A team led by professor Yuji Oya of the Kyushu University Research Institute for Applied Mechanics, Japan, has come up with a refinement to wind turbine design that is said to triple the output of a standard unit. To date it has been demonstrated only by a very small scale-model that can generate 8 W of power, but when a specially designed hoop with a brim around the periphery is attached to the blades, the system's power output jumps to 22 W.
"This structure yields two to three times the output of a normal wind turbine," Oya said of his proprietary device, which he has named a Wind Lens wind turbine. Concenration is achieved by pulling the wind through the blades faster owing to the presence of a low pressure zone behind the turbine, the result of the air vortices created by air passing through the brimmed hoop.
Since 3 December there has been a demo 'plant' in Hakata Bay in Fukuoka, 600 metres off the sandbar that links Fukuoka city with Shikanoshima Island. The platform is floating, and is expected to simultaneously help solve a major problem for wind power development in Japan, namely that the sea depths increase rapidly with distance from the coast, leading to the necessity of developing machines that are not mounted on the seabed.
On this platform there are two small 'Wind Lens'-equipped turbines and some solar panels. At wind speeds of 10m per second, one turbine can generate 3kW of power. Combined with the solar panels, the overall structure can produce 7.5kW.
The platform is secured from wandering by six concrete anchors, and it is believed capable of withstanding waves as high as 2m. To protect against damage during typhoons and otherwise excessively windy weather, the turbines rest on posts that tilt automatically as needed to let the wind blow past. For the next year this floating wind power system will be used for verification experiments by Kyushu University together with the Environment Ministry and the city of Fukuoka.
Data collected on power output, noise generation and other factors will be compared with similar 'Wind Lens' turbines positioned nearby on shore. After these verification experiments have been completed, a new round of testing will be carried out in the southwestern tip of the Sea of Japan using a 60m platform with a pair of 200 kW class units, and thereafter to build an offhosre wind farm with 5000 kW class 'Wind Lens' turbines, located at ocean depths exceeding 100m.