VAWT versus HAWT wind power

Henry duPont of Lorax Energy Systems in Block Island, Rhode Island, dropped by electronically to  enlighten us on the matter of vertical versus horizontal axis wind turbines (VAWT versus HAWT). 

Henry says the advantages of the VAWT configuration (like the Quietrevolution elsewhere in the Wind Power section ) are that the generator and gearbox can be housed on the ground, and even some distance away from that turbine; and that a VAWT is omnidirectional and requires no yaw mechanism.

The disadvantages of typical VAWT systems are that they usually operate near the ground where there's not much wind; they produce wavy (sinusoidal) power pulses to drive mechanism; they don't start themselves in a breeze; and repair of the main bearing usually means having to take the whole machine apart. (The Quietrevolution appears to solve at least the first problem by being mount ed on a tower.) Most importantly, the VAWT is typically about 40% less efficient than the HAWT in energy production. According to Henry, you would need a VAWT almost twice the size of a HAWT to get the same amount of juice. 

The main advantage of the HAWT is the increased efficiency in power production, and the smooth transfer of that power from the rotor to the gearbox. HAWTs are also generally mounted on taller towers, where they have exposure to higher wind velocities and present smaller footprints on the ground. However, they require tall cranes for set-up; they require a yaw system; and any maintenance required has to be done at the top of a tower. The photo here shows Henry duPont's colleague Kim Granbery at altitude during the installation of a new HAWT above the Western desert.

Comments

[Robert Webb]

It is not true that HAWTs are inherently more efficient than VAWTs. There are good aerodynamic studies showing the efficiency is similar in theory. The issue is simply that to date vastly more has been spent on developing HAWTs.

In fact for small scale applications near the ground, where the wind is turbulent, we predict a 20% to 40% better output for a VAWT due to responsiveness to rapidly varying wind conditions.