Wind Turbines and Power Generators

The Low Down

Wind turbines are machines that change the kinetic energy present in wind into mechanical energy. Wind turbines are categorized into how that power is used. If the energy is used to power machinery directly - like with a pump or grinder, then the turbine is categorized as a windmill. However if the energy generated is then converted into electricity, it's called a wind generator, wind turbine or wind energy converter (WEC).

Horizontal Axis Wind Turbines (HAWT)

Horizontal Axis Turbines must be pointed in the direction of the wind to work. Their primary rotor shaft and electrical generator sits at the top of a large tower. They find the wind either through the use of a wind vane (for smaller towers) or a wind sensor powered by a servo motor. With stiff blades to prevent them from damaging the tower behind them, the turbine is pointed upwind of the tower to avoid the turbulence behind it. They can also be built downwind, because then they won't have a problem finding the wind, but turbulence can make turbines less reliable in bad weather.

Vertical Axis Wind Turbines (VAWT

A Vertical axis wind turbine has the main rotor shaft running vertically, which means you can then put the generator/gearbox closer to the ground. This version of wind power is advantageous because it means less weight strain on the tower and there is no need for the turbine to find the direction of the wind. There are more pitfalls to this type, however, as they must be operated closer to the ground and therefore produce less energy from wind.

"This does mean they are easier to maintain, however, and also cheaper because they require less building materials."

Offshore Wind Power

This is often among the most popular brand of wind power pursued by developers, as they don't interfere with local landscapes too much, and are generally far away from diverse ecosystems. Their size and noise level is also not as much of a factor because there are few people who have to look at/hear them. The power is transmitted by underwater cables, which is pricier than on-land cables, but necessary given the power is far from where it will eventually be used. These cables also fare better in fresh water, where there is less erosion than from the saltwater of the ocean. In the Great Lakes region of Ontario, Canada, Trillium Power has started an offshore project about 20 kilometers from the shore that should supply over 700 Megawatts to the province.

Offshore wind power is currently the most popular type, and will continue in this way because of the large scale energy production they can handle on the open ocean, and because few people on land want a wind farm in their neighbourhood, as they can affect plane radar, and some people consider them an eyesore.

Rotor Blades

Rotor blades come in two different types. They are either drag style - which are more successful in less windy areas due to their flat nature. They are what you would most commonly see in the wind mills of the past. Lifting style blades (or airfoils, as they are referred to in the industry) are curved and usually require fewer blades to generate power. They are also much more efficient than drag style blades in higher winds.

Dealing with Intermittency

Unfortunately, with both solar and wind power, there is the problem of intermittency. They are not completely reliable constant power sources because of the fact they take their power from the sun, which goes down at night, and the wind, which doesn't always blow at the same rate. However, there are methods to combat this problem by storing excess energy when it's especially gusty, and using it as back up when wind turbines produce less energy.

This is what's done at the Some Hill Wind Farm in Ireland. Erected in Ireland in 2004, the facility has plans to add a massive battery to their energy farm to account for fluctuations in wind energy flow. According to American Scientist magazine, they are planning to us a Sa vanadium redox flow battery, which is almost like a really big fuel cell, and can hold up to 12 megawatt hours of backup electricity. However unlike a fuel cell, the redux flow battery can be charged and discharged over and over.

"The magazine has reported that studies suggest if all goes according to plan, the battery will pay itself off in ten to fifteen years."

Although buying large batteries like this may be expensive, there are also other ways to compensate for intermittency in power output. Even conventional electricity sources can be used as back-up when wind power falls a tad short. Instead of closing the power generation stations currently open (those that use conventional fossil fuels or hydroelectricity) they could be kept open at low cost as an emergency energy source. In fact, Denmark currently backs up their wind-powered section of the national grid with hydro-electricity, both of which are renewables. And although there needs to be back up power available, wind power now supplies a fifth of their national energy.

Although wind power may have it's pitfalls, they can be overcome fairly easily. Plus, the benefits greatly outweigh any problems that may arise from using an intermittent power source. There are investments worth making if it means preserving a cleaner planet and atmosphere for future generations.

Source(s): Schneider, David. "Penetrating Winds." American Scientist; Nov/Dec2007, Vol. 95 Issue 6, pg. 490-491.