With the growing demand for electricity,
rising cost of conventional fuels and environmental issues by consumption of
fossil fuel the need for renewable source of energy is always increasing. Wind
turbines are one such source that produce electricity from the Wind energy.
According to the Global Wind Energy Council, during past 18 years, wind power
production is increased globally by 23%. Target is set for producing 18% of
total energy globally using wind power by 2050. The recent peak in wind power
industry is because of great improvement in wind turbine technology. Some major
improvements in design technique, construction of taller structure with light
and better material, better understanding of aerodynamics and advances in
materials, particularly polymers has led to achieve energy efficiency and cost
effectiveness in Wind Turbines. It is vital to develop optimized design
procedure for wind turbine in order to achieve the future goal.
In this report we will focus on the
material selection, manufacturing processes and some of the design concepts of
the Wind Turbine. Some of the crucial parts of a Wind Turbine are the blades,
tower, gears and yaw brakes. The horizontal axis wind turbine was selected over
vertical axis for the study as it has high tip-speed ratio, self-start ability
and controllable power output by pitching. Also, maximum possible power factor
is double in HAWT compare to VAWT 4. The reason for choosing three
blades in wind turbine was also explained briefly. However, design of yaw and
pitch control mechanism was omitted. After doing in depth research on
blade profile, comparing NACA 4412 with NACA 0012 using blade element moment
theory, standard profile NACA 4412 was chosen for the blade design 4.
SOLIDWORKS model of blades and turbine assembly is also presented to get a
better idea of geometry.
A lot of parameters are to be
considered when selecting a material for these various parts. The blades should
be made of high stiffness material so that the optimal shape of the blade can
be obtained moreover the blades are at good height so to decrease the
gravitational forces the material should be of low density. To reduce the
material degradation and to withstand 4*10^8 fatigue stress cycles, the
material should have high cycle fatigue level of resistance 3.
Polyesters, vinyl esters and epoxies-composites and carbon fiber composite will
be the optimum choice for wind turbine blades. High tensile strength, high
endurance strength to withstand dynamic loads, low coefficient of friction,
good manufacturability is desired for the gears mechanism 1. Gear box
is made of 98-100% of steel and some amount of aluminum and copper 2.
For breaking system short carbon fibers, silicon, heat molded resins, carbon
powders are used because of their good strength even at high heat dissipation
when the brakes are applied.
The blades are mostly manufactured by
Resin Transfer Molding, Pultrusion or Fiber Placement process 6.
However, the common process of blanking and annealing are used for gears and
gear mechanism 2. The towers are manufactured by roll bending and
tack welding as shown in the figure 2 7. Considering the
fact that the breaks has to be strong and should have a good frictional and
high operating temperature condition powdered compaction method is used for
skin layup inner
1 Resin transfer molding 6
One of the major findings of the
research is asymmetrical blade can produce more coefficient of power by
fetching more lift coefficient. As the selected profile is standard profile,
more optimization can be obtained in this area. Furthermore, well established
manufacturing method was reviewed for the project, new and better process can