Wind Energy Technologies

While old-fashioned windmills are still seen in many rural areas for pumping water, modern wind turbines are divided into two major categories: horizontal axis turbines and vertical axis turbines.

Producing 204 megawatts, this is the third largest wind power plant in the world.

Photo by Michael McDiarmid, Courtesy of New Mexico Energy Conservation and Management Division

The New Mexico Wind Energy Center has 136 turbines, 320 feet high.

Figure 6-27

Horizontal Axis Turbine

Producing 204 megawatts, this is the third largest wind power plant in the world.

Photo by Michael McDiarmid, Courtesy of New Mexico Energy Conservation and Management Division

The New Mexico Wind Energy Center has 136 turbines, 320 feet high.

Figure 6-27

Horizontal Axis Turbine

Horizontal axis turbines like the one pictured in Figure 6-27 are the most common turbine configuration used today. They consist of a tall tower, atop which sits a fan-like rotor that faces into or away from the wind. Most horizontal axis turbines built today have two or three blades, although some have fewer or more blades. The newer, larger and more powerful horizontal axis turbines have blades that are longer then those of a 747-jet airliner! Plus, they are the most efficient in terms of energy production, to date.

A vertical axis wind turbine (VAWT) is likely to fall into one of two major categories: Savonius and Darrieus, however neither turbine type is in wide use today.

The Darrieus turbine was invented in France in the 1920s. Often described as looking like an eggbeater, this vertical axis turbine has vertical blades that rotate into and out of the wind. Using aerodynamic lift, these turbines can capture more energy than drag devices. The Giromill and cyclo-turbine are variants on the Darrieus turbine.

Giromill Wind Turbine

Figure 6-28

A Darrieus-type Turbine

Photo Courtesy of Darrel Dodge

Figure 6-28

A Darrieus-type Turbine

Photo Courtesy of Darrel Dodge

The basic "theoretical" advantages of a vertical axis machine are that the generator and gearbox can be placed on the ground and do not require a tower. Plus, you do not need a mechanism to turn the blades into the wind as you do with a horizontal axis machine. That said, the disadvantages of a Darrieus turbine far outweigh its advantages. First of all, wind speeds are much lower close to the ground so the overall power generating efficiency is not very impressive. Plus it needs a push to get started and must also have a wide network of guy wires to hold it in place, which occupy valuable farm land that can't be used for grazing or planting. Finally, when the main bearings or other parts need maintenance the whole machine must be torn down. That's why the Darrieus turbine picture here has been out of service for many years, rusting away on a hill above the St. Lawrence Seaway in Canada.

First invented in Finland, the Savonius turbine is S-shaped if viewed from above. This drag-type VAWT turns relatively slowly, but yields a high torque. It is useful for grinding grain, pumping water, and many other tasks, but its slow rotational speeds are not good for generating electricity.

Figure 6-29

A Savonius-type Wind Turbine

Photo courtesy of Lance Turner

Figure 6-29

A Savonius-type Wind Turbine

Photo courtesy of Lance Turner

Some practical electrical applications for Savonius wind turbines still exist, however, like the one pictured here. When there is a need for a small amount of electricity and solar panels are not practical due to climate or lots of trees, etc. a home-built Savonius wind turbine will do nicely. This one in particular provides the user with enough electrical power to open and close a gate to the driveway entrance as well as power safety lights.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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