The need of the hour is sustainable and green energy. We can no longer afford to emit tones of carbon dioxide into the atmosphere, nor can we cope with the rising fuel prices anymore. The myth of infinite natural reserves has been dispelled. We have lot other renewable sources of energy all around us to be tapped.
Wind is a form of solar energy. The irregular heating of the atmosphere by the sun, the irregularities of the earth’s surface, plus rotation of the earth causes winds. This wind flow, or wind energy, when “harvested” by wind turbines produces energy which can be trapped to generate electricity and perform many functions.
Vertical-axis wind turbines (VAWT) are a form of wind turbine in which the blades are connected to a vertical axis. They are omni-directional which implies that it can instantaneously accept wind from any direction not like Horizontal Axis Wind Turbines (HAWTs) which have to constantly rotate so that they are facing the wind.
VAWT is near the ground, having all of the main components close to the ground. Early designs (Savonius, Darrieus, giromill and cycloturbine) had some drawbacks like the pulsatory torque that can be produced during each revolution and the huge bending moments on the blades. But the later designs like Turby, quietrevolution and aerotecture solved these shortcomings. VAWTs provided an economical alternative for domestic applications having the ability to self-start in light winds and are noise free.
Vertical axis wind turbines usually are created from lift-based or drag based designs. Following are some of examples of VAWT:
The 3-cup anemometer for measuring wind speed is an example of drag based vertical axis wind turbines (VAWT). If the cup’s velocity is same as the wind speed, it can be said that the instrument is working with a tip speed ratio (TSR) of 1. These cups can never go faster than the wind; therefore TSR will always be 1 or less.
Lift based models can provide more efficiency and more power than drag based turbines. Darrieus Vertical-Axis Machines is an example of Lift- based designs. This vertical axis wind turbine is shaped like an “eggbeater”. This VAWT produces large torque ripple and cyclical stress on the tower, which contributes to poor dependability. Generally they also require some external power source, or an additional Savonius rotor to start turning, as the starting torque is very low.
It is a brand of vertical-axis Darrieus wind turbine. This wind turbine consists of three vertical symmetrical airfoil blades, with each blade having a helical twist. Due to symmetry of the turbine and of the blades, there is no torque on a stationary turbine, as with a Darrieus turbine. Starting is attained by operating the generator as a motor. Torque is created by a change in the apparent wind direction relative to the moving blades.
The quietrevolution qr5
This is an inventive wind turbine which works well in the urban environment, where wind directions change frequently. This design is the result of a grouping of sound engineering principles and state-of-the-art aerospace technology. The quietrevolution qr5 differs from a horizontal axis wind turbine in that it doesn’t need to change its orientation to track the wind.
People are interested in vertical axis wind turbines as along with new technologies they are making them a more viable alternative. These Vertical axis wind turbines are best suited for home as well as residential use as they are smaller and can be installed on a rooftop or in a backyard. These turbines come in many different sizes, shapes and colors.
Some advantages of vertical axis wind turbines are:
- Lots of VAWT’s are bladeless, turning instead with flanges or other wind-catching outcroppings that don’t obstruct with the birds’ flight and hence they tend to be bird-friendly.
- Design and efficiently of VAWT’s make them generally turn at lower wind speeds than other varieties. This is particularly true of magnetic wind turbines or (Maglev turbines) that have low resistance because of the use of magnets.
- Unlike horizontal turbines, VAWT’s can be mounted closer to the ground for instance upon a rooftop rather than a 50 ft. to 300 ft. tower.
- Various VAWT’s have a cylindrical or helical design, which makes them less affected by cross winds.
- Quieter than other models
- VAWT need not be pointed in to the wind.
- VAWT’s don’t need as much wind to start spinning and they can utilize wind from any direction. Unlike horizontal wind generator they are not that effected by cross winds.
- VAWT has the compact size which can fit almost anywhere, and don’t necessarily need to be posted on a high spot. They can be fitted in the yard, on an outdoor porch, and on top of a home or garage.
Wind Energy Facts and Figures
- Germany is the world’s largest wind energy producer and United States is second in wind energy production.
- Denmark, Ireland, Sweden, The Netherlands and the United Kingdom are the five countries currently having offshore wind turbines.
- The top known U. S. state for wind energy is Texas which is followed by California.
- One megawatt of wind energy created translates to $1 million in economic development together with site planning, building, delivery, assembly and other benefits.
- According to American Wind Energy Association, the use of U. S. wind turbines may lessen the amount of carbon dioxide in the air by one-third.
- Over 80% of the costs for wind energy are because of construction materials and building.
- Wind turbines have been used to generate electricity for over 100 years.
- Wind is an alternating energy source and does not provide power on demand as will fossil fuel power plants.
- Homeowners can sell excess wind energy back to the utility companies.
- One megawatt of wind energy is sufficient to power 250 to 300 houses.
- The majority of home wind turbines are rated at 50 kilowatts or less.
- Wind turbines use the kinetic energy of the wind and convert it into mechanical power or electricity.
- Most of the older issues with wind turbines such as noise, visual impacts and bird mortality have been resolved with VAWTs latest improvements.
- As of 2008, 35 states in the U. S. are producing electricity from wind energy.[#2]
- Wind powered electricity generation has undergone considerable growth in installed capacity from ~6,100MW in 1996 to 94,123MW at the end of 2007 and a forecast of 240,300MW by the end of 2012.
- According to the Global Wind Energy Council, Canada increased its installed wind energy capacity by 113 per cent in 2006, bringing it up to 1,459 megawatts – enough capacity to provide the energy needs of nearly a million households, while preventing the emission of 3 million tones of carbon dioxide a year.