Wind site evaluation assign Steven Sweeney K00181764

Wind Turbine Site EvaluationMicro Wind Generation

By

Steven SweeneyK00181764

Submitted: 05/12/14

Wind Turbine Site Evaluation Steven Sweeney K00181764

Table of ContentsList 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

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10.5.1 Example of how long wind blow @ 8m/s...................................................23

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

List of TablesTable 1: HevAir 6kW specifications...................................................................................18Table 2: Annual Electricity consumption...........................................................................20

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1 IntroductionThis 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 Background of Wind EnergyLike 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 visitedAs 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 potential siteAfter 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 RegulationsThe 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 siteThis 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 Choosing the best location at the siteTo 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 ManufacturerThe 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


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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)


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)

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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.



8 Power curve for HevAir 6K

0 2 4 6 8 10 12 14 16 18 200

1

2

3

4

5

6

HevAir 6K

HevAir 6K

wind speed m/s

pow

er o

ut (K

w)

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

0 2 4 6 8 10 12 14 16 18 200.000.050.100.150.200.250.300.350.400.45

HevAir 6K

HevAir 6K

Wind speed m/s

Cp

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).

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9 Load demand on siteTable 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 siteIn 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 heightTo find the unknown wind speed at a known height the log law formula was used.

10.2 Log law formula

V2 = V1 * (Ln H 2z0 ¿/ (Ln H 1z 0 ¿

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 100.1

¿/ (Ln 750.1

¿ = 6.12m/s

The wind speed at the hub height is: 6.12m/s

10.3 Rayleigh distributionRayleigh 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 distributionWeibull 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

0 5 10 15 20 25 300.0000.0200.0400.0600.0800.1000.1200.140

Probability of a certain wind speed

6.12

wind speed (m/s)

Prob

abili

ty

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).

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 24 250.00

200.00400.00600.00800.00

1000.001200.00

Hours per year @ each wind speed

6.12

wind speed (m/s)

hour

s per

yea

r

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).

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10.4 Energy in the wind at 10m

0 5 10 15 20 25 300.00

50.00

100.00

150.00

200.00

250.00

300.00

Energy Density @ each wind speed

6.12

Wind speed (m/s)

Ener

gy D

ensit

y (K

wh/

M2/

yr)

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).

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10.5 Annual Energy Output (AEO) for 10m towerThe 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).

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10.6 Average EfficiencyThis is the annual energy output divided by the total available energy in the wind.

ȠAvg = AEOA∗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 FactorThis 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 =11543.878322∗5 * 100 = 27.74%

11 Wind turbine at a higher towerFor 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 H 2z0 ¿/ (Ln H 1z 0 ¿

V1 = 8.79m/s H1= 75m V2 =? H2 = 10m Z0 = 0.1m

V2 = 8.79 * (Ln 100.1

¿/ (Ln 750.1

¿ = 7.03m/s

The wind speed at the hub height is: 7.03m/s

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11.2 Probability of wind speeds occurring

11.3 Results

0 5 10 15 20 25 300.000

0.020

0.040

0.060

0.080

0.100

0.120

Probability of a certain wind speed

7.03

wind speed (m/s)

Prob

abili

ty

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)

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 24 250.00

200.00

400.00

600.00

800.00

1000.00

Hours per year @ each wind speed

7.03

wind speed (m/s)

hour

s per

yea

r

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

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proves that increasing the height of the tower will increase the probability of seeing greater wind speeds. (See appendix 6)

11.4 Energy density at 20m

0 5 10 15 20 25 300.00

50.00100.00150.00200.00250.00300.00350.00400.00

Energy Density @ each wind speed

7.03

Wind speed (m/s)

Ener

gy D

ensit

y (K

wh/

M2/

yr)

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 towerTo 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).

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11.6 Average Efficiency

ȠAvg = AEOA∗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 =14065.858322∗5 * 100 = 33.80%

12 Cost analysis

12.1 Installation costs for the 10m wind turbineThe 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 turbineThe 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.

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13 Payback Time for the two different tower 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 = 2280.50kWh2280.50kWh * 0.16 = €364.88

Energy produced for exporting to Electric Ireland @ 9c/kWh;(12151.44 – 2280.50) = 9870.94kWh9870.94 * 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 = Totalcost

net annual income = 16903.201203.71 = 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 = 2280.50kWh2280.50kWh * 0.16 = €364.88

Energy produced for exporting to Electric Ireland @ 9c/kWh; (14806.16 – 2280.50) = 11785.35kWh11785.35 * 0.09 = €1060.68

Annual operating and maintenance costs = €50 Total value of Energy produced = 364.88 + 1060.68 - 50 = €1375.56

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13.2.1 Pay back check

Payback = Totalcost

net annual income = 17748.361375.56 = 12.9 years

14 ConclusionThe 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.

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15 AppendicesAppendix 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

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

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

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Appendix 5: Excel Data for the 10m wind turbine

Wind speed (m/s)

Band Centre

Weibull Probability

Band Prob

Hours per year

power density (w/m2)

Energy Density (Kwh/M2)

power out (Kw) 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 0.09728.6

1 313.60 228.49 2.4 0.39 1748.669.5 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

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Appendix 6: Excel data for the 20m wind turbine

Wind speed (m/s)

Band Centre

Weibull Probability

Band Prob

Hours per year

power density (w/m2)

Energy Density (Kwh/M2)

power 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 0.09 764.29313.6

0 239.68 2.4 0.39 1834.309.5 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 14065.8

5

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Appendix 7: Cable manufactures calculator & prices

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16 ReferencesDanish Wind Energy Association, 2003. Wind Shade Calculator. [Online] Available at: http://www.motiva.fi/myllarin_tuulivoima/windpower%20web/en/tour/wres/shelter/index.htm[Accessed 19 November 2014].

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!1s0x485f127baafcb855:0x2600c7a7bb4f0732[Accessed 16 October 2014].

Gumbley, J., 2010. Proven 11 wind turbine. [Online] Available at: http://www.bettergeneration.co.uk/wind-turbine-reviews/proven-11-wind-turbine.html[Accessed 28 October 2014].

Heverin Renewable energies, 2014. HevAir 6k Wind Turbine. [Online] Available at: http://www.hevenergies.ie/index.php/products/hevair-6k/[Accessed 20 November 2014].

Heverin, R., 2014. Info on Product including prices and warranty [Interview] (28 October 2014).

Kingspan Wind, 2014. Kingspan Wind 6KW turbine. [Online] Available at: http://www.kingspanwind.com/products/kw6/[Accessed 20 November 2014].

Krewer, H., 2014. Owner of Proven 11 [Interview] (27 October 2014).

Moloney, K., 2014. Wind Resource at a chosen site [Interview] (1 October 2014).

Money Guide Ireland, 2014. Comparison of Electricity Prices in Ireland. [Online] Available at: http://www.moneyguideireland.com/electricity-prices[Accessed 24 November 2014].

Ordance Survey Ireland, 2014. OSI.ie. [Online] Available at: http://maps.osi.ie/publicviewer/#V1,572183,893493,6,10[Accessed 16 October 2014].

SSE Airtricity, 2014. Login to My SSE Airtricity. [Online] Available at: https://my.sseairtricity.com/oss_web/login.htm[Accessed 20 November 2014].

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Sustainable Energy Authority of Ireland, 2013. Wind Energy. [Online] Available at: http://www.seai.ie/Renewables/Wind_Energy/[Accessed 27 October 2014].

The Renewable Energy Website, 2006. Wind Speed Distribution Weibull. [Online] Available at: http://www.reuk.co.uk/Wind-Speed-Distribution-Weibull.htm[Accessed 20 November 2014].

The stationary office, 2007. Planning and development regulations. [Online] Available at: http://www.environ.ie/en/Legislation/DevelopmentandHousing/Planning/FileDownLoad,1486,en.pdf[Accessed 29 October 2014].

TLC Electrical Supplies, 2002. Voltage drop calculator. [Online] Available at: http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html?cable=SWA_4_CoreXLPE&application=underground&max_perct_volt_drop=5&ambient_temp=30&no_circuits=1&circuit_layout=touching&power=5&power_units=1000&voltage=400&length=150&submit=Calculate+Min+Cab[Accessed 23 November 2014].

Wikipedia, 2014. Enercon. [Online] Available at: http://en.wikipedia.org/wiki/Enercon[Accessed 28 October 2014].

Wikipedia, 2014. Wind. [Online] Available at: http://en.wikipedia.org/wiki/Wind[Accessed 27 October 2014].

WINDFINDER, 2014. Wind & weather statistics Donegal Airport/Carrickfinn. [Online] Available at: http://www.windfinder.com/windstatistics/donegal_airport_carrickfinn[Accessed 19 November 2014].

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Wind site evaluation assign Steven Sweeney K00181764

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