Seminar MWT

8/6/2019 Seminar MWT

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MODERN WIND TURBINES

Under The Guidance Of

Prof. S.B. WADKAR

Presented By:

Prakhar AgrawalB.E. Mechanical

Bharati Vidyapeeth University College Of Engineering, Pune


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INTRODUCTION

Wind power is a major source of renewable energy. The first development of wind

turbines to generate electricity began more than a century ago.

Wind turbine technology has rapidly accelerated since the oil crisis of the

1970s due to the requirement for an alternative to the ever rising cost of fossil fuels.

Governments are taking this very seriously, and have imposed ambitious targets forthe proportion of energy to be generated from renewable sources. There is a much

greater public awareness of the environmental damage and pollution from fossil and

nuclear fuels.

Renewable energy sources are freely accessible and essentially inexhaustible

resources. They are non-polluting a wind turbine produces no carbon dioxide.The environmental impact is low, although there is sometimes public concern about

the siting of wind turbines.


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WIND TURBINE COMPONENTS


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WIND TURBINE OPERATION

Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity

to make wind, like a fan, wind turbines use wind to make electricity. The wind turns

the blades, which spin a shaft, which connects to a generator and makes electricity.


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POWER EXTRACTED FROM WIND

The actualpower extractedPoby the rotor blades is less than the total power

in the wind Pw it is the difference between the upstream and downstream

wind powers.Where,Po = turbine output power

V= upstream wind velocity

V0 = downstream wind velocity

The mass flow rate of air passing through the blades is related to the density and

average velocity:

The power extracted is therefore:

where Cp is the fraction of power captured

by the rotor blades, also called the rotorpower coefficient orrotor efficiency.

The practical limits forCp are 0.46 for highspeed two-blade and 0.50 for three-blade turbines.


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Power ratings for different wind turbine designs can be difficult to compare

because there is no globally accepted industry standard for a consistent wind

speed at which to measure their output. Manufacturers give power ratings of

wind turbines for a chosen wind speed and efficiency. Instead of comparingmanufacturers quoted power outputs it is better to compare swept rotor blade

area. In fact, nothing tells you more about a wind turbines potential than its rotor

diameter.

POWER RATING


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WHY TO USE A GEARBOX ?

Could the generator be driven directly with

the power from the mainshaft?

If we used an ordinary generator, directly connected to a 50 Hz AC three phase grid

with two, four, or six poles, we would have to have an extremely high speed turbine

with between 3000 and 1000 rpm.

For a rotor of diameter 43 m the blade tip speed would then be more than twice the

speed of sound, which is not feasible.

The mass of the rotor of the generator has to be roughly in proportion to the amount

of torque (moment, or turning force) it has to handle, making a directly driven

generator too heavy and expensive to be viable.

The practical solution therefore is to use a gearbox to connect the rotor to the

generator. This converts the slowly rotating, high torque power from the wind

turbine rotor to the high speed, low torque power, required for the generator

with only a few pole pairs.

Without Gearbox


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WHAT CAUSES GEARBOXES TO FAIL?

It is been expected that life of the wind turbine is 20 years but mostly gearbox

failures takes place earlier than other components of wind turbine assembly.

The majority of gearbox failures originates at bearing level.NOISE: A turbines gearbox is a major contributor of

machine noise. Reason is the tooth mesh of the gear

wheels.Frequent and complex maintenance increases the

financial risks.Gearbox failures account for the largest amount of

downtime, maintenance, and loss of power production.

These costly failures can total 15-20% of the price of

the turbine Gearbox Failure May Results.


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MODERN GEARBOX DESIGN

Modern wind turbine gearboxes employs the latest developments in flexiblepins

with the epicyclic gear train on the first stage employs 8 planetwheels to provide

minimum volume gearing with maximum bearing life.

A differential gearon the output shaft which

can be controlled via a shunt hydraulic or electrical

drive provides a mechanism by which the speed of

the generator remains constant whilst the speed

of the wind turbine varies thus providing torque

protection and the use of simple fixed speedgenerators.

Installation of the gearbox is compatible with

the new form of twin taper rotor support bearing

and this combined with torque neutral suspension

ensures that the gearbox is only subjected to the

steady state rotor torque.

Mixed iron oxide coating for cylindrical bearings,

which provides increase resistance to slippage duringalternating load conditions.


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MODERN GEARBOX DESIGN TRANSMISSION ADVANTAGES

Flexible pin technology providing uniform gear tooth, and bearing loading

providing high actual bearing life.

Torque protection of the gear train and rotating elements against wind

gusts and grid lockout, resulting in high reliability.

Considerably reduces the weight of the gear train. 20 tonnes for 3.4 MW

2, meters diameter.Allows synchronous or fixed induction generators to be used without full

power converters.

Allows all of the main power electrics and transformers to be placed on the

ground further reducing the weight in the nacelle.

Improves wind energy capture at low speeds by using a more aggressive

wind turbine blade pitch and a variable ratio gearbox.

High power density due to optimized gearbox.


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A GEARLESS FUTURE

The philosophy that formed the basis for the advanced gearless technology of the

wind turbine -

Less subsystems, more reliabilityLess moving parts, more energy

Less maintenance, more savings.

GEARLESS

WITH GEARBOX


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CONCLUSIONS

A new approach is needed to overcome conventional barriers and accelerate

the development of more robust gearbox designs.

The technology has to compete on cost of energy against other renewables

and against conventional generation.

It is preferred to have more offshore wind turbines because of the availability

of higher average wind speed in comparison to wind speed over land.

In accordance with our country, a heavy coal user, turbines will help in

overcoming the reliance on polluting fossil fuel.


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Thank You

Seminar MWT

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