Wind Speed – Is There Enough Wind Where You Live
Wind energy has come along way over the last few decades or so, and most of us have seen many wind turbines arranged together both on-land and off-shore, which are known as “wind farms”, to capture large amount of power at once and feed it directly into the national grid. Back in the day the wind’s energy was only used to power sailing boats or drive windmills for irrigation and milling, but today through advancements in modern turbine and generator technology we can now use the wind’s energy to help power our homes.
Wind energy systems are one of the most cost-effective home-based renewable energy systems transforming the kinetic energy of the wind into mechanical or electrical energy that can be harnessed for practical use. Depending on your wind resource, a small wind energy system could substantially lower your electricity bill. But does the wind blow hard and consistently enough at your site to make the investment into a small wind turbine system economically viable.
There are many different types of wind turbine models available for domestic, camping and farmstead use both on-grid and off-grid connected. However, not all of them would be good for each location since the wind speed varies depending on where you live.
People who live near to the oceans are aware of the force of the winds speed and how it affects their lives, while those living in cities, the speed of the wind is much less or only experienced at high levels during rains and storms. Wind speed is quite simply the speed at which wind moves through the atmosphere and as such can be measured.
When we are looking to buy a new house we are constantly being told, location, location, location, and the same is also true about wind energy. The location of the wind turbine is critical, as there are areas around the world where the winds blows virtually non-stop, 24 hours a day, 7 days a week, while there are other areas that receive very little. So in order to generate sufficient amounts of electricity and be a cost effective renewable energy source, a wind turbine generator needs to be in the right location.
The wind’s energy can vary significantly over a small area, as sites only a few hundred yards apart can see big differences in wind flow, better known as “wind velocity”. This variation is mainly due to the type of local terrain, hills, mountains, etc and potential obstacles, trees, buildings, that are in the winds path. The wind possesses energy by virtue of its motion and this type of energy — the energy of motion — is called kinetic energy which turbine generators used to produce electricity.
The potential power output over the course of a day is directly related to the amount of wind velocity at a certain site. Wind speed in any site is naturally highly variable and although we cannot see the air moving, we can still feel it. So any wind energy device capable of slowing down this mass of moving air can extract some of its energy and convert it into useful work but there is actually a fine line between enough wind speed and too much.
It’s all well and good to have a shiny new wind turbine at the bottom of the garden or fixed onto a roof, but if the wind does not blow the wind turbine will not rotate and produce any electricity. Likewise, if the wind energy is to strong the wind turbine may rotate so fast as to damage itself or overheat.
So it is important when siting a wind turbine as part of a wind energy system to know beforehand is there enough wind where you live and how fast the wind is actually blowing over a period of time. Wind speed is important because the amount of electricity that wind turbines can generate is directly determined by the wind speed, or velocity. Using a good quality anemometer like those made by Reed Instruments will help you determine the wind speed in your area.
Before you invest in a wind energy system you need to estimate or measure the wind resource in your area or site. Wind resource maps, or wind speed maps, are available from libraries, local town halls and even local airports which can be used to estimate the wind resource in your region. They are also used by architects in the design of buildings and structures. Windy sites and areas can be developed, but they cannot be created so to produce electricity from the wind we must identify sites where the wind blows as steadily and consistently as possible.
A typical turbine requires wind speeds of about 10 miles (15 kilometres) per hour to start generating. This minimum wind velocity is generally referred to as the wind turbines cut-in speed. So for best results, a wind turbine should be positioned in an area where there is a consistent wind speed greater than this minimum cut-in speed before power starts being produced. But winds are three-dimensional things, and the characteristics of the wind depends very much on the elevation above the ground as well as across it.
If you live in an area of low wind speed you may need turbine blades with more surface area by using multiple blades. Most commercial wind turbines are three-bladed designs, but using a rotor with more than 3 blades will help capture more of the winds energy. But increasing the blades surface area will also have the effect of increasing its drag through the air at higher speeds, but you will have a much lower start up or cut-in speed. Multi blade designs benefit the most in low wind speed areas.
One of the most common type of low wind speed turbine design is the three bladed Popsport wind generator that generates 12 or 24 volts from its light and powerful 400W DC generator making this wind generator kit ideal for Home Use.
Winds that are close to the ground are very turbulent due to the breaking up of the winds flow by the obstacles it encounters on the ground. If you are lucky enough to live in an area that has wind speeds between 10-20 mph (or 15-32 kph), then you are in business as the available wind power is proportional to the cube of the winds velocity, ( K*V3 ). In other words, if the wind speed doubles, you can get eight times the wind power from it up to the turbines maximum wind speed. Most commercial wind turbines have some form of automatic over speed protection which stops the rotor blades from spinning out of control in very high winds.
If wind resource maps are not available for your given location, the wind speed available in your location can be measured using a weather vane or a type of wind gauge known scientifically as an Anemometer. An anemometer is a device used to measure the velocity and direction of the wind giving an idea of the amount of wind energy available at a particular location. It is usually consists of a rotating, arrow-shaped instrument mounted on a shaft high in the air and is designed to point in the direction of the wind as shown in the image.
So now you can see how important it is to know is there enough wind where you live and what your average speed is in your area as ideally, a wind turbine should be operated at its maximum power output most of the time. But before you install a wind turbine you need to study the proposed site and height to determine the general wind power potential that exists there as well as the predicted energy production from the new wind turbine. After all, if you buy a new wind turbine you will want it to rotate as much as possible generating electricity and providing a quick return on your investment.
We have seen that wind turbines convert the kinetic energy of the wind speed into mechanical power that runs a generator to produce clean electricity. Today’s turbines are versatile modular sources of electricity. Their blades are aero-dynamically designed to capture the maximum energy from the wind. The wind turns the blades, which spin a shaft connected to a generator that makes electricity.
The size and power rating of the wind turbine you need will obviously depend upon your application and whether you require one to charge batteries or be grid connected. Most small scale wind turbine generator designs range in size from about 40 watts to many hundred’s of kilowatts (kW). The smaller micro-scale turbines 40-to-500 watt turbines are generally used for charging 12 volt batteries in a variety of applications such as remote cabins, recreational vehicles and sail boats.
As long as the sun continues to shine we will never run out of wind, which makes it a great source of renewable energy. Wind energy has shown to be one of the most abundant forms of renewable energy freely available around the globe and is a viable option to complement other types of pollution-free generation. The potential for domestic wind power has grown considerably in the last few decades due to advances in technology helping us reduce our dependency on fossil fuels, decreasing greenhouse gas emissions. But before we can purchase or install our wind turbine we need to measure and understand the wind speed and its strength for our given location to understand is there enough wind where you live.
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