Wind Turbine Icing and De-Icing

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47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

1

47
th

AIAA Aerospace Science Meeting and Exhibit

Orlando, Florida, 5
-
8 January 2009

Anti
-
icing Materials International Laboratory

Wind Turbine Icing and De
-
Icing

Guy Fortin and Jean Perron


Université du Québec à Chicoutimi

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

2

Overview


INTRODUCTION


ICING EVENT FORMATION


WATER COLLECTION


ICE ACCRETION


WIND TURBINE


ICE PROTECTION SYSTEMS


CONCLUSION

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

3

Introduction

Atmospheric Icing


Ice

accretes

on

structure

(overhead

cables,

pylons,

satellite

dishes,

communication

towers,

airplanes,

helicopters,

wind

turbines,

offshore

drilling

rigs,

ships,

docks,

bridges,

roads,

dams,

buildings

)

causing

of

great

damages

to

electric

lines,

telecommunication

networks,

in

the

maritime,

road

and

air

transport,

causing

materials

damages

and

human

safety

risk
.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

4

Introduction

Problem Description



Wind turbine atmospheric icing

a)
Ice accumulates on the rotor blades

b)
Reducing aerodynamic efficiency leading to

a)
less power production.

b)
vibration

c)
ice shedding

d)
wind turbine stop

e)
worst case, blades collapse


47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

5

Icing Event Formation

Atmospheric Icing


Icing

occurs

when

hot

air

mass

meet

an

air

mass

below

freezing

leading

to

hydrometeors

such

as

1.
Freezing

drizzle

2.
Freezing

rain

3.
Wet

snow

Or

in

presence

of

1.
Cloud

in

altitude

(>

400

m)

2.
Fog

at

ground

level

When

temperature

is

below


freezing

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

6

0
10
20
30
40
50
60
70
80
90
100
110
0
10
20
30
40
50
60
70
80
90
100
Diameter (µm)
Frequency (%)
Diameter
Volume
MVD = 20.8 µm
Icing Event Formation

Atmospheric Icing


Hydrometeors

are

characterized

by

1.
Liquid

Water

Content

which

is

the

quantity

of

water

contained

in

the

air

expressed

as

g/m³
.

2.
Median

Volumetric

Diameter

of

water

droplet

which

is

a

representative

value

of

the

water

droplet

distribution

expressed

as

µm
.

0
2
4
6
8
10
12
1
5
9
13
17
21
25
29
33
37
41
45
49
53
57
61
65
69
73
77
81
85
89
93
97
101
105
109
113
117
121
125
129
133
137
141
145
149
Diameter (µm)
Droplet Frequency (%)
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

7

Icing Event Formation

Atmospheric Icing


How

ice

accrete

on

blade

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

8

Water Collection

Water Collection


The

first

parameters

to

evaluate

ice

accretion

is

the

Impingement

Mass

Collection Efficiency

Air Speed

Impingement Surface

Liquid Water Content

imp
a
imp
A
U
LWC
E


m




sup
inf
1
s
s
ds
H
E

Local Collection Efficiency

Impingement Distance

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

9

Water Collection

Water Collection


Lower Limit

Local Collection Efficiency

Upper Limit

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
-0.16
-0.14
-0.12
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
Curvilinear Abscissa
Local Collection Efficiency
Stagnation Point

dy
ds


47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

10

Water Collection

Water Collection


Water

Droplet

Trajectory

Calculations

1.
Droplets

are

spherical

2.
No

collision

or

coalescence

3.
Small

water

droplet

concentration
.



g
v
v
K
C
dt
v
d
w
a
d
a
d
d
D
d


















1
1
24
Re
Drag

Gravity

Buoyancy

Reynolds Number

Inertia Parameter

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

11

Water Collection

Water Collection



Local collection efficiency increases when the
Median Volumetric Diameter increase

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
Curvilinear Abscissa
Local Collection Efficiency
MVD = 10 µm
MVD = 20 µm
MVD = 50 µm
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

12

Water Collection

Water Collection



Local collection efficiency decrease when the
Chord increase

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
Curvilinear Abscissa
Local Collection Efficiency
Chord = 0.5 m
Chord = 1.0 m
Chord = 3.0 m
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

13

Water Collection

Water Collection



Local collection efficiency increase when the
Speed increase

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
Curvilinear Abscissa
Local Collection Efficiency
U = 15 m/s
U = 30 m/s
U = 67 m/s
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

14

Water Collection

Water Collection



Local collection efficiency increases when the
Angle Of Attack increase

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
Curvilinear Abscissa
Local Collection Efficiency
AOA = 0º
AOA = 4º
AOA = 8º
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

15

Ice Accretion

Thermodynamic of Ice Accretion



Supercooled

water

droplet

will

freeze

completely

at

impact

to

form

ice

on

the

impingement

area

or

freeze

partially

to

form

ice

on

the

impingement

area

and

remaining

water

which

runback

outside

of

the

impingement

area
.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

16

Ice Accretion

Thermodynamic of Ice Accretion



Rime ice form when all water freeze at impact


Rime ice is associated to


colder temperature, below
-
10
°
C


lower Liquid Water Content


smaller Median Volumetric Diameter


Iced zone is small and close to the leading edge
and quite closely takes the original contour

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

17

Ice Accretion

Thermodynamic of Ice Accretion



Glaze ice form when a fraction of the water
freeze at impact


Glaze ice is associated to



warmer temperature, above
-
10
°
C



high Liquid Water Content



greater Median Volumetric Diameter


Iced zone is large and tend to deform the
aerodynamic profile due to horns formation


47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

18

Ice Accretion

Thermodynamic of Ice Accretion



The capacity of ambient environment to absorb
the latent heat of solidification while determine
if rime or glaze ice


is formed

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

19

Ice Accretion

Thermodynamic of Ice Accretion



Surface Temperature and Freezing Fraction

If

the

resulting

surface

temperature

is

above

freezing,

only

a

fraction

of

the

impinging

water

is

solidified

at

impact
.

The

freezing

fraction

is

calculated

assuming

a

surface

temperature

equal

to

freezing
.


0
/








rad
cd
ss
evap
sub
cv
kin
adh
f
Q
Q
Q
Q
Q
Q
Q
Q








47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

20

Ice Accretion

Thermodynamic of Ice Accretion



Ice Mass



sub
evap
imp
ice
m
f
m
m
m







Ice Thickness

ice
ice
ice
m
e



47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

21

Ice Accretion

Thermodynamic of Ice Accretion



Ice Shapes

predict with CIRALIMA 2D

-0.100
-0.075
-0.050
-0.025
0.000
0.025
0.050
0.075
0.100
-0.075
-0.050
-0.025
0.000
0.025
0.050
0.075
0.100
0.125
0.150
0.175
-28.3ºC
-13.3ºC
-7.8ºC
-4.4ºC
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

22

Wind turbine icing
simulated in icing wind
tunnel at AMIL

LWC = 0.24 g/m³

Temperature =
-
5.7
°
C

Air speed = 4.2 m/s

Wind Turbine Speed = 16 RPM

Wind Turbine Diameter = 80 m

Time = 4.5 hours

Ice Accretion

Wind Turbine

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

23

Ice Accretion

Wind Turbine


Aerodynamic Degradation





s
s
s
old
s
new
s
T
T
f
T
f
T
T




Lift decreased from
the hub to the tip.

Drag increased

from
the hub to the tip
and was more
affected than lift.

Ice impact on
drag and lift was
more significant
after 20 m.

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0
5
10
15
20
25
30
35
40
45
r(m)
Lift Coefficient
0
0.05
0.1
0.15
0.2
0.25
0.3
Drag Coefficient
Lift Coefficient Clean Airfoil
Lift Coefficient Iced Airfoil
Drag Coefficient Clean Airfoil
Drag Coefficient Iced Airfoil
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

24

Ice Protection System



Type used with wind turbine



Electro
-
thermal


Hot airflow



Microwaves



Icephobic coating



Method



Anti
-
icing:

no ice is allowed to form




Deicing:

allow small ice thickness to form



before the deicing sequence is activated






s
s
s
old
s
new
s
T
T
f
T
f
T
T




47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

25

Ice Protection System



Advice


Protect the collected area, about 14% of the
chord with AOA of 6
º


Maintain blade temperature below 50
ºC to
reduce the blade delamination risks


Do not protect the first third part of the blade


Split blade into individual areas and
controlled individually in power to reduce
energy consumption

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

26

Ice Protection System



Advice


3.5 more power to de/anti
-
ice the leading
edge at the tip compared to the hub


1.5 more power to de/anti
-
ice the lower
surface then the upper surface


47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

27

Ice Protection System



Anti
-
icing


Maintain the surface blade temperature
above freezing


With thermal system about 10 W/in² at the
tip


Electro
-
thermal, hot airflow or microwaves

-0.04
-0.02
0
0.02
0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0.22
(m)
(m)
without heating
with heating
About 5 times more energy is needed
in evaporative mode

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

28

Ice Protection System



Deicing


Less expensive than anti
-
icing and
minimizes runback water and refreezing
water on unheated areas


The allowed accreted ice is not sufficient to
lead to significant aerodynamic penalties or
to become a hazard


With mechanical system about 2 W/in²/ice
millimetre

Ice thickness is not uniform

Ice detector for each blade area

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

29

Conclusions


Icing

is

a

problem

in

cold

climate

for

wind

turbine

due

to

freezing

rain

and

drizzle,

freezing

fog

at

ground

level

or

icing

clouds

when

installed

in

altitude

or

frost

when

installed

near

water

bodies
.


Ice

accretion

lead

to

aerodynamic

penalties

and

decrease

output

power
.


Impact

of

glaze,

rime

or

frost

is

difficult

to

quantify

without

more

experimental

and

numerical

simulations

due

to

lack

of

data

and

knowledge
.


Existing

ice

protection

systems

are

not

adapted

to

wind

turbine,

low

energy

ice

protection

systems

should

be

developed
.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

30

Conclusions


Moreover,

anti
-
icing

systems

are

efficient

when

high

frequency

of

icing

event

is

expected

or

security

is

the

most

important

factor
.


Dei
-
icing

is

more

efficient

than

anti
-
icing

,

but

is

difficult

to

implement

and

more

expensive
.


To

reduce

ice

protection

system

power

consumption



Optimize

power

in

function

of

the

wind

turbine

rotating

speed
.


Protect

the

2
/
3

extremity

parts

of

the

blade

only


47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009

31

Conclusions

Question?