Wind site evaluation assign Steven Sweeney K00181764

Wind Turbine Site Evaluation
Micro Wind Generation
By
Steven Sweeney
K00181764
Submitted: 05/12/14

Wind Turbine Site Evaluation Steven Sweeney K00181764
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Table of Contents
List of Figures................................................................................................................. 4
List of Tables.................................................................................................................. 4
1 Introduction ............................................................................................................. 5
2 Background of Wind Energy................................................................................... 6
2.1 Turbulence.......................................................................................................7
2.2 Measuring wind speed and direction .............................................................. 8
3 Extracting energy from the wind............................................................................. 9
4 Example of a site visited....................................................................................... 10
5 Evaluating the potential site.................................................................................. 12
5.1 Planning Regulations .................................................................................... 12
5.2 Sourcing data for the area at the site............................................................ 13
6 Choosing the best location at the site .................................................................. 15
6.1 Wind rose from Carrick Finn Airport ............................................................. 15
6.2 Obstacle Analysis.......................................................................................... 16
7 The Manufacturer ................................................................................................. 17
7.1 Turbine blade features .................................................................................. 17
7.2 Turbine specifications ................................................................................... 18
8 Power curve for HevAir 6K ................................................................................... 19
8.1 Power Coefficient for HevAir 6K ................................................................... 19
9 Load demand on site ............................................................................................ 20
10 Wind speed & Wind Energy on site.................................................................. 20
10.1 Find wind speed at 10m hub height.............................................................. 21
10.2 Log law formula............................................................................................. 21
10.3 Rayleigh distribution...................................................................................... 21
10.3.1 Weibull distribution................................................................................. 21
10.3.2 Results ................................................................................................... 22
10.4 Energy in the wind at 10m ............................................................................ 23
10.5 Annual Energy Output (AEO) for 10m tower ................................................ 23
10.5.1 Example of how long wind blow @ 8m/s............................................... 23

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10.6 Average Efficiency ........................................................................................ 24
10.7 Capacity Factor............................................................................................. 24
11 Wind turbine at a higher tower.......................................................................... 24
11.1 Finding wind speed at a 20m hub height ...................................................... 24
11.1.1 Log law formula...................................................................................... 24
11.2 Probability of wind speeds occurring............................................................ 25
11.3 Results........................................................................................................... 25
11.4 Energy density at 20m .................................................................................. 26
11.5 Annual Energy Output (AEO) for 20m tower ................................................ 26
11.5.1 Example of how long the wind blows @ 8m/s....................................... 26
11.6 Average Efficiency ........................................................................................ 27
11.7 Capacity Factor............................................................................................. 27
12 Cost analysis..................................................................................................... 27
12.1 Installation costs for the 10m wind turbine ................................................... 27
12.2 Installation costs for the 20m wind turbine ................................................... 27
13 Payback Time for the two different tower heights ............................................ 28
13.1 The 10m wind turbine.................................................................................... 28
13.1.1 Pay back check...................................................................................... 28
13.2 The 20m wind turbine.................................................................................... 28
13.2.1 Pay back check...................................................................................... 28
14 Conclusion ........................................................................................................ 29
15 Appendices ....................................................................................................... 30
16 References........................................................................................................ 37

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List of Figures
Figure 1: Diagram showing effects that turbulence has on wind turbines .................... 7
Figure 2: Two different methods of measuring wind speed and direction .................... 8
Figure 3: A Wind turbine rotor extracting energy from the wind ...................................9
Figure 4: Power curve of Proven 11 with wind speed (m/s) vs. power output (W)..... 10
Figure 5: The Proven 11 down wind turbine ............................................................... 11
Figure 6: The Guide vane and the controls for the wind turbine................................. 11
Figure 7: The Proven 11 grid connect and rectifier .................................................... 12
Figure 8: Data of wind speed and roughness length at the site ................................. 13
Figure 9: Satellite imagery showing distance of the turbine from grid connection ..... 14
Figure 10: OSI Image of the farm and the Turbine site............................................... 14
Figure 11: Nearest wind rose data .............................................................................. 15
Figure 12: Wind Shade Calculator............................................................................... 16
Figure 13: Blades in normal operation ........................................................................ 17
Figure 14: Blades design in the event of a storm........................................................ 17
Figure 15: The Controller & Data logger ..................................................................... 18
Figure 16: Power curve for the HevAir 6K................................................................... 19
Figure 17: Power coefficient for the HevAir 6K ........................................................... 19
Figure 18: Graph of probability Vs wind speed for 10m tower.................................... 22
Figure 19: Histogram of wind speed Vs Time in hours for 10m tower........................ 22
Figure 20: Graph of the energy density Vs wind speed for 10m tower ...................... 23
Figure 21: Wind speed probability for a 20m tower .................................................... 25
Figure 22: Frequent wind speeds over a year for 20m tower ..................................... 25
Figure 23: Energy density at a 20m hub height .......................................................... 26
List of Tables
Table 1: HevAir 6kW specifications............................................................................. 18
Table 2: Annual Electricity consumption ..................................................................... 20

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1 Introduction
This is a report to discover if it is feasible to install a small scale grid tied wind turbine
for producing micro wind generated electricity on a small farm in the remote town
land of Beagh, Ardara which is located on the North West Coast of Co. Donegal.
This site was chosen as it has reasonably good wind resource at a height of 75m
above ground level and has a low roughness length. The wind turbine is to be
installed roughly 150m from the farm and will follow the relevant regulations set out
by the County Council regarding the installation of this type of turbine. The size of the
cable to deliver the electricity to the grid connection will also be analysed and the
exact cost of that cable will be added to the make up the total price of installation.
There is a grid connection on the farm that will enable the supply of electricity to the
load and the sale of any excess power that is produced back to the supplier to help
shorten the payback time of the installation. A smart meter will need to be installed so
the supplier will know how much electricity is being consumed on the farm and how
much is available for exporting. The wind turbine is called the HevAir 6K, which has a
single phase generator and is rated at a 5kW maximum output and has a life time
expectancy of about 20 years. For this assignment, option one was to review the
performance of the wind turbine when placed at a tower height of 10m. Option two
was to see the performance of the wind turbine when placed at a 20m tower height.
For both these options a probability curve of each wind speed was graphed using
Rayleigh distribution and the Weibull function in excel, a histogram representing how
long each wind speed was expected to blow at in hours over a year and another
graph showing the energy available for harvesting at each wind speed. The actual
annual demand for electricity on the farm will be available from the owner as they use
the online e-bill method. A cost analysis will be completed on both tower heights to
decide if it is feasible to install and how long the installation will take to pay for itself.

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2 Backgroundof Wind Energy
Like most other renewable energy sources wind energy is also heavily linked with
solar energy. The sun heats the earth surface unevenly and it is this uneven heating
that creates a difference in atmospheric pressure. High pressure is the air that the
sun is heating and this hot air rises leaving a low pressure area. Wind is created
when the high pressure area moves to fill the void of the low pressure area. Down
near the earth’s surface wind will be slowed down due to friction from obstacles such
as buildings, trees, mountains etc. This is a very important factor in choosing a site
for a wind turbine. (Wikipedia, 2014).
Wind energy is heavily dependent on wind speed .The wind shear which is the force
of friction between the wind and the ground mean that the rotor must be placed as
high as possible to increase the speed of the wind reaching its swept area.
When analysing a site there are two other types of winds that must be checked out
called local wind and surface wind. Local wind can be a sea-land breeze. The sea-
land breeze could be become a factor in a lot of coastal sites similar to the one being
researched as its effects can be felt inland up to 40Km. The sea- land breeze is
formed by the temperature difference of the air above the land being heated to a
higher temperature than the air above the sea. This difference causes air mass to
flow from the land to the sea during the day and from the sea to the land during the
night. This wind can get to a speed of 10m/s. (Sustainable Energy Authority of
Ireland, 2013)

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2.1 Turbulence
Figure 1: Diagram showing effects that turbulence has on wind turbines
Surface wind is largely affected by the turbulence that exists close to the ground and
is caused by the surface roughness due to different obstacles and the shape of the
landscape. Each obstacle is categorised into certain roughness classes ranging from
0 to 4. The closer to zero the less the wind speed is affected. Each Roughness class
has a specific roughness length which is used in calculating the wind speed at a
certain site. The lower the roughness length the quicker the wind speed rises. This is
why the wind offshore is faster than the wind onshore. When a turbine is erected it
itself becomes an obstacle to the wind. Wind has to move around the turbine causing
a speed and direction change behind it (See figure 1). This turbulence is known as
wake.

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2.2 Measuring wind speed and direction
Figure 2: Two different methods of measuring wind speed and direction
Wind speed is measured using an anemometer. For a micro installation a cupped
Anemometer would suffice and would usually be collecting wind data at a site for at
least a year. It is a reliable piece of equipment that rotates creating an electrical
signal that is counted. The disadvantages are they can freeze in cold weather and
requires a separate wind vane to measure the wind direction. It is not advised to
place an anemometer on an already erected turbine as the turbulence generated
from the rotor blades would give a false reading. A reliable alterative would be the
sonic anemometer which can record both the wind speed and direction. It has
different pairs of sensors that detect the speed difference that caused by the wind
moving the ultra sound that travels between both sensors (See figure 2).

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3 Extracting energy from the wind
Figure 3: A Wind turbine rotor extracting energy from the wind
A wind turbine is a wind energy converter. Its sole purpose is to extract the kinetic
energy available in the wind and convert it into mechanical rotation to drive a
generator that produces electrical energy. Unfortunately not all the wind available can
be extracted because the air must flow over the rotor blades similar to an air craft’s
wing. The air at the upper part of the blade is curved so it takes that air longer to
catch up to the air passing under the blade. It is this difference in pressure that
makes the blades spin. The amount of energy that can be extracted from the wind is
known as the Betz limit. The Betz limit states than only 59% of the winds energy can
be extracted (See figure 4). In figure 3 the air V1 approaches the rotor, builds up and
spreads out as it passes the blades. To prevent a complete build up of air at the
turbine the same amount of mass that arrived at the rotor must leave. This is the
reason for A2 being greater than A1. (Wikipedia, 2014)

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4 Example of a site visited
As part of the research for this assignment a site visit was under taken to get some
insight in to an actual small scale wind turbine installation. This wind turbine was
installed five years ago by a farmer at a site in The Burren, Co.Clare. It is a robust
very simple design that has a max output of 6kW. The diameter of the Rotor is 5.5m
and the hub height is 13M. Besides the rotor the other pieces of equipment is a three
phase generator. There is a 4 core 10mm2
Steel wire armour cable connected to the
generator that delivers the A.C voltage underground to a Rectifier in the house. This
wind turbine was erected without any planning issues because of the tower height
being under 20m and the max output being 6kW. The average wind speed at hub
height is 5m/s. According to the specifications this wind turbine will extract 500W
from the wind when operating at this average wind speed. This turbine is producing
more power than is required to supply the power to the 4 chicken houses, 1 slatted
house and the farmers home therefore a smart meter was installed, so the excess
electricity could be exported to the grid and decrease the payback time significantly.
The price of electricity being bought by the grid is 9c/kWh. The wind turbine cost
€30000 to install and this covered everything from grid connection to pouring the
foundation and the owner said the payback time will be eight years. Proven is now
taken over by Kingspan and the wind turbine design has not changed. (Krewer,
2014)
Figure 4: Power curve of Proven 11 with wind speed (m/s) vs. power output (W)
This is a graph showing the actual output compared to the Betz limit. The cut in
speed is 4m/s and the cut out speed is 20m/s. (Gumbley, 2010)

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Figure 5: The Proven 11 down wind turbine
This turbine seen in figure 5 unfortunately suffered some damage from a previous
storm and is missing a plastic cover on the front side covers the nacelle. The noise
level has increased slightly but everything else is working as normal. The only
maintenance required is to grease the bearings every two years. The turbine by
regulation had to be installed at least 25m from a neighbour’s fence. A cupped
anemometer was installed to testing and recording the wind speed and wind direction
for one year prior to installation. (Krewer, 2014)
Figure 6: The Guide vane and the controls for the wind turbine
In figure 6 the picture on the left shows the wind vane located below the hub. This is
how the turbine achieves being able to face the wind at all times. For downwind
turbines this is where the guide vane is located and for up wind facing wind turbines it
would be on a tail opposite the rotor. The picture on the left is the complete
electronics control system. On the top left there is an auxiliary heater to dump power
to two large heating elements when there is a massive overproduction even for grid
export, this is very rarely required. (Krewer, 2014)

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Figure 7: The Proven 11 grid connect and rectifier
The grey panel in figure 7 monitors the voltage and current being produced by the
wind turbine. The Red panel on the right inverts the frequency and does all the
rectification. The red panel is a windy boy rectifier that takes the incoming A.C
voltage from the turbine, changes it to D.C before changes it back 230V A.C at a
frequency of 50 Hz. (Krewer, 2014)
5 Evaluating the potentialsite
After careful consideration in evaluating a potential site it was decided to place the
wind turbine in an open field located at the top of a gradually sloping hill. It is roughly
150m from the load it is intending to supply. There are some spacious trees located
on the west side of the turbine that will cause a slight reduction in the wind speed.
(See appendix A) The field is wide therefore there is scope to move the turbine
around and avoid being too close to the neighbouring border.
5.1 Planning Regulations
The regulations state that the total height of the turbine including rotor must not
exceed 13m. The rotors diameter must not be greater than 6m. The distance from a
neighbour’s border must be the height of the turbine plus 1m. The noise level of the
turbine will be measured from the nearest dwelling and should not exceed 43db
during normal operation. The turbine being installed will be at heights of 10m and
20m therefore it will not need any planning permission because it is being installed
on a farm. For domestic use only the maximum height of the turbine is 13m. (The
stationary office, 2007)

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5.2 Sourcing data for the area at the site
This data was sourced by using a software package to find the wind speed at a
known height of 75m. It was used also to determine the roughness length at the site,
which is 0.1. These figures will be important when trying to find the wind speed at the
wind turbines hub height.
(Moloney, 2014)
Figure 8: Data of wind speed and roughness length at the site
The data in figure 9 is consistent with this particular site as it is relatively flat
agricultural land and the site itself is located at the top of a gradually sloping hill.
The wind speed at a height of 75m is 8.79m/s which are above average.

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Figure 9: Satellite imagery showing distance of the turbine from grid connection
(Google , 2013)
Figure 9 is a satellite image taken from Google maps showing the distance the
turbine is from the farm, it is estimated to be 150m. This is the distance to the grid
connection. The cabling required will be expensive to purchase as it will have to be
steel wire armour underground cable. There is a mini digger on site; therefore no
plant hire is necessary.
Figure 10: OSI Image of the farm and the Turbine site
(Ordance Survey Ireland, 2014)
Figure 10 is an OSI image of the site. Clearly marked in a red circle is the farm and
below it is a symbol which represents the site. It can be seen that it is not a large
farm. Also the nearest house is located 500m away. Therefore there will be no
problem with noise pollution.

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6 Choosingthe best location at the site
To help with choosing the exact location to install the wind at the site, wind rose data
from the nearest weather station was sourced.
6.1 Wind rose from Carrick Finn Airport
Figure 11: Nearest wind rose data
(WINDFINDER, 2014)
This is a wind rose recorded at Carrick Finn Airport in Co. Donegal. The direction that
the wind blows from the most is from SSE to WNW. This has a large impact on
where the wind turbine will be erected as there are some light trees to the west of the
site. The image on the left shows the location of the site to the location of the Airport.

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6.2 Obstacle Analysis
Figure 12: Wind Shade Calculator
(Danish Wind Energy Association, 2003)
In figure 12 the picture on the left is the wind shade calculator. This is a crude way of
estimating the effect that the different types of obstacles have on the wind energy
reaching the turbine. The different parameters to be entered are the turbines hub
height, its distance from the obstacle and the roughness length at the site. The type
of obstacle and the width and height of the obstacle needs to be included. The
picture on the right is the resulting table and shown in grey is the height of the
obstacle which casts a dark shadow behind it. Marked in yellow is the height of the
tower which only reaches 86% of the winds energy. If the hub height could be raised
on a higher tower and placed further away from the obstacle then the wind energy
seen by the rotor would increase. At this particular site the trees that are the obstacle
are planned to be taken away as part of the rural development scheme in the future.
(See appendix 1)

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7 The Manufacturer
The manufacturer contacted about installing a wind turbine was Heverin Renewable
Energies. They are a small Irish renewable energy company based in Crossmolina in
Co. Mayo. First contact was made via a phone call and then several emails were
exchanged. The price given was €13000 excluding VAT but might vary slightly
depending on conditions at the site. This included a 10m tower, a 5m rotor, cabling
up to 20m and all the required electronics and grid connection. The warranty on the
tower and rotor is three years and the electronics have a one year warranty.
(Heverin, 2014) (See Appendix 2)
7.1 Turbine blade features
(Heverin Renewable energies, 2014)
Figure 13: Blades in normal operation
Figure 14: Blades design in the event of a storm
Figure 13 shows the blades fully
extended and at normal operation
between the cut in and cut out
speeds. (Heverin Renewable
energies, 2014)
Figure 14 shows the blades fully retracted to dump the
wind in the event of a storm bringing the rotor to a
standstill. This is done to protect the turbine from
damage and is known as active pitch. (Heverin
Renewable energies, 2014) It is highly inefficient
compared to other turbines such as the Proven 11 in
figure 5 that uses cone pitch control. This allows it to
generate electricity safely in a storm. (Kingspan Wind,
2014)

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7.2 Turbine specifications
Table 1: HevAir 6kW specifications
Figure 15: The Controller & Data logger
The controller is a small micro processor unit with a sole function of controlling the
turbine. It can also send data to a data logger or a computer (See figure 15).This
makes it possible to monitor the performance of this wind turbine at all times. The
manufacturer can also see the turbines performance and can update the necessary
software from its head quarters. (Heverin Renewable energies, 2014)
Table 1 gives all the specifications of the
wind turbine. Although it has the name
HevAir 6k its maximum output is 5kW. It
has a 5m rotor with a rated wind speed
of 13m/s.

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8 Power curvefor HevAir 6K
Figure 16: Power curve for the HevAir 6K
This graph in figure 16 shows the electrical power output in kW at each wind speed.
The generator will be at full output when the wind speed is 14m/s achieving just over
5kW before dropping off to zero if wind speed increases above this. This power curve
was produced using data from the manufacturer. (Heverin, 2014) (See appendix 3)
8.1 Power Coefficient for HevAir 6K
Figure 17: Power coefficient for the HevAir 6K
Power coefficient is the measure of how efficient a wind turbine is at converting the
kinetic energy in the wind into electrical energy. This wind turbine is most efficient
when operating at wind speeds between 7m/s and 8m/s as it reaches its maximum
Cp of 0.39 (See figure 17).
0
1
2
3
4
5
6
0 5 10 15 20
powerout(Kw)
wind speed m/s
HevAir 6K
HevAir 6K
0.00
0.10
0.20
0.30
0.40
0.50
0 5 10 15 20
Cp
Wind speed m/s
HevAir 6K
HevAir 6K

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9 Load demand on site
Table 2: Annual Electricity consumption
(SSE Airtricity, 2014).
Table 2 shows the annual load demand for the site which was sourced directly from
the electricity providers website. Using the six estimated 60 day figures the total
amounts to 4561kWh (11138kWh-6577kWh) .Currently the provider is SEE Airtricity
and they charge 15.57c/kWh for electricity. SSE Airtricity does not pay for electricity
exported from your own wind turbine. The only electricity provider that will pay is
Electric Ireland. Electric Ireland pays 9c/kWh to you for generating electricity and
charges you 16c/kWh for consuming electricity. (Money Guide Ireland, 2014) (See
Appendix 4)
10 Wind speed & Wind Energy on site
In figure 8 the wind speed was recorded at a height of 75m above the site. The hub
height of the turbine will be 10m therefore a calculation will have to be performed
using the log law formula to discover the wind speed that the rotor will see known as
the hub height.

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10.1 Find wind speed at 10m hub height
To find the unknown wind speed at a known height the log law formula was used.
10.2 Log law formula
V2 = V1 * (Ln
𝑯𝟐
𝒛𝟎
) / (Ln
𝑯𝟏
𝒛𝟎
)
 V1 = the wind speed collected at the known height e.g. 8.79m/s
 H1= the known height that data is recorded from e.g. 75m
 V2 = the unknown wind speed at the hub height. ?
 H2 = the hub height of the wind turbine e.g. 10m
 Z0 = the roughness length at the site e.g. 0.1m
V2 = 8.79 * (Ln
10
0.1
) / (Ln
75
0.1
) = 6.12m/s
The wind speed at the hub height is: 6.12m/s
10.3 Rayleigh distribution
Rayleigh distribution is the most common method to get a good approximation of
wind speed distribution in Ireland. This is because Ireland is located in Northern
Europe and work off a shape parameter of 2. (The Renewable Energy Website,
2006)
10.3.1 Weibull distribution
Weibull distribution is the probability that the wind speed will be below a certain
value. This is done to get a good annual estimate of how frequent the wind blows at
a certain speed at a specific site. The faster the wind the more energy it has and the
more power it will produce. Once the Weibull probability is calculated the energy
density can now be found. There is a Weibull function in excel inserted as follows. =
Weibull( value, shape, scale, true) (The Renewable Energy Website, 2006)
 Value = mean wind speed = (6.12m/s)
 Shape = (Rayleigh) = 2
 Scale = mean wind * 1.128 = (6.9)
 True = typed in.

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10.3.2 Results
Figure 18: Graph of probability Vs wind speed for 10m tower
This graph in figure 18 provides a reasonable estimate of how often a certain wind
speed is likely to occur. This is useful to give a rough indication on what the annual
power output will be as a higher wind speed will generate more power. Wind speeds
of between 2.5-7.5m/s have the highest probability to occur at this particular site with
the hub height being 10m. (See appendix 5).
Figure 19: Histogram of wind speed Vs Time in hours for 10m tower
Figure 19 is a histogram representing how frequent a particular wind speed occurs
over the course of a year. A wind speed of 5m/s occurs most often with winds of
15m/s and above not very common. The HevAir wind turbine has a cut in speed of
3m/s which means any wind speed below this isn’t taken in to consideration as the
power generated at these low wind speeds is very small. (See appendix 5).
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
0 5 10 15 20 25 30
Probability
wind speed (m/s)
Probabilityof a certain wind speed
6.12
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
0.25
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
hoursperyear
wind speed (m/s)
Hours per year @ each wind speed
6.12

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10.4 Energy in the wind at 10m
Figure 20: Graph of the energy density Vs wind speed for 10m tower
Figure 20 shows how much energy in kWh/m2
is extracted from each wind speed
over the course of a year. The total extracted annually is 2354.63kWh/m2
. (See
appendix 5).
.
10.5 Annual Energy Output (AEO) for 10m tower
The total number of hours that the turbine will run for in the year assuming a t 95%
up time is 8322 hours. If the number of hours each wind speed occurs is multiplied by
the average power produced by the turbine at that particular wind speed then the
energy each wind speed contributes can be calculated in kWh.
10.5.1 Example of how long wind blow @ 8m/s
 V = 8m/s
 Power out = 2.4kW (Manufactures power curve)
 Hr/yr = 728.61
 Energy output = Power out * number of hours
 = 2.4kW * 728.61
 = 1748.66kWh
Therefore to achieve AEO (AEO = ∑ Total Energy out @ every wind
speed). Ans = 11543.87kWh (See appendix 5).
0.00
50.00
100.00
150.00
200.00
250.00
300.00
0 5 10 15 20 25 30
EnergyDensity(Kwh/M2/yr)
Wind speed (m/s)
Energy Density @ each wind speed
6.12

24
10.6 Average Efficiency
This is the annual energy output divided by the total available energy in the wind.
ȠAvg =
𝑨𝑬𝑶
𝑨∗𝑬𝒂
The figure below is a typical value expected for small scale wind turbines.
 AEO = 11543.87kWh
 Rotor Area (A) = 19.63m2
 Total energy density (Ea) = 2348.48kWh/m2
. ȠAvg =
𝟏𝟏𝟓𝟒𝟑.𝟖𝟕
𝟏𝟗.𝟔𝟑∗𝟐𝟑𝟒𝟖.𝟒𝟖
* 100 = 25.04%
10.7 Capacity Factor
This is a measurement of how effective the generator is at utilising the available
power. To achieve the CF, first multiply the maximum generator capacity (kW) by the
number of hours the turbine runs for in the year. The AEO (kWh) is now divided by
the outcome and the answer is usually expressed as a percentage.
 CF =
𝑨𝑬𝑶
𝟖𝟑𝟐𝟐∗ 𝑷𝒎𝒂𝒙
=
𝟏𝟏𝟓𝟒𝟑.𝟖𝟕
𝟖𝟑𝟐𝟐∗ 𝟓
* 100 = 27.74%
11 Wind turbine at a higher tower
For option 2 the wind turbine was analysed to see what the outcome would be if the
height of the tower was raised from 10m to 20m.
11.1 Finding wind speed at a 20m hub height
11.1.1 Log law formula
V2 = V1 * (Ln
𝑯𝟐
𝒛𝟎
) / (Ln
𝑯𝟏
𝒛𝟎
)
 V1 = 8.79m/s
 H1= 75m
 V2 =?
 H2 = 10m
 Z0 = 0.1m
V2 = 8.79 * (Ln
10
0.1
) / (Ln
75
0.1
) = 7.03m/s
The wind speed at the hub height is: 7.03m/s

25
11.2 Probability of wind speeds occurring
11.3 Results
Figure 21: Wind speed probability for a 20m tower
In Figure 21 when the hub height is at 20m the rotor will see higher wind speeds
more often. Than if it was at 10m. This would have an increase in the output power
being produced. (See appendix 6)
Figure 22: Frequent wind speeds over a year for 20m tower
Figure 22 shows how often a wind speed interval occurs annually. When the hub
height is at 20m Wind speeds from 4-8m/s don’t occur as often as they did when the
hub height was at 10m but wind speeds from 9-16m/s do occur more often. This
proves that increasing the height of the tower will increase the probability of seeing
greater wind speeds. (See appendix 6)
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0 5 10 15 20 25 30
Probability
wind speed (m/s)
Probability of a certain wind speed
7.03
0.00
200.00
400.00
600.00
800.00
1000.00
0.25
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
hoursperyear
wind speed (m/s)
Hours per year @ each wind speed
7.03

26
11.4 Energy density at 20m
Figure 23: Energy density at a 20m hub height
This graph shows the energy density distributed over the course of a year at various
wind speeds and at a hub height of 20m. In comparison to figure 18 that is at a 10m
hub height. This graph shows that when the hub height is raised the energy density
at 10m/s increase by 100kWh. This will have yielded a higher annual energy output.
(See appendix 6)
11.5 Annual Energy Output (AEO) for 20m tower
To show how each wind speed contributes energy a wind speed of 8m/s was chosen
to show how its energy output is found (See appendix 6), All the energy received
from each wind speed is summed to find the annual energy output.
11.5.1 Example of how long the wind blows @ 8m/s
 V = 8m/s
 Power out = 2.4kW
 Hr/yr = 764.292
 Energy output = Power out * number of hours
 = 2.4kW * 764.292
 = 1834.3kWh
Therefore to achieve AEO (AEO = ∑ Total Energy out @ every speed).
Ans = 14065.85kWh (See appendix 6).
0.00
100.00
200.00
300.00
400.00
0 5 10 15 20 25 30
EnergyDensity(Kwh/M2/yr)
Wind speed (m/s)
Energy Density @ each wind speed
7.03

27
11.6 Average Efficiency
ȠAvg =
𝑨𝑬𝑶
𝑨∗𝑬𝒂
 AEO =14065.85kWh
 Rotor Area (A) = 19.63m2
 Total energy density (Ea) = 3391.77kWh/m2
. ȠAvg =
14065.85
19.63∗3391 .77
* 100 = 21.13%
11.7 Capacity Factor
 Run time = 100%
 CF =
𝐴𝐸𝑂
8760∗ 𝑃𝑚𝑎𝑥
=
14065 .85
8322∗ 5
* 100 = 33.80%
12 Cost analysis
12.1 Installation costs for the 10m wind turbine
The cost of the HevAir 6K wind turbine is €15990 including 23% VAT fully installed.
The cable run from the load to the wind turbine is 150m. Using a cable company’s
cable sizing calculator it was discovered that 16mm2
Steel wire armour (SWA)
underground cable is the required size. The price of the cable is €913.20 (TLC
Electrical Supplies, 2002). The turbine falls into the micro generation category
therefore there is no grid connection fee. The Total cost to install the 10m tower wind
turbine is €16903.20 (See appendix 7).
12.2 Installation costs for the 20m wind turbine
The cabling costs don’t change. However the extra height of the tower and the
strength of the foundation must be considered and a rule of thumb would be to allow
for an extra 5% of the wind turbines cost to be added to the original price. This gives
an estimated cost to install the 20m wind turbine at €17748.36.

28
13 Payback Time for the two differenttower heights
To avail of the export incentive the electricity provider was changed to Electric
Ireland. It was now investigated how long it would take to pay back the initial cost of
installing the wind turbine at the two different tower heights
13.1 The 10m wind turbine
 Total cost of Installing turbine = €16903.20
 Energy produced by the turbine = 12151.44kWh
 Energy produced by the turbine @ 95% up time = 11543.87kWh
 Energy required on site currently being purchased @ 16c/kWh = 4561kWh
Therefore an estimated 50% of load demand will be met by the wind turbine;
4561*0.5 = 2280.50kWh
2280.50kWh * 0.16 = €364.88
 Energy produced for exporting to Electric Ireland @ 9c/kWh;
(12151.44 – 2280.50) = 9870.94kWh
9870.94 * 0.09 = €888.83
 Annual operating and maintenance costs = €50
 Total value of Energy produced annually = 364.88 + 888.83 -50 = €1203.71
13.1.1 Pay back check
Payback =
𝑇𝑜𝑡𝑎𝑙 𝑐𝑜𝑠𝑡
𝑛𝑒𝑡 𝑎𝑛𝑛𝑢𝑎𝑙 𝑖𝑛𝑐𝑜𝑚𝑒
=
16903.20
1203.71
= 14.02 years
13.2 The 20m wind turbine
 Total cost of Installing turbine = €17748.36
 Energy produced by the turbine = 14806.16kWh
 Energy produced by the turbine @ 95% up time = 14065.85kWh
 Energy required on site currently being purchased @ 16c/kWh = 4561kWh
Therefore an estimated 50% of load demand will be met by the wind turbine;
4561*0.5 = 2280.50kWh
2280.50kWh * 0.16 = €364.88
 Energy produced for exporting to Electric Ireland @ 9c/kWh;
(14806.16 – 2280.50) = 11785.35kWh
11785.35 * 0.09 = €1060.68
 Annual operating and maintenance costs = €50
 Total value of Energy produced = 364.88 + 1060.68 - 50 = €1375.56
13.2.1 Pay back check
Payback =
𝑇𝑜𝑡𝑎𝑙 𝑐𝑜𝑠𝑡
𝑛𝑒𝑡 𝑎𝑛𝑛𝑢𝑎𝑙 𝑖𝑛𝑐𝑜𝑚𝑒
=
17748.36
1375.56
= 12.9 years

29
14 Conclusion
The evaluated site proved to be a potential site as it has a good wind resource and a
low roughness length. After carefully investigating the results achieved in theory by
placing a wind turbine at two different tower heights of 10 and 20 metres, it can be
said that the best choice for this installation would be the 20m wind turbine. The 20m
wind turbine gets up into higher wind speeds and achieves a slightly quicker payback
time of roughly 13 years as opposed to the 10m wind turbine which takes just over 14
years. At the present time in Ireland there are two key factors that are opposing the
growth of micro wind generation. One obstacle is the lack of incentives currently in
place, such as the low rate paid for exporting the electricity generated and the
second obstacle is the variability of wind that occurs at every site which makes it
extremely challenging to supply a load consistently. This was evident when
calculating the payback time, because of the unreliability of the wind over the course
of a year only 50% of the load demand could realistically be met and the other 50%
would have to be exported to the grid. This evaluation was kept as realistic as
possible with a real load demand figure and real prices. The beginning of this
evaluation briefly introduces the reader to the background of wind energy and how it
works. To help get a more in depth understanding of what components are involved
in micro wind generation a site visit was under taking to interview an owner of a
Proven11before commencing evaluating the site in Donegal. A copy of this report
was submitted to the Farm owner to show the potential that this site has for small
scale micro wind generation.

30
15 Appendices
Appendix 1: The site that the wind turbine will be installed
Appendix 2: An Email from Heverin Renewables regarding information
on the HevAir 6K Wind Turbine

31
Appendix 3: The 3 PDF file received from Heverin Renewables regarding
data for the HevAir 6K.

32

33
Appendix 4: The Small Farm in Beagh Co. Donegal which is the load to
be supplied

34
Appendix 5: Excel Data for the 10m wind turbine
Wind
speed
(m/s)
Band
Centr
e
Weibull
Probabil
ity
Band
Prob
Hours
per year
pow er
density
(w /m2)
Energy
Density
(Kw h/M2)
po
wer
out
(K
w ) cp
Energy
output
(KWh)
0.5 0.25 0.01 0.01 43.62 0.01 0.00 0 0.00 0.00
1.5 1 0.05 0.04 340.81 0.61 0.21 0 0.00 0.00
2.5 2 0.12 0.08 640.11 4.90 3.14 0 0.00 0.00
3.5 3 0.23 0.10 864.69 16.54 14.30 0 0.00 0.00
4.5 4 0.35 0.12 995.68 39.20 39.03 0.2 0.26 199.14
5.5 5 0.47 0.12 1030.76 76.56 78.92 0.55 0.37 566.92
6.5 6 0.59 0.12 982.36 132.30 129.97 1 0.38 982.36
7.5 7 0.69 0.10 872.89 210.09 183.38 1.6 0.39 1396.62
8.5 8 0.78 0.09 728.61 313.60 228.49 2.4 0.39 1748.66
9.5 9 0.85 0.07 574.11 446.51 256.35 3.1 0.35 1779.74
10.5 10 0.90 0.05 428.46 612.50 262.43 3.7 0.31 1585.30
11.5 11 0.94 0.04 303.57 815.24 247.48 4.2 0.26 1275.00
12.5 12 0.96 0.02 204.56 1058.40 216.50 4.7 0.23 961.42
13.5 13 0.98 0.02 131.27 1345.66 176.64 4.9 0.19 643.20
14.5 14 0.99 0.01 80.30 1680.70 134.96 5.05 0.15 405.51
15.5 15 0.99 0.01 46.87 2067.19 96.88 0 0 0.00
16.5 16 1.00 0.00 26.11 2508.80 65.51 0 0 0.00
17.5 17 1.00 0.00 13.90 3009.21 41.83 0 0 0.00
18.5 18 1.00 0.00 7.07 3572.10 25.25 0 0 0.00
19.5 19 1.00 0.00 3.44 4201.14 14.44 0 0 0.00
20.5 20 1.00 0.00 1.60 4900.00 7.83 0 0 0.00
21.5 21 1.00 0.00 0.71 5672.36 4.03 0 0 0.00
22.5 22 1.00 0.00 0.30 6521.90 1.97 0 0 0.00
23.5 23 1.00 0.00 0.12 7452.29 0.92 0 0 0.00
24.5 24 1.00 0.00 0.05 8467.20 0.41 0 0 0.00
25.5 25 1.00 0.00 0.02 9570.31 0.17 0 0 0.00
Total 1.00 8321.99 2231.05 11543.87

35
Appendix 6: Excel data for the 20m wind turbine
Wind
speed
(m/s)
Band
Centr
e
Weibull
Probabilit
y
Band
Prob
Hours
per year
pow er
density
(w /m2)
Energy
Density
(Kw h/M2
)
pow er
out (Kw ) cp
Energy
output
(KWh)
0.5 0.25 0.00 0.00 32.97 0.01 0.00 0 0.00 0.00
1.5 1 0.04 0.03 259.12 0.61 0.16 0 0.00 0.00
2.5 2 0.09 0.06 494.20 4.90 2.42 0 0.00 0.00
3.5 3 0.18 0.08 684.86 16.54 11.33 0 0.00 0.00
4.5 4 0.27 0.10 817.32 39.20 32.04 0.2 0.26 163.46
5.5 5 0.38 0.11 885.93 76.56 67.83 0.55 0.37 487.26
6.5 6 0.49 0.11 893.13 132.30 118.16 1 0.38 893.13
7.5 7 0.59 0.10 848.09 210.09 178.17 1.6 0.39 1356.95
8.5 8 0.68 0.09 764.29 313.60 239.68 2.4 0.39 1834.30
9.5 9 0.76 0.08 656.87 446.51 293.30 3.1 0.35 2036.29
10.5 10 0.83 0.06 540.19 612.50 330.87 3.7 0.31 1998.70
11.5 11 0.88 0.05 426.08 815.24 347.36 4.2 0.26 1789.54
12.5 12 0.92 0.04 322.91 1058.40 341.76 4.7 0.23 1517.66
13.5 13 0.94 0.03 235.44 1345.66 316.82 4.9 0.19 1153.65
14.5 14 0.96 0.02 165.33 1680.70 277.87 5.05 0.15 834.90
15.5 15 0.98 0.01 111.90 2067.19 231.32 0 0 0.00
16.5 16 0.99 0.01 73.05 2508.80 183.27 0 0 0.00
17.5 17 0.99 0.01 46.02 3009.21 138.49 0 0 0.00
18.5 18 1.00 0.00 27.99 3572.10 99.99 0 0 0.00
19.5 19 1.00 0.00 16.44 4201.14 69.09 0 0 0.00
20.5 20 1.00 0.00 9.33 4900.00 45.73 0 0 0.00
21.5 21 1.00 0.00 5.12 5672.36 29.04 0 0 0.00
22.5 22 1.00 0.00 2.71 6521.90 17.70 0 0 0.00
23.5 23 1.00 0.00 1.39 7452.29 10.37 0 0 0.00
24.5 24 1.00 0.00 0.69 8467.20 5.84 0 0 0.00
25.5 25 1.00 0.00 0.33 9570.31 3.16 0 0 0.00
Total 1.00 8321.73 3391.77 14065.85

36
Appendix 7: Cable manufactures calculator & prices

37
16 References
DanishWindEnergyAssociation,2003. Wind ShadeCalculator. [Online]
Available at:
http://www.motiva.fi/myllarin_tuulivoima/windpower%20web/en/tour/wres/shelter/index.
htm
[Accessed19 November2014].
Google , 2013. Google maps. [Online]
Available at:https://www.google.ie/maps/place/Beagh,+Co.+Donegal/@54.7949213,-
8.4410228,1906m/data=!3m2!1e3!4b1!4m2!3m1!1s0x485f127baafcb855:0x2600c7a7bb4f0
732
[Accessed16 October2014].
Gumbley,J.,2010. Proven 11 wind turbine. [Online]
Available at:http://www.bettergeneration.co.uk/wind-turbine-reviews/proven-11-wind-
turbine.html
HeverinRenewableenergies,2014. HevAir 6k Wind Turbine. [Online]
Available at:http://www.hevenergies.ie/index.php/products/hevair-6k/
Heverin,R.,2014. Info on Productincluding prices and warranty [Interview] (28October
2014).
KingspanWind,2014. Kingspan Wind 6KW turbine. [Online]
Available at:http://www.kingspanwind.com/products/kw6/
Krewer,H.,2014. Ownerof Proven 11 [Interview](27October2014).
Moloney,K.,2014. Wind Resourceat a chosen site [Interview] (1October2014).
MoneyGuide Ireland,2014. Comparison of Electricity Prices in Ireland. [Online]
Available at:http://www.moneyguideireland.com/electricity-prices
Ordance SurveyIreland,2014. OSI.ie. [Online]
Available at:http://maps.osi.ie/publicviewer/#V1,572183,893493,6,10

38
SSE Airtricity,2014. Login to My SSE Airtricity. [Online]
Available at:https://my.sseairtricity.com/oss_web/login.htm
Sustainable EnergyAuthorityof Ireland,2013. Wind Energy. [Online]
Available at:http://www.seai.ie/Renewables/Wind_Energy/
The Renewable EnergyWebsite,2006. Wind Speed Distribution Weibull. [Online]
Available at:http://www.reuk.co.uk/Wind-Speed-Distribution-Weibull.htm
The stationaryoffice,2007. Planning and developmentregulations.[Online]
Available at:
http://www.environ.ie/en/Legislation/DevelopmentandHousing/Planning/FileDownLoad,14
86,en.pdf
TLC Electrical Supplies,2002. Voltagedrop calculator. [Online]
Available at:http://www.tlc-
direct.co.uk/Technical/Charts/VoltageDrop.html?cable=SWA_4_CoreXLPE&application=und
erground&max_perct_volt_drop=5&ambient_temp=30&no_circuits=1&circuit_layout=touch
ing&power=5&power_units=1000&voltage=400&length=150&submit=Calculate+Min+Cab
Wikipedia,2014. Enercon. [Online]
Available at:http://en.wikipedia.org/wiki/Enercon
Wikipedia,2014. Wind. [Online]
Available at:http://en.wikipedia.org/wiki/Wind
WINDFINDER,2014. Wind & weatherstatistics DonegalAirport/Carrickfinn. [Online]
Available at:http://www.windfinder.com/windstatistics/donegal_airport_carrickfinn

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