What Is a Wind Turbine?

What is a Wind Turbine?

Wind turbine are considered to be a evolutionary versions of a windmill, whose purpose is to  reduce the use of fossil fuels by harnessing the power of natural occurring resources such as wind power. a wind turbine utilizes the  power of the wind by spinning the blades of the turbine thus converting kinetic energy into electrical energy.

Problem Statement

a typical 10kW wind turbine system will cost approximately 40,000$ to produce, and the cost of the wind turbine blade alone is about 15 - 20% of the production cost, therefore, when designing a wind turbine, the goal is to maximize efficiency of the turbine in order to achieve the highest possible power output, and in order to achieve high outputs the design depends on the shape of the blade and its ability to with stand high velocities and deformation. the design of the blade determines the stiffness and stability of the blade and therefore influences the aerodynamic efficiency of the turbine.

another factor that may influence the aerodynamic efficiency and mechanical properties of a wind turbine is to enhance the composite materials used in the blade.

determining the optimal shape and what composite to use for the blade is complex, and a large number of constraints need to be satisfied.

Wind Turbine System

A wind turbine system consists of a blade or rotor which is attached to the center piece (shaft). The blades are designed so that when the wind pushes against them they turn thus transforming wind energy into kinetic energy which drives the generator producing electrical energy.

a yaw is used  in order to rotate the blade and generator housing (or Nacelle) with the help of the Wind Vane to keep the blades facing the wind and stabilize the system the yaw is the pivot on which the housing rotates, an example of that is the automatic stowage , this happens when there is excessive wind where the turbine produces torque against the yaw  which moves the wheel into a stowed position.

the nacelle or also known as the housing, is used to house various components such as the Wind Vane generator, yaw, shafts, breaks, and the gear box.

Breaks are necessary in order to slow down the rotor speed if the wind picks up and prevent the blade from reaching its fatigue or failure point.  

a low speed shaft and is used when wind speeds are high and the rotor speed is sufficient (turns on a 1:1 ratio ), where as the high speed shaft, attaches to the gearbox in order to increase the speed of the rotor in case of low wind speeds. the gearbox serves the function as in a car where it changes the gear ratio according to the wind in order to maintain a consistent speed/ output.

Wind Turbine Materials

 Selection of Materials

when selecting the materials to be used , a number of factors should be studies, for example, performance requirements, reliability of the material, the properties of the material selected, its safety factor , availability of the product, physical attributes and economic factor, in short you can study most of these factors using the Ashby plots in order to select the appropriate material.  

1) when selecting material properties it is important to study the mechanical, thermal, and chemical properties of the material.

2) study its functionality to insure that failure will not occur during operation

3) the material selected for a specific function should be reliable.

4) the material selected must have a safety factor which is high enough to perform without failure(safely)

5) Physical properties such as size, weight, and sustainability should be taken into consideration

6) material abundance

8)material cost  

The material selection involves :

• application analysis .

• material selection.

1. High material stiffness is needed to maintain optimal shape of performance.
2. Low density is needed to reduce gravity forces,
3. Long-fatigue life is needed to reduce material degradation.

• material evaluation.

 Materials

in the past wind turbines were made out of wood, but was then discontinued due to its sensitivity to moisture and its production cost,  therefore modern materials are now being used such as

 (GFRP)glass fiber reinforced plastic  and (CFRP) carbon fiber reinforced plastic and steel /aluminum.

Wood has been a common construction material due to its interesting properties such as their low density, but on the other hand, rather low stiffness (elastic) made it difficult to maintain their shape in heavy load situations.

 Steel or nickel alloy replaced wood in Older  wind turbines , which caused high inertia build up and were considered to be more stable since they buffered the change in rotation speed

steel was then treaded with a nickel which possesses good corrosion resistance  and oxidation resistance.

steel was later abandoned due to its heavy weight and low fatigue.

Aluminium was then introduced due to its low weight (1/3 that of steel), ductile, good heat conductor, low price, good reliability and  low tensile strength, but was weaker and less stiff than steel and found to have low fatigue rate.

fibers were later introduced such as polyesters, vinyl esters, epoxies etc., which had good properties like mechanical, thermal and chemical properties.

1) glass fibers(fiber glass) or  glass-reinforced products which were a mixture of E-glass (electrical glass) and had properties like heat resistance moderate stiffness, high strength, and moderate density. E-glass is available as chopped fiber, milled fiber, continuous roving, woven roving, woven fabric, and reinforcing mat.

In recent years carbon fibers have become dominant due to ever-larger rotor blades and the decreasing price of carbon fibers which also have properties such as very high stiffness, high strength, light weight and low density.