We have already covered this subject a while ago, when we presented some CalTech researchers studying the effect of air vortexes on vertical axis wind turbines. It looks like the CalTech guys are not the only ones involved in such inventions, as a company called “Wind Harvest International” says they can double the ourput of large horizontal axis wind farms by placing one-megawatt vertical axis wind turbines (VAWT) between them, in a way that would boost their power output.

“We can put a megawatt of turbines between two horizontal megawatt turbines,” said Kevin Wolf, the company’s chief operating officer. “We can double the power output and maybe increase the power of the other turbines.”

The company intends to commercialize a 25 kW version, a 75 kW one and another 75 kW for low-speed wind conditions, hoping to start selling them as early as 2011.

Wind Harvest places three or more turbines very close to each other, as close as a meter apart, and they rotate in alternating direction, generating a vortex between them. The vortex creates more torque and lift, hence the improved efficiency. “It is only effective in a three turbine array or more,” Wolf said, adding that Sandia National Labs has conducted several simulations on the coupled vortex effect in wind.

The company will likely sell to the U.K. and Italy first, because of favorable government incentives, which just passed generous feed-in tariffs in the 30 to 40 cent/kWh range. The U.K. also favors these VAWTs because turbies 15 meters or shorter are exempted from local planning objections. Of course, Wind Harvest can’t do anything without proper funding, and that’s why they’re interested in investors.

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