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Rain Erosion Maps for Wind Turbines Based on Geographical Locations: A Case Study in Ireland and Britain


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Erosion rates of wind turbine blades are not constant, and they depend on many external factors including meteorological differences relating to global weather patterns. In order to track the degradation of the turbine blades, it is important to analyse the distribution and change in weather conditions across the country. This case study addresses rainfall in Western Europe using the UK and Ireland data to create a relationship between the erosion rate of wind turbine blades and rainfall for both countries. In order to match the appropriate erosion data to the meteorological data, 2 months of the annual rainfall were chosen, and the differences were analysed. The month of highest rain, January and month of least rain, May were selected for the study. The two variables were then combined with other data including hailstorm events and locations of wind turbine farms to create a general overview of erosion with relation to wind turbine blades.
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Journal of Bio- and Tribo-Corrosion (2021) 7:34
Rain Erosion Maps forWind Turbines Based onGeographical Locations:
ACase Study inIreland andBritain
K.Pugh1 · M.M.Stack1
Received: 8 September 2020 / Revised: 15 December 2020 / Accepted: 1 January 2021
© The Author(s) 2021
Erosion rates of wind turbine blades are not constant, and they depend on many external factors including meteorological
differences relating to global weather patterns. In order to track the degradation of the turbine blades, it is important to analyse
the distribution and change in weather conditions across the country. This case study addresses rainfall in Western Europe
using the UK and Ireland data to create a relationship between the erosion rate of wind turbine blades and rainfall for both
countries. In order to match the appropriate erosion data to the meteorological data, 2months of the annual rainfall were
chosen, and the differences were analysed. The month of highest rain, January and month of least rain, May were selected
for the study. The two variables were then combined with other data including hailstorm events and locations of wind turbine
farms to create a general overview of erosion with relation to wind turbine blades.
Keywords Wind· Turbine· Maps· UK· Ireland· Erosion· Rainfall· Composites· Testing
1 Introduction
Wind energy has become an increasingly popular choice
of renewable energy with many countries across the world
attempting to become carbon neutral [1]. This has resulted
in a major research focus within the wind energy sector,
addressing all aspects of energy conversion. This boom has
had a very significant impact on the design, manufactur-
ing and efficiency of the turbines and their blades [2]. One
common advance is to install much larger blades, however,
this is coupled with substantially greater tip velocities of
the blades. These increased velocities create a higher risk
of degradation of the leading edge due to impacts from rain
erosion [3]. With tip speeds from turbines reaching 300mph,
the repeated impact of raindrops is sufficiently energetic to
erode the material. The erosion rates of wind turbines have a
direct relationship to the environment they are erected. More
rainfall will result in more erosion of turbine blades [4].
Typically wind turbine farms are constructed in barren
locations due to land availability, wind speeds and away
from local beauty spots; however, this results in turbines
being subjected to harsh conditions and in some locations
heavy rainfall. Within this case study, data from the Met
Office [5, 6], Irish weather data [7] and experimental data
will be combined to map the UK and Ireland in terms of
erosion on wind turbine blades. This is being carried out
to display the relationship between the locations of wind
turbine farms and their environment. This will, in turn, also
aid in visualizing the wind farms that are at higher risk from
erosion degradation and will require more maintenance. This
is to mitigate failures and increase power output by keep-
ing the blades smooth and promoting greater aerodynamic
2 Methodology andResults
The procedure began by collating data from the Met office
and Irish weather data. With this data an average rainfall map
over the last 20years was created. It should be noted that
the turbine blades will inevitably experience varying rainfall
rates throughout the year, which will, in turn, result in vary-
ing erosion rates. To map this phenomenon, the months of
highest and lowest rainfall were chosen which were January
and May, respectively. Showing the two extremes of rainfall
months will provide more insight than a yearly average and
* K. Pugh
1 Department ofMechanical Engineering, University
ofStrathclyde Glasgow, 16 Richmond St, GlasgowG11XQ,
Journal of Bio- and Tribo-Corrosion (2021) 7:34
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allow for contrast to be observed between the 2months. The
result of this can be seen in Fig.3.
Upon the completion of this map an experimental pro-
cess in the Tribology laboratory at the University of Strath-
clyde was carried out to relate rainfall across the country
to the degradation of wind turbine blades. There are many
different ways to test for rain erosion [8]; however, the test
method used for this case study is the whirling arm setup
[9]. This consists of a large chamber with induced rainfall
from hypodermic needles; in the centre of the chamber is
a rotating arm which holds the material sample at the end.
Adjusting the rotational speed of the spinning arm will
adjust the impact velocity the sample encounters with the
water droplet. The experimental setup can be seen in Fig.1
and a schematic is shown in Fig.2.
The material used in this experiment was G10 epoxy
glass which is a similar glass fibre epoxy composite used
within the wind turbine manufacturing industry [10]. The
impact velocity was set to 60ms−1 as this will simulate the
leading edge of 2MW turbines with a diameter of 100m.
One of the assumptions that was made to relate the experi-
mental data to the weather data was that the wind turbines
were always turning when it was raining. Although this
might result in an overestimation in erosion, it is deemed
a worst-case scenario that has a possibility of occurring.
All the variables which were kept constant includ-
ing impact velocity, temperature and rainfall were all
calibrated before the experimental campaign began. The
impact velocity was calibrated using light transducer
which was held close to the rotating shaft where a thin
reflective strip was placed. A light source was focused
onto the shaft and the transducer would give an electri-
cal output when the light was reflected from the reflec-
tive strip each time it would rotate. The rain fall was cali-
brated by running the rain system for five hours and the
water tank which feeds the rig was weighed periodically
every 30min to calculate the water consumed and hence
the rainfall rate. The pump used was a peristaltic pump
which proved to be extremely reliable and hence outputted
50mm/h every 30min. The temperature inside the rig was
also measured and kept at 29°C, a temperature calibration
test was carried out during the calibration of the rainfall
where the temperature was measured using a probe inside
the chamber and a reading was taken every 30min for the
five hours and the temperature only fluctuated ± 1°C.
The same procedure was carried out for all samples
which included a 48-h drying period before measuring
the mass and kept in the same container to ensure the con-
ditions when the sample was drying were kept constant.
After the 48 drying period the samples were weighed on a
balance accurate to 0.00001g and the mass of the sample
was measured five times equally spaced out over one hour.
From this a measurement error of ± 0.001% and standard
deviation of 1.09E−05 was calculated for the neutral water
and a measurement error of ± 0.019% and standard devia-
tion of 1.16E−04 for the saltwater experiment.
The construction of the rainfall map (Fig.3) allows the
setup for the experiment to be finalised. The key to the
map displays: Below 50mm, 50mm, 75mm, 100mm,
150mm, 200mm, 300mm, 500mm and above 500mm.
The rainfall rate of the whirling arm rig is 50mm/h there-
for the time each sample exposed to rain erosion can be
determined, this is.
shown in Table1.
The chosen measurement for erosion is mass loss as a
percentage of the original sample. The mass of the test
material was measured before the experiment and after
each exposure time. This would result in a direct numeri-
cal relation between the average monthly rainfall and the
erosion as a mass loss.
Fig. 1 Whirling arm rain erosion rig
Fig. 2 Whirling arm schematic
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This methodology was repeated with saltwater instead of
rainwater to simulate offshore conditions. The saltwater used
was a 3.5% saline solution which most accurately describes
the seawater in the UK and Ireland [11]. The results and
errors can be seen in Table2
Fig. 3 The average rainfall in the months of January and May
Table 1 Exposure time in
erosion rig to achieve required
Rainfall (mm) Exposure
50 60
75 90
100 120
150 180
200 240
300 360
500 600
Table 2 Mass loss results from
erosion testing Exposure time
Cumulative rainfall
Neutral water mass loss (%)
(± 0.001%)
Saltwater (3.5% saline
solution) mass loss (%)
(± 0.019%)
60 50 0.037 0.001
90 75 0.046 0.014
120 100 0.055 0.071
180 150 0.073 0.075
240 200 0.091 0.120
360 300 0.127 0.205
600 500 0.199 0.276
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3 Rainfall Map
The rainfall mostly averages between 50 and 500mm of
rain with some few areas showing more extreme rain. It
is clear that the month of May experiences considerably
less rain as it shows highs of 300mm whereas this rate is
fairly common in January. The areas of intensity are very
similar in both months with the west coast of Scotland
showing a high rainfall and also the west coast of Ireland,
predominantly the south west coast of Ireland displaying
very heavy rainfall. These are historically harsher climates
due to the prominent westerly wind from the Atlantic [12].
This leads to further erosion as the largest windfarms are
located in these areas due to the increased power output
from the consistent wind [13]. This is a very common
trade-off when building a windfarm as the conditions that
yield the most power generation are also the conditions
which deteriorate the turbine blades most rapidly, there-
fore the life of the turbine blade will be reduced [14].
Part of the experimental process was also to under-
stand sea water effects which help describe the erosion
behaviour of offshore wind turbines. This was completed
by running a saltwater solution (3.5% saline solution)
through the experimental rig to simulate offshore condi-
tions. Previous work on this topic by the current research
group showed similar results to the saltwater exposure in
this investigation. This had concluded that the saltwater
proved more erosive when subject to high velocity impacts
from the leading edge of the turbine blade and would cre-
ate larger, more destructive cracks and loss of material
from the sample [15]. The added effect of the more con-
sistent wind from offshore conditions with the sea water
climate is conducive to an erosive atmosphere and hence
a short life span of turbine blades. Offshore wind farms
have many other problematic characteristics including the
corrosive nature of sea water which will attack any metal-
lic parts and the anchoring of the structure to the seabed.
However, the remote locations and the large blade size
allows very significant energy capture [16]. Even though
offshore wind turbines encounter major drawbacks such as
increased levels erosion and corrosion, the advantage of
having the open space to build larger, more efficient wind
turbines with more consistent wind makes them economi-
cally viable [17].
4 Erosion Maps
Once the rainfall maps were created the link between
rainfall rate and erosion rate could be made as mentioned
previously. This allowed the same maps to be created with
the key displaying erosion as a percentage mass loss of a
theoretical turbine blade.
The results showed a maximum mass loss of 0.199%
which relates to 500mm of rainfall and a minimum
mass loss of 0.037% which relates to 50mm of rainfall.
Although mass loss is not the most precise measurement
for erosion when compared to imaging samples and iden-
tifying gauges, cracks and loss of material [18, 19]; it does
allow for a broader comparison between samples.
The measurement of mass loss can be loosely linked
to the efficiency of the turbine, which is also why this
measurement was used to map erosion across the UK and
Ireland. With all material lost from the wind turbine blades
it will affect the aerodynamic profile of the blades, with
more mass lost the greater the effect it will have. The dis-
turbed airflow over the blade will impede the performance
of the turbine. A damaged blade will require a higher air-
flow or blade angle to produce the same output [20]. This
has been proved experimentally within the literature which
considered the drag coefficients of compromised blades
[21] and also the microscopy of material subject to rain
droplets at high velocities [22].
The degradation of the sample should erode in three
distinct stages. The first is the initiation period; where the
sample is at its smoothest and difficult to penetrate, this
is when the turbine blades are brand new and operating at
optimal efficiency. Secondly is steady state erosion; where
the sample has been impacted by a critical number of drop-
lets to affect the surface roughness of the sample enough
to instigate more considerable erosion which continues at
a constant rate. It is during this stage that the turbine starts
to decline in efficiency. Lastly the third stage is the final
erosion region where the erosion rate decreases, however,
this is when the turbine blade is at its most vulnerable and
the erosion on the blades can begin to become structural
weak points [23]. It is important to locate areas of signifi-
cant erosion across the country as the timing of mainte-
nance to repair or replace blades is crucial in the optimisa-
tion of power production from wind turbine blades.
The rainfall data is only available on land, therefore
there was no offshore rain data to compare to the offshore
erosion data. From the experiments using saltwater (3.5%
saline solution) there was a higher mass loss at the higher
exposure times compared to the neutral water tests. To
compensate for this a border of approximately 10 miles
was created offshore around the islands and assumed to
be one grade above the adjacent onshore erosion rate. For
example, the mainland of Shetland displayed an erosion
of 0.046% mass loss therefor a 10-mile boundary off the
coast of Shetland was created displaying the next grade up
in the key which is an erosion of 0.055% mass loss. This
is displayed in Fig.4.
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5 Points ofInterest onErosion maps
Construction of these maps now allows for further com-
parison to be made including locations of major wind
farms and also areas of high hail rates which is displayed
in Fig.5. Even though the rainfall rate maps cover all
precipitation, it is important to locate areas of high hail
impact as these tribological actions can be detrimental to
its structural integrity. Although the probability of hail
striking wind turbine blades is very low and the dam-
age would be difficult to ascertain, and it could possibly
be masked as the outcome of heavy rainfall erosion, the
implications of hail impacts have been proven experimen-
tally to cause substantial damage. In a study looking into
ballistic ice impacts, it was shown that the impact would
delaminate and crack the composite material [24]. This
would not only create a weak point in the blade structure
itself but also create an initiation site for rain erosion to
occur and for crack propagation into the structure of the
blade. The areas of frequent hail are shown in Fig.5 as
the red overlay, and from the maps it is clear that the west
coast is more adversely affected by hail. Unfortunately,
there was limited data on hail in The Republic of Ireland;
therefore, assumptions on this issue for this area of the
map need to be treated with caution.
Also superimposed onto the map in Fig.5 is the loca-
tions of some large wind farms and the largest in Scotland,
England, Ireland, Wales, Northern Ireland and The Republic
of Ireland have been labelled [25]. This not only allows for
a comparison between the size of the various windfarms in
each region but also how adversely affected each one is by
the climate and the subsequent erosion. Most of the wind-
farms are in compromising locations but, as discussed previ-
ously, this is a trade-off between greater access to consistent
wind to the lifetime of the blades.
6 Areas Which May be Addressed inFuture
There are some additional modifications which will help
optimise these maps when they are recreated with future
results. The main extension would be the use of additional
data to help aid the validity of the results and as mentioned
previously if enough datapoints are available then a dynamic
map could be potentially created.
There are many additions which could be made to the ero-
sion data and the weather data which could provide further
insight into geographical differences including the droplet
size, pH value and intensity which would aid the erosion
Fig. 4 The monthly erosion rates in January and May
Journal of Bio- and Tribo-Corrosion (2021) 7:34
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data. These data sets however are difficult to pinpoint as they
are mostly stochastic.
The most important evolution for these maps would
be the inclusion of offshore rain data to include the large
offshore wind farms that could not be included within this
study. With almost half of the UK wind energy coming from
offshore wind farms [26] the inclusion of this data would
provide a more thorough overview of the erosion of the
UK and Ireland’s wind turbine blades and hence the loss in
power due to aerodynamic inefficiencies.
7 Conclusions
In conclusion, the data from the rainfall within the UK and
Republic of Ireland were formatted together to produce an
Ireland/Britain map showing the average rainfall across the
two countries in both January and May averaged over the
last 20years. These maps were then used as the basis for an
erosion experiment converting the rainfall to exposure time
within the erosion rig. These results were then arranged on
the map to display the degradation of the turbine blades from
rain droplet impacts. This was coupled by a saltwater erosion
experiment that used 3.5% saline solution as the droplets to
simulate offshore wind turbines which are subject to being
eroded by sea water (salt spray corrosion enhanced erosion)
in the atmosphere. These two maps were then superimposed
to display areas of frequent hail and the locations of each
country’s largest wind turbine farm. This was carried out
in an attempt to visualise the erosion patterns across both
Ireland and the UK.
It is clear that the general trend consists of greater ero-
sion in the west coast of both the UK and The Republic of
Ireland with the highest erosion areas being the north west of
Scotland where the land tends to be at a higher elevation and
also the south west of Ireland where there is no protection
from the prevailing wind over the Atlantic.
The locations of frequent hailstorms across the UK and
the republic of Ireland could be considered stochastic, how-
ever, the locations of some major wind farms overlap with
frequent hail; this can be seen predominantly in Northern
Ireland. This overlap could potentially reduce the lifetime of
the turbine blades at an increased rate due to more powerful
impacts from hailstones.
Fig. 5 The monthly erosion rates in January and May with overlays of major wind turbine farms and areas of frequent hail
Journal of Bio- and Tribo-Corrosion (2021) 7:34
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These mapping methods have potential to be used in life-
time modelling of wind turbine blades and have the possi-
bility to be developed into a dynamic map that can display
changes in new wind farms and changing climates. This is
particularly important due to weather changes over long
periods of time on the annual cycle.
Acknowledgements The authors would like to acknowledge the sup-
port of the Interreg (Northern Ireland—Ireland—Scotland) Special EU
Programmes Grant No SPIRE2_INT-VA-049 ‘‘Storage Platform for the
Integration of Renewable Energy (SPIRE 2)’’.
Compliance with Ethical Standards
Conflict of interest On behalf of all authors, the corresponding author
states that there is no conflict of interest.
Open Access This article is licensed under a Creative Commons Attri-
bution 4.0 International License, which permits use, sharing, adapta-
tion, distribution and reproduction in any medium or format, as long
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... Salt concentrations are typically much higher than acidic pollutants and are of interest in situations where materials (including polymers) are prone to corrosion [15,16,24]. Recent evidence [12,[25][26][27] suggests enhanced degradation due to the presence of sea salt, acidity or at sites in close proximity to quarries. The influence of salt will be more pronounced at sites near the coast or offshore. ...
... As noted by Rasool et al. [27], data from RET experiments show enhanced degradation in both the presence of saline and acidic solutions. Pugh et al. [25,26] supports this, noting that the presence of salt within the working fluid appears to enhance rain erosion through the crystallisation of salts on the surface. The data presented by Law and Koutsos [12] support this with wind parks closer to the coast displaying more severe damage in a shorter period than those in remote regions. ...
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... In the wind energy sector, this information would be the most valuable, Lubricants 2021, 9, 60 3 of 12 allowing wind turbine owners to anticipate when the turbine blade will need maintenance to optimise energy production. Studies have investigated this in single exposure cycles [9]; however, this study analyses the erosion effects as a function of various impact angles over time, as well as the standard erosion rates. This is accomplished by running multiple samples at desired impact angles under an identical erosive environment. ...
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Landscape in Pain is a body of digital art works made in response to the distress, solastalgia (Albrecht), produced by the environmental change to the environment caused by the development of the Viking Energy Wind Farm in the Shetland Islands, the northernmost archipelago in Scotland. The industrial scale wind farm will cover most of Shetland’s north central mainland and be visible from the majority of the islands. With 103 wind turbines, it will become one of the largest onshore wind farms in Europe. While Shetland is anxious to tackle the climate crisis, nonetheless many believe this project is not a green solution. Local objections to the wind farm include its disproportionate scale, destruction of peatlands and negative human impact. How do we achieve balance between sustainable development and care for the communities rich in resources, such as wind and tidal power, being mined by multi-national corporations across the northern region?
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This paper represents the investigation of rain erosion on wind turbine blade materials under load in the simulation of onshore and offshore environmental conditions. The experimental work was carried out on a whirling arm rig with the material under a static 3 point bend to simulate large multi-megawatt wind turbine blades flexing during operation. This experiment was run with both fresh water and salt water to simulate onshore and offshore turbines. The results showed that the effects of a pre-stress on the samples resulted in a higher degradation rate following rain drop erosion. The microscopic analysis of the samples exposed to pre-stress identified distinctive surface features which has been termed a surface impact circular deformation. These features showed signs of cracking which enhanced the erosion rate. The pre-stressed samples also encountered a larger crossover in erosive mechanisms of abrasion and direct impacts; this was theorised to be due to the material being close to its yield stress and more likely to plastically deform.
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This paper represents the investigation of liquid impacts on wind turbine blade materials in the simulation of onshore and offshore environmental conditions. G 10 epoxy glass laminate was used as a specimen material. The experimental work was carried out on a raindrop erosion test rig at the varying angles of attack for a range tip speed. Two solutions, i.e. pure and salt water, were used to highlight the effects of offshore environment on this material when it is being used as wind turbine blades. Test results show that the erosive wear increased with an increase in droplet impact velocity. Erosion mapping techniques were used to compare the erosive wear behaviour of this material for application to onshore and offshore applications as candidate wind turbine materials.
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A Geographic Information System can be used in order to store, analyze and predict data regarding wind parks. Such data can refer to the natural factors that can affect the wind turbines, the placement of the turbines or their power capacity. In this paper we discuss the possibility to manage wind parks in Romania, based on the wind speed and altitude of different regions.
In renewable energy, wind capture has been expanding to now have one of the largest presences in the global green energy sector. With the drive to expand low carbon technologies; maintenance of the engineering components of wind turbines is crucial and in particular the monitoring of the leading edge of turbine blades which experience high impact velocities in service. Surface changes due to rain drop erosion can reduce energy con-version due to a loss of aerodynamic efficiency. This is one of the key areas of interest, as even small aerodynamic changes can lead to 2–3% loss in annual energy. Inspection methodologies of turbine blades are basic, involving an observation and high-definition photographs of the damage. Recent studies on the rain erosion of turbine blade materials show that this standard procedure often fails to characterise the loss of aerodynamic efficiency in these turbine blades in. With the industry moving in the direction of leading-edge profile samples, there is a consensus that whirling arm type test rigs are the most applicable testing regimes. Presently there is little overlap in the analysis used in different studies. This review considers various techniques which may be used to inspect and characterise the materials performance following exposure to rain drop erosion. These techniques will be evaluated based on their potential use within the industry. Findings conclude that a combination of techniques is optimal to analyse surface defects and that subsurface analysis is an important factor that must be considered in any investigation of long-term blade integrity.
Leading edge erosion of modern wind turbine blades is a growing and developing issue within the wind industry, effecting blade performance and efficiency. Little is known, researched or published on the phenomenon and there are currently no apparent full-proof material solutions for the issue. The research presented here looks to develop a fuller understanding of the issue of leading edge erosion, through first reviewing the literature (both within and outwith wind energy) on the topic to put the issues in context, and then subsequently further exploring and investigating the key damage mechanisms associated rain droplet and hailstone impact on the blade leading edge; identified as two of the most erosive types of environmental exposure. Both numerical (finite element) and experimental methods are employed to identify the key damage mechanisms associated with each form of impact in the different possible blade material coating and substrate systems. It is found that for rain exposure, surface degradation and erosion is a real risk for classical gelcoat coating systems. Whereas, for newer flexible and more erosive resistant materials, interface damage and debonding from the substrate is the most likely form of damage creation. Hailstone impact is found to pose a heightened erosive threat in comparison to rain, based on individual impact damage creation; although it is recognised that hailstorms are far more infrequent than rain showers in most regions. However, it is predicted that for extreme hailstones of sufficient mass, significant substrate composite damage could also be created through impact on the leading edge. Future work and further research development aimed at further understanding the issues of blade leading edge erosion are also identified and discussed.
Conference Paper
In the industry of renewable energy, wind has been expanding to become one of the biggest markets. With this increase in popularity, the maintenance of wind turbines is crucial, especially the care of the turbine blades. Rain erosion is widely accepted as one of the key areas of interest, as a even a 2-3% loss in annual energy output significantly reduces the energy efficiency. Inspection of turbine blades as of late is very basic, simply involving a visual observation which is accompanied by photographs of the damage. Recent studies investigating the rain erosion of turbine blade materials show that this standard procedure fails to characterise the loss of aerodynamic efficiency in these turbine blades or evaluate their performance in an inter-study comparative approach. Previous studies have focused on using smaller test coupons and the industry moving in the direction of leading edge profile samples, there is a broad consensus that whirling arm type test rigs are the most applicable testing regimes. However, there is little overlap in the analysis used in different studies. This review will look into the various techniques used to inspect and characterise the samples, materials and performance used in rain erosion testing. The focus will be on their practicality, benefit and application to overall use within the industry of wind energy.
The development of offshore wind power has become a pressing modern energy issue in which the UK is taking a major part, driven by the need to find new electrical power sources, avoiding the use of fossil fuels, in the knowledge of the extensive wind resource available around our islands and the fact that the environmental impact of offshore wind farms is likely to be low. However, there are major problems to solve if offshore wind power is to be realised and these problems revolve around the need to capture energy at a cost per kWh which is competitive with other sources. This depends upon the longevity of the wind turbines which make up offshore wind farms. Their availability, reliability and the efficacy and cost-effectiveness of the maintenance needed to achieve that availability, are essential to improve offshore wind life-cycle costs and the future of this emerging industry. This book intends to address these issues head-on and demonstrate clearly to manufacturers, developers and operators the facts and figures of wind turbine operation and maintenance in the inclement offshore environment, recommending how maintenance should be done to achieve low life-cycle costs.
Conference Paper
Leading edge erosion of wind turbine blades is an important issue within the industry and has been found to have a substantial impact on the annual energy output of generators. This forces operators to make blade repair a necessity, adding to the operation and maintenance costs of a project. A wind turbine’s tip speed can in some cases have an upper limit based on the erosion exhibited on the leading edge. This paper explores the variables of rainfall rate and impact velocity of the impinging droplets in an attempt to explore the recovery time of the tri-axial composite material used. It is shown that an increase in impact velocity results in a higher mass loss than an increase in the rainflow rate. Analysis using a scanning electron microscope reveals that pin holes in the laminate surface are exploited by the droplets, acting as initiation point for erosion of the composite. Overall the results suggest that the tip speed of the wind turbine blade is of greater importance when compared to the relevant rainfall conditions as to where the wind turbine is situated