What is a Darrieus Wind Turbine & Its Working

Renewable energy sources around the world are used by many people to decrease the cost of energy as well as to defend the world. We know that renewable energy can be obtained through solar, wind, turbines, etc. Raising the levels of pollution & sea levels has generated global attention by developing wind turbines. At present, these turbines are used by many people to assist them to obtain these steps. Wind turbines are available in two types namely VAWT (vertical axis wind turbine) & HAWT (horizontal axis wind turbine). The VAWT is the most frequently used turbine where the people are using these turbines in their homes like a renewable energy source, whereas the HAWT is used at residential locations & many more. Here, vertical axis wind turbines are classified into two types namely Darrieus Wind Turbine and Savonius Wind Turbine. This article discusses an overview of Darrieus Wind Turbine.

What is a Darrieus Wind Turbine?

An alternate name of Darrieus Wind Turbine is an Eggbeater turbine. This kind of turbine was invented in the year 1931 by Georges Darrieus. A Darrieus machine is a low torque and high-speed device used to generate AC (alternating current). Generally, Darrieus requires physical push so some exterior power source is used to start rotating because the initial torque is extremely low. This machine consists of two blades that are vertically oriented and rotating around a perpendicular shaft.

A Darrieus wind turbine is one kind of VAWT. Not like the Savonius type, the Darrieus type is a lift-type VAWT. Instead of gathering the airstream within cups, the turbines will drag around. Darrieus utilizes lift forces which are produced through the airstream hitting aerofoils to make revolution.

Features

The features of the Darrieus wind turbine include the following.

• These turbines are eggbeater shaped which includes high efficiency, but, they are not consistent.
• In order to utilize this turbine, you should have an exterior power source to start them
• This turbine includes two blades so it is the best choice to select instead of selecting a three-blade wind turbine.
• This wind turbine can be supported by using a superstructure that will fix it close to the pinnacle bearing.

A Darrieus wind turbine spins many times than the wind hitting speed. Therefore, a Darrieus wind turbine produces low torque as compared to a Savonius turbine however it turns very fast. So, this turbine rotates very fast to generate electricity instead of water pumping as well as related activities. This turbine generates centrifugal forces which are extremely large & performs on the turbine blades. But the bearings & generator are generally lower as compared to a Savonius.

Darrieus Wind Turbine Design

The design of the Darrieus wind turbine can be done using a number of curved aerofoil blades which are arranged on a rotary framework or shaft. The Darrieus wind turbine is a type of vertical axis wind turbine, used to produce electricity using wind energy. The blade curve of this turbine allows being stressed only in anxiety at high rotary speeds.

There are numerous closely related wind turbines that utilize straight blades. The Darrieus Wind Turbine Design was patented by a French aeronautical engineer namely Georges Jean Marie Darrieus and filing for the copyright was done on 1st Oct in 1926. There are many troubles while protecting this turbine from severe wind situations and also in designing it as self-starting.

Darrieus Wind Turbine Working Principle

These turbines are not self-starting but it requires a motor which is small powered to begin the revolution. Once it has sufficient speed then the wind flows across the aerofoils starts to produce torque & the rotor can be driven in the region of the wind. In the Darrieus turbine, two mini Savonius rotors are placed on the shaft to start a revolution. These reduce the Darrieus turbine once it gets going but they make the complete device very simpler as well as easier to keep.

Darrieus Wind Turbine Efficiency

The efficiency of the Darrieus Wind Turbine is less as compared to the horizontal axis wind turbine (HAWT) due to the operational characteristics and design.

Generally, the efficiency of a HAVT (horizontal axis wind turbine) ranges from 40 % to 50 % which means the turbine is capable of converting 40% – 50 % of the KE (kinetic energy) it obtains into real electrical power. Alternatively, the efficiency of a Savonius vertical axis wind turbine ranges from 10 % to 17 %, whereas the Darrieus vertical axis wind turbine achieves 30 % to 40 %. A Savonius wind turbine can generate sufficient power to hold yearly utilization of a usual two-person family.

Darrieus Wind Turbine Power Calculation

The power of wind turbines can be calculated by estimating two values like accessible wind power as well as the wind turbine efficiency. So by multiplying these two values we can get the output power of the turbine.

The sweep area of the wind turbine can be calculated like the following.

To calculate the wind power, we need to find out the swept region of the wind turbine based on the following equations:

For HAWT, A = π * L²

For VAWT, A = D * H

From the above equations, ‘L’ is the blade length

‘H’ is the turbine’s height

‘D is the diameter

The available power of wind can be calculated like the following.

If we know the sweep area, we can discover the accessible wind power based on the following formula.

Pwind = 0.5 * ρ * v³ * A

From the above equations, ‘A’ is the sweep area

‘ρ’ is the density of air

‘v’ is the wind speed

‘Pwind’ is the accessible wind power.

The turbine efficiency can be calculated like the following.

μ = (1 – k) * (1 – kₑ) * (1 – ke,t) *(1 – kt) * (1 – kw) * C

Where,

‘kw’ is the wake of losses

‘kₑ’ is the electrical losses of the wind turbine

‘ke,t’ is the electrical losses of transmission to the grid

‘kt’ is the % of the time out of order because of failure

‘μ’ is the real efficiency

To find out the power of the wind turbine, simply multiply the efficiency through the available wind power

Poutput = μ * Pwind

Advantages

The advantages of the Darrieus Wind Turbine include the following.

• The rotor shaft of this turbine is vertical. So it is feasible to situate the load similar to a generator otherwise a centrifugal pump at earth level. When the generator is not turning, then the wire toward the load is not bent & no brushes are necessary for huge twisting angles.
• The rotor receives the wind from each direction.
• Easily arranged in the buildings
• The arrangement of the windmill over a building might be bigger as compared to a horizontal-axis windmill.
• Scalability
• Safety for workers
• Very easy to operate, so they don’t upset people in housing neighborhoods.
• Portable from one place to another.
• It is allowable wherever taller structures are forbidden.
• Includes low-speed blades so that it reduces the risk to birds & people.
• It works in severe weather through uneven winds as well as mountain conditions.

Disadvantages

The disadvantages of the Darrieus Wind Turbine include the following.

• Low efficiency
• It is difficult to start as compared to the Savonius wind turbine
• Self-starting mechanism
• Rotation efficiency is low
• Low efficiency
• Wind speed is less available
• Component wear-down

Applications

The applications of the Darrieus wind turbine include the following.

• The Darrieus wind turbine is used to produce electricity using wind energy.
• It is also used for water pumping,  cooling, or heating.

Thus, this is all about an overview of the Darrieus wind turbine and its working. This kind of turbine is also known as an egg beater. An alternate model of this turbine includes three straight blades which are connected parallelly to the shaft to form an “H” shape. Darrieus uses the “lift” aerodynamic power to revolve. Once wind flows around the structure, then it creates suction over the face side of this turbine, so that blades will drive to revolve. When the rotation begins, Darrieus wind turbines will speed up to turn faster as compared to the speed of the wind. Here is a question for you, what are the two types of vertical axis wind turbine (VAWT)?