Ever since I was a “youngin”, I was in awe of windmills(mechanical action), wind turbines(electrical action), solar panels and other alternative/renewable energy displays at different locations my family and I visited. In this post, I intend to concentrate on wind turbines (generators).
There are two broad classifications of wind turbines: 1) Horizontal Axis (HAWT), and 2) Vertical Axis (VAWT). I’ll start with a brief rundown of the Horizontal Axis wind turbines and wind up with a short discussion of the Vertical Axis wind turbines.
Horizontal Axis wind turbines dominate the market and have been described as a “propeller on a stick” They are called “horizontal” because their rotating axis is parallel to the ground.
Horizontal Axis Wind Turbines 
On the whole, Horizontal Axis wind turbines are more efficient and effective in relatively high, steady winds. One reason why they’re more efficient, the full length of the blades catch the full face of the wind during their entire rotation. Some of the disadvantages are: 1) they require a greater amount of steady wind to be efficient, which requires higher mounting to achieve the necessary altitude; 2) most of the operating components are mounted on top of the tower, making servicing them a more complicated task; 3) they require an additional “yaw” mechanism to keep the blades facing into the wind; 4) HAWTs require expensive equipment, like cranes and heavy duty dozers to build them, along with the personnel to operate the equipment and 5) specialized transportation is required for the blades.
On the other side of the coin are the Vertical Axis wind turbines (VAWTs). Their main rotor shaft is situated vertically, with respect to the ground.
Vertical Axis Wind Turbines
The two main types of VAWTs are: 1) Savonius – drag based like an anemometer and 2) Darrieus – named after the French inventor, Georges Darrieus. They are predominently lift based (aerodynamic design with the blades exceeding the speed of the wind).
VAWTs have several advantages which include: 1) the wind can come from any direction; 2) lower startup wind speeds reqired for electrical production; 3) less noise; 4) works better with gusting winds, wind changing directions and speed; 5) usually easier to service because closer proximity to the ground and 6) they can usually be built where taller structures are prohibited.
The disadvantages include: 1) not as efficient use of the wind (blades do not have constant head on wind); 2) some designs place blades directly on top of the generator, making maintenance a real chore and 3) they are subject to “surface drag”.
An excellent book I’ve been reading on wind turbines that cuts through a lot of hype is “The Ultimate Consumer Guide to Wind Power I was a little disappointed that their book only deals with HAWTs but their research, actual lessons and applications are honest and can be used for any type of wind turbine.
In conclusion, I would surmise that HAWTs would be a superior choice for large wattage output, commercial applications and some residential while the VAWTs would be a better choice for most residential applications. This is my personal opinion. There are new and improved designs being developed all the time, I could change my opinion next week, though that would be unlikely.
Thank you for your visit to my site. Feel free to leave me any questions, comments and/or suggestions by clicking on the “comments” link immediately following this post May God Bless You and may you enjoy a favorable wind. Tim
What type are the offshore wind turbines?
Hi Kelly,
Most of the off shore wind turbines are the traditional horizontal axis. Some are a hybrid horizontal axis with the transformer and generator components mounted at platform level enabling a lighter weight at the top.