Next generation wind lens have been developed. This

version has shorter diffuser to reduce structural weight

and narrower brim to reduce wind loads. This can be

an advantage for the application to larger wind turbines.

Performances of wind lenses with different length:

Field test result of 5kW Cii-type Wind-Lens turbine:

Further optimization of the wind-lens shape (Ci):

Also an optimization study of the shape of wind lens

has been done. The newest type has cycloid cross

section.

1) Two-five time increase in output power

compared to conventional wind turbines

2) Brim-based yaw control

3) Significant reduction in wind turbine

noise due to suppression of tip vortices

4) Improved safety

5) Possible reduction in Doppler radar

interference

Numerical simulation by DNS for original and new

wind lens (Ci):Abstract Field Experiment for a 500W Wind-lens

Ongoing and future wind farm projects

Objectives

Remarkable merits of the Wind Lens

EWEA 2011, Brussels, Belgium: Europe’s Premier Wind Energy EventEWEA 2011, Brussels, Belgium: Europe’s Premier Wind Energy Event

This study presents an innovation related to wind

power enhancement technology named “Wind Lens”.

Wind power generation is proportional to the third

power of the wind speed. If we can increase the wind

speed, specifically by capturing and concentrating the

wind energy locally, the output power of a wind turbine

can be increased substantially. To embody the

scenario, we have devised a simple shroud structure

which intentionally creates vortices behind it to draw

more mass flow into the wind turbine. The structure has

been named “Wind Lens”.

The wind lens has a compact diffuser shroud with a

broad-ring rim at the exit periphery. Our wind turbine

system consists of the wind lens and a turbine inside.

This system has demonstrated power augmentation for

a given turbine diameter and wind speed by a factor of

about 2-3 compared with a bare wind turbine.

Next generation diffusers have been developed and

the details are given in this study also. The significant

features of the wind-lens technology include, improved

safety, reduction of acoustic noise and Doppler radar

interference. We believe the wind lens can be quite

suitable for installation in a variety of sites, even in well-

populated areas. This study also discusses the latest

development on 100kW scale wind-lens turbine system.

Development of highly efficient

small-type wind turbine

Concentration of wind energy

Wind turbine +

WIND LENS

collection and acceleration

device for wind

Brimmed Diffuser - Wind Lens

A “Brim” is attached to a diffuser shroud to improve

wind collection and acceleration. The idea is to induce

formation of strong vortices.

A wind turbine with the wind lens

The mechanism:The strong vortices created by the diffuser and the brim

produce low pressure region behind the turbine. This increased

pressure difference helps the wind to flow more into the wind

lens.

WIND LENS

A collection-acceleration

device

(Inlet shroud + Diffuser +

Brim)

Result of 500W wind-lens turbine field test:

The result shows a significant increase of power output

as much as 400% compared to conventional turbine.

However, for larger turbines, reduction of the mass of

the wind lens, and the size of the brim is important.

Short brimmed wind lens

Cw

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

2 3 4 5 6 7

通常型（つば高さ5%)

延長型(つば高さ

5%)通常型(つば高さ

10%)延長型(つば高さ

10%)

Old WL 5%

New WL 5%

Old WL 10%

New WL 10%

λλλλComparison between original WL and new WL

Original wind lens has curved

diffuser and straight brim. Two

parts are assembled together.

The new version of the WL has

continuous structure and has

Cycloid shape cross section.

Original (old) diffuser shroud with brimOriginal (old) diffuser shroud with brimOriginal (old) diffuser shroud with brimOriginal (old) diffuser shroud with brim of 10% heightof 10% heightof 10% heightof 10% height

Unified (new) diffuser shroud with cycloid sectionUnified (new) diffuser shroud with cycloid sectionUnified (new) diffuser shroud with cycloid sectionUnified (new) diffuser shroud with cycloid section

streamlinesstreamlinesstreamlinesstreamlinespressurepressurepressurepressurevorticity

Wind Energy Utilization Project in Fukuoka city:

Hundred kW Wind Lens turbine at Kyushu-U:

Ocean Energy Farm project:

Development of combined energy farm on the ocean

surface is currently ongoing at Kyushu University. The

project begins with building an experimental wind farm

on a floating structure on the ocean surface.

5kW Wind-lens turbines on the seashore of Fukuoka, Japan

Wind-lens

turbines

Wind-lens

turbine

Numerical Simulation of Airflow around Numerical Simulation of Airflow around

Urban Area by the RIAMUrban Area by the RIAM--COMPACTCOMPACT®® CFDCFD

Hakata bayHakata bayFlowFlow

Hakata bayHakata bay

streamlinesstreamlinesstreamlinesstreamlinespressurepressurepressurepressurevorticity

Brim

0

50

100

150

200

250

300

350

0 2 4 6 8 10

Wind Speed [m/s]

Ou

tpu

t P

ow

er [

W]

Power Curve of Cw=1.4

Field Data (10min. ave.)

W.T. only

four times increase

conventional wind turbine

Power coefficient

Cw=P/0.5ρU∞3A

P: Power output

A: Rotor swept area

0.0

0.2

0.4

0.6

0.8

1.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0rω/U0

Cw

C0

Cⅰ

Cⅱ

Cⅲ

W.T. only

λ: Tip speed ratioC0C0C0C0

CCCCⅰⅰⅰⅰ

CCCCⅱⅱⅱⅱ

CCCCⅲⅲⅲⅲ

Performance Curves for C-type diffusers with different length (h=0.1D, Uo=8m/s)

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0.0 2.0 4.0 6.0 8.0 10.0 12.0

m/s

WField Data (1min. average)

Cw=1.0 （Wind-lens Turbine）

Cw=0.4 (Conventional Wind Turbine）

Conventional

Wind Turbine

Wind-lens

turbine

2.5 timesincrease

Cw*=0.54based on the lens diameter

DEVELOPMENT OF SHROUDED WIND TURBINES

WITH WIND-LENS TECHNOLOGYYuji Ohya1, Takashi Karasudani1, Tomoyuki Nagai1, Chris Takashi Matsuura2,3, Hugh Griffiths2

1) Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan

2) University College London, London, UK, 3) ENGRID ltd, London, UK

PO.IDPO.ID

255_B255_B