Download Impacts and Causes of Icing on Wind Turbines

Impacts and Causes of Icing on
Wind Turbines
Made by:
For:
Date:
Matthew Carl Homola, Narvik University College
Interreg IIIB Project partners
November 2005
THIS PROJECT IS SUPPORTED BY THE EUROPEAN UNION
NARVIK
UNIVERSITY
COLLEGE
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Table of Contents
1.
INTRODUCTION ....................................................................................................................................... 2
2.
PROBLEMS DUE TO ICING.................................................................................................................... 2
2.1.
PRESENTATION OF ICING EFFECTS ......................................................................................................... 2
Complete stop due to icing ............................................................................................................................ 2
Disruption of aerodynamics .......................................................................................................................... 4
Overloading due to delayed stall................................................................................................................... 5
Increased fatigue due to imbalance............................................................................................................... 5
Harm to people or property due to ice shedding ........................................................................................... 6
2.2.
SUMMARY OF ICING EFFECTS ................................................................................................................ 6
3.
REMOVAL OR PREVENTION OF ICING ............................................................................................ 6
4.
DEFINITIONS AND CAUSES OF ICING ............................................................................................... 8
4.1.
IN-CLOUD ICING .................................................................................................................................... 9
Rime............................................................................................................................................................... 9
Glaze.............................................................................................................................................................. 9
4.2.
PRECIPITATION ICING .......................................................................................................................... 10
Wet snow...................................................................................................................................................... 10
Freezing rain ............................................................................................................................................... 10
4.3.
FROST ................................................................................................................................................. 10
4.4.
METEOROLOGICAL PARAMETERS AFFECTING ICING ............................................................................ 11
4.5.
PHYSICAL MODEL OF ICING ................................................................................................................. 11
4.6.
EMPIRICAL MODELS OF ICING ............................................................................................................. 13
Empirical models for precipitation icing..................................................................................................... 13
Empirical models for in-cloud icing ............................................................................................................ 13
5.
CONCLUSIONS AND SUGGESTIONS FOR FURTHER WORK ..................................................... 13
5.1.
5.2.
6.
CONCLUSIONS..................................................................................................................................... 13
SUGGESTIONS FOR FURTHER WORK..................................................................................................... 14
REFERENCES .......................................................................................................................................... 14
Page 1
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
1. Introduction
In recent years the interest in renewable energy production has grown as the disadvantages
associated with the burning of fossil fuels have become better known. Wind power is an
excellent source of renewable energy in areas with sufficient wind resources, and as such has
experienced tremendous growth in recent years. Unfortunately, often the best locations for
wind turbines are on the tops of hills and ridges where they experience lower temperatures
than surrounding areas and where they are subject to icing of the blades. This icing of the
blades can cause a variety of problems. Complete loss of production [Ronsten 2004],
reduction of power due to disrupted aerodynamics [Jasinski, et al 1998], overloading due to
delayed stall [Jasinski, et al 1998], increased fatigue of components due to imbalance in the
ice load [Ganander, et al 2003], and damage or harm caused by uncontrolled shedding of large
ice chunks [Seifert, 2003].
When planning construction of new wind power production, accurate prediction of power
production from the planned wind turbines is needed to be able to calculate the return on the
investment. Uncertainties in the effects of icing for a wind park, requires larger safety
margins for recovery of investment capital before the project will be undertaken. To effect
the realization of as much wind power production as possible, and to help planners and
investors, a summary of the effects of icing as well as the causes of icing are presented. The
goal of this paper is to present information on icing to reduce uncertainties surrounding icing
such that good projects are realized and that unexpected problems due to icing are avoided.
2. Problems due to icing
The problems due to icing are presented here as some of the worst case situations that can be
encountered. This is not to over dramatize the effects of icing, but rather to give a perspective
such that the possibility of icing is considered in the planning stages, and appropriate steps are
taken.
2.1.
Presentation of icing effects
Complete stop due to icing
An example illustrating how a wind turbine can be completely stopped by icing, with
resulting loss of all possible production can be seen in the following information from the
Äppelbo wind turbine in Sweden, as discussed in [Ronsten 2004]. This wind turbine is a 900
kW unit from NEG Micon, and was stopped by icing for over 7 weeks in the winter of 20022003, as can be seen in Figure 2.1.1.
Page 2
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Figure 2.1.1 – Relative performance of Äppelbo compared to two other wind turbines in southern Sweden,
showing the result of complete stop due to icing in December 2002. [Ronsten 2004, p.40]
Figures 2.1.2 and 2.1.3 show the difference between ice-free conditions on the Äppelbo
turbine, and icing conditions which caused a stop.
Figure 2.1.2 – Ice-free conditions at Äppelbo. Pictures taken from the nacelle Dec. 5, 2003. Photos: Göran
Ronsten, FOI
Page 3
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Figure 2.1.3 – Icing conditions causing a stop of Äppelbo. Pictures taken from the nacelle Jan. 15, 2004.
Photos: Kjell Jansson, Malungs Elnät AB.
Disruption of aerodynamics
Disruption of aerodynamics can cause a reduction in power production. As shown by
[Jasinski, et al 1998], even the onset of ice accretion causing a slight surface roughness leads
to an increase in the drag coefficient and corresponding reduction in power production.
Further growth of rime ice causes a continuing increase in the drag coefficient and reduction
in power production, as can be seen in figure 2.2.1.
Figure 2.2.1 – Calculated power curve for a pitch controlled fictitious turbine with different types of ice
accretion. [Siefert, et al 1998, p.10]
Page 4
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Overloading due to delayed stall
It has been shown that under certain conditions, stall regulated wind turbines can experience
an increase in power production when accreted ice causes delayed stalling. This is clearly
demonstrated by [Jasinski, et al 1998], and can be seen in figure 2.3.1.
Figure 2.3.1 – Illustration of how power production can increase due to delayed stall in some icing conditions.
[Jasinski, et al 1998, pp.62-64]
Increased fatigue due to imbalance
Operation of a wind turbine with an imbalance caused by icing causes an increase in the loads
imposed on all components of the turbine. Though the extreme loads are already covered
when design for the loss of a blade is calculated, the fatigue loads will cause a shortening of
the lifetime for the components [Ganander, et al 2003]. Figure 2.4.1 shows how the bending
loads of the tower increase dramatically when one turbine blade is loaded with ice.
Figure 2.4.1 – FFT of tower bottom showing increase in load, for mass (0,25,50,75) kg imbalances. [Ganander,
et al 2003, p.6]
Page 5
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Harm to people or property due to ice shedding
The pieces of ice shed from wind turbines can be quite large, and are definitely not
insignificant, as can be seen in figure 2.5.1. Though no instances of personal harm due to ice
shedding from wind turbines have occurred so far, it can be assumed that something will
occur eventually if preventive measures are not implemented. Though the risks are greatest
for service personnel who must approach the wind turbine, others can be at risk when the
wind turbine is located near a road or recreation area.
The possible distances for thrown ice have been roughly estimated by equation 2.5.1
[Tammelin, et al. 2000].
d = ( D + H ) × 1.5
(2.5.1)
d is the possible distance ice can be thrown.
D is the diameter of the rotor.
H is the height of the nacelle.
This equation can only be considered a rough estimate, but gives a general idea of the area
which is at risk for ice throw.
Figure 2.5.1 – Examples of ice fragments found near wind turbines, or taken from blades. [Seifert, 2003, p.3]
2.2.
Summary of icing effects
As can be seen from this section, the worst-case effects of icing can be quite significant. The
effects of icing at any given site will be dependent on a range of variables presented in the
section on the causes of icing.
Luckily there are options for prevention and removal of icing in the areas with the greatest
problems, and more techniques are under development.
3. Removal or prevention of icing
A number of methods have been proposed and tested for prevention and removal of ice on
wind turbine blades. Each approach is detailed individually below.
Direct heating of the surface, either through the use of microwaves, or with electrical
resistance heating is a relatively straight forward method. The JE-System of direct resistance
heating has been shown to work effectively, but has not come into normal production. LM
Page 6
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Glasfiber has tested both microwave based systems and electrical resistance heating systems
[LM Glasfiber 2004]. Their results showed positive results for the microwave system when
surface absorbers were applied, but that further research is necessary. The resistance heating
elements, or heating foil as it is called, functioned well, and was able to deice the blades both
during operation, and in standstill conditions. Painting the blades black has also been done to
more effectively absorb solar radiation after a period of icing.
Indirect heating of the surface has been proposed and tested, where typically the inside of the
blade is heated with warm air or a radiator and the heat is then transferred to the outer surface.
Such a system was installed on an Enercon turbine in Switzerland [Horbaty 2005], and though
the experience with this system is limited, the initial results are promising, as can be seen in
figure 3.1.1.
Mechanical removal, as is done on the leading edges of aircraft wings [Botura, G., et al 2003]
appears to be a promising alternative, though further development is needed before a system
for wind turbines is available. A system where the blades were flexible enough to crack loose
the ice has also been proposed, as the flexing of the blades already is known to help shed ice.
The disadvantage of trying to crack loose the ice is that thin layers of ice can adhere quite
strongly to the blade, and are not brittle enough to crack loose from just vibration of the blade.
A surface treatment that prevented ice build up has been sought since it is known that without
nucleation sites small water droplets can remain liquid at temperatures well below 0°C. Even
a coating that significantly reduced the adhesion strength should aid in spontaneous shedding
of ice accretion. Several anti-icing coatings tested by [Kimura, et al 2003] appeared to have
little effect, but later work with another coating has shown very promising results, with a 10
fold reduction of adhesion strength [Kimura, et al 2004].
Figure 3.1.1 – Successful deicing with hot air system. [Horbaty 2005, p.9]
Page 7
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
A system where the blade surface is protected by a layer of clean air was presented by
[Battisti 2004 and 2005] and is shown in figure 3.1.2. This system used an air flow from
inside the blade, and rows of small holes near the leading and trailing edges to generate a
layer of clean and, if necessary, heated air directly around the blade surface. This layer of air
would deflect the majority of water droplets in the air, and could melt the few droplets that
managed to strike the surface.
Figure 3.1.2 – Wing protected by a layer of warm dry air from small holes at the leading and trailing edges.
[Battisti 2004, p.33]
A large number of the wind turbine manufacturers were contacted to determine what types of
deicing systems they have available. None of the manufacturers who replied had a system
available for reduction or removal of icing other than Bergey who paints their blades black.
The manufacturers who responded were Vestas / NEG Micon, Siemens Windpower / Bonus,
Scanwind, and Bergey. LM Glasfiber said that they have several different methods for
deicing wind turbine blades, but none of them are in production today, and they could not
comment on them because they have patent applications pending. They also mentioned that if
their came a demand for deicing systems from their customers, they would include deicing
capabilities in their wings, but it did not appear that this would occur in the current year. In
addition, requests for information were submitted to GE Energy, Enercon, Nordex, Gamesa,
WinWinD and Suzlon, but no responses were received from these manufacturers. It was
unfortunate that these manufacturers did not respond and particularly Enercon, because it has
been stated elsewhere that Enercon sells a system for deicing stationary blades [Ronsten
2004], and such a system was shown to work in Switzerland.
4. Definitions and causes of icing
To better understand why icing occurs in some areas more often than others, and what causes
wind turbines to be especially susceptible to icing, it is necessary to examine how icing
occurs. In addition, several models for icing are presented.
Two main types of ice accumulation are traditionally defined, in-cloud icing and precipitation
icing [ISO 12494, 2001]. Frost, a third method of ice accumulation is not thought to cause
Page 8
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
any problems for wind turbines, and therefore is not considered here, though it will be
defined. The main icing types, with under types are as follows:
1) In-cloud icing
a) Rime
b) Hard rime
c) Soft rime
d) Glaze
2) Precipitation icing
a) Wet snow
b) Freezing rain
3) Frost
4.1.
In-cloud icing
In-cloud icing is formed by the impacting of supercooled droplets on the surface.
Supercooled droplets occur often in clouds in the atmosphere down to temperatures as low as
-20°C, and sometimes even as low as -35°C [Mason 1971, p.155]. These supercooled
droplets will freeze when they impact a surface which allows formation of ice. The
temperature and size of the droplets determines whether it is hard rime, soft rime or glaze ice
that forms.
Rime
Rime is formed when the thermal energy released by the formation of ice from the droplets
that are impacting the surface is removed quickly enough by wind and radiation so that no
liquid water is present on the surface. Rime appears white, and breaks off easier than glaze.
Soft rime forms when the droplet size is small and water content in the air is lower. It has a
lower density than hard rime due to larger air gaps between the frozen particles. Hard rime
forms with medium droplet size and a higher water content in the air. It is harder due to
smaller air gaps between the frozen particles and better bonding. Formation of rime is shown
in figure 4.1.1. [ISO 12494, 2001]
Figure 4.1.1 – Growth of rime ice. [ISO 12494, 2001, p.40]
Glaze
Glaze is formed when the thermal energy released by the formation of ice from the droplets
impacting the surface is not as quickly removed, and some portion of the droplets remains as
liquid water. This means that there is always some liquid water present, and therefore the
surface temperature will be 0°C. Glaze forms as a solid covering of clear ice, since the
Page 9
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
amount of trapped air is very low. Glaze has a higher density, and is more difficult to remove
than rime. The formation of glaze is shown in figure 4.1.2 [ISO 12494, 2001]
Figure 4.1.2 – Growth of glaze ice. [ISO 12494, 2001, p.41]
4.2.
Precipitation icing
Precipitation icing occurs when precipitation, either rain or snow, freezes after striking the
surface.
Wet snow
Wet snow can stick to a surface if the temperature is between 0°C and 3°C. This is due to the
snow having some liquid water present, which allows the snow crystals to bind together when
they come in contact on the surface. Wet snow often has a low binding strength while
forming, but can become very hard and strongly bound if the temperature subsequently falls
below 0°C.
Freezing rain
When rain falls at temperatures below 0°C it leads to what can be called glaze, freezing rain
or drizzle. This often occurs in connection with a temperature inversion where cold air is
trapped near the ground beneath a layer of warmer air [ISO 12494, 2001]. This can also occur
in the case of a rapid temperature rise where an object still has a temperature below freezing
even though the air temperature is above freezing. This last situation is of special concern for
aircraft when descending.
4.3.
Frost
Frost, sometimes called hoarfrost, forms when the temperature of the surface is lower than the
dew point of the air. This causes water vapor to deposit on the surface forming small ice
crystals.
Page 10
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
4.4.
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Meteorological parameters affecting icing
Table 4.4.1 shows under what types of meteorological parameters the various types of icing
form. Figure 4.4.1 shows how wind speed and air temperature effect the formation of incloud icing.
Table 4.4.1 – Table of meteorological parameters controlling atmospheric ice accretion. [ISO 12494, 2001, p.7]
Figure 4.4.1 – Types of accreted ice as a function of wind speed and air temperature. [ISO 12494, 2001, p.7]
4.5.
Physical model of icing
The rate of accretion of ice and snow is described by formula 4.5.1, as detailed in [Makkonen,
1994 p.53] and [ISO 12494, 2001].
dM
= α1 * α 2 * α 3 * w * v * A
dt
(4.5.1)
A is the cross sectional area of the object with respect to the direction of the particle velocity
vector.
w is the mass concentration of the particles.
v is the relative velocity of the particles.
The α terms are correction factors that vary between 0 and 1.
Page 11
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
The collection efficiency (or collision efficiency), α1, represents the flux density of particles
striking the surface in relation to the maximum possible. This is usually less than 1 since
small particles will attempt to follow the air stream, and thereby be deflected from striking the
surface. Figure 4.5.1 illustrates this point, and also makes it clear that the droplet size has an
effect on the collection efficiency. Another important point regarding the collection
efficiency is that smaller objects are generally more efficient collectors than large objects.
This is due to the fact that with small objects the airflow in front of the object will have
shorter radius flow lines when flowing around the object, which makes it more difficult for
the water droplets to follow the airflow, due to their mass and velocity. This means that more
droplets will strike the surface than in the case of a larger object, where the droplets will be
diverted from the surface by the flow of air. This means that two different objects can have
entirely different rates of ice accretion, even in the same conditions. As described by [Poots
1996, p.5] from [Rodgers 1977] where the large body of a radio tower collected very little ice
while the stay lines collected some 70 tons, eventually ending in collapse.
Figure 4.5.1 – Small droplets follow the air streamlines, while large droplets collide with the object.
[ISO 12494, 2001, p.7]
The sticking efficiency, α2, represents the ratio of the flux density of particles sticking to the
surface to the flux density of the particles striking the surface.
The accretion efficiency, α3, represents the rate at which ice builds up on the surface in
relation to the flux density of particles sticking to the surface. If this is under 1, it means that
some portion of the particles sticking to the surface are melting and running off. In the case
of dry rime icing this term is 1.
The conditions necessary for icing can be vary slightly, depending on what type of icing is
occurring, but the temperature of the surface must be 0°C or below. The air temperature can
be above 0°C if there is some combination of radiative and / or evaporative cooling, or in the
case of a rapid increase in air temperature, such that the temperature of the surface is below
0°C. It has been thought that the relative humidity would also need to be at or near 100%, but
the work done by [Laakso, et al 2003] showed that icing occurred also at relative humidity
levels lower than 90%. It was mentioned that it is possible that the humidity sensors used
were not reporting the correct values for exposed surfaces due to radiation shielding of the
sensors. Later work by [Makkonen, et al. 2005] with a new relative humidity sensor has
shown that icing does not occur during periods of low relative humidity, and cast doubt over
the accuracy of earlier humidity sensors for high relative humidity combined with
temperatures below freezing.
Page 12
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
4.6.
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Empirical models of icing
Many different empirical models for icing have been proposed, with varying degrees of
complexity. These can be divided into two main classes; models for precipitation icing, and
models for in-cloud icing. These models were not critical to the study of icing sensors and
therefore not studied in detail in this report, but are mentioned for the sake of completeness.
Empirical models for precipitation icing
Many of the previous icing models are studied in detail by [Makkonen 1998], which is
recommended reading if an in depth study of these models is desired. Equation 4.6.1, from
[Goodwin, et al. 1983] was modified by [Dobesch, et al. 2005] to equation 4.6.2, and
compared against an icing event observed in Austria, with mixed results.
dM
= 2rwV
dt
(4.6.1)
I = wV = 0.26 P 0.88V
(4.6.2)
Where M is the mass per unit length at time t, r is the radius of the cylinder, I is the ice
accretion intensity, w is the liquid water content (LWC) of the air, P is the precipitation rate,
and V is the wind speed.
Empirical models for in-cloud icing
The simplest model depends only on the wind speed, as found by [Ahti, et al. 1982]. The
equation found for ice accretion intensity is as follows.
I = 11.0 × 10 −3 V
(4.6.3)
Where I is the ice accretion intensity in g cm-2 h-1 and V is the wind speed in m s-1.
Later work by [Tammelin, et al. 1996] and [Dobesch, et al. 2005] has shown this equation to
overestimate the amount of ice accretion, and it was suggested that it is possibly due to icing
of the anemometer causing underestimation of the wind speed. Work by [Tammelin, et al.
1996] adjusted the empirical constant down to 4.8, from 11, as shown in equation 4.6.4.
I = 4.8 × 10 −3 V
(4.6.4)
These equations require of course that the conditions of being within a cloud and having a
temperature below freezing are fulfilled.
5. Conclusions and suggestions for further work
5.1.
Conclusions
As shown in this paper, icing of wind turbines is by no means trivial. For accurate analysis of
the risks associated with icing it is necessary to understand how icing occurs, and the effects
of icing. These two processes are explained in this paper, and the literature cited can be
reviewed if more details are desired.
The best position for detection of icing on a wind turbine is on the wing itself, and as close to
the tip as possible, for two reasons. The first reason is based on the model for icing as
described in formula (4.5.1). The rate of ice accretion is directly related to the relative
Page 13
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
velocity of the supercooled water droplets, and it is at the wing tip that the highest velocity
occurs. The second reason is that the blade tips can experience icing due to low clouds even
thought the nacelle is ice-free. At Pori, in Finland, measurements showed the number of incloud icing periods at 84 m was six times the number of in-cloud icing periods at 62 m
[Säntti, et al. 2003]. These reasons dictate that locating the sensor on the wing will be more
and more necessary as the length of the wings used on wind turbines increases.
It can also be seen that the height of the wind turbines affects their susceptibility to icing, due
to taller structures being more likely to reach the cloud base.
5.2.
Suggestions for further work
An analysis and review of the tools used to predict the frequency and intensity of icing for a
particular area was outside the scope of this paper, but should be examined.
Development of icing sensors which can indicate ice thickness, in addition to a sensor which
indicates whether ice is present or not, must continue. This is especially important for
consideration of ice cast danger. A turbine without de-icing possibilities can perhaps be used
with 1 or 2 mm of accreted ice, and decreased performance, but if ice thicknesses increase
beyond that there comes an increasing risk from ice which may be shed from the blades, and
stoppage of the turbine must be considered.
6. References
Ahti, K., Makkonen, L., (1982), “Observations on rime formation in relation to routinely measured
meteorological parameters”, Geophysica Vol 19:1, p.75-85.
Battisti, L. (2004), “Anti-icing system for wind turbines”, World Intellectual Property Organization,
International publication number WO 2004/036038 A1. April.
Battisti, L. (2005), emailed presentation, June 28.
Botura, G., Fisher, K. (2003), “Development of Ice Protection System for Wind Turbine Applications”,
Proceedings of the 2003 BOREAS VI Conference. Pyhätunturi, Finland. April
Dobesch, H., Nikolov, D. (2005), “Icing measurements and model results from Oberstrahlbach, Austria”,
Proceedings of the 2005 BOREAS VII, Saariselkä, Finland. March
Ganander, H., Ronsten, G. (2003), “Design Load Aspects due to Ice Loading on Wind Turbine Blades”,
Proceedings of the 2003 BOREAS VI Conference. Pyhätunturi, Finland. April
Goodwin, T.J., II, Mozer, J.D., Di Gionia, A.M., Jr., Power, B.A., (1983), “Predicting ice and snow loads for
transmission lines”, Celerino Grandiosa, In the proceedings of the first IWAIS, pp. 267-273.
Horbaty, R. (2005), “Wind energy in cold climates – The Swiss experience”, Proceedings of the 2005 BOREAS
VII, Saariselkä, Finland. March
ISO 12494 (2001), “Atmospheric icing of structures”, ISO copyright office, Geneva, Switzerland
Jasinski, W.J., Noe, S.C., Selig, M.S., Bragg, M.B. (1998), “Wind Turbine Performance Under Icing
Conditions”, Transactions of the ASME, Journal of solar energy engineering. New York, NY, USA.
February, Vol. 120, pp 60-65.
Kimura, S., Sato, T., Kosugi, K. (2003), ”The effect of anti-icing paint on the adhesion force of ice accretion on
a wind turbine blade”, Proceedings of the 2003 BOREAS VI Conference. Pyhätunturi, Finland. April
Kimura, S., Furumi, K., Sato, T., Tsuboi, K., (2004) “Evaluation of anti-icing coatings on the surface of wind
turbine blades for the prevention of ice accretion”, Proceedings of the 7th International Symposium on
Cold Region Development, CD-ROM, No.63
Laakso, T., Peltola, E., Antikainen, P., Peuranen, S. (2003), “Comparison of Ice Sensors for Wind Turbines”,
Proceedings of the 2003 BOREAS VI Conference. Pyhätunturi, Finland. April
LM Glasfiber, (2004), “Why De-icing of Wind Turbine Blades?”, presented at Global WINDPOWER 2004,
Chicago, March 28-31. Downloaded, June 16, 2005 from
http://www.lmglasfiber.dk/DK/Events/Conference/default.htm
Makkonen, L. (1994), “Ice and Construction” – Rilem report 13, First edition, Chapman & Hall; London,
England.
Makkonen, L. (1998), “Modeling power line icing in freezing precipitation”, Atmospheric Research, Vol. 46,
pp.131-142.
Page 14
Matthew Carl Homola, Narvik University College
INTERREG III B PROJECT
WIND ENERGY IN THE BSR: IMPACTS AND CAUSES OF ICING ON WIND TURBINES
Makkonen, L., Laakso, T., Säntti, K., (2005), ”Humidity in Icing Conditions”, Proceedings of the 2005
BOREAS VII, Saariselkä, Finland. March
Mason, J (1971), “The Physics of Clouds”, Oxford University Press, Ely House, London, England
Poots, G. (1996), “Ice and Snow Accretion on Structures”, Research Studies Press LTD; Somerset, England.
Rodgers, G. G. (1977), See Poots, G., 1996.
Ronsten, G. (2004), ”Svenska erfarenheter av vindkraft i kallt klimat – nedisning, iskast och avisning”, Elforsk
rapport 04:13, May
Säntti, K., Tammelin, B., Laakso, T., Peltola, E. (2003), ”Experience from Measurements of Atmospheric Icing”.
Proceedings of the 2003 BOREAS VI, Pyhätunturi, Finland. April
Seifert, H. (2003), “Technical Requirements for Rotor Blades Operating in Cold Climate”, Proceedings of the
2003 BOREAS VI, Pyhätunturi, Finland. April
Tammelin, B., Cavaliere, M., Holtinnen, H., Morgan, C., Seifert, H., Säntti, K. (2000), ”Wind Energy in Cold
Climate, Final Report WECO” (JOR3-CT95-0014), ISBN 951-679-518-6, Finnish Meteorological
Institute, Helsinki, Finland, February
Tammelin, B., Säntti, K., (1996), “Estimation of rime accretion at high altitudes – preliminary results”,
Proceedings of the 1996 BOREAS III, Saariselkä, Finland. March
Page 15
Matthew Carl Homola, Narvik University College