The development of renewable energy sources is crucial in the fight against global warming and for the preservation of our planet’s natural resources. Wind and solar harvesting technologies are on the rise. This leads to the growing demand of types of vertical axis wind turbines. Let us find out more about them.
Types of Vertical Axis Wind Turbine
2 types of VAWT available in the market are the Darrieus wind turbine and the Savonius wind turbine.
A type of wind turbine that is mostly used for residential purposes is a vertical axis wind turbine. It has 2 or 3 blades and a vertically moving rotor shaft. In a VAWT, the generator is placed at the bottom and blades are covered around the shaft of the tower.
These turbines are often installed on highway dividers and the moving vehicles make the turbine’s curved blades turn and generate power. The turbine uses different wind speeds in different ways based on the requirements.
1. Darrieus Wind Turbine (Lift-Type)
This wind turbine got its name from Georges Darrieus, the person who invented it. Darrieus wind turbines have long and curved blades linked to the top and bottom of the rotor shaft. Also known by the name of an egg beater, this turbine’s each end is connected to the rotor shaft.
Darrieus turbines rotate from the lift provided by the aerodynamic force. A suction is produced on the front side of the turbine by the wind flow, causing the blades to rotate in the opposite direction.
2. Savonius Wind Turbine (Drag-Type)
This turbine has a solid wind-receiving surface and the blades are wrapped around the vertical shaft due to their helix-like arrangement. Savonius turbines are primarily dependent on the flow resistance process to activate the motors.
This is necessary apart from the dynamic wind force acting as an active force to turn the rotors. The reverse side of the blades faces an aerodynamic resistance force, simultaneously. Because of this, these turbines revolve proportional to the wind speed.
Both wind turbines have specific shapes of wings that reduce the amount of drag suffered by them. Once the revolution begins, the speed of the turbine also increases to exceed the wind speed, for better performance.
Vertical Axis Wind Turbine Working Principle
Let’s have a look at vertical axis wind turbine components.
- Gear Box – It increases the rotational speed of a low-speed shaft for it to connect to a high-speed shaft, which is connected to the generator.
- Generator – It converts mechanical energy into electrical energy in the wind turbine.
- Rechargeable Battery – It stores the electricity output which was created by the generator.
- LDR Circuit – It works to on/off the light in the system. It is made up of Light Dependent Resistor (LDR), battery, LED, transistor, and resistor.
Read more about the basic principle of wind energy conversion.
Working
A VAWT is connected to the gearbox that includes gears and this gearbox is directly connected to the electric generator shaft. The wind starts turning the turbine generating mechanical energy.
The gearbox improves the revolutions of the turbine internally and transfers these rotations to the generator as a mechanical input. The generator uses this energy and converts it into electrical energy, which is then stored in the batteries. This stored energy is used via an automated lighting system.
Functioning of the Circuit
The transistor’s emitter is connected to GND and the collector is linked to the negative terminal of the LED. The terminals of the resistor are directly connected to the voltage source and LDR is connected to the negative terminal. Once the LDR circuit is linked directly to the battery it can sense the presence of light. After this, the LED automatically turns on once the amount of light (sunlight) received is less intense.
Vertical Axis Wind Turbine Applications
The following is a list of ideal applications of a types of vertical axis wind turbines.
- In small wind projects and less extensive wind power installations
- In construction or usage in residential buildings.
- In areas with unstable weather or wind conditions to generate power.
Advantages of Vertical Axis Wind Turbine
The pros of vertical axis wind turbine are as follows:
1. Omnidirectional Rotor
The rotor blades in VAWT are capable of picking up wind coming from any direction. Thus, these turbines can generate power in unstable weather conditions like gusty and turbulent winds. Moreover, they are also ideal for coastal and mountainous areas.
2. Closer Spacing
Each turbine is placed 5 diameters apart across the wind and around 10 diameters apart extending downside. This spacing pattern helps to avoid disruption of airflow. It also reduces the chances of reduction in wind speed caused by turbines to each other. With closer spacing, vertical axis wind turbines effectively capture more energy per square meter of land.
According to a 2017 research by Stanford University mechanical engineering doctoral candidate, Anna Craig, VAWT can generate 10 times more power per unit of land in comparison to a group of horizontal axis wind turbines (widely-spaced).
3. Lower Starting Wind Speed
Vertical axis turbines’ starting wind speed is 2 to 3 m/s, which allows them to generate power even with weak incoming wind. Although the overall output is lower at slow wind speed, these turbines are not useless in weaker wind conditions, unlike their counterparts.
4. Less Environment Impact
Vertical axis wind turbines are smaller than traditional turbines. As they are build around the shaft, the rotor blades do not cast drop shadows. Birds can also easily see the blades, which reduces the chances of casualties. Also, VAWT operates with the least noise, thus, they do not cause noise pollution.
5. Easy to Install and Maintain
Due to their small size, these turbines are easy to transport, install, and maintain. A single large truck can easily transport an entire turbine in one round. There is no need to climb extreme heights to fix or repair it. Thus, it is easy to maintain vertical axis turbines.
6. Fewer Restrictions on Installation
Due to their size, types of vertical axis wind turbines are easily permissible in comparison to other turbines. Different regions have different rules and regulations for the maximum construction height. Since vertical turbines are not very tall, their construction is approved in most states.
7. Aesthetic Appeal
Vertical wind turbines have modern geometrical designs that give them better performance and aesthetic appeal. Their appearance goes nicely with neighboring infrastructures like school/college campuses, parks, and other buildings.
Read the interesting piece of information on wind turbine and solar panel combination and outcome.
Disadvantages of Vertical Axis Wind Turbine
Despite being beneficial in many places, cons of vertical axis wind turbines restrain their performance. Let us find out.
1. Less Rotation Efficiency
Due to their rotor design, all the blades do not receive incoming wind simultaneously. Blades facing the wind will turn while others simply follow them leading to less rotation efficiency. Moreover, Savonius wind turbines experience more drag due to their wide blade surfaces.
2. Access to Lower Wind Speed
VAWTs are installed at ground level, thus they cannot harness higher wind speeds flowing at high altitudes. This makes the working of turbines confined to lower levels of wind speed.
3. Quick Wear Down of Components
Since vertical wind turbines are installed in populated areas on ground level, they face more issues like vibrations and turbulence. Blades have to withstand more force, bearings between mast and rotor also endure higher pressure. This sometimes leads to cracks or bends in the blades.
4. Less Overall Efficiency
Vertical axis wind turbines have lower efficiency in comparison to horizontal axis wind turbines (HAWT) due to their design and operational characteristics.
5. Manual-Starting Mechanism
Darrieus wind turbines have a manual starting mechanism because of their wing design which does not form enough torque for autorotation. They do not start automatically like Savonius and horizontal turbines.
So, the 2 types of vertical axis wind turbines are a sustainable and easy solution for generating power on roads and highways. However, their design and build work both in their favor and against them. Yet, they are still the better option rather than fossil fuel-based solutions.
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