FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
1. INTRODUCTION
Wind energy is one of the most important types of renewable energy using which is
inevitable in today’s world. Using this energy has been taken into consideration from the
past and first it was used as windmills for daily use and now, in developed countries, it is
utilized in different kinds of wind turbines with multi-megawatt power of energy
generation. In our country, extreme reliance to non-renewable resources and production of
pollutions in metropolises has encouraged the researchers and officials to find a renewable
replacement, which is dependent on the construction and designing of wind turbines
through the available technologies. Currently two kinds of wind turbines, among different
designs considered by the designers, are horizontal axis wind turbine (HAWT) and vertical
axis wind turbine (VAWT), used mainly to generate power. In comparison, each one has
its own advantages and disadvantages. Some advantages of vertical axis turbine are easy
designing and construction, lower cost, no need to rotor yaw mechanism (Yaw) to find that
wind direction and sound pollution and ecosystem damage reduction. Among its
disadvantage are less efficiency, power production with higher fluctuation, lower speed of
the blades and lower energy yield.
However, there are also downfalls to the VAWT. Firstly, boundary layer affects from the
ground influence the air stream incident on the VAWT, which in some cases leads to
inconsistent wind patterns. Secondly, VAWT are not self - starting currently, an outside
power source is required to start turbine rotation until a certain rotational speed is reached.
The global need for energy increases as our civilization ages. Homes that once were
powerless are now connecting to an electricity grid. New homes are being built as the world
population grows. These new homes also require power from an aging electricity grid, a
supplemental system is required. This system will offset cost reduction to power my home
and in turn reduce the load on the existing electricity grid. If this idea were to be adopted
by others, then the negative impact of additional energy plants on the environment can be
reduced. This project determines the optimal size for a wind turbine to supplement power
requirement to light at least a bulb in single household. The system design requirements
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for the desired wind turbine system are identified in this project. This project documents
the processes required for designing and implementing a wind turbine system.
Classification of Wind Turbine According to Axis;
(i) Vertical Axis Wind Turbine
(ii) Horizontal Axis Wind Turbine
Horizontal-Axis Wind Turbines (HAWTs) contains blades which are attached to a central
perpendicular to axis shaft. The shaft is attached to an alternator located at the bottom of
the shaft, sometimes even at ground level. When the blades rotate, they spin the rotor of
the generator, producing electricity. In this type the main rotor shaft is set vertically and
the main components are located at the base of the turbine. Though it provides enough
power source but still it is less advantages than vertical axis wind mill/turbine.
Vertical-Axis Wind Turbines (VAWTs) are a type of wind turbine where the main rotor
shaft is set traverse, not necessarily vertical, to the wind and the main components are
located at the base of the turbine. This arrangement allows the generator and gearbox to be
located close to the ground, facilitating service and repair. VAWTs do not need to be
pointed into the wind, which removes the need for wind sensing and orientation
mechanisms. Major drawbacks for the early designs (Savonius, Darrieus and giromill)
included the significant torque variation during each revolution, and the huge bending
moments on the blades. Later designs solved the torque issue by providing helical twist in
the blades. A VAWT tipped sideways, with the axis perpendicular to the wind streamlines,
functions similarly. A more general term that includes this option is "transverse axis wind
turbine".
In today’s scenario the world had been developed by the technologies like microcomputer,
3G, 4G devices, sixth sense devices etc. By using these we can communicate from any
corner of the world. if we think which leads this technology development means the
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solution takes us to the root and say’s “Energy” so without energy nothing will move in
this world.
In this 21st century there are more methods to produce energy. Some of them are
ecofriendly and some of them might be pollutable. Once we aim to produce energy by
ecofriendly means the best idea is by using renewable energy. In renewable energy field
sector, the windmill plays an important role in energy production.
The present design of windmill might not be implemented in our normal surroundings. As
it is not suitable for all wind direction and it gives partial efficiency and also increase in
cost of design, installation, and maintenance. To overcome all these problems a new unique
method of wind is to be introduced. This paper has kept one step forward of windmill
technology with use full application.
The main aim of this project paper is to produce energy by using renewable energy
resources in that manner the wind is very much eco-friendly and very compactable one. By
using that energy in a useful manner we can produce a continuous power. The main
advantage of VAHW is it can generate power in all direction of wind flow. And the other
advantages are the maintenance are less and the height of the tower is less.
This VAHW is a new method which overcomes the previous windmill problems. By
adjusting the windmill blade, it suits itself with efficient energy generation in all direction.
Wind turbines produce rotational motion; wind energy is readily converted into electrical
energy by connecting the turbine to an electric generator. A step-up transmission is usually
required to match the relatively slow speed of the wind rotor to the higher speed of an
electric generator.
In Indian the interest in the windmills was shown in the last fifties and early sixties. A part
from importing a few from outside, new designs was also developed, but it was not
sustained. It is only in the last few years that development work is going on in many
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institutions. An important reason for this lack of interest in wind energy must be that wind,
in India area relatively low and vary appreciably with the seasons. Data quoted by some
scientists that for India wind speed value lies between 5 km/hr. to 15-20 km/hr. these low
and seasonal winds imply a high cost of exploitation of wind energy. Calculations based
on the performance of a typical windmill have indicated that a unit of energy derived from
a windmill will be at least several times more expensive than energy derivable for electric
distribution lines at the standard rates, provided such electrical energy is at all available at
the windmill site.
The above argument is not fully applicable in rural areas for several reasons. First electric
power is not and will not be available in many such areas due to the high cost of generation
and distribution to small dispersed users. Secondly there is possibility of reducing the cost
of the windmills by suitable design. Lastly, on small scales, the total first cost for serving
a felt need and low maintenance costs are more important than the unit cost of energy. The
last point is illustrated easily: dry cells provide energy at the astronomical cost of about
Rs.300 per kWh and yet they are in common use in both rural and urban areas.
Wind energy offers another source for pumping as well as electric power generation. India
has potential of over 20,000 MW for power generation and ranks as one of the promising
countries for tapping this source. The cost of power generation from wind farms has now
become lower than diesel power and comparable to thermal power in several areas of our
country especially near the coasts. Wind power projects of aggregate capacity of 8 MW
including 7 wind farms projects of capacity 6.85 MW have been established in different
parts of the country of which 3 MW capacities has been completed in 1989 by DNES.
Wind farms are operating successfully and have already fed over 150 lakes units of
electricity to the respective state grids. Over 25 MW of additional power capacity from
wind is under implementation. Under demonstration programmer 271 wind pumps have
been installed up to February 1989. Sixty small wind battery charges of capacities 300
watts to 4 kW are under installation.
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Wind result from air in motion. Air in motion arises from a pressure gradient. On a global
basis one primary forcing function causing surface winds from the poles toward the equator
is convective circulation. Solar radiation heats the air near the equator, and this low density
heated air is buoyed up. At the surface it is displaced by cooler denser higher pressure air
flowing from the poles. In the upper atmosphere near the equator the air thus tend to flow
back toward the poles and away from the equator. The net result is a global convective
circulation with surface wins from north to south in the northern hemisphere.
It is clear from the above over simplified model that the wind is basically caused by the
solar energy irradiating the earth. This is why wind utilization is considered a part of solar
technology. It actuality the wind is much more complex. The above model ignores the
earth’s rotation which causes a Coriolis force resulting in an easterly wind velocity
component in the northern hemisphere. Wind farms are operating successfully and have
already fed over 150 lakes units of electricity to the respective state grids. Over 25 MW of
additional power capacity from wind is under implementation.
Under demonstration programmer 271 wind pumps have been installed up to February
1989. Sixty small wind battery charges of capacities 300 watts to 4 kW are under
installation. Likewise, to stand-alone wind electric generators of 10 to 25 kW are under
installation. Wind energy is the fastest growing source of clean energy worldwide. This is
partly due to the increase in price of fossil fuels. The employment of wind energy is
expected to increase dramatically over the next few years according to data from the Global
Wind Energy Council. A major issue with the technology is fluctuation in the source of
wind. There is a near constant source of wind power on the highways due to rapidly moving
vehicles. The motivation for this project is to contribute to the global trend towards clean
energy in a feasible way. Most wind turbines in use today are conventional wind mills with
three airfoil shaped blades arranged around a vertical axis. These turbines must be turned
to face into the wind and in general require significant air velocities to operate. Another
style of turbine is one where the blades are positioned vertically or transverse to the axis
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of rotation. These turbines will always rotate in the same direction regardless of the fluid
flow.
A very novel way of re-capturing some of the energy expended by vehicles moving at high
speeds on our nation’s highways. We know how much air turbulence is generated by
vehicles moving at speed particularly trucks. This would involve mounting vertical axis
wind turbines at the center of the roads that would be driven by the moving air generated
by the passing traffic. The excess energy generated could be fed back into the grid or power
up the villages nearby. While we’ll never recover much of the energy wasted pushing air
out of the way of a sixteen wheeler, even a fraction could be a significant source of power.
Average vehicle speeds on the valley highways are approximately 70 mph. This power
production estimate will increase exponentially with an increase in wind turbulence speed.
We believe that the wind stream created over the freeways by our primary mode of
transportation will create an average annual wind speed well beyond the baseline of 10
mph. Consideration of the flow velocities and aerodynamic forces shows that, nevertheless,
a torque is produced in this way which is caused by the lift forces. The breaking torque of
the drag forces in much lower, by comparison. In one revolution, a single rotor blade
generates a mean positive torque but there are also short sections with negative torque.
Based on the air flow profile, an analysis will be done whether displaced air can able to
rotate the air wind. The utilization of wind to generate power provides an alternative and
renewable energy source compared to current fossil fuels based power generation. The
world's fossil fuel energy is finite and is depleting at a faster rate. Moreover, the fossil fuel
is directly related to air pollution, land and water degradation. Despite significant
progresses have been made in power generation using large scale wind turbines recently,
domestic scale wind turbines especially vertical scale wind turbines have been received
less attention which have immense potentials for standalone power generation.
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Wind energy is the fastest growing source of clean energy worldwide. A major issue with
the technology is fluctuation in the source of wind. There is a near constant source of wind
power on the highways due to rapidly moving vehicles. The motivation for this project is
to contribute to the global trend towards clean energy in a feasible way. The price of
turbines is increasing in accordance with the rising cost of energy and commodities. The
cost of designing the turbine, calculated in energy savings must be recovered in a
reasonable time period.
Each vehicle on the highway offers an intermittent and uncontrolled source of wind power.
The design of the wind turbine must include storage of power and a system to distribute
the generated power effectively. Operational noise level and space are other important
design considerations. The wind turbines should have as little negative impact on the
placement location as possible. Wind turbines are traditionally used in remote locations.
This offers the additional challenge of having to transport the power generated to the
location wherein it will be utilized.
Fortunately, the wind turbine in this project is designed for use in high traffic areas where
the demand for power is high. Safety is another major design consideration. The turbines
must be placed in high traffic areas therefore several safety provisions are incorporated into
the design. These safety measures include stationary highway guards surrounding the
rotating turbine blades and warning labels. Lastly, on small scales, the total first cost for
serving a felt need and low maintenance costs are more important than the unit cost of
energy.
A wind turbine converts the kinetic energy in wind into mechanical energy, which will be
reflected on its axis. To convert this mechanical energy into electrical energy, the turbine
has to be coupled to an electrical generator, becoming a wind turbine. To perform this task,
several types of turbines are used, differentiated into two types by the position of its axis
of rotation with respect to the surface on which it is fixed, and can be then Horizontal Axis
Wind Turbines (HAWT), the most common turbines, used mostly in wind farms for high-
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energy production, and Vertical Axis Wind Turbines (VAWT), latter less common and
currently are the subject of numerous studies and developments of new models. Within the
VAWT’s, there are two types, differentiated by the morphology of their blades.
Savonius type or S turbine, created in 1922, is composed of two circular cross-sections
blades, one placed concavely and one convexly towards the wind position and vertically
arranged along an axis of rotation with the particular feature that the blades are overlapping
in the vicinity of the rotation axis, making the effect of support by exchanging the flow
between both blades, thus achieving assistance for the starting factor that receive both
blades to be positive in the wind direction and thereby getting movement.
The second type of VAWT is the Darrieus type, which was created in 1931, has the
particularity that the blades are aerodynamically shaped, usually NACA style, with
different layouts and with a certain distance from the axis of rotation. Among the VAWT,
the substantial differences between them are: The Savonius Wind Turbine, starts at lower
velocities than the Darrieus one, in fact, Darrieus Wind Turbines need electric support in
order to boot, and its removal rates are 4-5 m/s, while the Savonius wind starts at 1 m/s or
even lower. In order to exploit these starting properties from each of the technologies, there
are hybrid turbines, which consist of two turbines; a Savonius type for starting at low speed,
and therefore saving power supply necessary for the second turbine starter, one Darrieus
type, which obtains a power coefficient (CP) higher than the Savonius type at high speed
winds. The CP is one of the other differences, being higher those obtained in studies for
Darrieus Wind Turbine, and can reach values close to 0.4, compared to 0.3 which can reach
a Savonius Wind Turbine. As regards the differences between HAWT and VAWT wind
turbines with capacities below 10 kW, these include:
(i) They do not need to be at great height to produce energy, since they boot at low
wind speeds.
(ii) They generate electric power at high and very high wind speeds, at which the
horizontal axis generators would not work for possible damage.
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(iii)They are easy to install and a very low maintenance and easier than the horizontal
axis ones since the generator is located at the lower part of the structure, making it
easier to access it when you perform any maintenance.
(iv) They produce a low or zero noise pollution, which means that it can easily be
adapted to urban noise pollution regulations.
(v) They could be assembled several wind turbines on a small surface since they do not
need to keep large distances between them because of the lack of braking air
production.
(vi) They provide us wide ranges of benefit from recoverable wind energy in buildings,
facades and in any urban area where low altitude winds are remarkable and the
construction of a conventional wind farm is unfeasible.
(vii) They do not imply a visual impact, as they suit to images that can be viewed at
any building or urban area.
In Spain the use of these technologies for small productions isn’t exploited in practice, it
does not even have a specific regulatory framework, while in some countries around us
(Portugal, Italy and France), have specific regulations for small wind energy. In more
advanced nations, such as the UK, they have set a target for 2050, this is that the country's
electricity production will be 30-40% from distributed generation in buildings through the
program "Low Carbon Buildings". UK currently has about 100,000 micro-generation
facilities and producers even receive tax incentives. It should be noted that the European
Union, through the directive 2009/28/EC of European Parliament, set that a minimum of
20% of the energy consumed should be from renewable energy in 2020, and Spain as a
member state must comply legislation and this technology help to meet that goal.
Although predicting the future based on data is not always fully conclusive, we can deduce
that: The VAWT technology is sliding into the use in small generating installations,
especially in urban environments that currently have winds that are not exploited. There
are studies about the omnidirectional-guide-vane which make power, speed and torque
increase markedly in these sorts of environments. Employing Wind VAWT in / PV hybrid
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power generation system can be the solution at many locations since the cost of this system
is considered to be lower than the use of both individual technologies. About the studies
devoted to the types of optimal generators for producing electricity from wind energy in
urban environments it can be drawn that the desired features are:
(i) Low cogging torque.
(ii) Very high electrical and mechanical efficiency (including the operation of main
charge).
(iii) Compact size and high specific torque / power.
(iv) Lower noise and vibration.
(v) Cheap and easy to manufacture and install.
These features are collected in a prototype of the University of Bristol, which may be the
type of generator to be used in the future, a permanent magnet generator (PMG), axial flow
and direct drive of 50 kW, with peak power 48 kW at 500 rpm and have achieved an
efficiency of 94%. The possibility that this type of design is scalable, together with its low
maintenance and compact size, opens up to the use of many powers and sizes in wind
turbines and can be used in all kinds of applications. In the design field of turbine geometry,
it seems to the helical arrangement of the blades, as has been verified by simulation using
numerical methods, the helical increases the power coefficient in comparison with the
straight arrangement of the blades increasing from 33% to 42% under the same operating
conditions. Within the geometry field, it would tend to the increase in the number of blades,
the use of different airfoils, the blade pitch angle range and the use of deflectors. Due to
the high cost and risk involved in the physical realization of a model to be submitted to the
testing necessary to meet the various operating parameters as well as how changes in the
environment and morphology evidence bearing on this, numerous studies have been
devoted, through computer programs and various calculation methodologies, to try to
improve the performance and efficiency of VAWT, and this will continue until noticeable
results are achieved and someone bets by the use of technology.
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For high volume productions using the technology HAWT large wind turbines will remain
the most common used technology, as yields and production are higher when compared
with the VAWT. But the use of VAWT small wind farms is not excluded, as it has been
concluded that, contrary to what happens to the HAWT. The closer they are between them,
the lower power coefficient they get, under certain provisions of proximity, VAWT
increases it. This does not exclude the situation of small VAWT wind farms on the roofs
of buildings or in high places either urban or rural environments. It would be a little
unconscious placing VAWT rather than HAWT in places where the latter generate more
production, even having VAWT that reach 4MW, as the case of hole, located in Cap Chat,
Quebec, Canada and with a height of 110 meters and 96 meters in diameter, is the largest
ever VAWT installed. We must remember that nowadays there are HAWT whose heights
are close to 130 meters and close to 100 meters in diameter that can generate up to 10MW
such as the case of offshore wind turbines last generation, such as the Sea Titan of USA
company AMSC or ST10 of the Norwegian company Sway, which is compatible for both
fixed and floating installations.
The use of VAWT for offshore situation for great productions is discarded, but it can be
said that the use of offshore ones can be designed to supply weather buoys and boats, either
individually or through a wind hybrid system.
Power production from wind technology has evolved very rapidly over the past decade.
Capital costs have plummeted, reliability has improved, and efficiency has dramatically
increased, resulting in robust commercial market product that is competitive with
conventional power generation. Investments in R&D as well as the development of robust
standard design criteria have helped to mitigate technology risk and attract market capital
for development and deployment of large commercial wind plants. High-quality products
are provided by every major turbine manufacturer. Complete wind generation plants are
now being engineered to seamlessly interconnect with the grid infrastructure to provide
utilities with a dependable energy supply, free of the risks of future fuel price escalation
inherent in conventional generation.
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No major technical breakthroughs in land-based technology are needed for a broad
geographic penetration of wind power on the electric grid. Advancement requires a systems
development and integration approach, reflecting the high level of engineering already
incorporated into modern machines. No single component improvement in cost or
efficiency can achieve significant cost reductions or dramatically improved performance.
Capacity factor can be increased over time using enlarged rotors on taller towers. Market
incentives will remain necessary to sustain the industry growth in the near term, but in the
longer term subsidies can probably be eliminated. In addition, with continued R&D,
offshore wind energy has great potential to allow the United States to greatly expand the
contribution from wind in its electrical energy supply.
The transportation industry consumes about 28% of total energy consumed by all sectors
in the United States. According to the EIA Annual Energy Outlook 2010, the transportation
sector consumes more than 600 million kilowatt hours (kWh) every month. Innovations in
green transportation can significantly reduce the sector’s energy demand. This can
eventually reduce the energy production cost, offset the need of building new power plants,
and reduce pollutants from generating electricity with fossil fuels. The city of Lincoln,
Nebraska, has 418 signalized intersections under its jurisdiction. The total electricity
consumption at these intersections is nearly 92,500 kWh per month. Electricity
expenditures account for 5% of the city’s traffic operating budget. The electricity price
charged by the local utility provider, Lincoln Electric System (LES), usually changes once
per year.
The annual inflation rate for utility prices in Lincoln, as stated by LES personnel, is
between 2.5-3%. This utility price can inflate by as much as 17% if the Cap and Trade bill
is approved in the U.S. Renewable electric energy generated by an existing transportation
infrastructure will cut the energy purchased to operate and maintain the roadway systems,
and will therefore reduce operating costs of the transportation agency. This paper proposes
a renewable wind power system (RWPS) which includes a grid-connected wind turbine
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installed on a traffic signal pole and a battery bank to be housed in an existing traffic signal
cabinet. The proposed RWPS has two benefits:
(i) The power generated by the system can support the existing traffic signals and any
excess power produced can be sold back to the power grid.
(ii) The reliability of traffic operations will be enhanced due to the presence of backup
power in the case of the grid failures.
The structural and economic feasibility of an RWPS are investigated. Methodologies have
been developed to estimate costs and economic benefits of the system. These
methodologies can be used by agencies to evaluate the economic practicality of an RWPS
and streamline investments to potentially more productive sites. Outlines the overall
procedure for the analysis. The numbering next to the headers indicates the section that
will have an in-depth discussion on that specific topic.
Fig. 1.1 Structural Diagram of Blade and its Assembly
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1.1 Problem Statement
In day to day life, electricity is one of the major requirement in each and every aspect of
life. The production of electricity in India is far away less than its consumption. To
eliminate the problem of cut off electricity or load shedding problems can be done with an
increase in electricity production providing sufficient power to industrial, commercial,
household applications.
The cost of generation of electricity by conventional process is comparatively high. To
reduce this cost, use of unused energy from sunlight, wind, tides of water, etc. can be used.
In this project we are using the wind energy generated by the vehicle moving on a highway
producing large amount of air velocity (up to 120 m/s) to generate sufficient amount of
electricity required to fulfill the power requirement to enlighten the roads by means of
street lights.
Hence, the problem of low production to consumption, load shedding and cost requirement
to generate electricity can be reduced.
1.2 Objective
In this project work, we were planning for design and fabricate a vertical axis highway
wind turbine which will produce electric energy as an output source and further with the
help of electricity distribution system we will be transmitting the power to other
equipment’s installed.
The objectives of this project are,
(i)
Incorporation of more renewable energy to the power system.
(ii)
Design of a new method of generation of electricity using the wind energy
generated by the moving vehicles on the highways.
(iii)
Development Stand-alone system for providing the power to the highways.
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(iv)
To determine air profile of airflow around moving vehicle on open roads.
(v)
To design a wind turbine to be placed on the open roads.
(vi)
To determine the amount of electricity be generated by wind turbine.
(vii) The overall conversion efficiency of the rotor, transmission system and generator
or pump.
1.3 Scope
The study will emphasize on large vehicles (bus), medium vehicles (MPV) and small
vehicle (sedan car) and determining profile of airflow around moving vehicle on open road
(highways) based on India’s standard climate and wind situation. These turbines can be
installed on Highways, Expressways, Runways of Air-crafts. Installation of Vertical Axis
Wind Turbine may be possible in between two consecutive railway tracks where both the
tracks are used to pass the train in opposite direction.
Following are the scope or limit of the study:
(i)
Development of 3D model of the selected vehicles by using Solid Works
Software.
(ii)
Simulation of an air flow (using Ansys software) around single moving vehicles
(in open roads) ME-03.
(iii)
Simulation of air flow around two vehicles in the front – rear and side by side
positions (in open roads).
(iv)
Determine the amount of electricity be generated by wind turbine.
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1.4 Methodology
The methodology of design for the design of Vertical Axis Highway Wind Turbine is
explained by following steps,
Problem Statement
Objective and Scope
Selection of Blade Material
1. Material 2. Strength 3. Stress
Design of System
1. Frame 2. Battery 3. Inverter 4. Generator
Result
Implementation
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1.5 Activity Sheet
Table No. 1.1 Activity Sheet
Sr.
Month
July
Aug Sept
Oct
Nov
Dec
No.
Act.
Plan
1.
Group
Formation
2.
Project Area
3.
Project Idea
4.
Final Topic
Selection
5.
Create
Synopsis
6.
Guide
Finalization
7.
Phase-1
8.
Phase-2
9.
Phase-3
10.
Phase-4
11.
Material
Selection
12.
Design and
Assembly
13.
Make
Report
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Jan
Feb
March
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2. LITERATURE REVIEW
Champagnie et. al. (2013) concluded, extensive data was collected on wind patterns
produced by vehicles on both sides of the highway. Using the collected data, a wind turbine
is designed to be placed on the medians of the highway. Although one turbine may not
provide adequate power generation, a collective of turbines on a long strip of highway has
potential to generate a large amount of energy that can be used to power streetlights, other
public amenities or even generate profits by selling the power back to the grid. This design
concept is meant to be sustainable and environmentally friendly. Additionally, a wind
turbine powered by artificial wind has a myriad of applications. Theoretically any moving
vehicle can power the turbine such as an amusement park ride. The highway wind turbine
can be used to provide power in any city around the globe where there is high vehicle
traffic.
Ambrosio et. al., (2010) carried a preliminary economic analysis, in order to figure out if
Vertical Wind project is competitive in the present market of wind power turbines. This is
the easiest option for economic analysis, but since many of the values are approximations,
it would be useless to perform further and deeper analysis. Starting from a real project of a
2 MW Enercon with a PBT of 9,44 years, the aim of the calculation is to find which price
of the VAWT turbine leads to the same value. Two cases are investigated: the small 200
kW type and the 2 MW commercial size, both for a lifetime of 20 years. It’s important to
note that some costs are the same for both HAWT and VAWT, while others are very
different. For example, it’s possible to say that foundations are cheaper for a VAWT
because on equal installed power the tower is lighter and smaller, being the generator and
most of the weight at ground level. The O&M costs are also lower, because of the same
reason and also because a PMSG generator requires less maintenance than other types.
Roy et. al., (2014) designed and fabricated vertical axis economical wind mill and reinforce
the conviction that vertical axis wind energy conversion systems are practical and
potentially very contributively to the production of clean renewable electricity from the
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wind even under less than ideal sitting conditions. It is hoped that they may be constructed
used high strength, low-weight materials for deployment in more developed nation and
settings or with very low tech local materials and local skills in less developed countries.
The wind turbine designed is ideal to be located on top of a bridge or bridges to generate
electricity, powered by wind. The elevated altitude gives it an advantage for more wind
opportunity. With the idea on top of the bridges, it will power up street lights and or
commercial use. In most cities, bridges are a faster route for everyday commute and in need
of constant lighting makes this an efficient way to produce natural energy.
Niranjana et. al., (2015), VAWT was designed and fabricated in such a way that the it can
able to capture wind from all the direction, power developed from the project is 1W for a
speed of 25m/s, the efficiency of VAWT can be increase by changing the size and shape
of the blade, the theoretical and experimental result is varying because in theoretical
calculation we consider the wind is hitting all the three turbine blades, practically it is
hitting only one turbine at a time.
Aashrith et. al., (2014) came to a conclusion that Vertical axis wind energy conversion
systems are practical and potentially very contributive to the production of clean renewable
electricity from the wind even under less than ideal sitting conditions. It is hoped that they
may be constructed used high-strength, low- weight materials for deployment in more
developed nations and settings or with very low tech local materials and local skills in less
developed countries. The Savonius wind turbine designed is ideal to be located on top of a
bridge or bridges to generate electricity, powered by wind. The elevated altitude gives it
an advantage for more wind opportunity. With the idea on top of a bridge, it will power up
street lights and or commercial use. In most cities, bridges are a faster route for everyday
commute and in need of constant lighting makes this an efficient way to produce natural
energy.
Kalyani et. al., (2015) wrote in his report for utilizing green energy and stated that Mankind
has started its journey to cover long distance by foot, slowly they invented wheel and that
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gives mankind the speed and power to shorten the long distances the travel time was cut
down to days and month from months to year. After the inventing the wheel the second
best idea was to develop roads on which the vehicle can travel easily as the advancement
of time we have fast moving vehicles all over the world and world class highways to ride
on it. Now, there is a need to make the highways a smart highway. A Smart highway is the
need of present time because a lot of energy is required to illuminate the highway at night
we can use Green energy and other supportive technologies like 5G, IoT , Cloud computing
for faster data communication and rapid action taking as and when demanded, altogether
there is a lot of scope on Indian highways specially to be converted into smart highway, as
it is well placed geographically it has abundant sunlight and other green resources,
population can also be used as a source of power generation like the vibration energy that
can be generated through moving on the “green path” so that the power can be collected
into storage batteries and that could be used at night. It is not a new concept people in the
other part of the world are already using these technologies. Everything in this world has
been smarten up i.e. smart cars, smart houses etc. but not highways, they are still of tarmac
and for same purpose of connecting one place to another. From this paper we are trying to
give an attention to innovating ideas that has been developed to make highways smart. We
can use the wide space of highway for electricity generation through solar panels and
windmills. By using the sensors, we can lighten up the streets of particular section through
which vehicle passes. New illuminating paints has been developed replacing street lights.
Vibration produced by vehicles are converted into electric energy. As all these vehicles are
running on non-renewable fuels generating pollution so green energy is the best substitute.
Fossil fuels are also used these days but limitedly available in nature and it also causes air
pollution. So electric vehicles are best option to make environment free from vehicle
pollution.
Chavda et. al., (2013) designed and fabricated a highway wind turbine and concluded that
a vertical axis highway turbine gives an idea about the new way of power generation and
also about a new windmill technology. The power generation using VAHT is an
ecofriendly method and power produced here is almost a continuous one. By using this
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technology all the highways can be lightened without use of non- renewable energy
resources. And if this method is implemented in all national highways we will able to
reduce use of large amount of conventional power and it will also save the environment
from pollution.
Kumar et. al., (2012) installed Savonius vertical axis wind turbine at open road side
(highway) to generate renewable electricity and Based on the CFD analysis and Analytical
Method result, it indicates that the air exerted by the moving vehicles will create air
displacement around the vehicles and along the path ways which will create enough wind
speed and air distribution to rotate the wind turbine. Besides that, the numerical method
shows that the amount of power produced by single SVAWT and it can be increased if
there are many SVAWT are being placed along the highway side and road tunnels. The
diameter of the total turbine will be 1m so that it will be cost saving and will not distract
motorists view. The mechanical power produced based on single Savonius Turbine
performance can be increased if more turbines are installed at the side ways and the center
of the path ways. The mechanical power (generated by rotating Turbine) shows that the
value of power increases when the speed of the vehicles is increasing. It also shows that
the location of wind turbine (at sideways and middle of path ways) does rotate due to the
air dispersed. It shows that the moving bus does helps the turbine to exert the most
mechanical power and concludes that it produces more Electric energy. The excellent
agreement of the analytical results and also the CFD result supports the objectives and
scope where by the air profile that was created by the moving vehicles can produce enough
wind speed to rotate the selected turbine design.
Devi et. al., (2012) designed and developed a prototype highway lighting with road side
wind energy harvester and concluded the cost effective, green energy source for power
generation can help to reduce power requirement. An efficient hybrid wind turbine is
designed to be use in road side application for energy generation. This turbine is specially
designed for road side applications which generate energy by utilization of natural wind
and wind turbulence. A microcontroller operated effective charge controller has been
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developed. Charge controller charge battery from generated voltage and utilize this energy
for later use. The presented system is cost effective, ready to use and user friendly system
which used to serve specifically in highway lightning system. It is very useful in the areas
which have heavy traffic on road without congestion. With the help of public aids, this
system can be used to facilitate many houses and home and will be very handy for
implementation.
Rathod et. al., (2014) designed a PVC bladed horizontal axis wind turbine for low wind
speed region and wrote in his report the present work demonstrates that PVC blade profile
has better power capacity. Creates scope for designing & Performance evaluation of a
specially designed micro wind turbine for area especially in plateau region where velocity
of wind is low, invariable average and dry, so where large wind turbine doesn’t give
satisfactory result. The small wind turbine and their wide scope of application need the
comprehensive attempt to be taken place. The small wind turbine i.e. multi blade turbine
with increase in number of blades can be run successfully with proper adjustment of swept
area and angle of attack. The advantage of the micro wind turbine is that, apart from its
low cost, it can be propelled by a wind speed as low as 2 m/s. It is the renewable source of
energy which is the clean source. It can be installed over the houses for power generation
in our local areas because of low cost and being of economical. Using of small wind
turbines for house hold would result in fewer burdens on grid and also plays a vital role in
reducing utilization of conventional energy and mobility to utilize the power.
Zhao et. al., (2013) stated in his report and proposed an RWPS as alternative power source
for traffic control signals. The proposed system will potential lead to following benefits at
suitable sites:
(i)
It will reduce the power purchased to operate and maintain the roadway systems,
which will reduce operating costs.
(ii)
It will provide a source of backup power for the transportation system. This will
reduce the risk of blackouts in case of catastrophic events.
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(iii) The system will utilize existing public right-of-way and roadway infrastructure.
The electricity production can be used locally and does not need extra investment
in power distribution systems.
(iv) The renewable energy production will reduce air pollution and contribute to
sustainable development of our society.
A disadvantage of the proposed technology is that feasible locations are limited by the
availability of wind resources. Some urban and suburban areas may not have sufficient
wind resources to provide efficient power generation. Methodologies were developed to
check the feasibility and conduct a benefit-to-cost analysis. This ratio can help in decisionmaking regarding RWPS applications. The intersections can be prioritized based on the
benefit-to-cost ratio to use budgets most effectively. The methodologies of this analysis
can be also used to evaluate different battery backup systems for traffic control signals.
The case study proved the RWPS was economically viable at the studied intersection. This
case study can directly help the local transportation agency in Nebraska to check the
benefits and costs of installing an RWPS at desired locations.
Thresher et. al., (2008) stated in his report, power production from wind technology has
evolved very rapidly over the past decade. Capital costs have plummeted, reliability has
improved, and efficiency has dramatically increased, resulting in robust commercial
market product that is competitive with conventional power generation. Investments in
R&D as well as the development of robust standard design criteria have helped to mitigate
technology risk and attract market capital for development and deployment of large
commercial wind plants. High-quality products are provided by every major turbine
manufacturer. Complete wind generation plants are now being engineered to seamlessly
interconnect with the grid infrastructure to provide utilities with 0a dependable energy
supply, free of the risks of future fuel price escalation inherent in conventional generation.
No major technical breakthroughs in land-based technology are needed for a broad
geographic penetration of wind power on the electric grid. Advancement requires a systems
development and integration approach, reflecting the high level of engineering already
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incorporated into modern machines. No single component improvement in cost or
efficiency can achieve significant cost reductions or dramatically improved performance.
Capacity factor can be increased over time using enlarged rotors on taller towers. Market
incentives will remain necessary to sustain the industry growth in the near term, but in the
longer term subsidies can probably be eliminated. In addition, with continued R&D,
offshore wind energy has great potential to allow the United States to greatly expand the
contribution from wind in its electrical energy supply.
Damota et. al., (2015) concluded that VAWT technology undoubtedly will be with us in
the future, and can be seen all around us, as has happened with other renewable
technologies for electricity production, such as HAWT and PV, thus becoming part of the
future renewable energy range and the business network, contributing to the reduction of
CO2 production and economic growth. Even after being a subject to which many studies
have been devoted, however we still have a long road ahead and certainly there continue
to be many areas to experience. That is why, after doing this article, the Department of
Energy and Marine Propulsion of University of A Coruña, have determined a preliminary
geometry for the development of a new model of VAWT, in which is working out, doing
various tests using computational methods in order to obtain optimal morphology and even
making a preliminary model prototype, thus doing their bit to the development of this
technology.
Derakhshan et. al., (2015) investigated the Aerodynamic performance of Phase VI wind
turbine. Flow around wind turbine was simulated with Navier-Stokes equations using three
difference turbulence models and results compared with experimental data. To simplify the
problem and due to the symmetry flow field, mesh was generated on one blade and similar
mesh on other blades extended. To increase the mesh density in important fields,
computation domain was divided to 16 component parts. For simulation of flow around
wind turbine blade, Navier Stokes equation used with different turbulence models include
Spalart- Allmaras, k-ε and SST k-ω. According to numerical results, at 5 to 10 wind speeds
(low speeds) three turbulence models have similar predictions in power but at higher wind
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speeds k-ε has predicted with more accuracy, so it’s best between three models. Some of
the figures showed large differences in prediction and experiment results. The reason is the
separation causes large vorticities and it’s hard for the turbulence models that investigated
in this paper to capture those. Mach number for the wind turbine was low so for more
accuracy, use of precondition was seemed helpful. In this paper Hakimi precondition was
used and results showed good agreement with actual data. Finally, for prediction of
performance of horizontal axis wind turbine, k-ε Launder Sharma turbulence model using
Hakimi precondition is suggested.
Balakrishnan et. al., (2103) modified multilevel inverter topology for grid connected
system. Multilevel inverters offer improved output waveforms and lower THD. This paper
has presented a novel PWM switching scheme for the proposed multilevel inverter. It
utilizes three reference signals and a triangular carrier signal to generate PWM switching
signals. The behavior of the proposed multilevel inverter was analyzed in detail. By
controlling the modulation index, the desired number of levels of the inverter’s output
voltage can be achieved. The less THD in the seven-level inverter compared with that in
the five- and three-level inverters is an attractive solution for grid-connected PV inverters.
Rajaprabhakaran et. al. (2015) analyzed spur gear tooth stress and stress reduction. The
main aim of their study was to relieve stress from the maximum value to as minimum as
possible. So the highest point of contact of teeth is selected as pressure application point
which causes highest stress. Stress relieving feature having a shape of aero-fin is used in
the path of stress flow which helped to regulate stress flow by redistributing the lines of
force. This also yielded better results when compared to elliptical and circular holes. In this
study, the best result is obtained by introducing aero-fin hole at (38.7653, 65.4083, 0) and
having scaling factor of 0.6. The result displayed a stress reduction by 50.23% and
displacement reduction by 45.34%.
Balu et. al. (2014) gave us an idea about the paper battery. the paper battery offers an
integrated design of the electrode and the electrolyte, the paper battery has many
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advantages over other batteries, including electrical efficiency and compactness. The
flexibility gives the paper battery a mechanical advantage in that the battery can be fit to
the electronic, instead of having to build the electronic around the battery. Such advantages
make the paper battery a good option for many applications such as smart cards and
temperature monitors. As technology trends towards thinner
electronics and electronic displays, the paper battery will play a larger role in small
electronics. While the paper battery is still in a stage of research and development, it is
clear that the paper battery will have significant impact on powering portable electronics
in the future.
Ghalamchi et. al. (2013) researched on Simple and Versatile Dynamic Model of Spherical
Roller Bearing and their study introduces a comprehensive and computationally efficient,
three-degree-of-freedom, SRB model that was developed to predict the transient dynamic
behaviors of a rotor-SRB system. The new SRB model can be used as an interface element
between a rotor and its supporting structure in an analysis of rotor dynamics. The model is
simple and useable for either steady-state or transient analyses. It takes into account the
influences of roller angular position on bearing contact forces. To verify the new bearing
model, a series of verifying numerical calculations were carried out for a single SRB
subjected to a simple radial load. Physical parameters such as contact force, bearing
displacement, elastic deformation, diametral clearance, osculation number, and the number
and arrangement of bearing rollers were examined to verify the model. The verification
calculations supported or revealed the following.
(i)
As theory predicts, roller contact forces change with increasing load. Fewer rollers
support
lower applied radial loads, and more rollers come into play as load
increases.
(ii)
Bearing displacement increases with increasing load.
(iii) Elastic deformation is not affected significantly by changes in 𝑐𝑑. Although elastic
deformation seems to be insensitive to changes in 𝑐𝑑, diametral clearance does
affect displacement between the bearing races.
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(iv) Osculation significantly affects bearing stiffness, and the force and displacement
responses are heavily dependent on bearing clearance and osculation number.
These parameters must be considered for an accurate assessment of system
performance.
(v)
SRB load carrying capacity increases with its number of rolling elements.
(vi) Even an ideal spherical roller bearing experiences varying compliance (VC)
vibration with a frequency equal to the roller-pass-outer-ring frequency of the
bearing. However, the VC effect can be reduced with an angular offset of the sideby-side roller arrays. A 11.25∘ angular shift seems to reduce the VC effect
significantly.
To demonstrate the application of the newly developed SRB model in a typical real world
analysis, a numerical simulation was carried out of a full rotor-bearing system comprising
a rigid rotor supported by SRBs on either end of the rotor axle. The governing differential
equations of motion for this specific rigid rotor-SRB system were solved numerically. The
predicted bearing displacements are consistent with the general theory of rotor dynamics.
After a brief initial transient vibration, the rotor settles into steady-state harmonic vibration
as a result of unbalanced forces. The rotor axis deflects in an elliptical orbit. Because of
the positioning of the unbalanced load, the deflections for SRB 𝐴 are greater than those for
SRB 𝐵. Elastic compression of the SRB structure seems to be only a few micrometers.
However, the elliptical orbit of rotor axis displacement shows greater displacement in the
𝑥-axis direction than in the 𝑦-axis direction. This difference is the result of bearing
clearance, which is taken up in the 𝑦-axis as the 𝑦-direction radial load acts on the bearing
and not taken up in the 𝑥-axis direction. This work can be extended in the future to include
consideration of the SRB misalignment specification. Distributed and local defects, such
as the waviness of the race surfaces or local defects in the inner and outer races, can be
included as non-idealities. Furthermore, lubrication effects can be taken into account,
especially for high operating speeds or high loads.
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Vaidya et. al., (2013) generated electrical power using Maglev windmill. The concept of
vertical axis wind turbine using magnetic levitation successfully worked. Comparing with
traditional horizontal wind turbines, single Maglev turbine having large capacity gives
more output. The turbine efficiency is improved by utilization of magnets helping to spin
with fast speed with negligible friction as it cancels out the stress on the shaft of the turbine.
This modern design of turbine gives more power output with higher efficiency compared
to conventional wind turbine. For avoiding the vibration of the rotor, shaft was used. The
standard windmills having set of 1000 windmills powers 5 lakhs homes while single
maglev wind turbine is capable supplying power to 7.5 lakhs homes. The require area for
single maglev windmill is less than 100 acres while field of 1000 windmills require more
than 64,000 acres. From this observation we can say that a single maglev wind turbine is
economical compared to Conventional Wind Turbine.
Yadav et. al. (2014) wrote that the energy requirement of the world is increasing day by
day that increases the demand of ecofriendly and low cost batteries like paper battery. A
paper battery is having a number of advantages over other energy producing devices and
has found its vast scope in future also. A lot of research work is still on the way for this
emerging technology.
Babu et. al., (2013) an attempt has been made in their paper to discuss the most-recent
research trends in the field of wind energy conversion systems. From the study, it can be
concluded that in case of generators and converters, most system adopts DFIG with backto-back converter due to their less weight and cost. However, for the large capacity wind
turbines where efficiency and reliability plays a major role has been utilizing PMSG’s even
though it has more weight and increased installation cost. Moreover, WECS based on the
multigrid concept, will become more attractive alternative technology in the future.
Regarding the controllers for the WECS, is still the most important and challenging topic
of research as there are various controllers had been proposed by various researchers has
been discussed in this paper. As there are lot of ongoing developments takes place at
various stages of WECS, it is noted that the most suitable (optimized) solutions to extract
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maximum power of the installed system is ad-hoc, rather than generalized solution. The
overview of this information highlights the current research progress in the field of wind
energy conversion system and this will be helpful for the new researchers to focus on the
above area.
Kadiran et. al. (2012) in their paper on charging and discharging methods of lead-acid
battery gave us an idea about the charging of the lead-acid battery particularly on different
electrical load acting on it. It also showed the amount of power a 12 volts lead-acid battery
can store and the time required to partially and fully charged the battery by means of a D.C.
generator.
Keerthi et. al. (2016) analyzed statics and dynamics of spur gear using different material.
They came to a conclusion that the stress values are calculated for composite materials is
approximately same as compared to the structural steel, gray cast iron and aluminum alloy.
So from these analysis results, they conclude that, the stress induced, deformation and
weight of the composite spur gear is almost same as compared to the structural steel spur
gear, gray cast iron spur gear and aluminum alloy spur gear. So, Composite materials are
capable of using in automobile vehicle gear boxes instead of existing cast steel gears with
better results. The natural frequencies of Structural Steel Spur Gear vary from 2019.7 Hz
to 6399.7 Hz. For Gray Cast Iron Spur Gear the natural frequencies vary from 1575.2 Hz
to 4990.8 Hz, whereas for Aluminum Alloy Spur Gear the natural frequencies vary from
2003.8 Hz to 6353.2 Hz. The design is safe since the frequencies obtained exceeded the
natural frequency of the spur gear (41.66 Hz).
Sonawane et. al. (2013) carried fault diagnosis of windmill by FFT analyzer and stated in
their paper various technique of fault diagnosis methods are combine with the FFT is
proposed to address non liner & non stationary fault signals of wind turbine parts. In this
study diagnosis technique of ball bearing defects, gear defects, blade defects were
investigated by vibration monitoring & spectral analysis as a predictive maintenance
tool.Ball bearing misalignment, corrosion and normal fatigue failure defects were
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successfully diagnosed by using defect frequency method. The SER algorithm recent
integrated wind monitoring system is designed to target the defection of gear related defect
within a wind gearbox. In SER algorithm was successful in demonstrating not only fault in
gearbox but also exactly which gear contain damage. For blade fault detection blade pass
frequency technique is used. From the above discussion it concluded that by using vibration
spectrum and from various techniques we can identified faults presented in windmills.
Salaisivabalan et. al. (2016) designed and analyzed a propeller shaft of an automobile using
composite materials. They concluded The Carbon/Epoxy and Glass/Epoxy composite
propeller shafts are designed to meet safe design requirements as the conventional steel
shaft. From the torsional buckling and model analysis, the deformation, Shear stress, VonMises stress, critical speed, bending natural frequency and weight are determined. In
overall comparison Glass/Epoxy composite shaft is better only in weight reduction and that
too only 1.56% lesser weight than Carbon/Epoxy composite shaft. Otherwise
Carbon/Epoxy composite shaft is better in shear stress and von-mises stress with very small
deformation and bending natural frequency of Carbon/Epoxy composite shaft is 100.9%
greater than Glass/Epoxy composite shaft. So it ticks all the boxes for a suitable material
to replace conventional steel material in an automobile shaft. Hence a Caron/Epoxy
composite shaft will be used as a propeller shaft for Maruti Omni vehicle.
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3. BASIC PRINCIPLES OF WIND ENERGY CONVERSION AND
POWER GENERATION
3.1 Nature of Wind
The circulation of air in the atmosphere is caused by the non-uniform heating of the earth’s
surface by the sun. The air immediately above a warm area expands; it is forced upwards
by cool, denser air which flows in from surrounding areas causing a wind. The nature of
the terrain, the degree of cloud cover and the angle of the sun in the sky are all factors
which influence this process. In general, during the day the air above the land mass tends
to heat up more rapidly than the air over water. In coastal regions this manifests itself in a
strong onshore wind. At night the process is reversed because the air cools down more
rapidly over the land and the breeze therefore blows off shore.
The main planetary winds are caused in much the same way: Cool surface air sweeps down
from the poles forcing the warm air over the topics to rise. But the direction of these
massive air movements is affected by the rotation of the earth and the net pressure areas in
the countries-clockwise circulation of air around low pressure areas in the northern
hemisphere, and clockwise circulation in the southern hemisphere. The strength and
direction of these planetary winds change with the seasons as the solar input varies.
Despite the wind’s intermittent nature, wind patterns at any particular site remains
remarkably constant year by year. Average wind speeds are greater in hilly and coastal
areas than they are well inland. The winds also tend to blow more consistently and with
greater strength over the surface of the water where there is a less surface drag.
Wind speeds increase with height. They have traditionally been measured at a standard
height of ten meters where they are found to be 20-25% greater than close to the surface.
At a height of 60 m they may be 30-60% higher because of the reduction in the drag effect
of the earth’s surface.
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3.2 Power in Wind
Wind possesses energy by virtue of its motion. Any device capable of slowing down the
mass of moving air, like a sail or propeller, can extract part of the energy and convert is
into useful work. Three factors determine the output from a wind energy converter:
(i)
The wind speed;
(ii)
The cross-section of wind swept by rotor; and
(iii)
The overall conversion efficiency of the rotor, transmission system and
generator or pump.
No device, however well designed, can extract all of the wind’s energy because the wind
would have to be brought to a halt and this would prevent the passage of more air through
the rotor. The most that is possible is for the rotor to decelerate the whole horizontal
column of intercepted air to about one-third of its free velocity. A 100% efficient aero
generator would therefore only be able to convert up to a maximum of around 60% of the
available energy in wind into mechanical energy. Well-designed blades will typically
extract 70% of the theoretical maximum, but losses incurred in the gearbox, transmission
system and generator or pump could decrease overall wind turbine efficiency to 35% or
loss.
The power in the wind can be computed by using the concept of kinetics. The wind will
work on the principle of converting kinetic energy of the wind to mechanical energy. We
know that power is equal to energy per unit time. The energy available is the kinetic energy
of the wind. The kinetic energy of any particle is equal to one half its mass times the square
of its velocity, or 1/2m V2. The amount of air passing in unit time, through an area A, with
velocity V, is AV, and its mass m is equal to its volume multiplied by its density  of air,
or
m=AV
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(m is the mass of air transverse the area A swept by the rotating blades of a wind mill type
generator). Substituting this value of the mass in the expression for the kinetic energy, we
obtain, kinetic energy = 1/2 AV.V2 watts.
= 1/2 AV3 watts
Equation tells us that the maximum wind available the actual amount will be somewhat
less because all the available energy is not extractable-is proportional to the cube of the
wind speed. It is thus evident that small increase in wind speed can have a marked effect
on the power in the wind.
Equation also tells us that the power available is proportional to air density 1.225 kg/m3 at
sea level). It may vary 10-15 percent during the year because of pressure and temperature
change. It changes negligibly with water content. Equation also tells us that the wind
power is proportional to the intercept area. Thus an aero turbine with a large swept area
has higher power than a smaller area machine; but there are added implications. Since the
area is normally circular of diameter D in horizontal axis aero turbines, then A = π/4 D2,
(sq.m), which when put in equation gives,
Available wind power P = 1/2  /4 D2V3 watts
= 1/8  D2V3 watts
The power extracted by the rotor is equal to the product of the wind speed as it passes
through the rotor (i.e. Vr) and the pressure drop p. in order to maximize the rotor power,
it would therefore be desirable to have both wind speed and pressure drop as large as
possible. However, as V is increased for a given value of the free wind speed (and air
density), increases at first, passes through a maximum, and the decreases. Hence for the
specified free-wind speed, there is a maximum value of the rotor power.
The friction of the free-flow wind power that can be extracted by a rotor is called the powercoefficient, thus
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Power of wind rotor
Power coefficient
=
Power available in the wind
Where power available is calculated from the air density, rotor diameter, and free wind
speed as shown below. The maximum theoretical power coefficient is equal to 16/27 or
0.593. This value cannot be exceeded by a rotor in a free-flow wind-stream.
COUPLING PIPE
GENERATOR 1
ROTATING DIRECTION
MIDDLE PIPE
BLADES
GENERATOR 2
Fig. 3.1 Schematic Diagram of Vertical Axis Highway Wind Turbine
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3.3 Maximum Power
The total power cannot be converted to mechanical power. Consider a horizontal-axis,
propeller-type windmill, henceforth to be called a wind turbine, which is the most common
type used today. Assume that the wheel of such a turbine has thickness b. Let pi and Vi
are the wind pressure and velocity at the upstream of the turbine. Ve is less than Vi because
the turbine extracts kinetic energy.
Considering the incoming air between I and a as a thermodynamic system, and assuming
that the air density remains constant (since changes in pressure and temperature are very
small compared to ambient), that the potential energy is zero, and no heat or work are added
or removed between i and a, the general energy equation reduces to the kinetic and flow
energy-terms only.
3.4 Lift and Drag
The basis for wind energy conversion. The extraction of power, and hence energy, from
the wind depends on creating certain forces and applying them to rotate (or to translate) a
mechanism. There are two primary mechanisms for producing forces from the wind; lift
and drag.
In other words, any change in velocity generates a pressure difference across the lifting
surface. This pressure difference produces a force that begins to act on the high-pressure
side of the lifting surface which is called an airfoil. A good airfoil has a high lift/drag ratio;
in some cases, it can generate lift forces perpendicular to the air stream direction that are
30 times as great as the drag force parallel to the flow. The lift increases as the angle
formed at the junction of the airfoil and the air-stream (the angle of attack) becomes less
and less actuate, up to the point where the angle of the airflow on the low-pressure side
becomes excessive.
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When this happens, the airflow breaks away from the low pressure side. A lot of turbulence
ensues, the lift decreases and the drag increases quite substantially, this phenomenon is
known as stalling. For efficient operation, a wind turbine blade needs to function with as
much lift and as little drag as possible because drag dissipates energy. As lift does not
involve anything more complex than deflecting the airflow, it is usually an efficient
process. The design of each wind turbine specifies the angle at which the airfoil should be
set to achieve the maximum lift to drag ratio.
In addition to airfoils, there are two other mechanisms for creating lift. One is the so-called
Magnus effect, caused by spinning a cylinder in an air stream at a high-speed of rotation.
The spinning slows down the air speed on the side where the cylinder is moving into wind
and increases it on the other side; the result is similar to an airfoil. This principle has been
put to practical use in or two cases but is not generally employed. The second way is to
blow air through narrow slots in a cylinder, so that is emerges tangentially; this is known
as a Thwarts slot. This also creates a rotation (or circulation) of the air flow which in turn
generates lift.
Fig. 3.2 Drag Force Acting on Vertical Axis Blades
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3.5 Wind Energy Conversion
Traditional windmills were used extensively in the Middle Ages to mill grain and lift water
for land drainage and watering cattle. Wind energy converters are still used for these
purposes today in some parts of the world, but the main focus of attention now lies with
their use to generate electricity. There is also growing interest in generating heat from the
wind for space and water heating and for glass-houses but the potential market is much
smaller than for electricity generation.
The term “wind mill” is still widely used to describe wind energy conversion systems,
however it is hardly adopting. Description any more. Modern wind energy conversion
systems are more correctly referred to as ‘WECS’, aero generations’, ‘wind turbine
generators’, or simply ‘wind turbines’.
The fact that the wind is variable and intermittent source of energy is immaterial of some
applications such as pumping water for land drainage – provided, of course, that there is a
broad match between the energy supplied over any critical period and the energy required.
If the wind blows, the job gets done; if it does not, the job waits. However, for many of the
uses to which electricity is put, the interruption of supply may be highly inconvenient.
Operators or users of wind turbines must ensure that there is some form of back-up to cover
periods when there is insufficient (or too much) wind available. For small producers, backup can take the form of:
(i)
Battery storage.
(ii)
Connection with the local electricity distribution system.
For utilities responsible for public supply, the integration of medium sized and large wind
turbines into their distribution network could require some additional plant which is
capable of responding quickly to meet fluctuating demand.
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3.5.1 Small Producers
Private Citizens in several countries have won the right to operate wind generators and
other renewable energy systems and to export power to the grid. For most small wind
generators this requires that the output is ‘conditioned’ so that is conforms to the frequency
and phase of the mains supply. Only a few small units are designed to maintain a constant
rotational rate so that can be synchronized to the mains frequency and feed electricity
directly into the grid. Most produce direct current (DC) or variable output alternating
current (AC).
Power conditioning is readily achieved using an electronic black box called a ‘synchronous
inverter’, and although this is an expensive item of equipment, it does eliminate the need
for batteries and for conversion of home appliances to run to DC.
Where there is no grid connection, electricity that is surplus to immediately requirements
must be stored on site using heavy-duty batteries. It can be recovered later when the
demand exceeds the supply. An alternative is to dump it (by generating a dissipating heat)
or better, to convert it into heat that can be stored, for example as hot water in a wellinsulated tank.
3.5.2 Large producers
Large and medium-sized wind generators are designed to give a stable and constant
electrical output over a wide range of wind speeds and to feed current directly into the grid.
They operate primarily as fuel savers, reducing the utility’s total fuel burn.
The choice of generator type depends on the size of the local distribution grids and its
associated generating capacity. An induction generator would normally be used where
there is a significant amount of other generating capacity (which could provide the
necessary reactive power for excitation). Induction generators are robust and reliable and
require minimal control equipment. For isolated networks where other local generating
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capacity is limited, and where a high degree of autonomous control is required, a
synchronous generator is more appropriate. Synchronous generators are more complex
and therefore more expensive than induction machines.
3.6 Emission Reduction
The environmental benefits achieved from an RWPS are twofold. The improved efficiency
in operation during power out ages due to the availability of backup power leads to a
reduction in vehicle emissions, which will be discussed. Secondly, the electricity produced
by the RWPS is cleaner than what is generated by traditional fossil fuels. The net electricity
generation from fossil fuel and total pollutants from conventional power plants was
obtained from EIA annual statistics (EIA, 2011). The emission per kWh generation was
calculated from these statistics. Knowing the electricity generation of the RWPS and the
unit cost of pollutant, researchers could estimate monetary benefits from green energy.
After an introduction about the historical background of wind power, the report deals with
a more accurate analysis of the main type of VAWT, showing their characteristics and their
operations. The aerodynamics of the wind turbines and a review of different type on
generators that can be used to connect the wind mill to the electricity grid are reported as
well. Several statistics are also presented, in order to explain how the importance of the
wind energy has grown up during the last decades and also to show that this development
of the market of wind power creates new opportunity also for VAWT, that are less used
than the horizontal axis wind turbine (HAWT).
In the end of 2009 a new kind of vertical axis wind turbine, a giromill 3 blades type, has
been built in Falk Enberg, by the Swedish company Vertical Wind. The tower of this wind
turbine is made by wood, in order to get a cheaper and more environment friendly structure,
and a direct driven synchronous multipole with permanent magnets generator is located at
its bottom. This 200 kW VAWT represents the intermediate step between the 12 kW
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prototype, built in collaboration with the Uppsala University, and the common Swedish
commercial size of 2 MW, which is the goal of the company.
A preliminary investigation of the characteristics of this VAWT has been done, focusing
in particular on the value of the frequency of resonance of the tower, an important value
that must be never reached during the operative phase in order to avoid serious damage to
all the structure, and on the power curve, used to evaluate the coefficient of power (Cp) of
the turbine. The results of this investigation and the steps followed to get them are reported.
Moreover, an energy production analysis of the turbine has been done using Wind Pro, as
well as a comparison with and older type on commercial VAWT.
From an aerodynamic point of view, the different VAWT, have a number of aspects in
common that distinguish them from the HAWT. The blades of a VAWT rotate on a
rotational surface whose axis is at right angle to the wind direction. The aerodynamic angle
of attack of the blades varies constantly during the rotation. Moreover, one blade moves on
the downwind side of the other blade in the range of 180° to 360° of rotational angle so
that the wind speed in this area is already reduced due to the energy extracted by the upwind
blades. Hence, power generation is less in the downwind sector of rotation.
Consideration of the flow velocities and aerodynamic forces shows that, nevertheless, a
torque is produced in this way which is caused by the lift forces. The breaking torque of
the drag forces in much lower, by comparison. In one revolution, a single rotor blade
generates a mean positive torque but there are also short sections with negative torque. The
calculated variation of the total torque also shows the reduction in positive torque on the
downwind side. The alternation of the torque with the revolution can be balanced with
three rotor blades, to such an extent that the alternating variation becomes an increasing
and decreasing torque which is positive throughout. However, torque can only develop in
a vertical axis rotor if there is circumferential speed: the vertical axis rotor is usually not
self-starting.
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The qualitative discussion of the flow conditions at the vertical axis rotor shows that the
mathematical treatment must be more complex than with propeller type. This means that
the range of physical and mathematical models for calculating the generation of power and
the loading is also wider. Various approaches, with a variety of weightings of the
parameters involved have been published in the literature. Most authors specify values of
0,40 to 0,42 for the maximum Cp for the Darrieus type wind turbine.
Wind is a natural resource and can be harnessed as an alternative energy. Wind energy is a
good choice to supplement for fossil energy demand. Other than that, wind energy is a
clean, abundant and can reduce the global warming problem due to the excessiveness of
conventional combustion with air assisted processes. VAWT has some advantages. The
heavy parts can be placed on the ground and they can be maintained easily. VAWT can
capture the wind from all the directions. Asynchronous generator connected directly to the
power grid is the one of the simplest methods for wind generation system. The models of
each part and the control schemes are proposed. Especially, the model of VAWT is given
in details including the phenomena such as tower shadow and wind shear. Simulation and
experimental results verify the analysis and the conclusion. Modifier types of vertical axis
wind turbine were tested and showed that this VAWT offered a higher efficiency. Wind
turbine may be an alternative choice for electricity generation in the areas of no electrical
grid power supply. There are two types of wind turbine, vertical axis wind turbine and
horizontal axis wind turbine. The vertical axis wind turbine has an assembly of rotor which
revolves about its vertical axis.
Compared to the more conventional horizontal axis wind turbine, this VAWT offered
several advantages, such as independent from wind direction, the transmission of rotational
parts can be mounted near the ground for ease of maintenance, lower acoustic noise
signature and less upset of gravity induced due to non-harmonic reversing stress at the root
of the blade. The development of the vertical axis wind turbine has been explored over 30
years. Recently, the vertical axis wind turbines are more on attentiveness in term of
optimization of power generation and cost effective. The factors influencing the output
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power of the wind turbine system the tip speed ratio is very important. The optimal power
controlling is to control wind turbine operating at optimal tip speed ratio and generating
maximum power. But inaccuracy of the controlling will introduce unnecessary loss of the
system. However, the Horizontal Axis Wind Turbines (HAWT) is still the favorite
configuration of turbine for electrical generation. Many types of rotor have designed and
tested for evaluating the behavior and efficiency. Additional of Savonious to Darrieus type
vertical wind turbine can increase the efficiency and decreased the wind speeds essentially
required for starting rotation. The present work studied the effect of the operating
conditions (tip speed ratio) to the starting rotation, rev up rotation, power and torque
coefficients of Curved Blades Vertical Axis Wind Turbine (CB-VAWT).
The wind as alternative source of Energy man has needed and used energy at an increasing
rate for his sustenance and well-being ever since he came on this planet a few million years
ago. He started to make use of wood and biomass to supply the energy needs for cooking
and for keeping himself warm. With further demand for energy man began to use wind
energy for sailing ships and driving windmills. In the era of industrial revolution man
started to use new source of energy, viz. coal, fossil fuels, oil, and natural gas. Using of
this commercial energy has led to man’s better quality of life. In past few years, it has
become obvious that fossil fuel resources are fast depleting and that the fossil fuel era is
gradually coming to an end at the same time it has created many problems like pollution
of environment, global warming leading to destruction of many plants and animal life.
A wind turbine is a rotating machine which enables the conversion of kinetic energy in
wind into mechanical energy. If the mechanical energy is used directly by machinery, such
as a pump or grinding stones, the machine is usually called a windmill. If the mechanical
energy is then converted to electricity, the machine is called a wind generator/ wind turbine
wind power unit (WPU), or wind energy converter (WEC). Virtually all modern wind
turbines convert wind energy to electricity for energy distribution. The turbine can be
divided into three components. The rotor component, which is approximately 20% of the
wind turbine cost, includes the blades for converting wind energy to low speed rotational
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energy. The generator component, which is approximately 34% of the wind turbine cost,
includes the electrical generator, the control electronics, and most likely a gearbox
component for converting the low speed incoming rotation to high speed rotation suitable
for generating electricity. The structural support component, which is approximately 15%
of the wind turbine cost, includes the tower and rotor pointing mechanism
Wind energy is a clean, inexhaustible and sustainable energy source. Wind energy is
rapidly emerging as one of the most cost effective form of renewable energy with very
significant increase in installed capacity being reported around the world. Since market
demand is high, the development of wind energy technology has been moving very fast in
many new dimensions, such as aerodynamics, structural mechanics and mechanical
engineering. The main trend of wind turbine development is large-scale wind energy
systems where annual average wind speed is high. On the other hand, a new branch of
development in this field recently emerged. In regions of low wind speed and in urban
areas, small or micro wind turbines are more suitable. There are various small wind
turbines designs already exist which are simple and cost effective, but there is little
literature available in the Selection of main designs Parameter as per geographical
Location, wind Pattern & its Profile. Design selections are usually driven by the
individual’s previous experiences and level of expertise.
The main motivation behind this project is to feed into the existing knowledge base with
appropriate technology & applications for the developing world. Building on the recent
explosion of mobile phone use, there is a huge market for affordable charging solutions in
rural off-grid locations. Current solutions include solar charging and pre-charged car
batteries, but there are many locations where wind energy could do the job. From a supply
chain point of view, the advantage of a wind based charging solution is that, the majority
of materials required are easily available in local market. Recent work by practical action
in Dalhousie India suggests that hand built 100W machine with wooden blades for off-grid
battery charging, where in Peru and Sri Lanka would cost approximately RS 8000.
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Modern electrical and electronics technology needs electrical energy to work. Every
automated system which works on electrical energy is useless without electricity. Current
energy scenario shows that there is not an adequate amount of conventional energy for
future. As demand of energy increases day by day in exponential order, energy
consumption is also increasing. Increased demand and less available supply of energy
creates huge energy gap which is increasing rapidly. So it is imperative to generate energy
from other sources along with conventional sources. Wind energy sources are one of the
highly available and reliable renewable energy resources. Discontinuous availability of
wind energy makes a limitation on its utilization. This limitation can be removed by
utilization of the area where wind flow is more. For this problem highways are the better
solutions.
Highways are the backbone of any nation for development, it remains busy day night. Wind
turbulence created by the vehicles on the road can help us to generate electrical energy.
Highway from the name it is very clear that any public street or other public path on land.
It is mainly used for major roads but also includes public ways and public routes.
About 65% of freight and 80% passenger traffic is carried by roads. National highway
constitutes only about 1.7% of the road network but carry about 40% of total road traffic.
Number of vehicles has been growing at an average of 10.16% per annum over the last five
years. As the number of vehicles are increasing simultaneously fuel (petrol, diesel etc.)
consumption by them is also increasing. Fuels used in vehicles produces harmful gases like
hydrocarbons, nitrogen oxides, carbon monoxide, sulfur dioxide etc. and these fuels are
limitedly available in nature. Today or tomorrow these fuels (used as energy source for
vehicles) are for sure, going to be vanish off the face of earth. So, there is a need to make
some revolutionary changes in concept of highways. So, in this paper we are trying to
throw some light on techniques of utilizing green energy on Indian highway in fruitful
manner. We will try to discuss various methods which will ultimately give us electrical
energy by harvesting green energy on highways.
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3.7 Wind Data and Energy Estimation
The seasonal as well as instantaneous changes in wind both with regard to magnitude and
direction need to be well understood to make the best use of them in windmill designs.
Winds are known to fluctuate by a factor of 2 or more within seconds (and thus causing
the power to fluctuate by a factor of 8 or more). This calls for a proper recording and
analysis of the wind characteristics.
There are various ways the data on wind behavior is collected depending on the use it is
intended to be put into. The hourly mean wind velocity as collected by the meteorological
observations is the basic data used in a windmill designs. The holy means is the one
averaged over a particular hour of the day, over the day, month, year and years. The factors,
which affect the nature of the wind close to the surface of the earth, they are:
(i)
Latitude of the place
(ii)
Altitude of the place
(iii)
Topography of the place
Winds being an unsteady phenomenon, the scale of the periods considered are an important
set of date required in the design. The hourly mean velocity (for many years) provides the
data for establishing the potential of the place for tapping the wind energy. The scale of
the month is useful to indicate whether it is going to be useful during particular periods of
the year and what storage if necessary is to be provided for. The data based on scale of the
hour is useful for mechanical aspects of design.
Since the winds near the surface of the earth are derived from large scale movements of
atmospheric winds, the location height above ground level at which the wind is measured
and the nature of the surface on earth have an influence on the velocity of wind at any given
time. The winds near the surface of the earth are interpreted in terms of boundary layer
concept, keeping in mind the factors that influence its development. The wind velocity at
a given height can be represented in terms of gradient height and velocity.
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In as much as the height of the windmill rotor depends on the design wind velocity and
cost of supporting structure. The above factors have a bearing on the design. Similarly,
winds being an unsteady phenomenon, the scale of periods considered for this the temporal
parameters (scale of month and year) is an important set of data required in the design.
While the hourly mean velocity (for many years) provides the data for establishing the
potential of the place for tapping the wind energy. The scale of the month is useful to
indicate whether it is going to be useful during particular periods of the year and what
storage if necessary is to be provided for as already mentioned above. The data based on
scale of the hour is useful for mechanical aspects of design. In addition to the data on the
hourly mean velocity, two other information’s required are:
(i)
Spells of low wind speeds, and
(ii)
Gusts
The site choice for a single or a spatial array of WECS (wind energy conversion system)
is an important matter when wind electric is looked at from the systems points of view of
aero turbine generators feeding power into a conventional electric grid. If the WECS sites
are wrongly or poorly chosen the net wind electric generated energy per year may be sub
optimal with resulting high capital cost for the WECS apparatus, high cost for wind
generated electrical energy, and no returns on investment.
Even if the WECS is to the small generator not tied to the electric grid, the sitting must be
carefully chosen if inordinately long break even times to the avoided. Technical, economic
environmental, social, and other factors are examined before a decision is made to erect a
generating plant on a specific site. Some of the main considerations are discussed below.
1. High annual average wind speed. A fundamental requirement of the successful use of
WECS, obviously, is an adequate supply of wind has stated above. The wind velocity is
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the critical parameter. The power in the wind Pw, through a given cross sectional area for
a uniform wind velocity V, is
Pw=KV3
Where K is a constant. It is evident; because of the cubic dependence on wind velocity that
small increases in V markedly affect the power in the wind, EX. Doubling V, increases Pw
by a factor of 0.8. it is obviously desirable to select a site for WECS with high wind
velocity. Thus a high average wind velocity is the principal fundamental parameter of
concern in initially appraising a WECS site. For a more detailed estimate value, one would
like to have the average of the velocity cubed.
Anemometer data is normally based on wind speed measurements from a height of 10m.
For the most accurate assessment of wind power potential it is absolutely essential that
anemometer data be obtained at the precise site and hub height for any proposed WECS.

Strategy for shifting is generally recognized to consists of
(i) Survey of historical wind data.
(ii) Contour maps of terrain and wind are consulted.
(iii)Potential sites are visited.
(iv) Best sites are instrumental for approximately one year.
(v) Choose optimal site.
2. Availability of anemometry data. It is another important sitting factor. The principal
object is to measure the wind speed, which basically determines the WECS output power,
but there are many practical difficulties with the instrumentation and measurement
methods. The anemometer height above ground, accuracy, linearity, location on the
support tower, shadowing and inaccurate readings there from, icing inertia of rotor whether
it measures the horizontal velocity component or vertical, and temperature effects are a few
of the many difficulties encountered. The anemometry data should be available over some
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time period at the precise spot where any proposed able over some time period at the precise
spot where any proposed WECS is to be built and that this should be accomplished before
a sitting decision is made.
3. Availability of wind V(t) curve at the proposed site. This important curve determines the
maximum energy in the wind and hence is the principal initially controlling factor in
predicting the electrical output and hence revenue returns of the WECS machines. It is
desirable to have average wind speed V 12-16km/hr(3.5_4.5m/sec) which is about the
lower limit at which present large scale WECS generators ‘cut in’ i.e. start turning. The V
(t)
curve goes to zero there will be no generated power during that time. If there are long
periods of calm the
WECS reliability will be lower than if the calm periods are short. In making such reliability
estimates it is desirable to have measured V(t) curve over about a 5-year period for the
highest confidence level in the reliability estimate.
4. Wind structure at the proposed site. The ideal case for the WECS would be a site such
that the V(t) curve was flat, i.e. a smooth steady wind that blows all the time; but a typical
site is always less than ideal. Wind especially near the ground is turbulent and gusty, and
changes rapidly in direction and in velocity. This departure from homogeneous flow is
collectively referred to as “the structure of the wind”.
5. Altitude of the proposed site. It affects the air density and thus the power in the wind
and hence the useful WECS electric power output. Also, as is well known, the winds tend
to have higher velocities at higher altitudes. One must be careful to distinguish altitude
from height above ground. They are not the same except for a sea level WECS site.
6. Terrain and its aerodynamic. One should know about terrain of the site to be chosen. If
the WECS is to be placed near the top but not on the top of a not too blunt hill facing the
prevailing wind, then it may be possible to obtain a ‘speed up’ of the wind velocity over
what it would otherwise be. Also the wind here may not flow horizontal making it
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necessary to tip the axis of the rotor so that the aero turbine is always perpendicular to the
actual wind flow. It may be possible to make use of hills or mountains, which channel the
prevailing winds into a pass region, thereby obtaining higher wind power.
7. Local Ecology. If the surface is bare rock it may mean lower hub heights hence lower
structure cost. If trees or grass or vegetation are present, all of which tent to restructure the
wind, then higher hub heights will be needed resulting in large system costs than the bare
ground case.
8. Distance to Roads or Railways. This is another factor the system engineer must consider
for heavy machinery, structures, materials, blades and other apparatus will have to be
moved into any chosen WECS site.
9. Nearness of site to local center/users. This obvious criterion minimizes transmission line
length and hence losses and costs. After applying all the previous sitting criteria, hope
fully as one narrows the proposed WECS sites to one or two they would be relatively near
to the users of the generated electric energy.
10. Nature of ground. Ground condition should be such that the foundations for a WECS,
destroying the foundations for a WECS are secured. Ground surface should be stable.
Erosion problem should not be there, as it could possibly later wash out the foundations of
a WECS, destroying the whole system.
11. Favorable land cost. Land cost should be favorable as this along with other sitting
costs, enters into the total WECS system cost.
12. Other conditions such as icing problem, salt spray or blowing dust should not present
at the site, as they may affect aero turbine blades, or environmental is generally averse to
machinery and electrical apparatus.
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The wind shear, and consequently the available wind power at a given altitude, is also
affected by the roughness of the earth’s surface in a given location. If the area contains
buildings, trees, wind machines, or other obstacles, the variation of the wind speed with
altitude above ground level is usually greater for these obstructed areas than for the case of
open water and flat plains. The characteristics of a good wind power site may be
summarized as follows:
(i)
A site should have a high annual wind speed.
(ii)
There should be no tall obstructions for a radius of 3 km.
(iii)
An open plain or an open shore line may be good location.
(iv)
The top of a smooth, well rounded hill with gentle slopes lying on a flat plain or
located on an island in a lake or sea is a good site.
(v)
A mountain gap that produces to wind funneling is good.
3.8 Power Generation
3.8.1 Generating Systems
Aero turbines convert wind energy into rotary mechanical energy. A mechanical interface,
consisting of a step-up gear and a suitable coupling transmits the energy to an electrical
generator. The output of this generator is connected to the load or system grid. The
controller senses the wind direction, wind speed, power output of the generator and other
necessary performance quantities of the system and initiates appropriate control signals to
take suitable corrective actions.
The system should be protected from excessive
temperature raise of the generator, electrical faults and extra wind conditions.
The choice of an electrical generator and control method to be employed (if any) can be
decided by consideration of the following three factors:
(i)
The basis of operation i.e. either constant tip speed or constant tip speed ratio.
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(ii)
The wind-power rating of the turbine and
(iii) The type of load demand e.g. battery connection.
Wind power ratings can be divided into three convenient grouping, small to 1kW, medium
to 50 kW and large 200 kW to megawatt frame size. Electrical generators types applicable
to each of these ratings are:
(i)
Small – permanent, magnet, D.C. generators.
(ii)
Medium-permanent magnet, D.C generator, induction generator, synchronous
generator.
(iii) Large – induction generator, synchronous generator.
The electrical control strategy employed for any particular scheme can be designed to effect
control of the generator, the power transmission link or the load.
3.8.2 Schemes for Electric Generation
Several schemes for electric generation have been developed. These schemes can be
broadly classified under three categories:
(i)
Constant speed constant frequently systems (CSCF).
(ii)
Variable speed constant frequency systems (VSCF).
(i) Constant Speed Constant Frequency System (CSCF)
Constant speed drive has been used for large generators connected directly to the grid
where constant frequency operation is essential.
(a) Synchronous Generator
For such machines the requirement of constant speed is very rigid and only minor
fluctuations about 1% for short durations (fraction of second) could be allowed.
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Synchronization of wind driven generator with power grid also will pose problems with
gusty winds.
(b) Induction Generator
If the stator of an induction machine is connected to the power grid and if the rotor is driven
above synchronous speed Ns (Ns = 120 x f/p), the machine becomes a generator and
delivers constant line frequency power to the grid (f = line frequency and p = number of
poles for which the stator winding is made). Per unit slip is 0 and 0.05. The output power
of wind drive and induction generator is uniquely determined by the operating speed. The
pull out torque ™ condition should not be exceeded. When this happens the speed
continues to increase and the system may ‘run away’ the torque-speed characteristics of an
induction machine in the motor and generating modes. Induction generators are basically
simpler than synchronous generators. They are easier to operate, control and maintain, have
no synchronization problems and are economical. However, they draw their excitation
from the grid and hence impose reactive volt ampere burden. But static capacitors can be
used to overcome this problem.
(ii) Variable Speed Constant Frequency Scheme (VSCF scheme)
Variable-speed drive is typical for most small wind generators used in autonomous
applications, generally producing variable frequency and variable voltage output. The
variable speed operation of wind-electric system yields higher outputs for both low and
high wind speeds. This results in higher annual energy yields per rated installed kW
capacity. Both horizontal axis and vertical axis turbines will exhibit this gain under
variable speed operation. The popular schemes to obtain constant frequency output are as
follows:
(a) AC-DC-AC link
With the advent of high powered thermistors and high voltage D.C. transmission systems,
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A.C. output of the 3-phase alternator is rectified using a bridge rectifier and then converted
back to A.C. using line commutated inverters. They utilize an A.C. source (power lines)
which periodically reverses polarity and causes the commutation to occur naturally. Since
frequency is automatically fixed by the power line, they are also known as synchronous
inverters. The block diagram of the system.
(b) Double Output Induction Generator
In this system a slip-ring induction motor is used. Rotor power output at slip frequency is
converted to line frequency power by rectification and inversion output power is obtained
both from stator and rotor and hence this device is called double output induction generator.
Rotor output power has the electrical equivalence of additional impedance in the rotor
circuit. Therefore, increasing rotor outputs led to increasing slips and higher speeds. Such
an operation increases the operating speed range from N3 to 2 N3, i.e. slip varying from 0
to 1.0.
(c) A.C. Communication Generator
This system is also known as Scherbius system employs two polyphone windings in the
stator and a commutator winding on the rotor. Basic problems in employing this device
for wind energy conversion are the cost and care required by the commutator and the brush
gear.
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4. COMPONENTS AND DESCRIPTION
The main components of our “HORIZONTAL TURBINE TYPE DOMESTIC WIND
MILL” as follows,
(i) Blade with Shaft
(ii) Spur Gear Arrangement
(iii) Battery
(iv) Inverter
(v) D.C. Generator
(vi) Mechanical design considerations (for blades)
Actual Working principle of wind mill with controller circuit is shown in fig.
Wind direction
(yaw control)
Wind
To load
Gearing
Aero turbine
Wind
speed
Pitch control
Coupling
Signal
Control
S
p
e
e
d
Electrical
generator
Control
Signal
Generator
Temperature
Controller
Output
Power
Fig. 4.1 Schematic Diagram of Aero-Turbine
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Aero turbines convert energy in moving air to rotary mechanical energy. In general, they
require pitch control and yaw control (only in the case of horizontal or wind axis machines)
for proper operation. A mechanical interface consisting of a step up gear and a suitable
coupling transmits the rotary mechanical energy to an electrical generator. The output of
this generator is connected to the load or power grid as the application warrants. Yaw
control. For localities with the prevailing wind in one direction, the design of the turbine
can be greatly simplified. The rotor can be in a fixed orientation with the swept area
perpendicular to the predominant wind direction.
Such a machine is said to be yaw fixed. Most wind turbine, however, are yaw active that
is to say, as the wind direction changes, a motor rotates the turbine slowly about the vertical
(or yaw) axis so as to face the blades in to the wind. The area of the wind swept by the
wind rotor is then a maximum. In a small turbine, yaw action is controlled by a tail van,
similar to that in a typical windmill. In large machines, a servomechanism operated by a
wind-direction sensor controls the yaw motor that keeps the turbine properly oriented.
The purpose of the controller is to sense wind speed, wind direction, shafts speeds and
torques at one or more points, output power and generator temperature as necessary and
appropriate control signals for matching the electrical output to the wind energy input and
project the system from extreme conditions brought upon by strong winds electrical faults,
and the like. The physical embodiment for such an aero-generator is shown in a generalized
form. The sub-components of the windmill are:
(i)
Wind turbine or rotor.
(ii)
Wind mill head.
(iii) Transmission and control.
(iv) Supporting structure.
Such a machine typically is a large impressive structure.
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4.1 Rotors
4.1.1 Rotors are Mainly of Two Types:
(i)
Horizontal axis rotor and
(ii)
Vertical axis rotor.
One advantage of vertical – axis machines is that they operate in all wind directions and
thus need no yaw adjustment the rotor is only one of the important components. For an
effective utilization, all the components need to be properly designed and matched with the
rest of the components.
The windmill head supports the rotor, housing the rotor bearings. It also houses any control
mechanism incorporated like changing the pitch of the blades for safety devices and tail
vane to orient the rotor to face the wind. The latter is facilitated by mounting it on the top
of the supporting structure on suitable bearings.
4.1.2 Transmission
Varying the pitch of the rotor blades, conveniently controls the rate of rotation of large
wind turbine generators operating at rated capacity or below, but it is low, about 40 to 50
revolutions per minute (rpm). Because optimum generator output requires much greater
rates of rotation, such as 1800 rpm, it is necessary to increase greatly the low rotor of
turning. Among the transmission options are mechanical systems involving fixed ratio
gears, belts, and chains, singly or in combination or hydraulic systems involving fluid
pumps and motors. Fixed ratio gears are recommended for top mounted equipment
because of their high efficiency; no cost, and minimum system risk.
For bottom mounted equipment which requires a right-angle drive, transmission costs
might be reduced substantially by using large diameter bearings with ring gears mounted
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on the hub to serve as a transmission to increase rotor speed to generator speed. Such a
combination offers a high degree of design flexibility as well as large potential savings.
4.2 Blade with Shaft
The horizontal type wind mill is having multi-bladed (10-16 Blades) type. The blade
surface is convex with the material of Mild steel. These blades are coupled to the shaft with
the help of guide bush. The distances between the two blades are equivalently divided.
4.3 Spur Gear Arrangement
The spur gears, which are designed to transmit motion and power between parallel shafts,
are the most economical gears in the power transmission industry. The vertical axis of the
turbine is coupled with the generator by using spur gear arrangement with the gear ratio
above 3 so that the generator generates maximum voltages.
4.4. Battery
In isolated systems away from the grid, batteries are used for storage of excess solar energy
converted into electrical energy. The only exceptions are isolated sunshine load such as
irrigation pumps or drinking water supplies for storage. In fact, for small units with output
less than one kilowatt. Batteries seem to be the only technically and economically available
storage means. Since both the photo-voltaic system and batteries are high in capital costs.
It is necessary that the overall system be optimized with respect to available energy and
local demand pattern. To be economically attractive the storage of solar electricity requires
a battery with a particular combination of properties:
(i)
Low cost.
(ii)
Long life.
(iii)
High reliability.
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(iv)
High overall efficiency.
(v)
Low discharge.
(vi)
Minimum maintenance.
We use lead acid battery for storing the electrical energy from the solar panel for lighting
the street and so about the lead acid cells are explained below.
4.4.1 Lead-Acid Wet Cell
LEAD ACID BATTERY
VENT
Electrolyte Level
Positive Plate
Molded Case
Negative Plate
Separators
Support
Fig 4.2 Internal Components of Lead-Acid Wet Cell
Where high values of load current are necessary, the lead-acid cell is the type most
commonly used. The electrolyte is a dilute solution of sulfuric acid (H₂SO₄). In the
application of battery power to start the engine in an auto mobile, for example, the load
current to the starter motor is typically 200 A to 400 A. One cell has a nominal output of
2.1 V, but lead-acid cells are often used in a series combination of three for a 6 V battery
and six for a 12 V battery.
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The lead acid cell type is a secondary cell or storage cell, which can be recharged. The
charge and discharge cycle can be repeated many times to restore the output voltage, as
long as the cell is in good physical condition. However, heat with excessive charge and
discharge currents shortens the useful life to about 3 to 5 years for an automobile battery
of the different types of secondary cells, the lead-acid type has the highest output voltage,
which allows fewer cells for a specified battery voltage.
4.4.2 Construction
Inside a lead-acid battery, the positive and negative electrodes consist of a group of plates
welded to a connecting strap. The plates are immersed in the electrolyte, consisting of 8
parts of water to 3 parts of concentrated sulfuric acid. Each plate is a grid or framework,
made of a lead-antimony alloy. This construction enables the active material, which is lead
oxide, to be pasted into the grid. In manufacture of the cell, a forming charge produces the
positive and negative electrodes. In the forming process, the active material in the positive
plate is changed to lead peroxide (PbO₂). The negative electrode is spongy lead (Pb).
Automobile batteries are usually shipped dry from the manufacturer. The electrolyte is put
in at the time of installation, and then the battery is charged to from the plates. With
maintenance-free batteries, little or no water need be added in normal service. Some types
are sealed, except for a pressure vent, without provision for adding water.
4.4.3 Chemical Action
Sulfuric acid is a combination of hydrogen and sulfate ions. When the cell discharges, lead
peroxide from the positive electrode combines with hydrogen ions to form water and with
sulfate ions to form lead sulfate. Combining lead on the negative plate with sulfate ions
also produces he sulfate. Therefore, the net result of discharge is to produce more water,
which dilutes the electrolyte, and to form lead sulfate on the plates.
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As the discharge continues, the sulfate fills the pores of the grids, retarding circulation of
acid in the active material. Lead sulfate is the powder often seen on the outside terminals
of old batteries. When the combination of weak electrolyte and sulfating on the plate
lowers the output of the battery, charging is necessary.
On charge, the external D.C. source reverses the current in the battery. The reversed
direction of ions flows in the electrolyte result in a reversal of the chemical reactions. Now
the lead sulfates on the positive plate reactive with the water and sulfate ions to produce
lead peroxide and sulfuric acid. This action re-forms the positive plates and makes the
electrolyte stronger by adding sulfuric acid.
At the same time, charging enables the lead sulfate on the negative plate to react with
hydrogen ions; this also forms sulfuric acid while reforming lead on the negative plate to
react with hydrogen ions; this also forms currents can restore the cell to full output, with
lead peroxide on the positive plates, spongy lead on the negative plate, and the required
concentration of sulfuric acid in the electrolyte.
The chemical equation for the lead-acid cell is
Charge
Pb + PbO₂ + 2H₂SO₄
2PbSO₄ + 2H₂O
Discharge
On discharge, the Pb and PbO₂ combine with the SO₄ ions at the left side of the equation
to form lead sulfate (PbSO₄) and water (H₂O) at the right side of the equation.
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One battery consists of 6 cells, each have an output voltage of 2.1 V, which are connected
in series to get a voltage of 12 V and the same 12 V battery is connected in series, to get a
24 V battery. They are placed in the water proof iron casing box.
4.4.4 Caring for Lead-Acid Batteries
Always use extreme caution when handling batteries and electrolyte. Wear gloves, goggles
and old clothes. “Battery acid” will burn skin and eyes and destroy cotton and wool
clothing.
The quickest way of ruin lead-acid batteries is to discharge them deeply and leave them
stand “dead” for an extended period of time. When they discharge, there is a chemical
change in the positive plates of the battery. They change from lead oxide when charge out
lead sulfate when discharged. If they remain in the lead Sulfate State for a few days, some
part of the plate dose not returns to lead oxide when the battery is recharged. If the battery
remains discharge longer, a greater amount of the positive plate will remain lead sulfate.
The parts of the plates that become “sulfate” no longer store energy. Batteries that are
deeply discharged, and then charged partially on a regular basis can fail in less than one
year.
Check your batteries on a regular basis to be sure they are getting charged. Use a
hydrometer to check the specific gravity of your lead acid batteries. If batteries are cycled
very deeply and then recharged quickly, the specific gravity reading will be lower than it
should because the electrolyte at the top of the battery may not have mixed with the
“charged” electrolyte. Check the electrolyte level in the wet-cell batteries at the least four
times a year and top each cell of with distilled water. Do not add water to discharged
batteries. Electrolyte is absorbed when batteries are much discharged. If you add water at
this time, and then recharge the battery, electrolyte will overflow and make a mess. Keep
the top of your batteries clean and check that cables are tight. Do not tighten or remove
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cables while charging or discharging. Any spark around batteries can cause a hydrogen
explosion inside, and ruin one of the cells, and you.
4.4.5 Current Ratings
Lead-acid batteries are generally rated in terms of how much discharge currents they can
supply for a specified period of time; the output voltage must be maintained above a
minimum level, which is 1.5 V to 1.8 V per cell. A common rating is ampere-hours (A.hr.)
based on a specific discharge time, which is often 8h. Typical values for automobile
batteries are 100 to 300 A.hr.
As an example, a 200 A.hr. battery can supply a load current of 200/8 or 25A, used on 8h
discharge. The battery can supply less current for a longer time or more current for a
shorter time. Automobile batteries may be rated for “cold cranking power”, which is
related to the job of starting the engine. A typical rating is 450A for 30s at a temperature
of 0° F.
Note that the ampere-hour unit specifies coulombs of charge. For instance, 200 A.hr.
corresponds to 200A x 3600s (1h = 3600s). the equals 720,000 A.S, or coulombs. One
ampere-second is equal to one coulomb. Then the charge equals 720,000 or 7.2 x 105ºC.
To put this much charge back into the battery would require 20 hours with a charging
current of 10A. The ratings for lead-acid batteries are given for a temperature range of 77
to 80º F. Higher temperature increases the chemical reaction, but operation above 110º F
shortens the battery life.
Low temperatures reduce the current capacity and voltage output. The ampere-hour
capacity is reduced approximately 0.75% for each decreases of 1º F below normal
temperature rating. At 0º F the available output is only 60 % of the ampere-hour battery
rating. In cold weather, therefore, it is very important to have an automobile battery unto
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full charge. In addition, the electrolyte freezes more easily when diluted by water in the
discharged condition
4.4.6 Specific Gravity
Measuring the specific gravity of the electrolyte generally checks the state of discharge for
a lead-acid cell. Specific gravity is a ratio comparing the weight of a substance with the
weight of a substance with the weight of water. For instance, concentrated sulfuric acid is
1.835 times as heavy as water for the same volume. Therefore, its specific gravity equals
1.835. The specific gravity of water is 1.280, since it is the reference.
In a fully charged automotive cell, mixture of sulfuric acid and water results in a specific
gravity of 1.280 at room temperatures of 70 to 80º F. As the cell discharges, more water
is formed, lowering the specific gravity. When it is down to about 1.150, the cell is
completely discharged.
Specific-gravity readings are taken with a battery hydrometer. Note that the calibrated
float with the specific gravity marks will rest higher in an electrolyte of higher specific
gravity. The decimal point is often omitted for convenience. For example, the value of
1.220 is simply read “twelve twenty”. A hydrometer reading of 1260 to 1280 indicates full
charge, approximately 12.50 are half charge, and 1150 to 1200 indicates complete
discharge.
The importance of the specific gravity can be seen from the fact that the open-circuit
voltage of the lead-acid cell is approximately equal to
V
=
Specific gravity + 0.84
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4.4.7 Charging The Lead-Acid Battery
The requirements are illustrated in figure. An external D.C. voltage source is necessary to
produce current in one direction. Also, the charging voltage must be more than the battery
e.m.f. Approximately 2.5 per cell are enough to over the cell e.m.f. so that the charging
voltage can produce current opposite to the direction of discharge current.
Note that the reversal of current is obtained just by connecting the battery VB and charging
source VG with + to + and - to -. The charging current is reversed because the battery
effectively becomes a load resistance for VG when it higher than VB. In this example, the
net voltage available to produce charging currents is 12 V. A commercial charger for
automobile batteries is essentially a D.C. power supply, rectifying input from the AC power
line to provide D.C. output for charging batteries.
Float charging refers to a method in which the charger and the battery are always connected
to each other for supplying current to the load. In figure the charger provides current for
the load and the current necessary to keep the battery fully charged. The battery here is an
auxiliary source for D.C. power.
It may be of interest to note that an automobile battery is in a floating-charge circuit. The
battery charger is an AC generator or alternator with rectifier diodes, driver by a belt from
the engine. When you start the car, the battery supplies the cranking power. Once the
engine is running, the alternator charges he battery. It is not necessary for the car to be
moving. A voltage regulator is used in this system to maintain the output at approximately
13 to 15 V.
The constant voltage of 24 V comes from the solar panel controlled by the charge controller
so for storing this energy we need a 24 V battery so two 12 V battery are connected in
series. It is a good idea to do an equalizing charge when some cells show a variation of
0.05 specific gravity from each other. This is a long steady overcharge, bringing the battery
to a gassing or bubbling state. Do not equalize sealed or gel type batteries.
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With proper care, lead-acid batteries will have a long service life and work very well in
almost any power system. Unfortunately, with poor treatment lead-acid battery life will be
very short.
4.5 Inverters
The process of converting D.C. into A.C. is known as “INVERSION”. In other words, we
may define it as the reverse process of rectification. The device, which performs this
process, is known as an INVERTOR. Inversion is, by no means, a recent process. In olden
days’ gas-filled tubes and vacuum tubes were used to develop inverters. Thermistors
inverter is popularly used as a large power device.
Vacuum tube inverters were generally used for high-frequency applications. Some of the
main disadvantages of the tube as well as the mercury pool type inverters are:
(i)
They are very costly.
(ii)
They are very big in size and heavy in weight.
(iii)
They have very poor efficiency.
(iv)
The voltage drop across these devices is very high.
The basic principle of an inverter can be explained with the help of a simple circuit, as
shown in figure 4.3
The D.C. battery storage is given to an inverter and this inverter inverts 12V D.C. to input
in to AC output, step upped in to 230V. The 230V AC supply is given to the lamp.
Lamp
Wind
mill
Generator
Battery
Invertor
Fig. 4.3 Inverting Circuit
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4.6 D.C. Generator
4.6.1 Permanent Magnet D.C. Generator
4.6.1.1 Voltage Production
DC Circuits, that there are three conditions necessary to induce a voltage into a conductor.
(i)
A magnetic field.
(ii)
A conductor.
(iii)
Relative motion between the two.
A DC generator provides these three conditions to produce a DC voltage output.
4.6.1.2 Theory of Operation
A basic DC generator has four basic parts:
(i)
A magnetic field;
(ii)
A single conductor, or loop;
(iii)
A commutator; and
(iv)
Brushes;
The magnetic field may be supplied by either a permanent magnet or an
electromagnet.
For now, we will use a permanent magnet to describe a basic DC
generator.
Basic Operation of a DC Generator A single conductor, shaped in the form of a loop, is
positioned between the magnetic poles. As long as the loop is stationary, the magnetic
field has no effect (no relative motion). If we rotate the loop, the loop cuts through the
magnetic field, and an EMF (voltage) is induced into the loop.
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When we have relative motion between a magnetic field and a conductor in that magnetic
field, and the direction of rotation is such that the conductor cuts the lines of flux, an EMF
is induced into the conductor. The magnitude of the induced EMF depends on the field
strength and the rate at which the flux lines are cut. The stronger the field or the more flux
lines cut for a given period of time, the larger the induced EMF.
Eg = K x F x N
Where,
Eg = generated voltage
K = fixed constant
F = magnetic flux strength
N = speed in RPM
The direction of the induced current flow can be determined using the "left-hand rule" for
generators. This rule states that if you point the index finger of your left hand in the
direction of the magnetic field (from North to South).
Magnetic field from field coil
which also have A.C. current
Slipped contacts
called “brushes”
A.C.
current
in coil
Fig. 4.4 Schematic Diagram of D.C. Generator
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4.7 Mechanical Design Considerations (For Blades)
For a wind turbine the main design characteristics stem from the choice of rotor. There
were a number of elements which to be considered for to finish up Savonius wind turbine
design. These include:
(i)
Aspect ratio.
(ii)
Overlap ratio.
(iii) Separation gap.
(iv) Cross-section profile.
(v)
Number of blades/ rotor
Aspect ratio as shown in Figure 4.5 is the ratio of the rotor height to the width. A large
aspect ratio of around 3 to 5 provides the rotor with good torque and power characteristics
where, H is the height of rotor and C is width of rotor.
Overlap ratio as shown in Figure 4.6 is the ratio of the diameter of the rotor blade to the
distance which the blades overlap. For buckets of semi-circular cross-section, the
appropriate overlap ratio is 20 to 30%.
Separation gap as shown in Figure 4.7 is determined by the distance of the rotor blades
from the vertical axis. An increase in the separation gap ratio results in a decrease in the
torque coefficient and the power coefficient; a small negative gap is therefore preferable.
The cross-section profile of a rotor blade is taken from a vantage point directly above the
blade (See Figure 4.7). There are two type of cross section profile including Semi-circular
type and Bach type. The number of buckets that rotor possesses has a direct effect on the
performance of the rotor.
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Fig. 4.5 Aspect Ratio
Fig. 4.6 Overlap Ratio
Fig. 4.7 Separation Gap
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4.8 Safety Precautions
4.8.1 Safety Systems of the Wind Turbines comprise the following features
(i) The Computer
The wind turbine is controlled by a computer which monitors the most important gauging
instruments and compares the results. If errors are found the wind turbine is stopped.
(ii) Emergency Stop
If a situation arises which calls for the wind turbine to be stopped immediately, the
emergency stop is used. The wind turbine will stop in few seconds by feathering the blades
directly into the wind. It cannot be stated again before what caused the emergency stop
has been rectified.
(iii) Revolution Counters
To prevent the rotor from racing, two revolution counters have been mounted on the shaft.
These operate quiet independently and activate the emergency stop if the revolutions of the
turbine exceed 24 rpm which is maximum.
(iv) Wind Velocity
This is measured and controlled by the computer in two ways. First gusts of wind are
registered and if they are too strong the turbine is stopped. Then average wind speeds are
measured over periods of 10 minutes, and the wind turbine is also stopped if there are too
high.
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(v) The Parachutes
Each blade tip has a parachute, which is activated if the rpm exceeds 28. An iron plumb
bob, otherwise held in place by a magnet, is released from the blade trip, the centrifugal
force exceeding the force of the magnet pulling out the parachute. This is decrease the
speed of the wind turbine considerable enough to stop it from racing. The parachute is an
extra safety device should other fail. Till now they never had been used.
(v) Lightning Rods
The tree blades and the mill or wind turbine cap are protected from lighting by these rods
going from the tip of each blade to the ground.
4.8.2 Environmental Aspects
Wind turbines are not without environmental impact and their operation is not entirely riskfree. Following are the main effects due to a wind turbine.
(i) Electromagnetic Interference
Interference with TV and other electromagnetic communication systems is a possibility
with wind turbines as it is with other tall structures. TV interference is most likely in areas
where there is a weak signal because of the distance from the transmitter, where existing
reception is none too good due to the surrounding hills and where the wind turbine is
exposed in good position to receive and scatter the signals. Dispensing with aerials and
sending TV signals by cable in areas that would otherwise be affected can overcome
interference.
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(ii) Noise
The noise produced by wind farms falls into two categories. The first type is a mechanical
noise from the gearbox, generating equipment and linkages and the second type of
aerodynamic in nature produced by the movement of the turbine blades. One component
of the latter is the broad band noise which ranges up to several kilo hertz and the other is a
low frequency noise of 15-20 Hz. Revolving blades generate noise which can be heard in
the immediate vicinity of the installation, but noise does not travel too far.
(iii) Visual Effects
Megawatts power generating wind turbines are massive structures which would be quite
visible over a wide area in some locations. Variety characteristics such as color pattern,
shape, rotational speed and reflectance of blade materials can be adjusted to modify the
visual effects of wind turbines including the land scape in which they are installed.
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5. DESIGN PARAMETERS AND MATERIAL CONSIDERATION
5.1 Design of Spur Gear
5.1.1 Speeds on Gear Box
Measured Specifications:
N1/N2
=
D2/D1
N1
=
Motor speed in RPM---40 RPM
N2
=
Output speed
D2
=
Diameter of the roller gear wheel
=
88 mm
=
Diameter of the motor gear wheel
=
35 mm
=
(D1/D2) x N1
=
(35 / 88) x40
=
16 rpm
Where,
D1
∴ N2
5.2 Design of Ball Bearing
Bearing No. 6202:
Outer Diameter of Bearing (D)
=
35 mm
Thickness of Bearing (B)
=
12 mm
Inner Diameter of the Bearing (d)
=
15 mm
r₁
=
Corner radii on shaft and housing
r₁
=
1 (From design data book)
Maximum Speed
=
14,000 rpm (From design data book)
Mean Diameter (dm)
=
(D + d) / 2
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
dm
=
(35 + 15) / 2
=
25 mm
5.2.1 Wahl Stress Factor
Ks
=
4C – 1 + 0.65
4C – 4
=
(4 X 2.3) -1 + 0.65
(4 X 2.3) - 4
Ks
=
C
2.3
1.85
5.3 Basic Shaft Design Formula
The drive shaft with multiple pulleys experience two kinds of stresses, bending stress and
shear stress. The maximum bending stress generated at the outer most fiber of the shaft.
And on the other hand, the shear stress is generated at the inner most fiber. Also, the value
of maximum bending stress is much more than the shear stress. So, the design of the shaft
will be based on the maximum bending stress and will be driven by the following formula:
Maximum bending stress,
Tb
=
(M x r) / I ………………………...……. Eqn.(a)
M
=
maximum bending moment on the shaft.
r
=
the radius of the shaft.
I
=
area moment of inertia of the shaft.
Where,
5.3.1 Design Procedure
(i)
Draw the bending moment diagram to find out the maximum bending moment (M)
on the shaft.
(ii)
Calculate the area moment of inertia (I) for the shaft.
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
(iii)
Replace the maximum bending stress (Tb) with the given allowable stress for the
shaft material.
(iv)
Calculate the radius of the shaft.
5.3.2 Shaft Design Problem
Bearing
Shaft
Blade
100 mm
200 mm
W = 1000 N
Refer the above picture, where a steel shaft is supported by two bearings and a pulley is
placed in between the bearings. You have to design the shaft. Weight of the pulley is
1000N.
Input Data:
Maximum allowable shear stress for the shaft material= 40 N/mm2
Solution:
(i)
From the bending moment diagram, the maximum bending moment (M) is
calculated as 66666.67 N/mm2.
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
(ii)
Area moment of inertia (I)of the circular shaft is:
I
(iii)
=
Pi x r4 x 0.25
=
0.785 x r4………………...Eqn. (b)
From Eqn. (a) we can write:
40
=
(66666.67 x r)
(0.785 x r4)
r
(iv)
=
12.85 mm
So, the minimum radius of the shaft should be 13 mm.
5.4 Design Diagram
5.4.1 Side View of the Assembly
Vertical Turbine Type Domestic Wind Mill
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
5.4.2 Blades
240
300
Al.
5.4.3 Bearing
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3
FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
5.4.4 Bush
5.4.5 Round Plate
SGOI, COE, B.E. (Mechanical Department)
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5.4.6 Shaft
20
5.4.7 Gear Wheel - 1
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
5.4.8 Gear Wheel - 2
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
5.5 List of Materials and Cost Estimation
Table No. 5.1 List of materials used and its cost
Sr. No.
Name of the Parts
Quantity
Type of
Amount (Rs.)
Materials Used
1
Blades
3
Aluminum
1,100/-
2
Frame structure
1
M.S
550/-
3
Battery
1
Lead-acid
750/-
4
Generator
1
Electronic
815/-
5
Bearing
2
Steel
300/-
6
Connecting Wire
6m
Cu
100/-
7
Gear Wheel
2
C.I
950/-
8
Inverter
1
Electronic
1,500/-
9
Bush
5
M.S
250/-
10
Round Plate
1
M.S
400/-
11
Main Shaft
1
M.S
1,000/-
12
Electrical Unit Box
1
Wooden Ply
500/-
TOTAL (Rs.)
8,215/-
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
6. ADVANTAGES AND DISADVANTAGES
6.1 Advantages
(i)
Highway wind turbines are Omni-directional and do not need to track the wind.
This means they do not require a complex mechanism and motors to yaw the rotor
and pitch the blades.
(ii)
They have the ability to take advantage of turbulent and gusty winds. Such winds
are not harvested by horizontal axis wind turbines (HAWTs) and in fact cause
accelerated fatigue to HAWTs.
(iii) Wings of a Darrieus type have a constant chord and so are easier to manufacture
than the blades of a HAWT, which have a much more complex shape and structure.
(iv) Can be installed on a wind farm below the existing HAWT; this will improve the
efficiency (power output) of the existing farm.
(v)
Can be grouped more closely in wind farms, increasing the generated power per
unit of land area.
6.2 Disadvantages
(i)
The turbines completely depend on the force of the air generated by the fast
moving vehicles on the roads.
(ii)
It totally depends upon the number of vehicles travelling on the road for
generation of long lasting electricity used for the street lights.
(iii) They have relative high vibrations because the air flow near the ground
creates turbulence.
(iv) They create noise pollution.
(v)
They need initial push to start, this action use few of its own produce
electricity.
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
7. FUTURE SCOPE
Further research, design and implementation on Vertical Axis Wind Turbine may be
useful for different types of fabrication providing different forms of energy. Some of
them are listed below,
(i)
Air borne wind turbines.
(ii)
Power from low speed winds.
(iii)
Blade-less wind power.
(iv)
Wind turbine lenses.
(v)
Quite wind turbines.
(vi)
Wind power storage.
(vii)
Community owned wind power.
(viii)
Multipurpose offshore wind turbines
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
8. RESULT AND CONCLUSION
8.1 Result
The Designed and Fabricated “Vertical Axis Highway Wind Turbine” (VAHW) is capable
of producing 200 watt-hr. when approximately 100 vehicles are moving from the side of
the turbine producing wind speed of 4.5 m/s which in turn strikes the blades of the turbine,
hence, generating a drag force on the surface of blades for the duration of 2 hours.
8.2 Conclusion
The extensive data is collected on wind patterns produced by vehicles on both sides of the
highway. Using the collected, wind turbine is designed to be placed on the medians of the
highway. Although, one turbine may not provide adequate power generation, a collective
of turbines on a long strip of highway has potential to generate a large amount of energy
that can be used to power the steer lights, other public amenities or even generate profits
by selling the power back to the grid. This designed concept is meant to be sustainable and
environmentally friendly. Additionally, a wind turbine powered by artificial has a myriad
of applications. Theoretically any moving vehicle can power the turbine such as an
amusement park ride. The highway wind turbine can be used to provide power in any city
around the globe where there is high vehicle traffic.
SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
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SGOI, COE, B.E. (Mechanical Department)
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FABRICATION OF VERTICAL AXIS HIGHWAY WIND TURBINE
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SGOI, COE, B.E. (Mechanical Department)
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