Wind Farming Essentials - Presentation to the Forestry Engineering Group Symposium

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

2. 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

3. Turbine Anatomy • Blades • Hub • Nacelle • Generator • Gearbox • Yaw Drive • Tower

4. Operate on an aerofoil principle: That is they create a lift force due to the pressure distribution around the aerofoil surface Wind Turbine Blades

5. 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

6. Turbine Size – Rotors and Blades • Rated Power varies with Rotor Diameter, but not in a linear fashion

7. The Hub and Nacelle: • Pitch bearings and drives • Gearbox • Generator • Yaw bearing and drives

8. Yaw Mechanism

9. Turbine Size – Towers & Hub Height • Wind speed varies with height above ground due to WIND SHEAR • Tower heights typically between 49m and 100m

10. Towers & Hub Height • Reasons to use a taller towers: • Greater ENERGY CAPTURE • Lower specific machine loading due to: • Lower shear profile • ‘Cleaner’ air flows i.e. lower turbulence

11. Optimal capture of the energy in the wind Cost effective generation of energy Survivability With the addition of a Control system these components enable:

12. Turbine Performance • Power varies with the cube of the wind speed • Pitch or stall • Variable or fixed speed

13. Turbine Performance • Power curve / wind speed • Cut-in (3-4m/s) • Rated Power (12-25m/s) • Cut-out (25+m/s)

14. Wind Farm Design 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)

15. 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

16. 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

17. Wind Farm Design Layout 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

18. Wind Farm Design Spacing between turbines is dependant on rotor diameterand wind direction

19. 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

20. 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

21. 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

22. 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

23. 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

24. Wind Resource • The UK is the windiest country in Europe with over 40% of the available resource BUT 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

25. 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

26. Wind Resource Wind data processed and presented in various ways Wind Rose Histogram N W E S

27. 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 Connection to the Electricity Grid

28. 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

29. 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

30. Market Drivers • 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

31. 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

32. Turbines and Trees

33. 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….

34. 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

35. 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

39. THANK YOU