## WIND TURBINE

A wind turbine converts the kinetic energy in the wind into mechanical power. We use a generator to convert mechanical energy in electricity.

• Depending on the technology, the blades of the wind turbine turns revolution per minute.,at a variable velocity of the rotor.
• whereas, velocity varies due to the velocity of wind in order to reach greater efficiency

### How does the blowing wind turns the wings?

• The blade has a lots of airfoil cross section consisting of different size and shape from root to tip.
• Airfoil technology make the wind turbine blades turn.
• That means the  lift force is produced when a fluid moves over an airfoil.
• In this way wind turbine receive a basic rotation .
• The turning of wind turbine blade experience the wind relatively.(CONCEPT OF RELATIVE VELOCITY)

i.e V relative=V wind – V blade

• Therefore,the wind turbine blade is position in a tilted mannered in order to align with the relative wind speed .
• As the blade velocity increases to the tip the relative wind speed become more inclined towards the tip .
• This means that a continous twist is given to the blade from root to tip.
##### GENERATOR
• However this rotation cannot be directly coupled to a generator.
• because the wind turbine blades typically turns at a very low rate at rpm due to issue of noise and mechanical strength.
• Considering this low speed rotation we cannot produce any meaningful electricity frequency from a generator .the speed is increases in gear box .
##### GEARBOX
• The gearbox use a planetary gear set arrangement to achive the high speed ratio.
##### BRAKE
• A break also sits in a nacelle the function of brake is to arrested the wind blade rotation during excessively windy condition.
• cut off speed≈ 80km/hr.
##### STEP-UP TRANSFORMER
• Consequently the electricity  is passed through the cable towards the base of step up transformer .
• The wind turbine should face the wind normally for max. power extraction .
• but wind direction can change at any time.
##### VELOCITY SENSOR
• A velocity sensor on the top of the nacelle measure the wind speed and direction .
• The deviation in the wind direction is sent to an electronic controller .Further, to correct the error ,the appropriate signal is send to yawing mechanism.
##### YAWING MECHANISM
• The yaw motor turn the nacelle
• thus the turbine will always be align with the blow direction.
• according to wind speed the relative velocity angle of the wind also changes
• a blade tilting mechanism tilt the blade and guarantee a proper alignment of the blade with the relative velocity.
• thus the blade are always at the optimum angle to attack with the relative wind flow.

## Instead of calculating why we not measure the stress?

Instead of calculating why we not measure the stress?

For.e.g

To check the temperature of water we need thermometer.

Ammeter used to measure the electric current,

Anemometer used to measure the wind speed,

Astrolabe used to measure the latitude and altitude of celestial body,

Audiometer used to measure the hearing purpose.

Instead of calculating why we not measure the stress?

Barometer used to measure the pressure,

there are to ways to  know the value of anything  i.e either you calculate or measure.

Like, In ancient time , instead of measuring we use to calculate the blood pressure of patient.

so from above , we can get the idea to measure the stress of  material  by using stress measuring device .

As we know , no practical possible without theory and theory based on observation.

Application:

stress measuring device can help to know about deformation occur on material by applying load at per unit area.

In engineering ,

stress is a internal resistive force to the deformation per unit area.

σ=p/A

where,

σ=stress

A=Area

There are 3 type of stress ,

• Tensile stress
• Compressive stress
• Shearing stress

So like that putting a theoretical formula and by designing and programming we can make stress measuring device.

Difference between the pressure and stress,

Normally , we say that” pressure is stress”

But its not like that , for any machine

stress is a internal resistive force to the deformation per unit area.

unit – N/m²

But,

Pressure is force per unit area.

P=F/A

unit-N/m²

Due to stress , the pressure will not develop .

But, Due to pressure the stress will develop

so we cannot say that pressure and stress and same .

So Basically the conclusion is pressure has measuring device ,but stress do  not have measuring device.

Although ,

we have stress measuring machine but not a stress measuring device.

S0, by using stress measuring device we can get the stress value of any material at any direction.

## Maximum efficiency

Ideal engine has a maximum efficiency,

If a heat engine goes through fixed thermodynamics stage of a specificed process,

four main parts:η

• Insulated – non conducting stand (the transfer of energy is not possible )
• Hot reservoir– heat capacity should be infinite.

Because , After taking  any energy from it, the temperature of reservoir should be constant .

• The reservoir in which infinite heat capacity will be conducting at high temperature is called to be cold reservoir.
•  Cylinder  should be kept for working substances .

Cylinder wall should be non-conductive so that heat transfer is impossible .but base should be conducting .

For this , first place the cylinder on the hot reservoir since the temperature of reservoir is higher than the temperature of gas, the heat flows from the heat reservoir to the gas .Due to which the gas start to expands .

Since due to heat transfer gas is expanding therefore the temp of gas remain constant

This process is called Isothermal expansion.

as the gas expand , the volume of gas increase and pressure decrease .

In next step , take off the cylinder from the hot reservoir and place it on the insulating stand , when doing so, the gas is confined to the non-conducting wall.

Now let piston rise slowly upward .

Due  to which the gas continue to expand .But this time the gas is not getting any heat to expand .such expansion called Adiabatic expansion.

Since this expansion is taking place without heat .

The temperature of gas starts to decrease .Due to this expansion ,the volume of gas also increase and pressure decrease

In next step, lift the cylinder from the stand and place it on the cold reservoir , now pressure the piston downwards which causes compression of gas.

In this way the gas compresses at the same constant temperature .this called Isothermal compression

Due to this compression the volume of gas decreases and pressure increase

In final stage , cylinder keep on stand again and pressure piston downward

But now there is no cold reservoir to absorbs the heat getting produced extra.

Therefore , the temperature of gas start increase . this compression is called Adiabatic compression .

Pressure the piston until the temperature of gas rises back to equal that of the hot reservoir . This decrease the volume of the gas and increase the pressure

At the end of this step , the gas return to its initial stage .

This complete cycle is called the carnot cycle .The engine work on it ,is called carnot engine.

η =1-T1/T2

The efficiency depend on the temperature of both reservoir.

If  T1 is  ∞ kelvin and  T2 is 0 kelvin

Either rise the temperature of hot reservoir to ∞ kelvin or low down the temperature of reservoir to 0 kelvin .

In both cases,the efficiency will be 100%.