Wind turbines and principle behind its blade design (https://science.howstuffworks.com/environmental/green-science/wind-power3.htm)When we hear the term wind turbine we all think that it is some device which gives out useful electricity using wind energy as its input. To have a more elaborated picture of process real mechanism involved behind in this simple yet very beneficial process, let us think “How the wind power works?” As we know that obsolete Dutch windmill design which solely used wind’s force to move the blades around the center hub, unlike in the modern and advanced turbines are amended by more and more science and technology is incorporated into the design of blades, the best example for this is the utilization of aerodynamic principles for blade design so that to extract wind’s energy effectively. For rotating the wind turbine rotors two primary forces of aerodynamics are been considered Lift and drag.
Drag acts parallel to the direction of flow whereas lift acts perpendicular to the direction of wind flow.Most of us are not aware that the turbine blades are designed using a lot similar concept of airplane wings, with one side of the blade being flat and another side kind of curved surface. Lift phenomenon is very complex to understand and explain, to put it in simple words the using the above figure ( ??), When wind gliding over the curved surface of the blade it has to move faster in order to match with the wind travelling across the flat surface, during this process the faster moving blade across the curved surface end tends to rise in the atmosphere and creating a low-pressure pocket just above it and this low-pressure pocket tends to SUCK the blade in a downward direction, which can be termed as “Lift” effect. On another hand, the wind gliding across the flat surface which will be traveling relatively at a lower speed compared to the wind traveling on the curved surface, this creates a higher pressure which in turn pushes the blade in the same direction. This combination of suck and push actions of the blades in the same direction will keep the turbine blades and hence rotor hub rotating more efficiently in one direction. So far we had taken only aerodynamics into the picture, but it is not the only factor involved in making wind turbines more effective.
Other factors to be considered are a) Size of the blades b) Tower height Size of the blades: More energy can be generated using the longer turbine blades. Which will lead to higher rotor diameter. In general, with doubling the rotor diameter produces four times increase in wind power. This can more clearly understand by having wind power equation.
P = (1/2) ?Av^3P- Wind power ? – Air density A- Area = (?/4)D^2V = velocity In above equation, P is directly proportional to Area and hence it is directly proportional to D^2, so by doubling diameter we can have Power output increase by 4 times. But with an increase in Rotor diameter and blade sizes, it makes the installation and transportation of blades and turbine setup more difficult and hence increase in overall initial cost which is the drawback of larger blades. Also In areas with lower wind speed smaller diameter rotor wind turbines could produce more electricity in comparison with larger wind turbine setups, the reason being: at lower wind speeds, smaller turbines operate to its maximum capacity and hence increasing overall output efficiency.Tower Height: Height of the tower also plays an important role in enhancing the generation capacity of the wind turbine unit, at a higher elevation, the wind speeds are higher due to the uninterrupted flow of winds, ground friction and objects at ground level obstruct the wind flow and hence reduces the wind speed.
It is estimated by scientists that 12% increase in wind speed with doubling the lower elevation. Components of the wind turbine and its working: Rotor blades: Blades are attached to the rotor hub, as explained above with the unique blade surface design the wind turns the blades and are main source and input to the rotor hub. Blades are the one which converts wind energy into mechanical energy with help of rotor hub and main shaft. Rotor Hub: Rotor hub is connected to the Main shaft and acts as input to the shaft. It spins around capturing part of the kinetic energy from wind and turns the main shaft.
Main Shaft: Shaft is connected to the rotor hub on one end and gearbox on another end, which is further connected to the GeneratorGenerator: Generator converts from mechanical energy into electrical energy using the properties of electromagnetic induction.Nacelle: Casing that holds gearbox, generator, ECU, yaw controller & brakes.Yaw controllers are used to aligning the rotor hub in the direction wind and brakes are used to restrict the blades to rotate beyond its capacity.
Many transmission and distribution components are used in between wind turbine tower and electricity utilization point say home or office to deliver the generated electricity in usable form Classification of Wind turbines. Based on the axis of rotationVAWT – Vertical axis wind turbines have their axis of blades rotation vertical as indicated by its name and are very rare to see in usage compared to its counterparts (HAWT). The rotor hub is long tube standing vertically with upper and lower hub as in figure(??) . The worlds tallest VAWT is built in Cap-Chat, Quebec. Further VAWT are classified in toa) Drag based (figure (??) ), b) Lift based. (left side image in figure (??) ),HAWT – Horizontal axis wind turbine have their axis of rotation in the horizontal direction and are very commonly seen wind turbines in most of the windy places. Blade/ Bladeless: Turbines can also be classified as a blade and bladeless considering the recent trends of the wind turbines which will be discussed in detail in next section “Recent trends in Wind turbines”. Recent Trends in Wind Turbines: Vortex bladeless(http://www.
vortexbladeless.com)Advantages of Vortex blades:- Less maintenance – Moving generator from top to bottom, which will reduce installation and maintenance cost – Usage of fiber-glass material for tower further helps in a weight reduction of set up and eases the installation process. – No lubrication needed. Less Noisy. Eco-friendly.
– Huge reduction of carbon footprint.- No gears or bearings. Vortex leads to a drastic reduction in material, manufacturing, and maintenance.- Vortex says its bladeless turbines will generate electricity for 40 percent less than the cost of power from conventional wind turbines. Drawback: Few wind turbine experts predict that: Startup Vortex Bladeless makes a turbine that looks intriguing, but it may not solve wind power’s challenges. – – Saphon wind turbines:Saphon wind turbines (bladeless horizontal axis wind turbines), No humming sound and a drastic reduction in harm caused to bats and birds in comparison to conventional blade wind turbines.Saphon energy is Tunisian green energy startup, these bladeless wind turbines are designed with the concept of design of the sails of a ship which promises the conversion of kinetic energy into electrical energy with having twice the efficiency and half the cost of the conventional wind turbines.
Saphonian turbines incorporate “Zero blade technology” which is patented system for harvesting wind energy. It involves channeling the wind back and forth till the wind energy is converted into mechanical energy using pistons. Further conversion from mechanical to electrical energy takes place using hydraulic motor and a generator Wind Tamer: (ducted wind turbine) It is handy and mobile to shift to desired locations in case existing location had inadequate wind speed and wind source. https://www.youtube.com/watch?v=mpUPlHx_2gw Its unique design creates two vacuums as shown in above figure, one behind the blade and another behind the duct, these two vacuums create a push and pull combination effect of air behind the duct and this setup helps wind tamer to produce the twice as much energy as compared to its counterparts, further which leads to exceeding the BELT limit efficiency (59.3%) Which is a very surprising factor, but this factor is not completely proved yet as many arguments and discussion are still active on this topic.
A few claim that efficiency of wind tamer is miscalculated Wind tamer is proved to be efficient even at the lower heights and slower wind speeds as seen in the above figures (??). Ducted design make the complete set up free from harm to birds unlike conventional blade wind turbines, the further ducted design makes set up noise free and vibration free. These turbines can be installed at agricultural, residential and commercial places due to its noise free and no harm to birds like features.
Wind tamer is proved to have faster returns of investment compared to conventional turbines. Recent trends in blade manufacturing: – Many approaches are made and for manufacturing the Wind turbine blade mold by additive manufacturing techniques such as 3-D printing rather than conventional manufacturing which will increase efficiency in manufacturing operations, faster design iteration cycles which will give freedom to innovate and design without penalties.