10-ME-04 FINAL

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Table of Contents Introduction .......................................................................................................................................................... 3

Purpose of the Turbine Design and background .................................................................................................... 3

Advantages and disadvantages of wind energy ..................................................................................................... 3

Turbine design goals................................................................................................................................................6

Summary of our design............................................................................................................................................7

Applications.............................................................................................................................................................8

Importance of off-grid small scale wind turbines in developing countries..............................................................8

WIND TURBINE MODELLING AND DESIGN ........................................................................................ .11

1. Make a plot of Wind Power vs. Wind Velocity.................................................................................................11

2. Measure and plot the Wind Turbine Power Output as a function of Wind Velocity (for the wind turbine with

number of blades)...................................................................................................................................................13

3. Decide blades design specification for Rated Power Output of wind turbine:

- Length =? -Maximum chord =? -Chord at the blade tip =? -Blade twist =?........................................................14

4. Determine the arrangement/number of blades that produces the maximum amount of power..........................18

5. Discuss the influence of wind turbine blade design on power generated..........................................................20

6. Investigate possible blade orientations...............................................................................................................23

7. To what extent pitch angle influence the in a wind turbine design on power generated...................................24

8. Discuss the influence of wind turbine height on power generated....................................................................28

Propeller Modelling In CREO.................................................................................................. .............................32

MALTAB Design and Simulation.........................................................................................................................36

Performance Test Results and Analysis.............................................................................................................38

1. Blade tip speed ratio, λ, at maximum power, increases/decreases with blade tip angle………………………39

2. Variation of the power coefficient with wind

speed…………………………………………………………………………………..………………….………40

3. The maximum power conversion efficiency at which tip

angle………………………………………………………...…………………………………………………....41

Appendix A………...……………….……………………….…………………………………………………..45

Appendix B…...…………………………………………………………………………………………………46

References…………………………………………………………………………………………….47

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List of Figures and Tables

Table 1: Design Summary.......................................................................................................................7

Table 2: Calculations.............................................................................................................................16

Table 3: Design Calculations................................................................................................................17

Table 4: Correlations of rotational speed (ω) with wind speed (v) and pitch angle (θ)……………....27

Fig 1: Wind power is proportional to cube of wind speed....................................................................11

Fig 2: Power factor Vs blade tip angle..................................................................................................19

Fig 3: Cut in wind speed Vs α blades....................................................................................................20

Fig 4: Rotor plane orientation………………………………………………………………………....24

Fig 5: Rotational speed versus pitch angle wind turbine for different wind speed…………………...27

Fig 6: Efficiency versus Pitch angle wind turbine………………………………………………….....28

Fig 7: Cp for 3 blades 0 degree………………………………………………………………...…37, 41

Fig 8: Cp for 3 blades 2 degree……………………………………………………………...……37, 41

Fig 9: Cp for 3 blades 5 degree………………………………………………………………...…38, 42

Fig 10: Power factor as a function of axial flow induction…………………………………………...40

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INTRODUCTION:

Purpose of the Turbine Design and background:

Pakistan is an under-developed country and we are paying a heavy amount on fossil fuels per

year to produce electricity. We are producing about 2/3 of our electricity by thermal energy.

We need to convert towards renewable energy technologies to avoid that much expenditure

per year.

Wind turbine technology is advancing at a very high rate. Wind energy is an economical and

environmental friendly source to get electricity from. The world is getting hotter, in fact by 1

degree centigrade over the last hundred years, and the overwhelming consensus of scientific

opinion is that human activity, particularly the emission of greenhouse gases, are the cause.

For example, UK Government has decided to shift about 20% of their electricity load by

converting it towards renewable energy technologies. [3]

Advantages and disadvantages of wind energy:

In the U.S., the greatest source of human-caused greenhouse gas emissions is the power

sector, at about 38%. The largest source of power is coal, which, even though it produces less

than 40% of the power, produces over 70% of the power sector’s greenhouse gas emissions.

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(20% of the greenhouse gas emissions are from natural gas-fired power plants.) [2] Although

wind turbines have become familiar in much of the U.S., wind power still (2013) only

accounts for about 4% of the power sector.

The potential for wind energy is immense, and experts suggest wind power can easily supply

more than 20% of U.S. and world electricity. The advantages and disadvantages of wind

energy are detailed here to help you decide what the future of wind should be in the United

States.

Economic Advantages

· Revitalizes Rural Economies: Wind energy can diversify the economies of rural

communities, adding to the tax base and providing new types of income. Wind turbines can

add a new source of property taxes in rural areas that otherwise have a hard time attracting

new industry. Each 100 MW of wind development in southwest Minnesota has generated

about $1 million per year in property tax revenue and about $250,000 per year in direct lease

payments to landowners.

· Fewer subsidies: All energy systems are subsidized, and wind is no exception. However,

wind receives considerably less than other forms of energy. According to Renewable Energy

World magazine, conventional energy receives US$300 billion in subsidies per year, while

renewable energy has received less than US$20 billion of tax-payers’ money in the last 30

years. A study published by researchers at Harvard in 2011 found that the full life cycle cost

of coal power is between about 9.5 and 27 cents per kilowatt-hour, most of which is paid by

taxpayers in the form of increased health-related costs. These “indirect” subsidies amount to

between $175 billion and over $500 billion/year. (Numbers are in 2008 dollars.

· Free Fuel: Unlike other forms of electrical generation where fuel is shipped to a processing

plant, wind energy generates electricity at the source of fuel, which is free. Wind is a native

fuel that does not need to be mined or transported; taking two expensive costs out of long-

term energy expenses.

· Price Stability: The price of electricity from fossil fuels and nuclear power can fluctuate

greatly due to highly variable mining and transportation costs. Wind can help buffer these

costs because the price of fuel is fixed and free.

· Promotes Cost-Effective Energy Production: The cost of wind-generated electricity has

fallen from nearly 40¢ per kWh in the early 1980s to 2.5-5¢ per kWh today depending on

wind speed and project size.

· Creates Jobs: Wind energy projects create new short and long term jobs. Related

employment ranges from meteorologists and surveyors to structural engineers, assembly

workers, lawyers, bankers, and technicians. Wind energy creates 30% more jobs than a coal

plant and 66% more than a nuclear power plant per unit of energy generated.

Social Advantages:

· National Security/Energy Independence: Wind turbines diversify our energy portfolio

and reduce our dependence on foreign fossil fuel. Wind energy is home-grown electricity,

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and can help control spikes in fossil fuel cost. Distributed generation facilities, like many

community wind projects, provide a safeguard against potential terrorist threats to power

plants.

· Supports Agriculture: It is not often a new crop emerges from thin air. Wind turbines can

be installed amid cropland without interfering with people, livestock, or production.

· Local Ownership: A significant contribution to the worldwide energy mix can be made by

small clusters of turbines or even single turbines, operated by local landowners and small

businesses. Developing local sources of electricity means we import less fuel from other

states, regions, and nations. It also means our energy dollars are ploughed back into the local

economy.

Environmental Advantages:

· Conserves and Keeps Water Clean: Turbines produce no particulate emissions that

contribute to mercury contamination in our lakes and streams. Wind energy also conserves

water resources. For example, producing the same amount of electricity can take about 600

times more water with nuclear power than wind, and about 500 times more water with coal

than wind.

· Clean Air: Other sources of electricity produce harmful particulate emissions which

contribute to global climate change and acid rain. Wind energy is pollution free.

· Negligible Greenhouse Gases: The sources of most of our power, coal and natural gas,

produce large quantities of greenhouse gases. (Coal more than natural gas.) Wind power

produces none, other than in the manufacture, installation and maintenance of the turbines.

On average those greenhouse gases are offset by the clean power the turbines produce within

9 months of operation.

· Mining & Transportation: Harvesting the wind preserves our resources because there no

need for destructive resource mining or fuel transportation to a processing facility.

· Land Preservation: Wind farms are spaced over a large geographic area, but their actual

“footprint” covers only a small portion of the land resulting in a minimum impact on crop

production or livestock grazing.

Disadvantages:

· A Variable Resource: Turbines produce electricity only when the wind blows. This

variability is monitored and compensated in the same way utilities monitor demand changes

each day, so there are not any actual changes in power supply for the end users.

· Aesthetics: People have widely varied reactions to seeing wind turbines on the landscape.

Some people see graceful symbols of economic development and environmental progress or

sleek icons of modern technology. Others might see industrial encroachment in natural and

rural landscapes. There are many ways to minimize the visual impact of wind turbines,

including painting them a neutral colour, arraying them in a visually pleasing manner, and

designing each turbine uniformly.

· Shadow Flicker: Shadow flicker occurs when the blades of the rotor cast a shadow as they

turn. Research has shown the worst-case conditions would affect, by way of light alteration,

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neighbouring residents a total of 100 minutes per year, and only 20 minutes per year under

normal circumstances. Designers of wind farms avoid placing turbines in locations where

shadow flicker would be a problem any significant amount of time.

· Sound: Wind turbines are not silent. The sounds they produce are typically foreign to the

rural settings where wind turbines are most often used, but as turbine technology has

improved over the years, the amount of sound has fallen considerably. The sounds of wind

turbines do not interfere with normal activities, such as quietly talking to one’s 6neighbours.

· Biological Resource Impacts: As with any construction project or large structure, wind

energy can impact plants and animals, depending on the sensitivity of the area. Loss of

wildlife habitat and natural vegetation are the primary wildlife concerns associated with wind

energy. With modern turbines, mounted on tubular towers and whose blades spin only about

15 times per minute, bird collisions are now rare. Extensive environmental impact analysis is

an integral part of project development to mitigate impacts as much as possible. The

Audubon Society and Sierra Club both support wind energy development, because the

environmental advantages far outweigh the disadvantages.

· Construction: Wind systems can involve the transportation of large and heavy equipment.

This can cause a large temporarily disturbed area near the turbines. Erosion is another

potential environmental problem that can stem from construction projects. The single most

reliable technique for limiting erosion is to avoid grading roads and to perform site

reclamation post construction.

· Radar: Radar interference by wind turbines is rare and easily avoided through

technological improvements and proper sitting of turbines that are close to sensitive areas. A

number of U.S. government installations have both wind turbines and functional radar, and

the British military has a track record of successfully addressing these challenges.

How does a wind turbine work?

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Turbine design goals:

As electricity from wind is a cheaper source and also environmental friendly so we designed

a wind turbine. This is the design to produce about 3 kilowatts of electricity to share the load

of average home appliances. We choose Sirkup (Taxila) in Pakistan to build the wind

turbine for electricity. We approximated the design values by using appropriate formulas of

wind energy design.

Some advantages of wind why we are making this design are following;

Minimum COE (Cost of Energy)

Maximum annual energy production

Environmental friendly

Noise free

Turbine design constraints:

Wind velocity in Pakistan is not relatively high as in some

other countries. This is been the major constraint to our work. We handle this problem by

knowing that we can produce a large amount of electricity by making low power wind

turbines.

1. Political constraints

2. Economics constraints

3. Cost Constraint

4. Efficient Equipment provision Constraint

5. Limited Air velocity

Summary of our design:

We have used the following parameters for designing our desired

wind turbine model.

DESIGN PARAMETRES Design Values Formulas

Site Selection sirkap hill top N/A

Wind Resource Assessment Avarage Upto 6m/s N/A

Wind Velocity Range 03-07m/s N/A

Swept Area (square m) 50.24Meter Squares

Rotor Diameter (m) 8 meters

Hub Height (m) 12 meters

Cut-in Wind Speed (m/s) 3.5

Cut-out Wind Speed (m/s) 25

Rated wind speed (m/s) 5

Air Power Density 1.225

Rated Output, watts 1018.9928 P= Cp 1/2 ρ A v3

Peak Output, watts 2796.116243 P = ½ ρ A v3

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Rotor (Rpm) 83.6 V x TSR x 60 / (6.28 x R)

Tip Speed Ratio (TSR) 7

Gearing Method direct-drive gearing

Electrical Generators direct-drive generator

Annual Energy Output (kWh)

kWh/month @ 4 m/s

kWh/month @ 5 m/s

kWh/month @ 6 m/s

kWh/month @ 7 m/s

kWh/month @ 10 m/s

kWh/month @ 12 m/s

130.4

254.7

440.2

699

2038

3521.6

Blade material E-Glass (Fiber)

Tower material Steel

Tower weight (kg) Depends upon turbine weight

Blade weight (kg) 20kg

Cost (PKR) 5 lac approx

Cost per sq.m of swept area,

(PKR)

Rs=9950/- rough idea

Table 1: Design Summary

What are the main Applications of Wind Trbine?

1) Energy-generating wind turbines: Wind turbines are installed to capture the power of

the wind and be able to convert it to energy. This can be on a broad scale, such as the wind

turbines found on wind farms or can be on a smaller scale, such as individual wind turbines

people use to generate power for their home. Companies even want to take advantage of the

wind. For example, Sam’s Club was the first retailer reported to install a “significant” number

of on-site micro wind turbines.

2) Wind-powered vehicles: You’ve probably heard about this one recently. A car, powered

primarily by wind (using kites), just completed a 3,100 mile journey across Australia. While

it wasn’t 100% powered by the wind, it was a good example of how cars can also be powered

using alternative energies. It used a combination of wind, kite and batteries. In total, it

reportedly used about $10-$15 of energy for the entire 3,100 mile journey. Not too shabby!

http://www.environmentalleader.com/2010/04/30/sams-club-first-retailer-to-install-on-site-wind-power/

http://www.environmentalleader.com/2010/04/30/sams-club-first-retailer-to-install-on-site-wind-power/

http://www.physorg.com/news/2011-02-wind-powered-car-mile-australia.html

http://www.physorg.com/news/2011-02-wind-powered-car-mile-australia.html

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3) Wind/Kite-Powered Cargo Ships: Another great example of tapping into the power of

the wind can be found with Cargill. Cargill has stepped up and gone with the innovative idea

of installing a large kite on one of its cargo ships in order to tap into the power of the wind

and thus reduce fuel consumption and CO2 emissions. Now, of course wind has been used

for hundreds and thousands of years to “power” sailing and smaller vessels, but now it is

being used to help power larger cargo ships as well.

4) Wind-Powered Sports: For many, many years the wind has been used to power our love

of sports, both literally and figuratively. Everything from simple kite-flying to sailing, wind-

surfing, kite-surfing, hang-gliding, Para-sailing, wind-skiing and more.

5) Wind-Powered Water Pumps: Using the wind to help pump water out of the ground is

not something new. It is however a very helpful and sometimes much needed tool when it

comes to some communities and countries. Tapping into the power of the wind makes sense,

esp. when it comes to the work needed to pump water.

WHY WIND ENERGY???

Energy is most discussing topic in these days: increased consumption, high cost, depleted

natural resources, our dependence on import, and the load on the environment and the danger

of global warming.

Something should change. Wind energy has very high potential to minimize our dependence

on traditional resources like oil, natural gas and coal and to decrease the damage to the

environment.

Importance of off-grid small scale wind turbines in developing countries:

As alternative energy sources gain prevalence in energy markets worldwide, small

wind turbines have emerged as a variable alternative to their larger and more expensive

counterparts. While most attention has been drawn to their domestic application in

developed countries, and various low cost commercial turbines are available to

consumers for several thousand dollars, they also offer great promise in electrification

of developing countries. However, because of the technology cal nature of small wind

turbines, as well as the socio-political characteristics of the regions in which their use

is most applicable, special care must be taken while developing policies to encourages

investment as well as during implementation o f construction plans. If these factors are carefully

considered, small wind turbines may prove to be an environmentally conscious option

for the electrification of developing countries.

Small wind turbines differ from large turbines in many important ways,

demonstrating their greater versatility. While large turbines require mature power grids,

small turbines have application both on and off existing power grids, as a result of their

size and low energy output. Their off grid application avoids the heavy cost of

expanding transmission lines to rural regions of developing countries.

http://www.greenbiz.com/news/2011/02/28/cargill-cuts-co2-emissions-worlds-largest-kite-powered-ship

http://www.greenbiz.com/news/2011/02/28/cargill-cuts-co2-emissions-worlds-largest-kite-powered-ship

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Additionally,small turbines operate on lower wind speeds than large turbines, giving

them more placement options. Experts also indicate that small turbines, if placed

correctly in suitable locations, generate more energy per dollar than other common

mentation of a renewable energy scheme should also consider exemption of import

tariffs on equipment. Such an exemption will lower start-up costs and further encourage

investment.

There are three overlapping phases in which introduction of small wind turbines must be

carefully considered: investment, planning, and implementation.

To encourage investment, successful policy initiatives in developed countries may offer

effective models for developing countries. In developed countries, investment in small wind

turbines usually originates at the individual household level. Here, feed in tariffs ("FITs"),

which compensate individuals per kilowatt-hour of electricity generated, offer an effective

method to encourage investment.

For investment, the availability of credit in these regions will be crucial for the viability of

any small wind project. Sources of credit include international financial institutions and

countries' development agencies, such as that of France (L'Agence Fran- çaise de

Development), which extends environmental credit lines to local banks in developing African

countries. NGO sub- sides are also a source of credit; however, their funding must be carefully

designed to create conditions under which they will no longer be needed in order to ensure

ultimate market sustainably for renewable energy.

To break even, small wind projects require approximately ten to twenty years before the

initial cost can be recovered. If connection to an outside established grid is likely, and in-

place FIT payments are not high enough, then a project's economic feasibility could

potentially be undermined by a sudden influx of cheaper electricity. Under this scenario,

individual, community, and institutional investors would never recover their construction and

maintenance costs, as the market rate for electricity would now be too low. For this reason, it

is imperative that investment in small wind turbines be incentivized in regions of developing

countries where connection to an established grid is not expected during the ten to twenty year

cost-recovery period.

Once a developing country has created investment incentives, planning and

implementation are the next steps for successful introduction of small wind turbines.

According to the Centre of Excellence for Renewable Energy, there are six critical

factors at this stage of development: management, local training capacity, and technical

support, viability of the energy source, ownership, and political interference. Dealing

with these issues first hand, Practical Action, an international charity based out of the UK

whose goal is to combat poverty through the use of technology, has introduced small wind

turbines to isolated villages in Sri Lanka and Peru. Before choosing project locations,

Practical Action assessed the demand for electricity, paying close attention to use

patterns. Ultimately, the distinguishing factor that made wind power in Sri Lanka

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more feasible than Peru was the existing demand for electricity. However, to forecast

energy demand purely based on current energy demand would be short-sighted;

potential demand should be comparably weighted. In making such determinations,

relevant factors include population size, level of infrastructure, and number of viable

financial institutions.

Investment in human capital is the final and perhaps most critical aspect in

implementing any small wind project. The construction, operation, and maintenance

of small wind turbines require a high degree of technical understanding. For

implementation to be successful, the local population must have proper training and

knowledge. Community involvement is pivotal, as without a sense of ownership, local

populations will have no sense of commitment to their small wind turbines and these

turbines could easily fall into disrepair.

Community involvement, in addition to investment incentives, comprehensive

planning, and adequate technical training, is just one critical factor that determines the

ultimate success of any small wind turbine project. If these factors are carefully

considered, small wind turbines offer promise towards electrification of developing

nations in a way that is both environmentally conscious and sustainable.

Final design comes to end after a long group discussion, meetings and with proof

calculations. During final design calculation the first step was the selection of site.

The site that we are choosing is feasible for wind turbine purpose. For selection of site

we took help from a software named as Geospatial Toolkit, with the help of this

toolkit we found the site that was feasible according to cost, design and transportation.

Taxila (Sirkup Taxila) site was selected. This software tool helped in finding wind

velocity range in that particular area.

After site location and wind speed we thought about the type of wind turbine, it

should be horizontal or vertical. The shape and scale parameters depend upon site

location. The horizontal wind turbine was selected because that type was suitable for

the site location.

When the basic need for designing was completed then other parameter like router

diameter, hub height cut in wind speed, rated wind speed, cut out wind speed and air

power density were collected from different source data. The balanced cost material

and performance were the main factor that were considered during finalizing our

design.

There were following constraints and requirement that that we have to be face and focus

during design finalizing and or completion of the design i.e. Air speed should be more than

3m/s. Power required should be 2kW. There was problem for time management. Time was

short for the completion of tasks. A single member task was related to anyone of the group

member, so there was problem and confusion in tasks completion. A mutual coordination

was required to drive design to the final form. With the help of each group member we

reached to final basic design for wind turbine.

Wind turbine parameters and calculations constraints and requirements for their completion

were also considered. There was constraint in selection of type of turbine, horizontal and

vertical. As horizontal wind turbine was selected due to site location, wind speed, cost,

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transportation and other factor that were comparably better suitable than vertical wind

turbine.

After selection of wind turbine type then other constraints were number of blades. How

many no of blades should be selected? As greater the number of blades will cause the

friction losses, reduce power output according to the wind speed and site location.so

minimum three number of blades were selected.

Similarly gearing method wasn’t selected due to friction losses and lubrication problems.

Generator was selected due to low starting torque required, low maintenance operations

and less mechanical components.

Blade material was kept in mind. E-glass (fiber) was finally selected.As a wide range

of fibers material stretching from glass to carbon are used in the composite to make

Wind blades. Fiber volume fraction determines the strength of the composite but up to

a certain limit, after which there isn’t enough resin to distribute the loading. Fiber

diameter and orientation also determines the magnitude and direction of the load

carrying ability of the composite and its cost as well. The E in E-glass fiber represents

electrical, as it has good electrical properties. The E-glass performs well in tension

and compression and has reasonable stiffness. Cost of the fiber is the lowest and is

commonly used fiber in wind blade manufacturing industry. So due to these

properties E-glass was selected.

Steel material was selected as for tower requirement it should be strong enough, cheap

and stiff. As tower must withstand fluctuating wind loading and loading resulting

from turbine blade rotation. There were constraints regarding corrosion and

transportation of tower. For corrosion steel material was best. And for transportation

he tower designed in section i.e. it was finally designed into three sections.

Will tower produce enough electricity to meet our needs? For this question we have to

focus the annual energy estimation and calculation. For annual energy estimation we

have to calculate particular wind turbine power curve, average annual wind speed at

our site, height of the tower that we plan to use. Is it at proper height? Wind frequency

distribution and estimate of the number of hours that the wind will blow at each speed

during an average year. These constraints properly carried out with proper solution,

data and calculations.

Other important projects requirements to find cut-in wind speed (m/s), cut-out wind

speed (m/s), rated wind speed (m/s), air power density, rated output in watts peak

output in watts, rotor (Rpm) and tip speed ratio (TSR) for 2kW power wind turbine

were calculated from different sources efficiently.

We have used online calculators for wind turbine calculation and after five group

meetings we are able to perform such a huge task. All members cooperate well and

at the end after including losses we have approximate our output power more than

1Kw in Taxila.

These constraints and requirements finally drove us to reach and to fulfill final design

for wind turbine with coordination of group members.

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WIND TURBINE MODELLING AND DESIGN

1. Make a plot of Wind Power vs. Wind Velocity.

Wind turbines use the kinetic energy of the wind flow. Their rotors reduce the wind velocity

from the undisturbed wind speed far in front of the rotor to a reduced air stream velocity

behind the rotor. The difference in wind velocity is a measure for the extracted kinetic energy

which turns the rotor connected to the electrical generator.

The total power of a wind stream is equal to the rate of the incoming kinetic energy of

that stream, or

𝑃𝑡𝑜𝑡 =(𝑉𝑤)2

2𝑚.

Where:

Ptot = total power, W

m. = mass-flow rate, kg/s

Vw = incoming wind velocity, m/s

The mass flow rate is given by the continuity equation as:

𝑚. = 𝜌𝐴𝑉𝑤

Where:

ρ= incoming wind density, kg/m3

A=cross-sectional area of stream, m2

By substituting value of mass flow rate in total power equation we have;

𝑃𝑡𝑜𝑡 =1

2𝜌𝐴(𝑉𝑤)3

Thus the total power of a wind stream is directly proportional to its density, area, and

the cube of its velocity.

0

5000

10000

15000

po

we

r o

utp

ut

(Wh

)

wind velocity (m/s)

variation in power output at different velocities

variation in power output with velocity

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Variation in Power Output at Different Wind Velocities

2. Measure and plot the Wind Turbine Power Output as a function of Wind

Velocity (for the wind turbine with number of blades)

Power output is a function of wind velocity hence both changes simultaneously by changing

the number of blades for a wind turbine. [16] For producing electricity by using wind turbine it

is desirable to operate at high speed but not too much torque is required. These turbines have

two or three blades which provide sufficient torque without adding weight more blades

increase the weight. First of all wind strikes the blade which rotates due to its pressure so

blade angle plays an important role and it should be designed properly. The rotor with odd

number of blades is more stable in this case we used three blades for small wind turbine.

We used three blades because three blade rotor yields much energy and high power output.

For different speeds power output can be calculated as:

P = (½)*A*ρ*Cp*v^3

Where

A: area of blade = πr^2

ρ: air density = 1.225 kg/m^3

Cp: power coefficient (according to Betz law always less than 0.59)

V: wind velocity (according to our site v=4.51)

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Efficiency of conversion is 70% so Cp= (0.59*70=0.4) and substituting other values obtained

power output is:

P= (1/2)*(1.225)*(50.24)*(0.4)*(4.51)^3

P=1.129KW

According to our site velocity ranges from 3to 7 m/s. Its calculations are:

3. Decide blades design specification for Rated Power Output of wind turbine:

- Length =?

- Maximum chord =?

- Chord at the blade tip =?

- Blade twist =?

The types of aerofoils recommended for horizontal axis wind turbine are NACA 23012,

NACA 4412, NACA 0018.[1]We have selected NACA 0018 because of simple geometry and

0

1

2

3

4

5

3 4.51 5 7

Po

we

r O

utp

ut

(kW

)

Wind Velocity (m/s)

Power and Wind Velocity

Sr. number Wind Velocity (m/s) Power Output (kW)

01 3 0.3

02 4.51 1.12

03 5 1.53

04 7 4.2

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high coefficient of lift up to o.90.[2] NACA 4412 have bit higher coefficient of lift but have

some complex geometry and may increase cost of manufacturing. The geometry of blade is

shown below.

NACA 0018

Different parameters related to blades design are discussed below

Blade length:

Length of blade:

As we know that swept Area is

A = π r2

50.24 = 3.14 r2

r = length of blade = 4 m

Blade length is determined from the rotor radius which we have already

calculated. The rotor radius is 4 meters but in order to calculate blade length we have to

subtract hub radius from radius of rotor. The rotor radius must be determined in such a way

that maximum chord of blade must not lie within hub.

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Blade length = rotor radius – hub radius [3]

Since the maximum chord lies at o.4m from centre so hub diameter may be chosen less than

that. In order to mount blades on hub without overlapping the hub radius chosen is 0.15m.

This value of hub diameter is chosen after adjusting different values while modelling in pro e.

So blade length comes out to be 3.85m (4-0.15)

Blade length = rotor radius – hub radius

Blade length = 4.0 – 0.15 = 3.85m

Maximum Chord and chord at tip:

The chord length of wind turbine blade varies as we move away from centre of rotor. We can

say that chord length is function of blade radius.[3].As we move away from centre blade radius

changes hence the chord length also changes. Chord length for blades is given by following

formula.

Where

C = chord length

B = number of blades

Cl = Co efficient

R = Blade radius

R = rotor radius

X = TSR

An excel program was made to perform calculation. This program gives us all values of

chord length at all points on blade length. It is found that maximum chord length occurs at

0.4m from centre and has value of 0.76m.

18

Table 2: Calculations

Variation of chord length

The chord length at hub is 0.52m increased to a maximum value of 0.76m and then starts

decreasing gradually. The chord length at the tip as calculated by formula is 0.17m.

Blade Twist:

The lift produced by an aerofoil section is a function of the angle of attack to the inflowing

air stream .The inflow angle of the air stream is dependent on the rotational speed and wind

velocity at specified radius. The angle of twist is dependent upon TSR and desired aerofoil

angle of attack. Normally the aerofoil section at the hub is angled into the wind due to the

high ratio of wind velocity to blade radial velocity. In contrast the blade tip is almost normal

to the wind. [4]

0.00

0.20

0.40

0.60

0.80

1.00

0.1 0.15 0.2 0.4 0.8 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4

cho

rd le

ngt

h

radius

chord length at different points on blade length

variation of chord length

19

The twist may be regarded as change in pitch angle of blades from hub to tip of blades. So if

we want to calculate twist we must calculate pitch angles throughout blade length. The

formula for pitch angle is given by

[5]

Where

ß = tip angle

R = Radius of rotor

X = TSR

α = angle of attack

r = radius of blade

A program was made in MS Excel to find pitch angles using above formula.

Table 3: Design Calculations

Variation of pitch angle

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0.2 0.4 0.8 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4

pit

ch a

ngl

e

radius

pitch angle variation at different points on blade length

variation of pitch angle

20

This is evident from above data that pitch angle varies continuously from hub to tip. Start

from very high values of tip angle at hub, the blades becomes almost normal at tips. Hence

blade twist is determined in terms of pitch angles.

4. Determine the arrangement/number of blades that produces the maximum amount

of power.

1. The number of blades will affect the power output from the turbine. The optimum

number of blades for a wind turbine depends on the purpose of the turbine. Turbines for

generating electricity need to operate at high speeds, but do not need much torque – these

turbines generally have two or three blades, since this gives enough torque without adding the

extra weight that can slow the turbine down.

Wind pumps need a lot of torque but not much speed, and so have many blades. [7]

Rotors with odd numbers of blades (and at least three) are more stable. Two-bladed rotors

require a hinged (teetering hub) rotor, since it needs to be able to tilt or bend in order to avoid

excessive shocks to the turbine under relatively strong winds.

The three-bladed rotor is the most popular model with a much smoother power output, more

efficient and higher energy yield, a balanced gyroscopic force and a much better mechanical

system compared to the rotors with two blades.

2. Practically speaking this means that adding more or larger blades will actually choke

the oncoming flow and lower the total efficiency instead of improve it.

As far as the aerodynamics of the blades they go, as they rotate around they leave a wake. If

you have another blade following too close to the one in front of it, the wake of the first blade

will negatively affect the efficiency of the one behind it.

3. Everything over underrated said is correct. In addition, wind turbines having three

blades works best with the wind speed profile as height above the ground increases and the

related torque on the turbine system. As your height increases, wind speed increases. This

increases the aerodynamic loading on the blades. With a single blade oriented straight up, and

the two blades facing 4 and 8 o’clock roughly, the torque on the hub (the connection between

the blades and tower) is much less than other blade configurations. This prolongs the life of

the turbine.

4. With the four blade setup, when oriented straight up down / across, the top blade will

have more force on it than the bottom blade. See here. This produces torque about the

connection of the hub and generator. With the three blade setup, it works out that the torque

from each blade evens out better

5. Let’s imagine we have 4 blades. Then let's freeze-frame for a moment when the 4

blades are at 12, 3, 6, and 9. The wind speed increases with altitude, so the blade at 12 is

feeling a huge wind load, so it's trying very hard to accelerate the rotation of the axel. But the

21

blade at 6 is feeling very low wind loads, in fact the axel is already spinning too fast to be in

that wind! It's actively giving energy back into the wind, instead of harvesting any. It is

actively decelerating the rotation of the axel.

This means the blades are just fighting each other, instead of working together to put work

into the axel. This causes huge stresses because it's as though, at this moment, there is a force

pushing the 12:00 blade toward 1:00, and there is a force pushing the 6:00 blade to 5:00.

What's really bad is that this force is only transient, and in 1/2 of a revolution, the forces will

be reversed. That is, the forces will look the same but the actual blades will have switched

places.

If you only have 3 blades, there is never a direct opposition between 12 and 6, only between

12 and 4, and 12 and 8. Because they aren't separated as far apart, the wind speed isn't as

different so the squishy forces are greatly reduced. That means less stress, less wear and tear,

more turbine uptime.

Fig 2 :Power factor vs blade tip angle

This diagram describes dependence of Blade Tip Angle for

maximum power Co-efficient for different no of blades. Co-efficient

is the average for all 3 power coefficients at reference wind speeds.

The wind turbine is faster when the number of blades decreases. As

can be seen in Fig, the tip speed radio, λ, decreases when blade tip

angle increases. Furthermore, as α increase, the speed at Cpmax, λmax, for 2 blades rotor

decreases much faster than 3 or 6 blades rotor. For 6 blades, λmax decreases much slower. It

to notice that at α=8, 2 blades rotor is as fast as 6 blades one. [8]

One of the most important characteristic of wind turbines is cut-in wind speed. In Fig. 16 is

the variation of cut-in wind speed vs. number of blades, having parameter blade tip angle, α.

It is known that as the number of blades increases, the cut-in wind speed decreases. Similarly,

the cut-in wind speed decreases as the blade tip angle increases. The role of wind turbine

design process, is the selection of the number of blades, the blade tip angle and cut in wind

22

taking into account the wind potential in

which the turbine would operate. The cut in

wind speed and power co-efficient have the

same variation with blade tip angle at a

given number of blades: both parameters are

decreasing. [8]

5. Discuss the influence of wind turbine

blade design on power generated.

The aerodynamic profiles of wind turbine

blades have crucial influence on

aerodynamic efficiency of wind turbine.

This involves the selection of a suitable airfoil section for the proposed wind turbine blade.

The NACA 63 series is chosen as the basic group for investigation because they have good

low speed characteristics and the power curve is better in the low and medium wind speed

ranges.

NACA 63-415 airfoil profile is considered for analysis of wind turbine blade. NACA 63-415

airfoil profile is created by using the co-ordinate file generated in JavaFoil. A C-Mesh

Domain for the fluid around the airfoil is created using Design Modeler in ANSYS

Workbench. The CFD analysis is carried out using STAR-CCM+ at various angles of attack

from 00 to 160. The coefficient of lift and drag values are calculated for low Reynolds

number and the pressure distributions are also plotted. The airfoil NACA 63-415 is analyzed

based on computational fluid dynamics to identify its suitability for its application on wind

turbine blades and good agreement is made between results. [9]

NOMENCLATURE

CL Lift coefficient

CD Drag coefficient

α Angle of attack

ρ Air density

Wind turbine blade profiles are often constructed using a combination of 2-D airfoil tools and

the Blade Element Momentum (BEM) theory. BEM theory gives the angle of twist and chord

length for a given cross section of the airfoil and rotation speed at a finite number of positions

along the blade span. A three dimensional shape can be extruded from these two dimensional

sections. The BEM theory considers a given airfoil cross section as independent, then

processes the wind with a speed and direction that is obtained from vector sum of the

23

oncoming wind speed and the wind speed generated by rotor rotation. Unlike aerodynamic

studies on higher Reynolds number flows, the numerical or analytical study of flows at very

low Reynolds numbers is not quite matured. The 2D airfoil geometries are considered for

study to understand the low Reynolds number flow.

Wind Power

The amount of energy in a column of wind seen by the swept area of a turbine can be found

from its kinetic energy and the power is expressed as follows

Lift and Drag

Lift force is the force perpendicular to direction of the oncoming air flow as a consequence of

the unequal pressure on the upper and lower airfoil surfaces.

Drag force is the force parallel to the direction of the oncoming air flow due both to viscous

friction forces at the surface of the airfoil and to unequal pressure on the airfoil surfaces

facing toward and away from the oncoming flow.

The NACA 63 series is chosen as the basic group for investigation because they have good

low speed characteristics with a minimum compromise from consideration of the high speed

characteristics. For NACA 63 series airfoil profiles, the power curve is better in the low and

medium wind speed ranges, but drops under operation at higher wind speeds [16]

24

Pressure plot – 2° Angle of attack

In this paper a Horizontal axis wind turbine blade profile NACA 63-415 is analyzed for

various angles of attack. The coefficient of Lift and drag is calculated for this NACA 63-415

for various angles of attack from 0° to 16° and the maximum / ratio is achieved at 2° of angle

of attack. The coefficient of Lift increases with increase in angle of attack up to 8°. After 8°,

the coefficient of lift decreases and stall begins to occur. The drag forces begin of dominate

beyond this angle of attack. The rate of increase in lift is more for angle of attack from 0° to

8° and then it starts to decrease. The drag increase gradually until 5° angle of attack and then

rapidly increases. The CFD analysis is carried out using STAR-CCM+ software. The

pressure distribution at various angles of attack of the blade is shown in Fig Above. [11]

25

6. Investigate possible blade orientations.

The possible orientation depends upon the following.

Angle of Twist:

The lift generated by an aero foil section is a function of the angle of attack to the inflowing

air stream. The inflow angle of the air stream is dependent on the rotational speed and wind

speed velocity at a specified radius. The angle of twist required is dependent upon tip speed

ratio and desired aero foil angle of attack. Generally the aero foil section at the hub is angled

into the wind due to the high ratio of wind speed to blade radial velocity. In contrast the blade

tip is likely to be almost normal to the wind. The total angle of twist in a blade may be

reduced simplifying the blade shape to cut manufacturing costs. However, this may force

aero foils to operate at less than optimum angles of attack where lift to drag ratio is reduced.

Such simplifications must be well justified considering the overall loss in turbine

performance. [15][7]

As the oncoming wind velocity directly affects the angle of incidence of the resultant airflow

onto the blade, the blade pitch angle must be altered accordingly. This is known as pitching,

which maintains the lift force of the aero foil section. Generally the full length of the blade is

twisted mechanically through the hub to alter the blade angle.

Smart Blade Design

The current research trend in blade design is the so called “Smart Blades”, which alter their

shape depending on the wind conditions. Within this category of blade design are numerous

approaches which are either aerodynamic control surfaces or smart actuator materials.

7. To what extent pitch angle influence the in a wind turbine design on power

generated.

This study implementation to trace the position of pitch angle wind turbine on the wind

energy conversion system (WECS). The accurate position could maximize mechanical

power. This evidence can be achieved by developing a prototype of wind turbine considering

of dimensions and components of wind turbines, blade type, blade radius, specified work area

of angular velocity and power production. Figure 1 describes the working principle of a wind

turbine blade which is the main determinant for the performance of wind turbines. Airfoil

will generate respective lift force vector (FL), drag force (FD) and resultant force (FT) as it is

subjected to wind from the front. Changes in lift and drag force are directly influenced by the

geometric shape of the blade. When wind speed and wind direction attack from position at an

26

angle relative to the main line chord, as sketched in Figure 1, then the wind speed and wind

direction will change of lift and drag forces so that the angular velocity and the torque shaft

chord changes as well. Changes in blade angle, due to wind direction, will eventually affect

the speed of rotating shaft. Thus the influence of blade angle positions is crucial to be further

investigated.

We report study to investigate the role of pitch angle in correlation with power generation. A

blade angle position tracking experiments were done on a prototype wind turbine, with

constrain to it’s the smallest angle step changes that can be set. Through the investigation, we

will know under what angle the maximum power can be achieved. The discussion starts from

the conversion of wind energy content towards wind power production, which is described as

follow. [16]

Fig 4 (a): Rotor plane orientation

By substituting we get.

27

Fig 4 (b): Rotor plane orientation

(see APPENDIX B)

28

Results and Discussion:

Relationship varied position blade angle and wind speed varied to produce wind turbine

rotational speed is varied as well, as a whole shown in Table 1. Testing of wind turbine

systems are also made to find relationships wind speed, angular position, rotational speed,

and coefficient of power and Tip speed ratio (TSR). The result of calculation and the

correlation shows that wind speed data varied 4-6 (m/s) during the period of 100 seconds

imposed on a wind turbine to see the performance of wind turbines. From the test data

obtained subsequently calculated the value of tip speed ratio. λ values obtained from the

relationship pitch angle position and rotational speed are then used to calculate the tip speed

ratio (TSR). λ and Cp values, obtained at a position angle between the (12-20)0.

Relationships of Cp, θ and λ from the calculation for the whole range. [13]

In the view of this experiment, there is correlation of all process variable including wind

speed, blade angle position, rotational speed, tip speed ratio, power production, and wind

turbines coefficient. After V, θ, λ, ω, Cp, is found, and then the input and output mechanical

power can be calculated.

Table 4: Correlations of rotational speed (ω) with wind speed (v) and pitch angle (θ)

29

Fig 5: Rotational speed versus pitch angle wind turbine for different wind speed

30

8. Influence of wind turbine height on power generated

In order to assure good access to their fuel, wind generators are mounted high atop towers.

There are two reasons for this. First, ground drag, the friction between moving air masses and

the earth, decreases with increasing height above the earth’s surface. Second, turbulence

caused by obstacles on the earth, trees, and buildings, for example, is reduced with height

above those obstacles.

One thing you need to pay attention to is not the current tree height, but the height that the

trees will grow to during the life of the wind system, that is, in 20 to 30 years. In my

neighbourhood, trees grow at a rate of about one foot per year, topping out at about 65 feet. If

we take mature trees into consideration in the above example, the numbers are now a 65-foot

tree height plus the 30-foot rule plus the blade length of 7 feet for a total hub height of 102

feet. Always remember the second rule of tower sizing: trees grow, but towers don’t,

regardless of how much it rains. This addresses the problems that turbulence poses for small

wind turbines. Note that the minimum hub height is just that – it’s the minimum tower height

that you can get by with and still produce electricity without the wind’s power either being

diminished by ground drag or compromised by turbulence. It is usually cost effective to

increase tower height up to a point, depending on the size of the system and the local

obstacles. [11][16]

However, increasing the tower’s height above the minimum still results in an increased wind

system energy output. The power equation for determining the amount of energy that a wind

turbine can generate states that P=1/2dAV3

, where P is the power available at the turbine

rotor, d is the density of the air, A is the swept area of the rotor, and V is the wind speed. At a

given location, we have no control over air density, so for any given wind generator with a

given rotor diameter, the only real variable is V, wind speed. Therefore, we can rewrite the

equation to say P~V, or more appropriately P~V3

.

Oftentimes, people rationalize a short tower height based on the cost of the turbine. I have

heard it said that a small wind turbine in the size range of 1 kW or so does not justify the

expense of a tall tower, which could be four or five times the cost of the turbine. This

reasoning completely ignores the physics of fluid dynamics that dictates the tall tower in the

first place. A wind turbine close to the tree tops suffers from lack of fuel, the wind, due to

ground drag. In addition, the turbulence caused by the surface clutter at the site will cause

increased maintenance on the turbine as well as shorten its life. In light of this, shorter towers

than the site requires are no bargain because the turbine is not producing much electricity and

its life expectancy is decreased.

The minimum acceptable tower height for a given site is always driven by the obstacles at

that site. Increasing the tower’s height above the minimum is driven by simple economics of

incremental tower height at a certain cost versus incremental energy production.

31

Winds at higher altitudes become steadier, more persistent, and of higher velocity. Because

power available in wind increases as the cube of velocity (the velocity-cubed law),assuming

other parameters remaining the same, doubling a wind's velocity gives 2x2x2=8 times the

power; tripling the velocity gives 3x3x3=27 times the available power. With steadier and

more predictable winds, high-altitude wind has an advantage over wind near the ground.

Being able to locate HAWP to effective altitudes and using the vertical dimension of airspace

for wind farming brings further advantage using high-altitude winds for generating energy.

High-altitude wind generators can be adjusted in height and position to maximize energy

return, which is impractical with fixed tower-mounted wind generators. 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. [9]

The tower height of the turbines should match the potential site to achieve maximum power

output per unit cost when constructing wind farm. The Turbine-Site Matching Index (TSMI)

is introduced as the objective function, with the consideration of the height effects both on the

capacity factor (CF) and the initial capital cost (ICC). A normalized power output (L) is

defined to analyse the matching problem. The optimal tower height is obtained through

modelling L. The computational results indicate that the proposed method can obtain the

approximated optimal height in short computational time. The height effects on the wake

flow and the distances among turbines reduce the optimal height. For the whole turbine

layout, the higher tower heights are not always desirable for optimality. There exists an

optimal tower height when maximizing TSMI. Normally, the wind data are measured by the

meteorological mast, the height of which is much lower than the turbine hub. Therefore, the

wind data should be modified for height. The wind speed increases with the tower height,

32

which is affected by the ground surface roughness. The height effect is commonly modelled

using the power law or the logarithmic law, which can be uniformly expressed as

where uref is the wind speed at the height of href , au is the wind shear coefficient and z0

is the ground surface roughness.

Power Generated Vs. Hub Height

2800

3000

3200

3400

3600

0 5 10 15 20 25

PO

WER

HEIGHT

P= 0.5*ᵨ*A*(V^3)

P= 0.5*ᵨ*A*(V^3)

4.4

4.6

4.8

5

0 5 10 15 20 25

VEL

OC

ITY

HEIGHT

v2

v2

33

The result shows that the higher tower heights are not always desirable for optimality. There

exists an optimal tower height when maximizing TSMI. Fig. 4 shows the normalized power

of the optimized results for various uref . The result show that L for various uref are the same

at the same h. L intends to decrease with h. The fluctuation may be due to the limit of the

grids, which can be reduced through using finer grids.

MODELING:

Propulsion

The method of propulsion critically affects the maximum achievable efficiency of the rotor.

Historically, the most commonly utilized method was drag, by utilizing a sail faced normal to the

wind, relying on the drag factor (Cd) to produce a force in the direction of the prevailing wind. This

method proved inefficient as the force and rotation of the sail correspond to the wind direction;

therefore, the relative velocity of the wind is reduced as rotor speed increases. The following TABLE

shows.

Figure 1: Propulsion Drag and lift [18]

34

For a lift driven rotor (in above TABLE) the relative velocity at which air strikes the blade (W) is a

function of the blade velocity at the radius under consideration and approximately, Two thirds

of the wind velocity. The relative airflow arrives at the blade with an angle of incidence (β)

dependent on these velocities. The angle between the blade and the incidence angle is known as the

angle of attack (α). [19]

HAWT Blade Design

A focus is now being made on the HAWT due to its dominance in the wind turbine industry.

HAWT are very sensitive to changes in blade profile and design. This section briefly discusses the

major parameters that influence the performance of HAWT blades.

The tip speed ratio defined as the relationship between rotor blade velocity and relative wind

velocity [Equation (2)] is the foremost design parameter around which all other optimum

rotor dimensions are calculated.

Aspects such as efficiency, torque, mechanical stress, aerodynamics and noise should be considered in

selecting the appropriate tip speed. The efficiency of a turbine can be increased with higher tip

speeds, although the increase is not significant when considering some penalties such as increased

noise, aerodynamic and centrifugal stress.

Figure 2: Influense of Tip Speed Ratio [19]

Blade Plan Shape and Quantity

The ideal plan form of a HAWT rotor blade is defined using the BEM method by calculating the

chord length according to Betz limit, local air velocities and Aero foil lift. Several theories exist for

35

calculating the optimum chord length which range in complexity, with the simplest theory based on

the Betz optimization [Equation (3)]. For blades with tip speed ratios of six to nine utilizing

Aero foil sections with negligible drag and tip losses, Betz’s momentum theory gives a good

approximation. In instances of low tip speeds, high drag Aero foil sections and blade sections around

the hub, this method could be considered inaccurate. In such cases, wake and drag losses should be

accounted. The Betz method gives the basic shape of the modern wind turbine blade.

However, in practice more advanced methods of optimization are often used.

A typical blade plan and region classification

Figure 3: Blade Plan

Assuming that a reasonable lift coefficient is maintained, utilizing a blade optimization method

produces blade plans principally dependent on design tip speed ratio and number of blades. Low tip

speed ratios produce a rotor with a high ratio of solidity, which is the ratio of blade area to the area of

the swept rotor. It is useful to reduce the area of solidity as it leads to a decrease in material usage and

therefore production costs. However, problems are associated with high tip speeds.

36

Optimal blade plan shape for alternate design tip speed ratios and number of blades

Figure 4: Blade Shapes [15]

Generally, in practice the chord length is simplified to facilitate manufacture and which involves some

linearization of the increasing chord length. The associated losses signify that simplification can be

justified by a significant production cost saving.

Efficiency losses as a result of simplification to ideal chord length

Figure 5: Efficiency Losses [13]

37

Aerodynamics

Aerodynamic performance is fundamental for efficient rotor design. Aerodynamic lift is the force

responsible for the power yield generated by the turbine and it is therefore essential to maximize this

force using appropriate design. A resistant drag force which opposes the motion of the blade is

also generated by friction which must be minimized. It is then apparent that an aero foil section with a

high lift to drag ratio [Equation (4)], typically greater than 30, be chosen for rotor blade

design.

The angle of attack is the angle of the oncoming flow relative to the chord line, and all figures for

CL and CD are quoted relative to this angle.

The differing aero foil requirements relative to the blade region are apparent when considering airflow

velocities and structural loads.

Angle of Twist

The lift generated by an aero foil section is a function of the angle of attack to the inflowing air

stream. The inflow angle of the air stream is dependent on the rotational speed and wind speed

velocity at a specified radius. The angle of twist required is dependent upon tip speed ratio and

desired aero foil angle of attack.

Blade Loads

Under special operational scenarios the main sources of blade loading are listed below:

Aerodynamic

Gravitational

Centrifugal

Gyroscopic

Operational

Aerodynamic Load

Aerodynamic load is generated by lift and drag of the blades aero foil section, which is dependent on

wind velocity (VW), blade velocity (U), surface finish, angle of attack (α) and yaw. The angle of attack

is dependent on blade twist and pitch. The aerodynamic lift and drag produced are resolved into

useful thrust (T) in the direction of rotation absorbed by the generator and reaction forces (R). It can

be seen that the reaction forces are substantial acting in the flatwise bending plane, and must be

tolerated by the blade with limited deformation. [14]

38

Structural Load Analysis

Modern load analysis of a wind turbine blade would typically consist of a three dimensional CAD

model analyzed using the Finite Element Method.

Flap wise Bending

To calculate these stresses the second moment of area of the load bearing material must be calculated

[Equation (6)]. Using classical beam bending analysis bending moments can be calculated at any

section along the blade.

Figure 6: Bending in the Blade

39

PROPELLER MODELING IN CREO

COMMANDS USED

Line, Arc, Revolve tool, Datum plane defining, sketching on datum planes, importing the

coordinates for blades in sketch section (different profiles), importing the sketch file in part

module, scaling the sketch, rotating and fixing on the datum plane, and repeating this

procedure for different scales, using swept and blend commands, pattern command to

produce 3 blades.

GEAR

Sketch circles, extrude, remove material, making tooth on surface by sketch tool, patterning

the tooth to produce the no. of teeth.

BEARINGS

Sketch circles, extrude, and remove material.

CASING

Sketch tool, simple line square circle, revolve, extrude, remove material, and blend.

ASSSEMBLY

Importing the impeller, importing the gear, joining axis of shaft and gear, importing the

bearing, joining the axis of bearing and shaft, importing the pinion and driven shaft. Matting

both the gear surfaces, importing the casing and inserting it onto the gear mechanism.

40

Propeller

41

Bearing

Gear

42

Gear Generator

Casing

43

MATLAB Design and Simulations

Signal Flow of Wind simulator on MATLAB

Response of Cp in TSR Angle of attack variations with speed ratios

44

Performance Test Results and Analysis

Discuss the impact on the power coefficient with the blade tip angle

The optimum operation of the rotor with the type blades is at small blade tip angle. Therefore,

the power coefficients are measured for 00, 20, 50, 70 and 100. At higher tip angles, the

power coefficient is small enough to be considered for the operation of a wind turbine.

When we simulated our turbine it was not giving us the required output according to our design

stresses produced in the turbine blades were very high and near to the yield strength of the selected

material. In first simulation steel is selected as material which is giving too much stress when

compressive stress is applied upon the blades. Streamline flow is also didn’t achieved in our 1st test

run simulation.

Our first model give errors because of the blade design and the selected material for the blade which

has low strength in case of compressive load. Our design calculations were under sized and blade

length is not enough to support the static load exerted by wind at high speed. Deviations occurred

because assumptions are made from the calculations not from the actually simulated results.

Simulated results give accurate know how of a model .We reverse calculated the length of the blade

and selected the material E-Glass fiber having high strength in case of compressive load. Aero foil is

also redesigned at the angle of attack 0 degree which gave maximum passage for air flow around the

blade. Our second simulated model gave stresses way below the yield strength of the material.

Turbine is stable in design in second model and also it meet the stated requirements of design [20]

Aero foil Simulation

We selected NACA 63-415 Air foil for our turbine blade. First we analyzed the performance of airfoil

at an angle of attack of 0 degree. At 0 degree due to high Cd the ratio of CL/CD achieved is about

40.Then after modification we ran the simulation for angle of attack of 2degree and achieved CL/CD

ratio of about 67 which is higher than the previous one. Finally for further verified results we ran the

simulation at 8 degree and found the CL/CD ratio of 25. [20]

From the above results we select the angle of attack 2 degree appropriate for blade design. Effect of

angle of attack upon the CL, CD and CL/CD can be understood from the following graphs.

45

CL/CD value increases by increasing angle of attack from 0 degree up to 2 degree after than it start

decreases and eventually become zero at 15 degree.CD increases by increasing the angle of attack

above 2 degree. So at 2 degree angle of attack our selected airfoil performs at its maximum. Drag

force increases by increasing angle of attack beyond 2 degree.

Structural Analysis

Structural analysis is necessary because the turbine components will develop stresses and creep when

high wind pressure is acted constantly upon them. So it is necessary that turbine blades must also have

enough strength to avoid structural failure. And deflection in turbine blades must be within the limits.

This analysis is done in SolidWorks Cosmo Simulation pack. Simulation is done at wind velocity

7m/s and pressure 100MPa. [Appendix]

Stresses in Blades

Maximum stress developed in turbine blades is up to 7464 N/m2 which is far more less than the yield

strength of blade material which is 2.25e+008 N/m^2 .Hence blade material and design is strong

enough to withstand the high pressures of wind. [Appendix]

CL /

CD

ANGLE OF ATTACK

ANGLE OF ATTACKVS CL / CD

F L A

ND

FD

ANGLE OF ATTACK

ANGLE OF ATTACK VS FL AND FD

FL FD F resultant

46

Displacement and Strain in Turbine Blades

Maximum displacement/deflection produced in blades is 0.00282583 mm and maximum equivalent

strain produced is 9.11879e-008.Both of these simulation results justified our design selected and

executed. [Appendix]

Impact on the power coefficient with the blade tip angle

Graph given below summarized all the impacts of blade tip angle upon different parameters.

Blade tip speed ratio, λ, at maximum power, increases/decreases with blade tip angle

It is evident from the graph given below that tip speed ratio at maximum power will increase by

increasing the blade tip angle up to 5 degree and then eventually decreases by increasing the blade tip

angle above 5 degree. Increasing tip angle moves the blades out of the wind, thereby reducing the

effective wind area.

From the graph the maximum power conversion is at 0 degree while it decrease by increasing the

value above 0 degree

Variation of the power coefficient with wind speed

At low speed of the wind below 3 m/s wind is so slow that it miss the turbine blades and does not

produce maximum power output. Wind between 3m/s to 7m/s is suitable for wind turbine blades.

When Speed of wind increases above 10m/s it act like a solid wall for blades due to which power

coefficient decreases.

47

Figure 7: Effect of Wind Speed on Power Coefficient [21]

48

1. Blade tip speed ratio, λ, at maximum power, increases/decreases with blade tip angle.

2. Variation of the power coefficient with wind speed.

where Pwind( u) is the power contained in the wind passing with speed u through the wind

turbine, and P( u) is the electrical power extracted. The power coefficient cp( u) represents

49

the amount of power converted by the wind turbine. Because the input Pwind( u) cannot be

controlled, improvements in wind power performance involve increasing the power

coefficient cp( u). Momentum theory can now be applied to determine this coefficient.

Ptheoretical( u), or more simply P( u) is the electrical power output and u is the input wind

speed ( u upstream), i.e. a power curve is roughly characterized by a cubic

50

increase of the power output with the wind speed. The functional behavior of the power

coefficient cp( u) is the result of certain control strategies as well as of Betz physical limit.In

the mechanical power extraction the usual way to control power production is achieved by

stall effects on the rotor blades. Stall effects happen when the critical angle of attack for an

airfoil is exceeded, resulting in a sudden reduction in the lift forces generated by the airfoil.

In modern wind turbines this is achieved by so-called active stall control or pitch controlThis

consists of a rotation of the blades into the plane of rotation and the blade cross-section. The

blade rotation angle is known as blade pitch angle q . The power coeffi cient cp is in this

case a function of the blade pitch angle q and the tip-speed ratio.

3. The maximum power conversion efficiency at which tip angle?

The maximum power conversion efficiency at which tip angle

The optimum operation of the rotor with the type blades is at small blade tip angle. Therefore,

the power coefficients are measured for 00, 20, 50, 70 and 100. At higher tip angles, the

power coefficient is small enough to be considered for the operation of a wind turbine.

The diagram shows the relations between TSR and power Co-efficient for three different

wind velocities. It shows that the Cp is maximum of 0.5 for TSR of 5 at a pitch angle of 0

degree. [12][13]

From this diagram and comparing it with the previous one it can be seen that the Co-efficient

of performance has decreased for same wind speeds with increased pitch angle 2 degrees

51

Result:

As it can be seen that as the pitch angle increases the co-efficient of performance decreases

Same as question first of this section maximum power conversion is achieved in case of

0 degree tip angle as shown

PLOTS FOR OUR DESIGN PARAMETERS

TSR Vs Wind Speed

As the wind speed increases tip speed ratio decreases.

0

2

4

6

8

10

12

3.5 4 4.5 5 5.5 6 6.5

λ

Wind Speed

Tip Speed Ratio vs Wind Speed

52

Cp Vs Wind Speed

Power coefficient shows the same behaviour as in case of tip speed ratio. It also

decreases as we go on increasing the wind speed.

TSR Vs Cp

Tip speed ratio and power coefficient have direct relation with each other. As we

increase the tip speed ratio power coefficient values also increases.

0.0000

0.2000

0.4000

0.6000

0.8000

1.0000

1.2000

3.5 4 4.5 5 5.5 6 6.5

Cp

Wind Speed

Power Coefficient vs Wind Speed

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

1.1000

5 6 7 8 9 10 11

Cp

λ

Tip Speed Ratio vs Power Coefficeint

53

CONCLUSION

At higher tip angles, the power coefficient is small enough to be considered for the operation

of a wind turbine.

The power coefficient decreases with the blade tip angle.

Blade tip speed ratio, at maximum power, decreases with blade tip angle.

The power coefficient varies slightly with wind speed: at low wind speed the power

coefficient is the higher than at higher wind speed.

Analysis and test results mentioned, clearly identifies the feasible design and material

composition of the wind turbine. Software’s like Creo and Ansys results in the feasibility of

the wind turbine. Although there exists conflict in the testing but the mentioned software’s

are thoroughly studied and are used for the design optimization. The design of the wind

turbine was one of the challenging task. The most important factor that must be kept in

mind is the provision of the required output with in the affordable first time investment.

Because we are using a small wind turbine for a single household appliances. That’s why the

performance and efficiency factor really matters and a small increment or decrement may

fail the design and effect the cost of the wind turbine. The most basic problem showed up

when the rotor diameter was calculated. The calculated diameter was beyond limits. So it is

then modified and calculated by some authentic references, like research papers and

journals. If we must have to make another turbine. We would change the site if it would be

available in future better than this and would have a look at the site and would estimate the

transmission cost and losses too, if it is for large scale.

RECOMMENDATIONS

Before installing the wind turbine one should has to notice some factors which are necessary.

They are

Site Suitability

Project Feasibility

Detailed Assessment

Planning Application

Construction

Operation

Decommissioning

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#suitability

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#feasibility

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#assessment

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#application

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#construction

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#operation

http://www.seai.ie/Renewables/Wind_Energy/Wind_Farms/Wind_Farm_Development/Guidelines_for_wind_farm_development/#decommissioning

54

During construction of turbine (blades) the design parameters are the main factors on which

output power depends a lot. For example the blade twist or angle of attack of air determines

the drag and lift in the rotor. Greater the lift greater will be the speed of rotor and thus

resulting the more power output. Drag decreases the speed if rotor. Secondly Hub height has

a major effect on power. The velocity of air increases as the altitude increases. So more hub

height is best option. Normally the hub height is kept 50 m because it gives better results. [16]

The detailed assessment includes the wind assessment. The velocity range of air is

determined. The locations with maximum air power density must be selected.

A detailed eye on all above factors will result the best output. A single flaw will reduce the

power output.

55

APPENDIX A

Wind energy terms are not always used in the same way across various countries or sources.

These definitions are based on how terms appeared to be most commonly used throughout

countries and sources in this document.

Wind Energy: The provision of energy from wind, usually harnessed through wind turbines.

Wind Energy Requirement, Rule, Law, or Policy: A wind energy setback or limit required

by a level of government.

Wind Energy Recommendation or Guideline: A wind energy setback or limit that is

suggested or encouraged, but not required, by a level of government.

Wind Turbine: A system used to convert potential energy found in wind to mechanical

energy to produce electricity. Wind turbines usually range in size from 9 to 200 meters (29-

427 feet), and may be located onshore or offshore.

Onshore Wind Turbine: A wind turbine that is located on land. Onshore wind turbines may

range in size from small wind turbines producing 50 kilowatts of electricity a day, to large

wind turbines producing up to 3 megawatts of electricity a day.

Offshore Wind Turbine: A wind turbine that is located in deep water such as seas or

oceans. Offshore wind turbines are much larger than onshore wind turbines, producing up to

6 megawatts of electricity a day.

Vertical-Axis Wind Turbine: A wind turbine where the blades rotate around an axis that is

perpendicular to the ground. Vertical-axis wind turbines are often described as resembling

egg-beaters.

Horizontal-Axis Wind Turbine: A wind turbine where the blades rotate around an axis that

is parallel to the ground. Horizontal-axis wind turbines are more common that vertical-axis

turbines, and usually contain three blades.

Hub Height: The height from the ground to the center of the hub the blades rotate around on

a horizontal-axis wind turbine.

Rotor Diameter: The diameter of the circular arc produced by the rotation of the blades.

Wind Turbine Mean Power Output: The average amount of energy produced by a wind

turbine or wind energy facility over a given period of time for an average wind speed, usually

measured in megawatts or kilowatts.

Megawatts (MW): One million watts, or one thousand kilowatts of energy.

Kilowatts (kW): One thousands watts of energy.

Watts (W): The amount of energy used or produced by an object.

Mean Wind Speed or Velocity: The average rate over a period of time of the flow of wind

with no blocking obstacles such as buildings or vegetation.

56

APPENDIX B

57

REFERNCES:

[1] Reliability of Wind Turbines Experiences of 15 years with 1,500 WTs Berthold Hahn, Michael Durstewitz, Kurt Rohrig,

Institut für Solare Energieversorgungstechnik (ISET), Verein an der Universität Kassel e.V., 34119 Kassel, Germany.

[2] SANDIA REPORT (20060), Unlimited Release, Printed March 2006 Wind Turbine Reliability: Understanding and

Minimizing Wind Turbine Operation and Maintenance Costs - Christopher A. Walford Global Energy Concepts, Prepared

by Sandia National Laboratories

Albuquerque, New Mexico 87185 and Livermore, California 94550

[3] http://www.flapturbine.com/hawt_power_change_efficiency.html

[4] http://warlock.com.au/030504.htm

[5] Modeling of Wind Power Plants for Short Circuit Analysis in the Transmission Network (2008), Nader Samaan, Member,

Robert Zavadil, Member, J. Charles Smith, Senior Member, and Jose Conto, Member, IEEE , 978-1-4244-1904-3/08/$25.00

©2008, IEEE.

[6]http://cdn.intechopen.com/pdfs-wm/16242

[7] (http://en.wikipedia.org/wiki/Wind_turbine_design)

[8] (http://en.wikipedia.org/wiki/High-altitude_wind_power)

[9] (journal homepage: www.elsevier.com/locate/jweia)

[10]http://web.mit.edu/windenergy/windweek/Presentations/Wind%20Energy%20101

[11]http://www.springer.com/cda/content/document/cda_downloaddocument/9781447122005-c2.pdf?SGWID=0-0-45-

1269248-p174177563

[12]http://www.ocgi.okstate.edu/owpi/educoutreach/library/lesson1_windenergycalc.

[13]http://www.nrel.gov/wind/systems_engineering/pdfs/02_2_ning_aning_optimization

[14] Soren gundtoft “wind turbines”, University college of Arhus, 2nd edition, page 16, June 2009.

[15] Peter J. Schubel * and Richard J. Crossley, "Wind Turbine Blade Design" , Energies journal, page 12, September 2012.

[16] John McCosker “Design and Optimization of a Small Wind Turbine”, Rensselaer Polytechnic Institute ,Hartford, Connecticut, page 14

December 2012

[17] (International Journal of Mechanical Engineering ISSN : 2277-7059 Volume 2 Issue 2)

[18]Modelling and Simulation of a 12 MW Active-Stall Constant-Speed Wind Farm by Lucian Mihet-Popa1 and Voicu Groza2

http://cdn.intechopen.com/pdfs-wm/16242

http://en.wikipedia.org/wiki/Wind_turbine_design

http://en.wikipedia.org/wiki/High-altitude_wind_power

http://www.elsevier.com/locate/jweia

http://web.mit.edu/windenergy/windweek/Presentations/Wind%20Energy%20101

http://www.springer.com/cda/content/document/cda_downloaddocument/9781447122005-c2.pdf?SGWID=0-0-45-1269248-p174177563

http://www.springer.com/cda/content/document/cda_downloaddocument/9781447122005-c2.pdf?SGWID=0-0-45-1269248-p174177563

http://www.ocgi.okstate.edu/owpi/educoutreach/library/lesson1_windenergycalc

http://www.nrel.gov/wind/systems_engineering/pdfs/02_2_ning_aning_optimization

58

Some References:

Tool kit for assessment of site location of Pakistan

http://www.nrel.gov/international/geospatial_toolkits.html

Wind energy Assessment:

http://www.3tier.com/en/products/wind/asset-management/

Wind speed minimum: 3m/s

http://defence.pk/threads/feasibility-report-pakistan-has-a-potential-of-50-gigawatts-of-wind-

power.296265/

http://www.nrel.gov/international/geospatial_toolkits.html

http://www.3tier.com/en/products/wind/asset-management/

http://defence.pk/threads/feasibility-report-pakistan-has-a-potential-of-50-gigawatts-of-wind-power.296265/

http://defence.pk/threads/feasibility-report-pakistan-has-a-potential-of-50-gigawatts-of-wind-power.296265/

59

Section Point

Breakdown

Points

Earned

Title Page 2

Table of Contents 2

List of Figures and Tables 2

Report Body 89

Introduction: Follow the guidelines in the Wind Turbine Report guideline to give a

summary in “Introduction Section” of your work. This summary should

demonstrate the importance and justification of your report.

10

Wind Turbine Design & Modeling and Simulation: Add your calculations as

discussed in Report template and your submitted design calculations. Also

incorporate the above mentioned points in this section.

14

Results: Provide the results of the project, in the form of tables, calculations, and

figures, with brief explanations of the data

The following results should be included with accompanying data and graphs.

20

Conclusion and Recommendations: Develop a conclusion from the results

obtained in the Wind Turbine Project and provide any recommendations for

design improvement.

15

Writing Style 15

Grammar: See Technical Communication Guide for guidelines. 10

Organization and Progression: make sure the summary has natural breaks, ideas

are properly separated by paragraphs and topic sentences, and ideas are fluently

connected.

5

Appendix 5

Provide the Wind Turbine Checklists along with any other relevant results not

addressed in the Results section. Format the additional results in accordance with

the Technical Communication Guide.

Note: Attach this Grading Assessment with your final report document

Documents

10-ME-04 FINAL