1.07.2008

What wind turbine is best for us?

There was much debate trying to decide on the windmill for the high school. One question to consider in choosing a windmill is what type of windmill to choose. Most people don’t know that there are even different types of windmills (I didn’t either until Windplanners!). There are two basic types of windmills: horizontal axis (HAWT) and vertical axis (VAWT).

When you picture a windmill, chances are you picture a horizontal axis windmill. There are several advantages to a HAWT. One of these is that it’s more stable than a VAWT because the blades are to the side of the turbine’s center of gravity. On a VAWT, the blades spin around the center of gravity, which decreases stability. Also, HAWTs are generally taller than VAWTs. The height of a HAWT ranges from 200 to 300 feet, while VAWTs are generally half that. HAWTs are also usually self-starting, so they don’t require a motor to start the rotation. HAWTs are also generally cheaper, mainly due to high production. However, the biggest advantage to a HAWT wind turbine is that the angle of the blades can be changed. This is helpful both in maximizing efficiency by catching the wind, but also in minimizing damage during a storm. There are disadvantages to HAWTs, though. For example, transportation can cost up to 20% of the total price due to difficulty transporting the tower and blades (which can be up to 180 feet long!) These tall towers are also difficult to install, requiring enormous cranes and specialists. Also, there are major concerns about tall towers interfering with radars at air force bases and with bird migration cycles.

The alternative to horizontal axis wind turbines are vertical axis wind turbines, or VAWTs. These are rather odd-looking structures that resemble egg beaters. The advantages of VAWTs are that they are easier to maintain and repair because most of the moving parts are near the ground. In some places such as mountains, mesas, and other high places can have winds closer to the ground in which a VAWT can produce more energy than a HAWT, which would be placed higher up. Also, the low height can be useful in avoiding conflict with local ordinances. VAWTs can also be easier and thus less expensive to transport and install because of the low height. They do, however, have many disadvantages. One major one is that most VAWTs produce only 50% as much energy as HAWTs. This is because of extra drag that is created when the blade faces into the wind. Also, most VAWTs must be installed on flat ground, and can’t handle steeper slopes that HAWTs could. Another disadvantage is many VAWTs require energy to start because the starting torque is so low that there is usually not enough wind power to start the turbine.

By taking these advantages and disadvantages into consideration, we decided to fundraise for a horizontal axis wind tower. This is mostly because the wind available at the high school is too high up for a VAWT to work. The taller tower of a HAWT is far more reasonable. The energy production of a VAWT is also not as good as that of a HAWT, particularly in our area. Also the price of a HAWT is more reasonable than that of a VAWT. VAWTs may be suitable for some locations and if you’re planning to install a windmill, please consider them carefully. Just because the HAWTs are the most common windmills, a VAWT could be better in your location. The goal is to produce as much energy as possible with wind power and avoid using fossil fuels. If a VAWT is the way to go, then by all means consider it.

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