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Home » Energy » Wind Mills
Wind Mills
WINDMILLS

The windmill is machine that converts wind into energy with the rotation of a wheel of adjustable blades. Though skilled craftsmen design windmills, it is possible to construct windmill on site using hand tools.

The wind found in all parts of world has its own wind energy; and in a bit to not let this source of energy go to waste, people have been using windmills to harness this energy. In fact, it is because traditionally wind energy was used to grind grain into flour that it the word ‘windmill’ had come to mind.
Wind’s kinetic energy is captured by the windmill blades. The energy collected is then converted to mechanical energy.   Further, the machine that uses this mechanical energy to convert it into electrical energy or electricity  (just like the energy in moving water can be captured by the turbine in a hydroelectric dam) is known as a wind generator, wind power unit or WPU, or aero generator. When the turbine blades capture wind energy and start moving, they spin a shaft that leads from the hub of the rotor to a generator. The generator turns that rotational energy into electricity, compatible with the electric system at your homes. At its essence, generating electricity from the wind is all about transferring energy from one medium to another.
Wind power all starts with the sun. When the sun heats up a certain area of land, the air around that land mass absorbs some of that heat. At a certain temperature, that hotter air begins to rise very quickly because a given volume of hot air is lighter than an equal volume of cooler air. Faster-moving (hotter) air particles exert more pressure than slower-moving particles, so it takes fewer of them to maintain the normal air pressure at a given elevation (see How Hot Air Balloons Work to learn more about air temperature and pressure). When that lighter hot air suddenly rises, cooler air flows quickly in to fill the gap the hot air leaves behind. That air rushing in to fill the gap is wind.

Types of Wind Mills
Today there is a large renaissance in windmill technology as it promises to be a feasible alternative to fossil fuels in the future. You can find two types of windmills that are used for harnessing energy; 

•    Horizontal axis Windmills
The wind turbine design for a horizontal turbine is simple. The turbine consists of two or three blades that, when powered by the wind, move a gear. The gear powers a generator, which produces electricity. The gear and generator are held within the nacelle which sits on top of the turbine shaft. A yaw drive on certain horizontal models adjusts the blades to maximize the position of the wind.

•    Vertical axis Windmills
It was during the early development of the windmill that the vertical axis design grew popular. However with its inefficiency in operations, researchers came up with the horizontal axis designs in windmills. There are numerous types of horizontal axes versions of windmills that include the post mill, fan mill, tower mill and smock mill.
Although vertical wind turbines are not as popular because they are less efficient, new designs and models are constantly being produced. One of the basic ideas for vertical wind turbine design is to minimize the noise pollution and potential harm to birds that the horizontal wind turbine produces. Vertical wind turbines do have have blades and their design varies greatly.
One vertical wind turbine design is the Darrieus, which is compared to an egg beater in appearance. The Darrieus has an airfoil design which uses the lift forces of wind to move, similar to the wings of an airplane. This vertical model is not self starting and needs a motor to generate speed before creating significant torque of its own. The Darrieus is highly inefficient in producing sufficient wind energy to produce electricity.
The Savonius is another vertical wind turbine design. Although slightly more efficient than the Darrieus model, the Savonius is best used for small-scale energy production. The Savonius uses drag force to move by cupping the wind in a shape that resembles a half barrel. This model is also extremely quiet and can sustain high winds without damage.

Windmills Technology / Design Evolution Brief
The post mill is the first design in horizontal axis windmills which was named so for the large and upright post where the body of the mill is found.  The smock mill is similar to the post mill, with some improvements. Its body looks like a dress or smock, and so the name. 


                  


Tower mills are more improved than smock mills which have rotating caps and have a permanent body of brick or stone. This makes it possible for towers to be rounded, which allows for taller and larger towers. These towers also make the windmills more weather resistant. All these windmill designs service entire towns, while fan mills are meant for individuals.
The Mariah Power company has created the Windspire®, a turbine model that also uses airfoil design. The wind turbine is extremely tall and narrow. It consists of three airfoils that catch the wind and spin on a large vertical axis shaft.
In addition to large scale wind turbine design, smaller models like the Honeywell and the WindCube® are being developed for household use. The Honeywell looks like a fan, while the WindCube® consists of horizontal blades moving within a cube. Both models would work on top of individual homes or buildings.

Parts of a Wind Turbine
The simplest possible wind-energy turbine consists of three crucial parts:
     Rotor blades - The blades are basically the sails of the system; in their simplest form, they act as barriers to the wind (more modern blade designs go beyond the barrier method). When the wind forces the blades to move, it has transferred some of its energy to the rotor.
     Shaft - The wind-turbine shaft is connected to the center of the rotor. When the rotor spins, the shaft spins as well. In this way, the rotor transfers its mechanical, rotational energy to the shaft, which enters an electrical generator on the other end.
     Generator - At its most basic, a generator is a pretty simple device. It uses the properties of electromagnetic induction to produce electrical voltage - a difference in electrical charge. Voltage is essentially electrical pressure - it is the force that moves electricity, or electrical current, from one point to another. So generating voltage is in effect generating current. A simple generator consists of magnets and a conductor. The conductor is typically a coiled wire. Inside the generator, the shaft connects to an assembly of permanent magnets that surrounds the coil of wire. In electromagnetic induction, if you have a conductor surrounded by magnets, and one of those parts is rotating relative to the other, it induces voltage in the conductor. When the rotor spins the shaft, the shaft spins the assembly of magnets, generating voltage in the coil of wire. That voltage drives electrical current (typically alternating current, or AC power) out through power lines for distribution. (See How Electromagnets Work to learn more about electromagnetic induction, and see How Hydropower Plants Work to learn more about turbine-driven generators.)
Now that we've looked at a simplified system, we'll move on to the modern technology you see in wind farms and rural backyards today. It's a bit more complex, but the underlying principles are the same. 


Modern Wind-power Technology
In a VAWT, the shaft is mounted on a vertical axis, perpendicular to the ground. VAWTs are always aligned with the wind, unlike their horizontal-axis counterparts, so there's no adjustment necessary when the wind direction changes; but a VAWT can't start moving all by itself -- it needs a boost from its electrical system to get started. Instead of a tower, it typically uses guy wires for support, so the rotor elevation is lower. Lower elevation means slower wind due to ground interference, so VAWTs are generally less efficient than HAWTs. On the upside, all equipment is at ground level for easy installation and servicing; but that means a larger footprint for the turbine, which is a big negative in farming areas. 


VAWTs may be used for small-scale turbines and for pumping water in rural areas, but all commercially produced, utility-scale wind turbines are horizontal-axis wind turbines (HAWTs).
We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent - a wind turbine - can use the wind's energy to generate electricity.
Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor.
A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. For utility-scale sources of wind energy, a large number of wind turbines are usually built close together to form awind plant. Several electricity providers today use wind plants to supply power to their customers.
Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners, farmers, and ranchers in windy areas can also use wind turbines as a way to cut their electric bills.

Wind Power- Global Trends
Wind power is the fastest growing of the renewable energy technologies, though it currently rovides less than 0.5 percent of global energy. Wind energy capacity has grown rapidly since 1990, doubling every three and a half years, to reach some 72 000 MW by end-2006, with annual output of around 160  TWh. Globally, wind power generation increased more than fivefold between 2000 and 2007.  Global installed capacity at the end of 2008 was almost 121 gigawatts producing approximately 260 terrawatt hours of electricity annually.

Moreover the size of wind turbines being installed continues to grow, with many new onshore machines in the 2 MW bracket, and offshore turbines substantially larger (up to 5 MW, with blade diameters up to 110 m).

In Australia
In 2007 the Government committed to ensuring that 20 percent of Australia's electricity supply would come from renewable energy sources by 2020 by establishing the expanded national Renewable Energy Target (RET) scheme. The major emphasize in on wind power and solar energy.
Australia has some of the world’s best wind resources. The total operating wind capacity at the end of 2008 was 1306 megawatts - a 37 percent rise on 2007. This equated to a generation of approximately 3,500 gigawatt hours of electricity annually. In 2009 a number of new wind farms have been commissioned and the total operating capacity now stands at 1476 megawatts - generating over 4,200 gigawatt hours of electricity annually.
Currently there are 47 operating wind farms in Australia, with a total of 834 operating turbines. South Australia has the largest installed capacity around 50 per cent of the nation’s total capacity.

Future Potential :
There are currently almost 6,000 megawatts (MW) of large-scale wind farm energy projects proposed around the country, many of them having already received planning permission.

Concerns for Home Windmill
Wind turbines can be installed on properties, on boats, or caravans. Getting a wind turbine depends entirely on the amount of wind generated in your area. The first thing you need to do is to find out the average speed in your area. 

Typically, the home does not rely entirely on the energy produced by a home wind turbine. If wind speeds are low, the home wind turbine will not generate electricity, so most homes are also connected to a local utility service or have other renewable energy sources as geothermal or solar. When wind speeds are very high and the home wind turbine generates more electricity than the household needs, the extra power can be sold to the utility company. Although it is possible to store electricity in batteries, most home wind turbine systems do not store it.

The average wind speed needs to be above 5m/s (18km per hour) to make installing a wind turbine worthwhile. Ideal locations for wind turbines are in the country, on farms, or on the coast: basically anywhere away from built-up areas. The more buildings around the wind turbine, the less wind there is. Energy Matters can do full installations of hybrid, wind and solar energy systems. Setting up a wind turbine is a big job that takes time but it can be a very cost effective way of creating power as long as the average wind speed is high enough.

                        


In most cases, a home wind turbine should be placed at least 30 feet (9 m) higher than any nearby object. Usually small towers are installed with a home wind turbine. Homeowners should check all local ordinances before purchasing one.
On an average, a residence of a normal size uses about 780-800 kilowatt (kWh) of power per month or around 9400 kWh of electricity per year. To meet such a high electricity demand, therefore, you would require a wind turbine that generates 5 to 15 kilowatts of electricity. To conclude, we can say that a wind turbine is powerful equipment used to run your electrical appliances.
Use of a home wind turbine usually reduces a home electricity bill from 50 to 90 per cent. Long-term savings depend on a many factors. A house located in areas with high average wind speed will obtain more electricity from a home wind turbine than one in area with light breezes. An all-electric home can use more of the electricity from a home wind turbine than one that also uses other kinds of power. Installation costs vary, but a home wind turbine usually pays for itself in six to 15 years.
Installing a home wind turbine is good for the environment. It produces no pollution and reduces demand for electricity produced by methods that do pollute. A home wind turbine does create some noise, but it is not extremely noisy. Many kinds of home wind turbine never get noisier than 35 decibels.
 It is equally important to check the zoning laws in your area too. One wind turbine can be sufficient to generate energy for a household.

Benefits of Wind Power

•    Wind power is a clean energy source that can be relied on for the long-term future.
•    Wind is a source of energy which is non-polluting and renewable, wind turbines create power without using fossil fuels, without producing greenhouse gases (as carbon dioxide and methane) or radioactive or toxic waste.
•    The wind power generator or a wind turbine, as it is commonly known as, helps you harness wind, a free and abundant natural resource and convert it into electricity, which can be used at your house, business or for grid connection.
•    The wind is free and with modern technology it can be captured efficiently
•    Once the wind turbine is built the energy it produces does not cause green house gases or other pollutants
•    A wind turbine creates reliable, cost-effective, pollution free energy.
•    The electricity so produced apart from being cheap and economical,
•    It can lower your electricity bill on a monthly basis.
•    It is affordable, clean and sustainable.
•    Their usage in remote areas such as cabins, camps, boats, for vacations, and so on is very advantageous as it reduce/ eliminate the cost of grid connections to remote areas.
•    Wind turbines take up less space than the average power station. Windmills only have to occupy a few square meters for the base, this allows the land around the turbine to be used for many other purposes. This is especially the case in agricultural areas as farming can still continue.
•    Many people find wind farms an interesting feature of the landscape.
•    Wind is free, and we are able to cash in on this free source of energy.
•    Wind turbines are a great resource to generate energy in remote locations, such as mountain communities and remote countryside. These remote areas that are not connected to the electricity power grid can use wind turbines to produce their own supply.
•    Wind turbines can be a range of different sizes in order to support varying population levels. Single households to small towns and villages can make good use of range of wind turbines available today.
•    In certain cases, installing a wind turbine can be even better than installing solar panels because it can create a bigger mass of the energy required.
•    Another advantage of wind energy is that when combined with solar electricity, this energy source is great for developed and developing countries to provide a steady, reliable supply of electricity.
•    It doesn’t let the ever-changing electricity prices affect you adversely.
•    Newer technologies are making the extraction of wind energy much more efficient.

•    Wind power help reduces global warming.

Going Green with Wind Power
Nowadays everybody is starting to feel the need to go green, and everybody is starting to think of ways that they can help the planet but still keep the lifestyles they’re accustomed to. Wind power is an excellent alternative energy source that has many benefits.
Generating electricity with the use of a wind turbine is a good alternative or supplement to solar power. If the sun isn’t shining, the wind will likely be blowing. You can save money on residential wind power if you build the wind turbine yourself.
The  wind turbine helps you harness wind, a free and abundant natural resource and convert it into electricity, which can be used at your house, business or grid connection. With modern technology it can be captured efficiently. Once the wind turbine is built the energy it produces does not cause green house gases or other pollutants. It is affordable, clean and sustainable.
In 2008 estimated wind energy generation saved Australia 3,530,744 tonnes of carbon dioxide. That is equivalent to:

• the removal of 784,610 cars from our roads or
• planting 5.26 million trees.

Consult WATEEN to get advise on windmill design that suits your requirements. We deal in residential, commercial /industrial wind generators, wind turbines and their associated components and technologies.