2. Group Members
1 ABHILASH D. DASH
2 ABHISEK DAS
3 ABHISEK PANIGRAHI
4 AMIYA RANJAN PATRA
5 ARDHENDU S. JENA
6
7
8
ASHUTOSH MAHAPATRA
BANDAN S. PRADHAN
SURYA P. LENKA
3. Contents
Introduction
Design principle
Generator
Blades
The Hub
Blade counts
Blade materials
Yawing
Tower height
Connection to the electric grid
Foundation
Cost
Specification of design
Safety concerns
4. Introduction
Electricity generation is the process of generating electric energy from
other forms of energy.
The fundamental principles of electricity generation were discovered
during the 1820s and early 1830s by the British scientist Michael
Faraday.
Electricity is most often generated at a power station by
electromechanical generators, primarily driven by heat engines fueled
by chemical combustion or nuclear fission but also by other means such
as the kinetic energy of flowing water and wind.
Wind power is the conversion of wind energy into a useful form of
energy, such as using wind turbines to make electricity, windmills for
mechanical power, wind pumps for water pumping or drainage,
or sails to propel ships.
The total amount of economically extractable power available from the
wind is considerably more than present human power use from all
sources.
5. Design principle
There are a lot of them out there in an amazing variety of designs
and complexities. All of them had five things in common though:
1. A generator
2. Blades
3. A tower to get it up into the wind
We reduced the project to just four little systems.
A Plastic blade attached with the motors sharp and fixed it on a
wood stick.
The o/p terminal of the motor is connected to a battery.
When wind blows that turbine rotates and electricity generates and
that stored in the battery.
That battery o/p is connected to LED lights through a switch. This
led works here as a street light.
6. Generator
In electricity generation, a generator is a device that converts mechanical
energy to electrical energy for use in an external circuit.
. Generators provide nearly all of the power for electric power grids.
Electromagnetic generators fall into one of two broad categories,
dynamos and alternators
Dynamos generate direct current, usually with voltage and/or current
fluctuations, usually through the use of a commutator.
Alternators generate alternating current, which may be rectified by
another (external or directly incorporated) system.
7.
8. GENERATOR
Mechanical:
Rotor: The rotating part of an electrical machine
Stator: The stationary part of an electrical machine
Electrical:
Armature: The power-producing component of an electrical machine. In
a generator, alternator, or dynamo the armature windings generate the
electric current. The armature can be on either the rotor or the stator.
Field: The magnetic field component of an electrical machine. The
magnetic field of the dynamo or alternator can be provided by either
electromagnets or permanent magnets mounted on either the rotor or the
stator.
9. Blades
The ratio between the speed of the blade tips and the speed of the wind is called tip
speed ratio.
. High efficiency 3-blade-turbines have tip speed/wind speed ratios of 6 to 7.
. Modern wind turbines are designed to spin at varying speeds (a consequence of
their generator design, see above).
Use of aluminum and composite materials in their blades has contributed to
low rotational inertia, which means that newer wind turbines can accelerate quickly if
the winds pick up, keeping the tip speed ratio more nearly constant.
The reduction of noise is linked to the detailed aerodynamics of the blades,
especially factors that reduce abrupt stalling.
A blade can have a lift-to-drag ratio of 120,compared to 70 for a sailplane and 15
for an airliner.
11. The Hub
In simple designs, the blades are directly bolted to the hub and hence are
stalled.
In other more sophisticated designs, they are bolted to the pitch
mechanism, which adjusts their angle of attack according to the wind speed
to control their rotational speed.
The pitch mechanism is itself bolted to the hub.
The hub is fixed to the rotor shaft which drives the generator directly or
through a gearbox.
12.
13. Blade counts
The number of blades is selected for aerodynamic efficiency, component
costs, and system reliability.
Theoretically, an infinite number of blades of zero width is the most
efficient, operating at a high value of the tip speed ratio, But other
considerations lead to a compromise of only a few blades.
System reliability is affected by blade count primarily through the
dynamic loading of the rotor into the drive train and tower systems.
In addition, the fewer the number of blades, the higher the rotational
speed can be , this is because blade stiffness requirements to avoid
interference with the tower limit how thin the blades can be
manufactured, but only for upwind machines.
Aesthetics can be considered a factor in that some people find that the
three-bladed rotor is more pleasing to look at than a one- or two-bladed
rotor.
14. Blade materials
Wood and canvas sails were used on early windmills due to their low
price, availability, and ease of manufacture.
Smaller blades can be made from light metals such as aluminium.
Manufacturing blades in the 40 to 50 metre range involves proven
fibreglass composite fabrication techniques.
Manufactures such as Nordex and GE Wind use an infusion process.
Other manufacturers use variations on this technique, some
including carbon and wood with fibreglass in an epoxy matrix.
Other options include prepreg fibreglass and vacuum-assisted resin
transfer molding.
Epoxy-based composites have environmental, production, and cost
advantages over other resin systems.
15. Yawing
Modern large wind turbines are typically actively controlled to face the wind
direction measured by a wind vane situated on the back of the nacelle.
By minimizing the yaw angle (the misalignment between wind and turbine
pointing direction), the power output is maximized and non-symmetrical loads
minimized.
However, since the wind direction varies quickly the turbine will not strictly
follow the direction and will have a small yaw angle on average.
The power output losses can simply be approximated to fall with (cos (yaw
angle))3.
Particularly at low-to-medium wind speeds, yawing can make a significant
reduction in turbine output, with wind direction variations of ±30° being quite
common and long response times of the turbines to changes in wind direction.
At high wind speeds, the wind direction is less variable.
16. Tower height
Wind velocities increase at higher altitudes due to surface aerodynamic
drag (by land or water surfaces) and the viscosity of the air.
Doubling the altitude of a turbine, then, increases the expected wind speeds by
10% and the expected power by 34%.
To avoid buckling, doubling the tower height generally requires doubling the
diameter of the tower as well, increasing the amount of material by a factor of
at least four.
For HAWTs, tower heights approximately two to three times the blade length
have been found to balance material costs of the tower against better utilisation
of the more expensive active components.
. A 3 MW turbine may increase output from 5,000 MWh to 7,700 MWh per
year by going from 80 to 125 meter tower height.
Wood is being investigated as a material for wind turbine towers, and a 100
metre tall tower supporting a 1.5 MW turbine has been erected in Germany.
17. Connection to the electric grid
As of 2003, nearly all grid-connected wind turbines operate at exactly constant speed
(synchronous generators) or within a few percent of constant speed (induction
generators).
many operational wind turbines used fixed speed induction generators (FSIG).
Variable-speed wind turbines can produce more power than the current wind conditions
can support, by storing some wind energy as kinetic energy (accelerating during brief
gusts of faster wind) and later converting that kinetic energy to electric energy
(decelerating, either when more power is needed elsewhere, or during short lulls in the
wind, or both) damping (electrical) sub synchronous resonances in the grid damping
(mechanical) resonances in the tower.
The generator in a wind turbine produces alternating current (AC) electricity. Some
turbines drive an AC/AC converter—which converts the AC to direct current (DC) with
a rectifier and then back to AC with an inverter—in order to match the frequency and
phase of the grid.
However, the most common method in large modern turbines is to instead use a doubly
fed induction generator directly connected to the electricity grid.
18.
19. Wind turbine foundations
Wind turbines, by their nature, are very tall slender structures , this can cause a number
of issues when the structural design of the foundations are considered.
The foundations for a conventional engineering structure are designed mainly to
transfer the vertical load (dead weight) to the ground, this generally allows for a
comparatively unsophisticated arrangement to be used.
In the case of wind turbines, due to the high wind and environmental loads experienced
there is a significant horizontal dynamic load that needs to be appropriately restrained.
In the current Det Norske Veritas (DNV) guidelines for the design of wind turbines the
angular deflection of the foundations are limited to 0.5°.
DNV guidelines regarding earthquakes suggest that horizontal loads are larger than
vertical loads for offshore wind turbines, while guidelines for tsunamis only suggest
designing for maximum sea waves.
20. Costs
The modern wind turbine is a complex and integrated system.
Structural elements comprise the majority of the weight and cost.
All parts of the structure must be inexpensive, lightweight, durable, and
manufacturable , under variable loading and environmental conditions.
Turbine systems that have fewer failures , require less maintenance, are
lighter and last longer will lead to reducing the cost of wind energy.
One way to achieve this is to implement well-documented, validated
analysis codes, according to a 2011 report from a coalition of researchers
from universities, industry, and government, supported by the Atkinson
Center for a Sustainable Future.
The major parts of a modern turbine may cost (percentage of total) :
tower 22%, blades 18%, gearbox 14%, generator 8%.
21. Design specification
The design specification for a wind-turbine will contain a power curve
and guaranteed availability.
With the data from the wind resource assessment it is possible to
calculate commercial viability. The typical operating temperature range is
−20 to 40 °C (−4 to 104 °F).
In areas with extreme climate (like Inner Mongolia or Rajasthan)
specific cold and hot weather versions are required.Wind turbines can be
designed and validated according to IEC 61400 standards.
22. SAFETY CONCERNS
All wind turbines have a maximum wind speed, called the survival
speed, at which they will not operate above.
When winds over this maximum occur, they have an internal brake
and lock to prevent them from going faster than this survival speed.
For turbines operating in cold winter conditions, be prepared to de-ice
as required, and store batteries in an insulated place.
Mounting turbines on rooftops is generally not recommended unless a
wind turbine is very small (1 kW of rated output or less).
Wind turbines tend to vibrate and transmit the vibration to the
structure on which they are mounted,as a result, turbines mounted on
a rooftop could lead to both noise and structural problems with the
building and rooftop.
