An introduction to Wind Energy
Concept of Free Energy:
Free Energy refers to extractable energy which is present in bulk amount
around us. We see the concept of free
energy since from the very early people
of the world. Man used solar energy in extracting salt from marine water, wind
energy in sailing ships in the waters and wind energy in drying wet clothes.
NEED OF FREE ENERGY
Limited resources of Energy: As
our natural resources are going to an end day by day, we need to discover new resources of energy.
Economical perspective:
The fuel prices have become
unaffordable for developing countries. To maintain the pace of economical progress
the developed countries also need means of cheap energy.
Environmental perspective:
After industrial revolution we have
caused great destruction to our environment. To encounter this we need to
switch to the environmental friendly sources of energy.
Available Resources of Energy:
There are different resources of
energy which are being utilized these days are:
· Solar Energy
· Tidal Energy
· Geo Thermal Energy
· Hydro Energy
· Wind Energy
· Nuclear Energy
Why Wind????
v Most
abundantly found
v Easily convertible
v Cheap
v Low maintenance cost
v Environment Friendly
v Easy to control
v Can be generated on small scale
v An inexhaustible supply of wind
energy
Calculation of Wind Power
There are many complicated calculations and equations involved in understanding and constructing wind turbine generators however the layman need not worry about most of these and should instead ensure they remember the following vital information:
1) The power output of a wind generator is proportional to the area swept by the rotor - i.e. double the swept area and the power output will also double.
The Power of Wind
Where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.
Air has a known density (around 1.23 kg/m3 at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:
And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:
Where Power is given in Watts (i.e. joules/second), the Swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.
Wind Turbine Designing
Calculation of Wind Power
Calculate
the power of the wind hitting your wind turbine generator
There are many complicated calculations and equations involved in understanding and constructing wind turbine generators however the layman need not worry about most of these and should instead ensure they remember the following vital information:
1) The power output of a wind generator is proportional to the area swept by the rotor - i.e. double the swept area and the power output will also double.
2)
The power output of a wind generator is proportional to the cube of the wind
speed - i.e. double the wind speed and the power output will increase by a
factor of eight
The Power of Wind
Wind is made up of moving air
molecules, which have, mass - though not a lot. Any moving object with mass
carries kinetic energy in an amount, which is given by the equation:
Kinetic
Energy = 0.5 x Mass x Velocity2
Where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.
Air has a known density (around 1.23 kg/m3 at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:
Mass/sec
(kg/s) = Velocity (m/s) x Area (m2) x Density (kg/m3)
And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:
Power = 0.5 x Swept Area x Air Density x Velocity3
Where Power is given in Watts (i.e. joules/second), the Swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.
Betz Limit
Understand the Betz Limit and how it affects wind
turbines
Albert Betz was a German physicist who in 1919 concluded that
no wind turbine can convert more than 16/27 (59.3%) of the kinetic
energy of the wind into mechanical energy turning a rotor. To this day this is
known as the Betz Limit or Betz' Law. This limit has nothing to do with
inefficiencies in the generator, but in the very nature of wind turbines themselves.
Calculation
of power for our wind turbine
So, we decided to make wind turbine having rotor diameter of 1m. As we know from previous record of wind in Karachi that Wind only blows from the month of March to the month of October. In these months some days wind speed is very slow while in the month of July wind speed is very high. Keeping these things in mind we decided to design our wind turbine on the average wind speed of 5.5 m/sec. The density of air is 1.23 kg/m3. Putting these thing in formula we get,
So, we decided to make wind turbine having rotor diameter of 1m. As we know from previous record of wind in Karachi that Wind only blows from the month of March to the month of October. In these months some days wind speed is very slow while in the month of July wind speed is very high. Keeping these things in mind we decided to design our wind turbine on the average wind speed of 5.5 m/sec. The density of air is 1.23 kg/m3. Putting these thing in formula we get,
Power = 0.5 x π x 12 x 1.23 x 5.53
Power = 321.45 watt
After applying Beltz limit we get,
Power = 321.45 x 59.3%
Power = 190 watts
For blade designing click on this link....
No comments:
Post a Comment