wind mill vs box mill

Vortec 7 DAWT Summary of Test Results
In 1997 Vortec installed 7.3 meter diameter DAWT prototype. Developers claimed that the Vortec 7 was the first full-scale DAWT ever built. It didn’t go well, though Vortec raised a lot of money before they went defunct—with the money.
This summary reflects my view at the time. Key participants were acknowledging the technical failure of Vortec 7, but they couched their failure in arcane technical language at arcane conferences.
I came across this paper while researching DAWTs for an upcoming book.
Unlike the hype leading up to the “demonstration” of the turbine, the damning conclusions seldom garner any press. By then it’s all to late.
Aerodynamic analysis and monitoring of the Vortec 7 diffuser-augmented wind turbine by Derek Grant Phillips, Trevor Nash, et al, paper presented at the 1998 IPENZ.

Selected conclusions with emphasis added.

• Simplified one-dimensional arguments lead to predictions of speed-ups of about 2 and power augmentations of about 4, but such power levels have not been observed to date.
• The velocity profile across the blade plane showed lower speeds closer to the hub, and a high speed region beyond the blade tips. As a consequence, power measurements were not as high as predicted by Foreman [Grumman Aerospace contractor to DOE], who assumed uniform velocity across the blade plane as measured beyond the blade tips.