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Wind Farming EssentialsSeptember 2009
Wind Farming Essentials - Presentation to the Forestry
Engineering Group Symposium
Dr. Conrad Trevelyan
Wind Farming EssentialsSeptember 2009
•Mech.Eng (Brighton), MSc Renewable Energy Technology (CREST) and completed doctorate 2002 (wind turbine aerodynamics)•Now a Senior Project Manager at Dulas Ltd (consultant to wind farm developers)•Currently working on one of the FCW wind farm sites (SSA D) with Airtricity•Dulas is a Workers’ Co-op with 27 years experience and 61 staff active in solar, wind, hydro, biomass and RE consultancy
Wind Farming EssentialsSeptember 2009
Turbine Anatomy• Blades• Hub• Nacelle
• Generator• Gearbox• Yaw Drive
• Tower
Wind Farming EssentialsSeptember 2009
Wind Turbine Blades• Operate on an aerofoil principle:
• That is they create a lift force due to the pressure distribution around the aerofoil surface
Wind Farming EssentialsSeptember 2009
• Blade size is between 20m (600kW machine) to approximately 50+m (3.6 – 4.5MW prototypes)
• Most commonly made of Glass Fibre Reinforced Plastic (GRP), but Carbon Fibre and Wood Laminates are also used
• Modern turbines are usually 3-bladed.
Wind Turbine Blades
Wind Farming EssentialsSeptember 2009
Turbine Size – Rotors and
Blades• Rated Power
varies with Rotor Diameter, but not in a linear fashion
Wind Farming EssentialsSeptember 2009
The Hub and Nacelle:
• Pitch bearings and drives
• Gearbox• Generator• Yaw bearing
and drives
Wind Farming EssentialsSeptember 2009
Yaw Mechanism
Wind Farming EssentialsSeptember 2009
Turbine Size – Towers & Hub
Height• Wind speed varies
with height above ground due to WIND SHEAR
• Tower heights typically between 49m and 100m
Wind Farming EssentialsSeptember 2009
Towers & Hub Height• Reasons to use a
taller towers:• Greater ENERGY
CAPTURE• Lower specific
machine loading due to:
1. Lower shear profile
2. ‘Cleaner’ air flows i.e. lower turbulence
Annual Energy Output with hub height and mean wind speed
0
1000
2000
3000
4000
5000
6000
7000
6.5 6.75 7
Mean Wind Speed (m/s)
An
nu
al E
ner
gy
Ou
tpu
t (M
Wh
/yr)
60m
70m
80m
Wind Farming EssentialsSeptember 2009
With the addition of a Control system these components enable:• Optimal capture of the energy in the
wind
• Cost effective generation of energy
• Survivability
Wind Farming EssentialsSeptember 2009
Turbine Performance
• Power varies with the cube of the wind speed
• Pitch or stall• Variable or
fixed speed
Wind Farming EssentialsSeptember 2009
Turbine Performance• Power curve /
wind speed • Cut-in (3-4m/s)• Rated Power
(12-25m/s)• Cut-out
(25+m/s)
Wind Farming EssentialsSeptember 2009
Other Components of a Wind Farm include:
• Road access and Grid Connection
• On-site tracks• Foundations • Crane pads• Sub-station and Control
Room• Electrical cabling• Met masts (temporary
and permanent)
Wind Farm Design
Wind Farming EssentialsSeptember 2009
• Access - Good road access is required for construction and decommissioning
• Modern wind turbines are large, heavy machines
- blades may be up to 44 metres in length and
specialised transport
• Ideally, a site should be adjacent, or very close to
the “A” road network
• Narrow “C” class roads, with tight bends should
be avoided
Wind Farm Design
Wind Farming EssentialsSeptember 2009
• Grid connection – The site should be close to grid
infrastructure at an appropriate voltage (usually 33 -
132kV)
• Capacity issues – the nearest grid may need
substantial reinforcing for a large development
• Small scale projects particularly need close
proximity to grid connection points
Wind Farm Design
Wind Farming EssentialsSeptember 2009
Wind Farm DesignLayout is dependent on:• Spacing between turbines • Distances to properties, roads, footpaths
and bridleways, EMI links• On-site constraints including
• Ecology (inc Ornithology)• Hydrology• Archaeology• Topography
Wind Farming EssentialsSeptember 2009
Wind Farm DesignSpacing between turbines is dependant on rotor diameter and wind direction
Wind Farming EssentialsSeptember 2009
• EMI and Air Safeguarding:
• Extensive list of consultees including MOD, CAA, NATS, local aerodromes, TV, radio and microwave operators
• Possible requirement for expert studies in mitigation of radar, navigational aids, air safeguarding, radio and TV
• Common mitigation: micro-siting of turbines, signal boosters, digital receptors, replace/upgrade equipment
Wind Farm Design - EIA
Wind Farming EssentialsSeptember 2009
• Ecology:
• Baseline studies – habitat survey, bird surveys and possible invertebrate, mammal and other protected species surveys
• Detailed appropriate assessments may be required – bird flight lines, bats, newts etc.
• Mitigation / habitat improvement often important to compensate for impacts
Wind Farm Design - EIA
Wind Farming EssentialsSeptember 2009
• Archaeology:
• Walkover of the site and desk review of SMR and aerial photographs
• Assessment of effects and potential mitigation
• Possible requirement for presence during construction – watching brief
• Usually there is a requirement for Historic Landscape and Visual Assessment
Wind Farm Design - EIA
Wind Farming EssentialsSeptember 2009
• Noise:
• Operational noise of the turbines is a concern and often strongly determines wind farm design and layout
• On-site measurements of background noise levels and wind speed (correlated)
• Recommended limits• DTI Noise Working Group guidelines (ETSU ’97)
• Given in relation to existing noise background and absolute limits
Wind Farm Design - EIA
Wind Farming EssentialsSeptember 2009
• Landscape and Visibility:
• Landscape architects assess effects to landscape fabric, character and designations,
• Zone of Theoretical Visual Influence (ZTVI) Map over 30km to illustrate visibility to main view point receptors
• Photomontages and wireframe representation of predicted views of wind farm from, on average, 15-20 viewpoints
Wind Farm Design - EIA
Wind Farming EssentialsSeptember 2009
Wind Resource•The UK is the windiest country in Europe with over 40% of the available resourceBUT the wind doesn’t blow all of the time!
•Capacity Factor = Actual Energy Produced / Rated Power*8760
•Capacity factors range from 28 - 40% with 30% often used as a general rule.
•Turbines generate 80-85% of the time dependent on location
Wind Farming EssentialsSeptember 2009
Wind Resource•The Wind Climate is measured with:
• anemometers (speed)• wind vanes (direction)
Mounted on temporary or permanent masts
•And characterised in a number of ways:•Mean wind Speed (at a given height)•Maximum Gust•Wind Shear•Direction•Turbulence Intensity
Wind Farming EssentialsSeptember 2009
Wind ResourceWind data processed and presented in various waysWind Rose Histogram
W E
N
S
Wind Farming EssentialsSeptember 2009
Connection to the Electricity Grid• Wind and other renewable energy generators
are notably different due to:– Intermittancy– Size– Location
• Connected to the Distribution system (132kV and below) rather than the Transmission system
• Hence, known as embedded generation
Wind Farming EssentialsSeptember 2009
• Constraining issues for wind include:– Fault levels– Voltage rise and fall– Power quality (such as voltage step
changes, voltage flicker and harmonics)• Distribution Network Operator (DNO) will
calculate effect on system using load-flow analysis and give a connection cost accordingly
Connection to the Electricity Grid
Wind Farming EssentialsSeptember 2009
• The electricity system is balanced continuously
• Load must be balanced by Generation • Wind is resource dependent in fairly short
time frames• With current and near future penetration
levels (up to the 20% by 2020 figure?) demand side fluctuation will dominate
• Beyond this, storage methods may be required
Connection to the Electricity Grid
Wind Farming EssentialsSeptember 2009
• Government policy to increase use of Renewable Energy
• Recent DTI/Carbon Trust Report concluded that wind is “the only scaleable technology and will deliver the majority of the 2010 Target”
• Similar conclusions in TAN 8 2005
• Target of 15.4% of electricity from RE by 2015 and new EU target of 20% by 2020
• Renewables Obligation is the financial driver in the UK
Market Drivers
Wind Farming EssentialsSeptember 2009
Renewables Obligation All electricity suppliers to acquire 10% of their electricity
from RE by 2010 The costs may be passed to customers Regulator responsible for supplier compliance Contract
terms determined between suppliers/generators themselves Suppliers that do not meet their obligations are effectively
fined through a “buyout” levy for the proportion of MWh of RE they fail to secure
Market Drivers
Wind Farming EssentialsSeptember 2009
Turbines and Trees
Wind Farming EssentialsSeptember 2009
• Manufacturer’s perspective = DO NOT SITE TURBINES NEAR TREES
• Developer’s perspective =TAKE OPPORTUNITIES WHERE AND WHEN THEY ARISE
• Both will face the same problems….
Turbines and Trees
Wind Farming EssentialsSeptember 2009
Turbines and Trees• Reduced Wind Speed• Increased Turbulence Intensity• Increased Wind Shear• Increased Uncertainty in Resource
Assessment• Increased Uncertainty in Turbine Power
Curve• Increased Turbine Loading• Reduced Turbine Availability
Wind Farming EssentialsSeptember 2009
• WindFarmer, Wind Farm, Wind Pro
• WAsP (potential flow, rules of thumb)
• CFD and Hybrid codes
• Measure Correlate Predict (MCP)
• Geographical Information Systems (GIS)
Wind Farm Design Tools
Wind Farming EssentialsSeptember 2009
Wind Farming EssentialsSeptember 2009
Wind Farming EssentialsSeptember 2009
Wind Farming EssentialsSeptember 2009
THANK YOU
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