I just came across this article in STRUCTURE magazine. Drum turbines do have some of the best turbine coefficients (Ct). They do produce more efficient power then horizontal turbines in urban areas. They will capture up to 95% of air mass going through, while horizontal turbines at best will capture 40% of air mass going through. But there are a few down sides, such as: vertical assembly has weight issues, the entire assembly sits on one gear box which carries both the weight and rotation of the turbine. And secondly, wind flows both on the force and drag side of the turbines; blades have to be aerodynamically shaped to capture wind on the one half and reduce drag on the other side as blades are rotating into the wind. Bahari Energy, LLC, has developed a new technology which overcomes all the issues with both vertical and horizontal. It is called the Wind Tower technology. This is a game changer technology in capturing wind energy for the urban environment.
Regards,
Habib Bahari
Rockville, MD