Walking the floor of WINDPOWER 2008, the annual conference and trade show for the wind energy industry, one couldn’t help but be transfixed by all of the different types of turbines – at least I couldn’t. The wind turbine has become the iconic of clean, renewable energy. But the classic three-bladed horizontal axis wind turbine, with its gracefully swooping blades, has become the symbol of not only renewable energy, but also of environmental consciousness and ecological possibility.
Despite the ubiquity of the three-bladed turbine, the oft-overlooked vertical-axes turbines are making quite a splash in the world of wind energy, especially in small and micro-applications. So what’s all the fuss about? Vertical-axis turbines apparently do not suffer from some of the same problems that plague small wind applications in urban settings including, aesthetic concerns, space requirements and sound levels
Other advantages of vertical-axis turbines:
- Can produce up to 50% more electricity per year than conventional turbines with the same swept area;
- Generate electricity at much lower wind speeds, as low as 4 mph (1.5 m/s)
- Will continue to generate power in high wind speeds, up to 130 mph (60m/s) depending on the mode;
- Direct-drive units with no gearbox means a more efficient transfer of energy and no leaking oil;
- Will not harm wildlife, in terms of bird and bat strikes.
Below, I’ll cover some more basic differences and show you a few photos and short videos of some of these turbines I saw down in Houston at WINDPOWER 2008.
The designers from Taiwanese start-up A.N.I.T.A. Energy (pictured above) showed me why their models have a low start-up wind speed, and that is because of the light metal bands you can see surrounding the turbine itself. Apparently this design allows users with a less substantial wind resource (particularly those in urban applications), squeeze some electricity from the local winds. The larger model pictured above (and in the second video below) is scalable and can be stacked as many as three-high and integrated with the rooftops of large buildings. (Caution: the mic used for this video was very sensitive to the sound of the electric blower at the display. This is not the sound of the turbine. Adjust your volume accordingly!)
Unlike three-bladed designs, vertical-axis turbines do not need to “right themselves” into the wind, they are always in a fixed position in terms of their orientation. A few of the models I saw, most notably the designs from the Korea-based KR Windpower, (video above) had a manifold-type device that would swing around and funnel more wind into the turbine from the direction the wind was strongest. Continued…