Key points: Because wind turbines are too expensive, the cost of wind power is 2/3 higher than the cost of thermal power. Therefore, although wind power is non-polluting and renewable, it is an ideal clean and sustainable energy source. But it cannot be promoted. The swing-wing vertical axis wind turbine has been developed into a 250-watt micro wind turbine product with a power generation cost that is more than 20% lower than that of thermal power. It is fully possible to further develop giant wind turbines with a power of more than 300 kilowatts. This can universally promote wind power, change the world energy pattern dominated by thermal power, and greatly alleviate the harm of atmospheric pollution and warming. The article discusses the characteristics of the wind turbine and analyzes the reasons for its extremely low cost. Finally, it is hoped that the “Tenth Five-Year Plan” will discuss policy issues for large-scale development of large, medium and small wind turbines.
Wind energy is pollution-free and renewable. It is an ideal clean and sustainable energy source, but it is difficult to promote. Currently, the electricity generated by wind energy worldwide is negligible. According to statistics in September 1996, wind power in California, USA, accounts for about 80% of the world's total wind power, but it is only equivalent to a little more than 1% of the state's total power generation. The current world energy pattern is that thermal power accounts for about 80%, and the rest is nuclear power and hydropower. The fundamental reason why wind power cannot be promoted is that the cost of wind turbines is too high. Currently, wind power costs about 5 cents per kilowatt hour (kWh), while thermal power only costs 3 cents [1].
According to foreign data, the cost of wind power was 7 cents per kilowatt hour in 1981, and dropped to 5 cents per kilowatt hour in 1993 [1]. The US Energy Agency hopes to reach 4 cents by the year 2000[2]. The cost of wind power is difficult to reduce quickly, mainly due to the limitations of modern horizontal-axis propeller wind turbines.
The swing-wing vertical axis wind turbine is a brand new wind turbine. The recently developed 250-watt micro wind turbine shows high technical and economic indicators, which has brought the cost of wind power down to 2.4 cents, which is lower than thermal power. Under the control of price rules, wind energy has the conditions to be fully promoted, thereby replacing thermal power and becoming the main energy source in the new century.
Compared with similar products, the technical and economic indicators of swing-wing vertical axis wind turbines have increased more than three times, as shown in the following table:
Products
Capacity (Watts) Rated wind speed (m/s) Weight (kg) Price (yuan)
Swing-wing vertical axis wind turbine 250 8 20 800
China Southern Star brand wind turbine 200 8 115 2100
Based on a service life of only 10 years and a full load rate of 18%, this product can generate electricity:
10 × 365 × 24 × 0.18 × 0.25=3945 (kwh)
So, each kilowatt hour only costs 0.202 yuan, equivalent to 2.4 cents, which is more than 20% cheaper than thermal power. If large, giant wind turbines are developed, the cost of wind power will fall even lower. There are inherent reasons why the swing-wing vertical axis wind turbine has such excellent technical and economic indicators. Compared with modern horizontal-axis wind turbines, it has the following characteristics:
No wind-facing mechanism is required
Vertical-axis wind turbines do not have the problem of wind direction changes, so no wind-facing mechanism is required. The horizontal axis wind turbine not only needs a windward mechanism, but also needs to move all the wind turbines to the top of the tower, which is very inconvenient.
Simple and effective automated aerodynamic layout
If the two wings of the aircraft are installed vertically on both sides, a vertical axis wind turbine is formed. Since the forces exerted by the wind on both sides of the wings cancel each other out, the wind turbine will not start to rotate. There are currently hundreds of design patents for vertical axis wind turbines around the world. Some use additional airfoils, and some use mechanical devices such as connecting rods and cams. They are all quite complex and difficult to implement cost-effectively. The only exception is the Darrius vertical axis wind turbine. . But it stalls when the wind is low, so it won't start on its own. The U.S. Department of Energy's Sandia National Laboratory specializes in developing such wind turbines. There are products that can compete with horizontal axis wind turbines, but have not yet surpassed them.
The swing-wing vertical-axis wind turbine uses the principle of aerodynamics to place the deflection axis of the wing in front of its aerodynamic center. Under the action of the wind, the wing automatically swings to the opposite side on both sides. As a result, a moment in the same direction is generated, which jointly drives the wind turbine to rotate. Its structure is extremely simple, see Figure 1 for details.
Figure 1: The principle of operation of the swing-wing vertical axis wind turbine
Figure 1 shows a top view of the wind turbine, and plots the speed of the blades in the working state in the upwind and downwind positions. and pneumatic vector illustration. The wind comes from the left. When it is upwind, the flow velocity of the airfoil relative to the airflow is V1. Its point of action, the aerodynamic center a1, is behind the deflection center, that is, the fulcrum P1. Therefore, the leading edge of the airfoil swings outward and is affected by the positioning pin. The limit of s1, stops at the position shown. The angle of attack at this time is α1, which produces a resultant force R1 of lift L1 and drag D1, which produces a driving moment f1r (r is the radius of the wind turbine) on the vertical axis of the wind turbine; while in downwind, the aerodynamic force causes the leading edge of the blade to move towards The internal swing stops at the position of the positioning pin s2. At this time, the angle of attack is α2, and the generated driving torque is f2r, which continues to push the wind turbine to rotate.
Automatically unload during extremely strong winds
The wings of the swing-wing vertical axis wind turbine can automatically feather when encountering catastrophic extremely strong winds, so that the angle of attack is zero, thus The load on the wing is almost completely relieved, and it will automatically recover after the strong wind passes. This reduces the wind speed of the wind turbine from more than 50 meters/second to 25 meters/second, and reduces the wind pressure by more than 4 times. Therefore, the entire wind turbine can be designed to be very lightweight, greatly reducing the cost. This is fully reflected in the weight of the wind turbine in Table 1.
Simple and effective centrifugal force control constant speed device
The speed control device of the swing-wing vertical axis wind turbine is very simple and very effective. Because the positioning pins when the blade deflects are controlled by centrifugal force, when the speed exceeds the rated speed, the positioning pins move inward, reducing the angle of attack, thereby reducing the driving torque and returning the wind turbine to the rated speed, and vice versa. Experimental results show that the wind turbine speed remains constant when the wind speed or load changes. This facilitates generator frequency setting.
Using pin gears to increase speed
The speed of the wind turbine itself is very low and must be increased by more than ten times to drive the generator. Therefore, the generator is extremely bulky and uneconomical. However, the cost of a large transmission ratio speed-increasing gearbox is very expensive. Therefore, we use a pin gear drive to increase the speed and solve the problem at the first level. It is very cheap to use the roller body of the rolling bearing as the pin tooth, which greatly reduces the price of the speed increasing mechanism. The mechanical efficiency of the pin set is poor, but this can be compensated by increasing the diameter of the wind turbine and the length of the blade. The latter does not increase the cost much, and the overall technical and economic indicators can be greatly improved.
Advanced process design
In product design, new processes such as sheet metal cold processing, resistance welding, plastics, bonding, and fiberglass are used as much as possible to facilitate mass production and improve Production efficiency, greatly reducing production costs, and ensuring interchangeability as much as possible, making maintenance and assembly convenient for after-sales service.
Because of the above characteristics, the swing-wing vertical axis wind turbine has outstanding performance.
Popularizing wind energy to replace thermal power can greatly improve air pollution and alleviate the harm of climate warming. This is certainly a cause worth pursuing. The high economic benefits of swing-wing vertical axis wind turbines have turned the price law, which was originally a constraint, into a powerful driving force. Relying on the market, wind energy development can be promoted and popularized on its own without requiring large investments from the state. However, government guidance and support are also very important. There are three issues that require attention:
First, the large-scale promotion of small wind turbines as energy-saving devices.
If small and micro wind turbines are adopted by households, they will be widely promoted. Therefore, the development and utilization of large-scale wind energy resources, whose overall capacity is very considerable, is worthy of attention as an energy-saving measure.
The independent operation of small wind turbines has the problem of energy storage. This can be solved with batteries so that electricity is available when there is no wind and the electricity is stored when there is no wind. Because batteries are expensive and difficult to maintain, and the cost of using electricity is greatly increased, they are not popular. This makes it difficult to popularize small-scale wind power and cannot achieve the purpose of saving electricity on a large scale. Nowadays, most of the rural areas in the country are electrified. In order to enable small wind turbines to be connected to the power grid to ensure power supply when there is no wind, and when there is wind and no power is needed, the power can be fed back to the power grid for storage, which can greatly reduce the cost of electricity. Reduced, so it is welcomed by the majority of users, and this does not cause any losses to the power plant. However, this technology urgently needs to solve the problem of power feedback, and it also increases the difficulty of power grid control. But in order to save energy, it is worth trying. I hope the government can advocate and regulate it.
The second is the problem of giant wind turbines.
Giant wind turbines are originally connected to the power grid and do not have the above problems.
However, supercomputers have yet to be developed. We plan to develop 3-kilowatt minicomputers first, and then develop 300-kilowatt supercomputers after gaining experience. This requires a certain amount of human and financial resources, and more importantly, government support.
The third is to cultivate a technical force.
Wind power generation is a highly comprehensive engineering technology, involving aerodynamics, structural mechanics, aircraft manufacturing technology, mechanical manufacturing technology, electrical engineering and automatic control and other disciplines. It can be applied where conditions permit. Colleges and universities set up majors, recruit only graduate students, and train a group of technical talents to further develop wind power engineering technology.