Over the past few years, wind turbines have become a very reliable option for sustainable power supply.
They are a small, easy-to-deploy, and extremely energy-efficient renewable energy solution for homeowners.
For industrial and commercial owners, they are large, energy-independent solutions that require a crane to install and generate electricity 24 hours a day.
In general, wind turbines are composed of wind turbine blades, generators, nacelles, controllers, transmission, yaw, hydraulic, braking and safety systems, towers, and foundation cages.
Classification according to its components will reflect the final cost difference. This blog will reveal to you why wind turbine prices and quality vary.
Wind blades
According to the direction of the main axis of wind turbines, they can be divided into horizontal and vertical axis wind turbines.
There are also wind turbines without blades on the market. However, due to higher costs and fewer production lines, it is not widely available at present and is mainly used in Europe.
Horizontal axis wind turbine
The rotation axis is perpendicular to the blades, generally parallel to the ground, and horizontal in the wind turbine.
Horizontal axis wind turbines have large blade rotation space and high rotation speed, making them suitable for massive wind power plants. Horizontal-axis wind turbines have a long history of development and have reached the stage of industrial production.
They have simple structures and are 2-3 times cheaper than vertical-axis wind turbines.
So far, the majority of large-scale energy storage systems have been horizontal axis.
In addition, PVMARS has compiled 3 price lists based on axis and powers. You can click here to download and compare.
Vertical axis wind turbine
The rotation axis is parallel to the blades, generally perpendicular to the ground, and vertical to the wind turbine.
The advantages of vertical axis wind turbines compared to horizontal axis generators are high power generation efficiency, no wind steering, small blade rotation space, strong wind resistance (can withstand 12-14 level typhoons), and low starting wind speed (2m /s), easy maintenance.
Spiral-axis wind turbine
The newly developed screw design not only increase the maximum rotation speed of the rotor but also reduce wind noise.
The increase in rotational speed means that the spiral shaft turbine will be more durable and stronger.
Able to withstand extremely high wind speeds while likewise harnessing strong winds to generate mechanical energy.
On a larger scale, spiral designs allow wind turbines to capture more kinetic energy. And convert it into mechanical energy as efficiently as possible.
Not to mention the design also allows the turbine to automatically point to the optimal value.
However, their power models are limited, and the largest power model is 5000W.
Output capacity
Wind turbines can be divided into small, medium, large, and megawatt series.
(1) Small size: 0.1~1kw wind turbine.
(2) Medium size: 1~100kw wind turbine.
(3) Large: 100~1000kw wind turbines.
(4) Megawatt level: wind turbines above 1,000.
Power adjustment - Pitch system
Depending on the type, there are fixed pitch speed-adjustable, variable pitch, active stall, and independent pitch types.
Fixed pitch stall wind
The blades are fixedly connected to the hub, and the windward angle does not change with wind speed.
It relies on the blades’ aerodynamic characteristics to automatically stall.
This is when the wind speed > rated wind speed of 8m/s, it relies on the stalling characteristics of the blades to keep the input power constant.
Pitch adjustment
When the wind speed is lower than 8m/s, ensure that the blades are at the best angle of attack to obtain maximum wind energy.
When the wind speed exceeds 8m/s, the pitch system reduces the blade angle of attack to ensure output power is within the rated range.
Active stall adjustment
When the wind speed is lower than 8m/s, the control system controls at several levels according to the wind speed.
The control accuracy is lower than pitch control. When the wind speed exceeds 8m/s, the pitch system increases the angle of attack of the blades.
This causes the blades to “stall” and limits the wind rotor’s power increase.
Independent pitch control wind turbine
Due to the large size of the blades, each blade weighs more than ten or even dozens of tons. The blades run in different positions and the stress conditions are also different.
Therefore, the influence of the blade on wind wheel torque cannot be ignored. By independently controlling the 3-5 blades, load, and torque fluctuations can be greatly lowered.
This further reduces the fatigue of the transmission and gearbox and reduces the vibration of the tower.
Classification according to the mechanical form of the separation generator
It can be divided into gearbox, gearless, and hybrid drive wind turbines.
Wind turbine with gearbox
Due to the limitations of blade tip speed, wind wheel rotation speed is generally slow.
When the wind wheel diameter is more than 100m, the wind wheel speed is 15r/min or lower.
To reduce the generator size, the input speed must be higher.
In this case, a gearbox must be used to increase the speed so that the engine input speed is 1500r/min or 3000r/min, and the generator volume can be designed. As small as possible.
No gearbox
A wind turbine with a structure where the impeller and generator are directly connected is a gearboxless wind turbine.
Since this kind of generator does not have a gearbox, it has a simple structure, is easy to manufacture, and is easy to maintain.
Therefore, wind turbines without gearboxes may be developed and used in offshore wind turbines in the future.
Hybrid drive type
Hybrid-driven wind turbines use one-stage gears for transmission, and the gearbox has a simple structure and high efficiency.
Due to the increased speed, its size and weight are smaller and lighter than ordinary direct-acting motors.
It has gradually become a trend in the design and development of large-scale wind turbines above 3GW.
Other generator-type classifications
There are synchronous and asynchronous wind turbines.
Asynchronous generators can be divided into
Cage asynchronous generator - the rotor is of a cage type.
Because the structure is simple, reliable, cheap, and easy to connect to the power grid. It’s used a lot in small and medium-sized businesses.
Coil-wound doubly-fed asynchronous generator - the rotor is wire-wound.
The stator is directly connected to the power grid to transmit electric energy. The wound rotor also transmits power to the power grid under frequency converter control.
Synchronous generator types
It can be divided into types according to the type of magnetic poles that generate rotating magnetic fields.
Electrically excited synchronous generator: the rotor is a wire-wound salient magnetic pole, which is excited by an external DC to generate a magnetic field.
Permanent magnet synchronous generator: the rotor is made of permanent magnet poles made of ferrite material.
It is usually of a low-speed multi-pole type. It does not require external excitation and simplifies the generator structure, so it has many advantages.
Rotating speed
According to wind turbine speed and grid tied, they can be divided into fixed-speed and variable-speed wind turbines.
Fixed speed type
The fixed-speed type generally adopts a speed-controlled blade control method and uses a synchronous induction motor directly connected to the power grid.
Due to wind energy’s randomness, wind turbines driving asynchronous generators operate at rated speed for 60% to 70% of the annual operating time.
To make full use of low wind speed wind energy and increase power generation, two-speed asynchronous generators are widely used, designed with 4-level and 6-level windings.
When running at medium speed, the efficiency of the two-speed asynchronous generator is higher than that of the nitrogen asynchronous generator, and the slip loss is smaller.
When the wind turbine runs at low wind speed, not only do the blades have a higher starting efficiency, but the generator efficiency can also be maintained.
Variable speed type
Variable-speed wind turbines are generally equipped with a variable pitch power adjustment method.
In a wind power system, there must be a control system to regulate and limit speed and power.
The primary task of the speed and power regulation device is to protect the wind turbine from operating failures and overloads in high winds (above 40m/s).
Secondly, it enables wind turbines to operate smoothly when starting, and power quality meets public grid requirements.
Different tower classifications
According to different structures, they can be divided into tower-type and truss-type wind turbines.
Tower type
The vast majority of wind turbines adopt a tower structure. This structure has high rigidity, which makes it safe to climb the tower in winter.
Compared with truss towers, there are far fewer bolts in the connecting parts, less maintenance work, and easy installation and adjustment.
Truss type
The truss type adopts a structural form similar to a power tower. This structure has low wind resistance and is easy to transport.
However, the assembly is complicated, and its bolts need to be tightened every year, which is a lot of work.
In addition, winter climbing conditions are harsh. This type of structure is more suitable for use on islands, especially in wind fields with gusty winds and unstable wind directions.
The truss tower can better absorb the torque and vibration generated by the wind turbine.
Summarize
There are many structures and types of wind turbines, so PVMARS is generally arranged according to the horizontal and the vertical axis. Can distinguish their differences intuitively.
Vertical axis and spiral wind turbines are recommended for urban households. They are less noisy, small, and easy to install.
For large-scale industrial and commercial projects, such as factories, hospitals, towns, and remote areas, choosing horizontal-axis wind turbines can reduce the initial investment amount and achieve energy independence and off-grid living.
PVMARS contains installation instructions and steps for different wind turbines. Please click on the orange font to learn more.
