Wind Farming Essentials September 2009 Wind Farming Essentials - Presentation to the Forestry Engineering Group Symposium Dr. Conrad Trevelyan

Wind Farming EssentialsSeptember 2009

Wind Farming Essentials - Presentation to the Forestry

Engineering Group Symposium

Dr. Conrad Trevelyan


•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


Turbine Anatomy• Blades• Hub• Nacelle

• Generator• Gearbox• Yaw Drive

• Tower


Wind Turbine Blades• Operate on an aerofoil principle:

• That is they create a lift force due to the pressure distribution around the aerofoil surface


• 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


Turbine Size – Rotors and

Blades• Rated Power

varies with Rotor Diameter, but not in a linear fashion


The Hub and Nacelle:

• Pitch bearings and drives

• Gearbox• Generator• Yaw bearing

and drives


Yaw Mechanism


Turbine Size – Towers & Hub

Height• Wind speed varies

with height above ground due to WIND SHEAR

• Tower heights typically between 49m and 100m


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


With the addition of a Control system these components enable:• Optimal capture of the energy in the

wind

• Cost effective generation of energy

• Survivability


Turbine Performance

• Power varies with the cube of the wind speed

• Pitch or stall• Variable or

fixed speed


Turbine Performance• Power curve /

wind speed • Cut-in (3-4m/s)• Rated Power

(12-25m/s)• Cut-out

(25+m/s)


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


• 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


• 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 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 Farm DesignSpacing between turbines is dependant on rotor diameter and wind direction


• 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


• 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



• 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



• 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



• 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 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 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 ResourceWind data processed and presented in various waysWind Rose Histogram

W E

N

S


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


• 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


• 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


• 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


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


Turbines and Trees


• 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


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


• 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





THANK YOU

Documents

Wind Farming Essentials September 2009 Wind Farming Essentials - Presentation to the Forestry Engineering Group Symposium Dr. Conrad Trevelyan