Download HIGHAWAY WIND ENERGY USING VERTICAL AXIS WIND

HIGHAWAY WIND ENERGY USING VERTICAL AXIS
WIND TURBINES
HARIPRASAD.K.V
Department of Mechanical Engineering, SCSVMV University,
Enathur, kanchipuram-631561.
[email protected]
ABSTRACT
Present day scenario is such that, energy is to be harnessed from every source possible.
Energy is the one commodity which even when produced in huge scale in various methods,
turns to be insufficient. This paper explains about harnessing wind energy with the use of
vertical axis wind mills. With the exploding population, wind mills can’t be erected as it
requires large empty fields. To accommodate this need, the wind mills are erected in medians
of highway where sufficient and constant wind force is available.
INTRODUCTION
Wind energy is harnessed by wind mills.
Wind mills are usually horizontal axis
mills having huge vanes erected on large
pillars in areas with abundant and fast air
flow. The wind mills require the following
criteria to generate power.
1.
2.
3.
4.
5.
Should be located in large
open fields for easy unobstructed
air flow.
Should be free from refuse
(garbage) to avoid interference
from birds.
Requires a large floor area if
multiple mills are erected in the
same place.
Since it’s located in open
fields, they are mostly situated in
city outskirts and hence power
transmission is a problem.
Due to transmission losses,
useful power is reduced by about
17%.
To avoid this, the wind mills should be
situated in city where all the above
pointers are satisfied.
GENERAL
WORKING
WIND MILLS
OF
Wind energy is a potential source of
energy. Winds are the motion of air caused
by uneven heating of the earth’s surface by
the sun. It generates due to various
phenomena such as ‘air-temperature
difference’ associated with different rates
of solar heating. Since the earth’s surface
is made up of varying contours, the surface
absorbs the sun’s radiation differently.
Locally, the strong winds are created by
sharp temperature difference between the
land and the sea. Wind resources in India
are tremendous. They are mainly located
near the sea coasts. Its potential in India is
estimated to be of
MW.
According to a news release from
American Wind Energy Association. The
installed wind capacity in India in the year
2000 was 1167 MW and the wind energy
production was
MWh. This is
0.6% of the total electricity production.
Winds are characterised by land and sea
breeze phenomenon.
W. But the total exploitable wind power is
only 2
W.
The theoretical wind power can be
estimated as:
LAND BREEZE
BREEZE
Power density = 0.6 k. ρ.
AND
SEA
During the day, air above the land heats
more quickly than air above water. The hot
air over the land expands and rises, and the
heavier, cooler air over a body of water
rushes in to take its place, creating local
winds. At night, the winds are reversed
because air-cools more rapidly over land
than over water. Similarly, the large
atmospheric winds that circle the earth are
created because land near the equator is
heated more by the sun than land near the
North and South Poles. Wind energy can
be used to produce electricity. Wind is a
renewable energy source.
Winds have two different origins.
1. Planetary winds are caused by
daily rotation of earth around its
polar axis and unequal temperature
between Polar Regions and
equatorial regions.
2. Local Winds are caused by unequal
and heating and cooling of ground
surface and ocean or lake surfaces
during day and night.
The vanes of wind mills are designed
based on the aerofoil model for easy air
flow through the vanes, thereby rotating it
to produce energy.
AEROFOIL DESIGN
A wind turbine changes the kinetic energy
of the wind into rotary motion.
The estimated total power capacity of the
winds passing over the land is about
= 0.6 π
Where;
k=Energy pattern factor (depends on type
of wind)
ρ= Wind density
v=average wind velocity.
The effect of this equation is that if the
wind speed doubles, the power output
increases eightfold. So small increases in
wind velocity can create large increases
in power output.
The large amounts of energy that are
produced at very high wind speeds means
that most wind turbines have a predesigned maximum power output to
prevent the failure of machinery. Large
wind turbines rated 150 kW and above are
very complex. All wind turbines must be
designed in a way such that the wind
moves over them thereby facilitating
smooth rotation. If this didn’t happen, the
centripetal force could rip the blades off.
Large turbines also have complex
automatic gear boxes that keep the
generator turning at the optimum speed for
power generation. Constant wind flow is
very rare. This means that the rated output
of the turbine will never be achieved as a
constant output. On average, turbines
produce about 30% of their rated capacity
as continuous power.
DESIGNING A WIND MILL
The larger the wind turbine, the higher the
tower that supports the blades must be.
This isn’t just to keep the blades a safe
distance off the ground. The higher you go
from ground level, the faster and more
uniform the wind so you get more power.
So, as the power output of turbines
increases, so does their size. The only
restriction on the size of a wind turbine is
the strength of the materials from which it
is built. This is a serious engineering
problem because whilst the turbine must
be light enough to turn in a light breeze,
the structure must be strong enough to
withstand storm force winds.
D = diameter of turbine wheel =
meter,
N=wheel revolutions per second in
in
.
For a turbine operating at power P, the
torque is given by
T=
For
a
efficiency,
by:
turbine
at
hence
maximum
is given
=
For axial force or axial thrust,
FORCES ON THE WIND VANES
There are two types of forces operating on
the blades of wind turbine. They are the
circumferential forces in the direction of
wheel rotation that provide the torque and
the axial forces in the direction of the wind
stream that provide an axial thrust that
must be counteracted by proper
mechanical design.
CALCULATIONS
The circumferential torque is obtained
from the equation,
T= P/ = P/
The axial force on a turbine wheel
operating at maximum efficiency where
v=1/3,
=
The axial forces are proportional to the
square of the diameter of the turbine wheel
which makes them difficult to cope with in
extremely large-diameter machines. There
is thus an upper limit of diameter that must
be determined by design and economic
considerations.
The performance of a wind mill rotor
stated as coefficient of performance is
expressed as:
Where,
T= torque in Newton,
= angular velocity of turbine wheel in
m
,
=
Where,
A= swept area,
v=velocity of wind.
The exploitation of wind mills in India is
feasible. Depending upon the survey of
velocity in a region the appropriate value
of design parameter may be computed.
The American Wind Energy Association
(AWEA) estimates wind energy could
produce more than 10 percent of the
nation’s electricity within the next 30
years.
HIGHWAY WIND TURBINES
As already discussed, the population is
exploding in India by each passing day.
Hence air fields cannot be allotted. Thus as
an improvisation, the wind turbines are to
be placed in such places where it won’t
consume useful land area.
Here, the wind turbines are to be installed
in medians of highways.
CONSTRUCTION
The wind mills employed here is vertical
axis wind turbine. The winds are generated
by vehicles passing by. Here vertical axis
turbines used since large area has to be in
contact with the winds as they are weaker
than the natural winds. The vanes are
helical in structure and are made of light
materials like aluminium or tin. They may
even be made of recycled plastic since the
winds in this case are comparatively weak.
A prototype of the vertical axis turbine is
shown:
These wind vanes along with their turbine
arrangements are installed in medians of
highways with guiding vanes.
GUIDING VANES
The guiding vanes are inclined vertical
sheets made up of aluminium or plastic or
plywood. These vanes are inclined in such
a manner that they remain normal to
direction of air flow, thereby guiding the
air onto the vanes of vertical axis wind
mills. Since this is situated in medians, the
air has to be channelled for the vanes to
rotate. Thus the use of guiding vanes are
employed. The top view of the proposed
model is shown below
The red arrows in the above diagram
indicate the direction of air flow. The
guiding vanes are usually supported on a
single hinge to facilitate the easy tilting of
the vanes. The whole highway wind
turbine is easily detachable. The vanes
produce electricity from the air produced
by vehicles passing by and this energy can
either be stored in batteries or transmitted
through transformers or can be routed to
run the street lights in the highway. Even
though the power produced is of small
quantity, it is enough to operate the street
lights and traffic signals.
ADVANTAGES
1. Power produced continuously since
there are vehicles passing by
constantly.
2. The whole setup can easily be
detached or assembled.
3. Low cost since even plastic or
recycled materials can be used.
4. Noise less operation.
5. Does not hinder the public or
traffic since it is located on the
medians.
6. Zero emissions. Pure green energy.
7. Less maintenance needed.
8. No
operators
needed.
100%automatic process.
9. Less initial cost.
10. No need to install in tall place. No
special foundation needed.
LIMITATIONS
1. Turbines will be flooded during
monsoon. Hence water proofing
has to be done.
2. Flying leaves, dust, sand, asphalt
etc... may damage the turbine.
Hence the turbine has to be dust
proof.
3. Dashing of vehicles in median
may break the vanes. Also vanes
which are in aerofoil shape may
have sharp edges. The vanes have
to be insulated.
CONCLUSION
Thus the following conclusions are drawn
from afore mentioned project:
1. Energy produced from highway
wind turbines is enough to operate
street lights and traffic signals.
2. No hindrance and can also be
easily dismantled and assembled.
3. 100% clean green energy (ecofriendly)
4. Initial cost very low.
5. Plastics can be used hence disposal
of stray plastic is done.
6. Suitable for Indian roads.
REFERENCE
1. Power Plant Engineering by
Nagpal.
2. Power Plant Engineering by A K
Raja, Amit Prakash Srivastava,
Manish Dwivedi.
3. Power Plant Engineering by
Dumkondwar.
4. Fluid Mechanics and Machinery by
G K Vijaya Raghavan and S
Sundaravalli.
5. A Textbook of Fluid Mechanics
and Hydraulic Machines by Dr. R.
K. Bansal.
6. Mechanical engineer’s hand book
volume-IV (Energy and Power)
Edited by Myer Kutz.