DEVELOPMENT OF SHROUDED WIND TURBINES
WITH WIND-LENS TECHNOLOGY
PO.ID
255_B
Yuji 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
Field Experiment for a 500W Wind-lens
Abstract
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 wellpopulated areas. This study also discusses the latest
development on 100kW scale wind-lens turbine system.
Original (old) diffuser shroud with brim of 10% height
Result of 500W wind-lens turbine field test:
Power coefficient
Cw=P/0.5ρU∞3A
350
Power Curve of Cw=1.4
Field Data (10min. ave.)
W.T. only
300
Output Power [W]
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”.
Numerical simulation by DNS for original and new
wind lens (Ci):
250
pressure
vorticity
P: Power output
A: Rotor swept area
200
Unified (new) diffuser shroud with cycloid section
four times
increase
150
streamlines
100
50
conventional
wind turbine
0
0
2
4
6
Wind Speed [m/s]
8
pressure
vorticity
10
streamlines
Ongoing and future wind farm projects
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.
Wind Energy Utilization Project in Fukuoka city:
Wind-lens
turbines
Wind-lens
turbine
5kW Wind-lens turbines on the
seashore of Fukuoka, Japan
Hakata bay
Short brimmed wind lens
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.
Flow
Hakata bay
Performances of wind lenses with different length:
Objectives
Numerical Simulation of Airflow around
Urban Area by the RIAMRIAM-COMPACT®
COMPACT® CFD
1.0
0.8
Cⅰ
Cⅱ
Cⅲ
W.T. only
0.6
Cw
Development of highly efficient
small-type wind turbine
C0
0.4
Hundred kW Wind Lens turbine at Kyushu-U:
Cⅲ
0.2
Concentration of wind energy
Cⅱ
0.0
0.0
collection and acceleration
Wind turbine +
device for wind
1.0
2.0
3.0 4.0
λ: rω/U0
5.0
6.0
Cⅰ
7.0
Tip speed ratio
C0
Performance Curves for C-type diffusers with different length
(h=0.1D, Uo=8m/s)
Ocean Energy Farm project:
Field test result of 5kW Cii-type Wind-Lens turbine:
WIND LENS
3,500
W
Field Data (1min. average)
3,000
Cw=1.0 （Wind-lens Turbine）
2,500
Brimmed Diffuser - Wind Lens
Wind-lens
turbine
A “Brim” is attached to a diffuser shroud to improve
wind collection and acceleration. The idea is to induce
formation of strong vortices.
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.
1,500
1,000
500
Conventional
Wind Turbine
0
2.0
4.0
6.0
8.0
10.0
12.0
m/s
WIND LENS
A collection-acceleration
device
(Inlet shroud + Diffuser +
Brim)
The mechanism:
Further optimization of the wind-lens shape (Ci):
Remarkable merits of the Wind Lens
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
Old WL 5%
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.
通常型（つば高さ
5%) New WL 5%
延長型(つば高さ
5%)Old WL 10%
通常型(つば高さ
New WL 10%
10%)
延長型(つば高さ
10%)
0.9
0.85
0.8
Cw
A wind turbine with the wind lens
2.5 times
increase
Cw=0.4 (Conventional Wind Turbine）
2,000
0.0
Brim
Cw*=0.54
based on the
lens diameter
0.75
0.7
2) Brim-based yaw control
3) Significant reduction in wind turbine
noise due to suppression of tip vortices
0.65
0.6
4) Improved safety
0.55
0.5
2
3
4
λ5
6
7
Comparison between original WL and new WL
Original wind lens has curved
diffuser and straight brim. Two
parts are assembled together.
5) Possible reduction in Doppler radar
interference
The new version of the WL has
continuous structure and has
Cycloid shape cross section.
EWEA 2011, Brussels, Belgium: Europe’s Premier Wind Energy Event