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Originally posted by Phage
I don't really get it. The illustrations show something like a ducted fan but that's not really anything new.
The increased efficiency is questionable.
A collection-acceleration devise for wind, “the brimmed diffuser”, which shrouds a wind turbine,
was developed. Significant increase in the output power of a micro-scale wind turbine was obtained.
With a relatively long diffuser (Lt = 1.47D), a remarkable increase in the output power of
approximately 4–5-times that of a conventional wind turbine is achieved. This is because a
low-pressure region due to a strong vortex formation behind the broad brim draws more mass flow to
the wind turbine inside the diffuser.
For the purpose of the practical application to a small- and mid-size wind turbine, we developed a
very compact brimmed diffuser (wind-lens structure). Using this compact brimmed diffuser, we
achieved two-three-fold increase in output power as compared to conventional (bare) wind turbines,
due to concentration of the wind energy. We are now developing a wind-lens turbine of 100 kW at the
Energies 2010, 3
rated wind speed of 12 m/s. The rotor diameter will be 12.8 m, which is much smaller than a
conventinal wind turbine of the same rated power; two-thirds the size.
Incidentally, if we adopt the swept area A* instead of A (due to the rotor diameter), where A* is the
circular area due to the brim diameter Dbrim at diffuser exit, the output coefficient Cw* based on A*
becomes 0.48–0.54 for those compact wind-lens turbines. It is still larger than the power coefficient
Cw (around 0.4) of conventional wind turbines. It means that the compact wind-lens turbines clearly
show higher efficiency compared to conventional wind turbines, even if the rotor diameter of a
conventional wind turbine is extended to the brim diameter.
For the examination of practical application, an international project and a local project using 5 kW
wind-lens turbines were initiated. Six units of 5 kW wind-lens turbines were installed to build a wind
farm for an irrigation plant in a desert area in northwest China, and their effectiveness for the greenery
project has been examined. Three 5 kW wind-lens turbines have been recently installed in seashore in
Fukuoka city, Japan, aiming at the efficient utilization of wind energy.
For the practical application to a small-size and mid-size wind turbine, we have been developing a compact-type brimmed diffuser. For the 500 W wind-lens turbine, the length of brimmed diffuser Lt is 1.47D and still relatively long as a collection-acceleration structure for wind (for Lt, see Figure 8). If we apply this brimmed diffuser to a larger wind turbine in size, the wind load to this structure and the weight of this structure becomes severe problems.