Wind-lens technology
Application to wind/water turbines and beyond
Tomoyuki Nagai , Ph.D.
on behalf of wind engineering section at RIAM, Kyushu
University
WREC 2015, June @ Bucharest
Wind-lens turbine team members
Professor
Associate Professor
Research Fellow
Joint Researcher
Joint Researcher
Technical staff
Technical staff
Y. Ohya (project leader, RIAM director)
T. Uchida
T. Nagai
K. Hayashida (Riamwind Corp.)
H. Nishimura (Riamwind Corp.)
K. Watanabe
K. Sugitani
Associate Professor T. Karasudani
Professor
S. Yoshida
Associate Professor W. Wang
Professor
C. Hu
Assistant Professor M. Sueyoshi
Professor
Y. Kyozuka
Ph.D. Student
And many more
U. Goeltenbott
Wind speed and wind energy
Wind Power P , Wind Speed V
V
P∝V3
The output of a wind turbine is proportional to the incoming wind speed cubed.
Therefore, a slight increase of the wind speed at the turbine rotor results in a
dramatic increase of the turbine power output.
Then, how can we accelerate the wind speed?
Nozzle or Diffuser? - cont.
Flow
We “re” discovered that diffuser type
shroud accelerates the incoming wind.
But, the size needs to be reduced for
practical application to wind turbines.
“Nozzle”
Additional “Brim” at
the peripheral part of
the exit
“Diffuser”
Diffuser
Nozzle
Wind speed distribution
Wind-lens turbine
Wind flow
Brim
Low-pressure region
due to strong vortices
Wind flows into this
region
Turbin
e
Diffuser
shroud
(Wind lens)
Active utilization of shedding
and vortex formation
Quite unique way of designing
an aerodynamic machine!
“Wind lens” = Brimmed diffuser
shroud
Vortex shedding creates
low pressure regions
Two-dimensional DNS animation
Diffuser shape
For the practical installation of the Wind-lens
diffusers to larger turbines, we have investigated
more compact diffuser shapes
Our dilemma is:
Compact diffuser
Current model
Early prototype
The prototype
Circular type
= less power enhancement….
Linear type
Cycloid type
3kW prototype field test
Cp*=0.54
based on the
lens diameter
（Rated Wind Speed 10m/s, Rotor dia. of 2.5m）
3,500
W
Field Data (1min. average)
3,000
Cw=1.0 （Wind-lens Turbine）
2,500
2.5 times
Increase
Cw=0.4 (Conventional Wind Turbine）
2,000
1,500
1,000
500
Conventional
Wind Turbine
0
0.0
2.0
4.0
6.0
The prototype 3kW WL turbine
8.0
10.0
12.0
m/s
Cancelation of tip vortices
Blue – Tip vortex
Red – Induced vortex
Diffuser surface
Tip vortex and induced
vortex interfere and
cancel each other as they
propagate downstream
Reduction of tip vortex noise!
A simulation result by DNS
Current Wind-lens turbine models
3kW Wind-lens turbine
Rotor D: 2.5m
Diffuser D: 3.4m
Rated wind speed: 11m/s
1kW Model
Rotor D: 1.4m
Diffuser D: 1.9m
Rated wind speed: 11m/s
100kW Model
Rotor D: 12.8m
Diffuser D: 15.4m
Rated wind speed: 12m/s
-Passive yaw system
-Fixed blade pitch
1kW WL turbine: NHK Robot Cam
1kW Windlens turbine
Solar panel(1.1kW)
Robot camera system equipped
with wind-lens turbine and
solar panel. 2012.8.1
A building remains in Watari-cho, south of Sendai
after the east Japan tsunami disaster
100kW Noise comparison
Blade tip noise
reduction works on
100kW Wind-lens
turbine as well.
20dB difference!
Sound pressure is 10
times smaller!
Noise comparison: Windlens turbine is quiet!
Wind-lens technology in the water
Tidal flow and Current
The same flow acceleration principle
works in the water.
• Density of water is 840 times the air
• The streams always flow in the rivers,
irrigation canals and in the ocean
Generator
A water channel
experiment carried out
at Kyushu University
Rivers : Mini-Hydro
Advantages of the Wind-lens turbine
• Two to five times increase in output power as compared
to conventional wind turbines with the same rotor D
• Brim-based yaw control
• Significant reduction in wind turbine noise
• Improved safety
• Reduction in interference with Doppler radar
• Less frequent bird strikes
Offshore hybrid farm experiment
The prototype design and a series of scaled model
experiments started in 2011. The construction of
the actual floating body finished on 2nd of
December 2011. The float is moored about 780m
offshore in Hakata bay.
CG image of the final design
Scaled model experiment
in a large water tank
Google map
18 m
Stage 1: Hakata-bay float
Diameter : 18m
Hub height: 10 m
Float weight: 130 ton (140 ton with turbine etc.)
Float: Prestressed concrete, semi-submersible
Wind turbine: 3 kW x 2
PV panel: 2 kW
Mooring : 6 cables with 20 ton
anchor block for each
Monitoring cable tension for cable
#2 (the one takes the max load)
Float behavior during extreme conditions
The floating body has survived several
typhoons including quite large ones in 2012.
The maximum wind speed exceeded 50m/s
during the season.
The Wind-lens power control system safely
operated the turbines, and no damages have
been found on either turbines or floating
body.
Roll and yaw angles were constrained within
the designed range (5 degrees). Also the
maximum tension on the cable with the
largest load was 8 ton, well under the spec
(max 31.2 ton).
Wind and power comparison
Data set from a turbine on the float is analyzed and compared to an equivalent system
of 3kW Wind-lens turbine installed in Minato Park at the vicinal coast in a distance of
3.7km from the floating platform between 2012 Nov to 2013 Oct.
Wind comp.
Power comp.
Minato park
Float
Ave. wind speed
3.5m/s
4.3m/s
Ave . power
79kWh
164kWh
Output power
200%!
Stage 2: 1MW offshore hybrid farm
Marine farm
•
•
Each side is ~70 m. Each Wind-lens turbine
generates 300 kW at the rated wind speed
of 12m/s. As a hybrid system, a triangular
unit farm produces > 1 MW in total
output.
Marine farm will be installed in and
around it.
300kW Wind-lens turbine:
Rotor D: 23m
Diffuser D: 26m
Nacelle height from the SL. : ~30m
Key words: Hybrid and multi purpose
Other activities:
●Larger wind turbines: Multi turbine design
Less wind-load oscillation amplitude
Scaling factor, 1/ 𝑛
smaller mass/weight
than single design
Joint research plan has started with Thailand and
other countries…
●Wind-Solar tower:
Diffuser type tower for enhanced power output
Low maintenance system
Two mechanisms of causing air flow inside of the
tower
Summary
• Wind-lens turbine utilizes a wind acceleration device and achieves 2-5 time
output power enhancement.
• Due to the Wind-lens structure, the blade tip noise from the turbine is
dramatically suppressed.
• Compact type diffusers enables an installation of the Wind lens to larger
turbines (current largest model is 100kW turbine).
• Offshore floating energy farm stage I has been installed for data taking since
Dec 2011 and demonstrating great advantage of the offshore wind energy
farming.
• Current research activities includes, Multi-rotor wind-lens turbine and
Wind-Solar tower and more…
Thank you for your attention!
Visit our web site,
www.riam.kyushu-u.ac.jp/windeng/en_index.php