite was used to pull the train back as far back as the early nineteenth century, but it was not until about 1980 that someone began to study the possibility of kite power generation.

Researcher Wanli Lloyd, who pioneered theoretical research in this area, calculated at Lawrence & Livermore National Laboratory in California that kites fly back and forth in the wind as opposed to hanging at some point in the air Kinetic energy produces more energy, and if the wingspan reaches the Lockheed C-5 transport aircraft wing size (68 meters long), theoretically megawatt-class energy is obtained from a wind of 10 meters per second Compared with today's large-scale on-site wind turbines.

Lloyd proposed two ways of kite power generation: one is to install propeller-like turbine blades on a kite wing, and the air rotates the blades to generate electric energy and then transmits the electric energy to the ground through a conductive rope, which is nicknamed as "Flying generator"; the other is to use the kite in the air to control the rope force, driving the ground equipment to generate electricity.

In addition, it was later suggested that turbine blades serve both as energy harvesting devices and as kite power devices.

This "zhengzai" high-altitude wind power generation system has its own advantages over the traditional high-tower and windmill-style wind turbines: the rope-laden aircraft can reach higher air where the wind energy is more robust and stable. In addition, the construction cost and installation time have been drastically reduced by eliminating the need for tall towers to support huge rotating blades.

Of course, compared with traditional wind power equipment, the kite power generation system still in the laboratory stage still has many difficulties to be overcome. For example, in this system, kites as wind energy harvesters convert wind energy at high altitude into mechanical energy, and at the same time it is also a stabilizer that keeps the system stable. However, the balanced movement and the work-done movement are mutually coupled and influence each other and it is difficult to design balance and work The best control model, system complexity, sustainability and stability is difficult to protect. In addition, we must also consider the safety issue. When the weather is thunderstorms, the power station is easily destroyed by lightning.

Rigid Wings Vs Fiber Wings

WindLift, founded by Robert Clayton as one of the "pioneers" in developing a prototype of precision kite-power generation worldwide, has been developing kite-generating systems since 2005 and is currently using power kites for power generation tests on land.

The experimental power generation system consisted of a 90-cm diameter drum connected to a 60-kilowatt generator. The kite pulled the drum through the rope to drive the generator to generate electricity and then released the kite through the control line. During this process, the motor was used to reverse the drum Tighten the kite again.

Now the problem with the experiment is that during the re-tightening process, the kite needs to release all the pulling force or preferably to make the pulling force negative so that the air pushes the kite downwards, but the kite can only release most of the pulling force As a result, researchers used an inflatable kite with an elongated air bubble in front of its wings to keep its wings in shape. Even so, the wings are still too flexible and difficult to control when tightened again.

WindLift's kites use fiber wings that are closer to traditional kites, while some of its competitors are studying the use of rigid wings based on the idea of ​​a third kite that is more expensive and harder to land on, but rigid wings More aerodynamic than fiber wings and more energy from the wind.

Makani Power in California is one of the "leaders" of this thinking. They made a large carbon composite kite with four propellers. When taking off, the generator acts as a motor to drive the propeller to rotate as a power for the kite to ascend to the sky. After takeoff, the resulting lift quickly enables the kite to fly without additional help. Once the wind brings the thrust balanced with the propeller pull, the generator begins to generate electricity .

Last year, Makani introduced a prototype of a kite power system rated at 30 kW. It is understood that its ultimate goal is to deploy a formed kite power system at sea and connect the generated electricity to the grid.

"Good weather" advantage how to use

In the field of high-altitude wind power, foreign research institutes have the "first mover advantage" and occupy the advantage of "favorable geographical conditions and timeliness". The prospects are equally promising.

According to statistics, the wind power density of major ground-based wind power plants in the world is lower than 1 kW / m on average, the wind density near the jet stream above New York can reach 16 kW / m 2, and the wind density in most areas above China's land at 10,000 m altitude exceeds 5 kilowatts / square meter, while the wind density near the high altitude jet stream in Zhasu area even reaches 30 kilowatts / square meter, which is the highest in the world.

With "geography", in recent years some domestic enterprises have begun to get involved in high-altitude wind power projects.

In November 2009, the first high-altitude wind power research and development center in China, "Guangdong High-altitude Wind Energy Technology Co., Ltd." settled in Guangzhou. The company plans to use a special large kite to raise and lower wind power and its own gravity at a height of several kilometers to tens of meters. The resulting pull drives the ground-based generators to generate electricity. The company's immediate goals are to build a 2-megawatt industrial prototype and build a 10 MW mid-to-high-altitude wind power generation demonstration power station.

The company website, the reporter saw the company's technology called "umbrella ladder combination of wind energy acquisition technology", high-altitude wind power generation system modular structure, the lift balance system and power system are separated from each other, respectively, control. At present, the company has developed the prototype "Tianfeng-1", the first high-altitude wind power generation prototype in China, and the entire system is installed on a modified truck. After several months of power generation tests, the overall performance of the prototype has basically met the design requirements. In addition, as the enlargement and combination of "Tiangong One", the "Tianfeng II" system has now completed the overall conceptual design of 2MW industrialized basic models.

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