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Wind 101 – Technical Basics

Wind 101 – Technical Basics. Clean Energy BC 2010 Mark Green – Wind Engineer, Natural Power Consultants. Natural power - About us. Practical consulting and risk management for the international renewable energy industry, providing services throughout the project life-cycle

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Wind 101 – Technical Basics

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  1. Wind 101 – Technical Basics Clean Energy BC 2010 Mark Green – Wind Engineer, Natural Power Consultants

  2. Natural power - About us • Practical consulting and risk management for the international renewable energy industry, providing services throughout the project life-cycle • 15 year track record in wind energy consultancy - established in 1995 • Over 200 employees worldwide across 7 offices in 5 countries • Consultancy services provided to more than 15,000MW of projects • 2,000MW where we have provided full project design & consenting • We have managed the construction of 500MW of wind energy • 300MW+ of wind plant under our asset management

  3. A Global Presence We have presence worldwide, including: • Scotland (head office) • British Columbia, Canada • France • Ireland • England • Wales • Chile • USA

  4. Our Core Services • Our core services: • Advanced resource assessment and site modelling • Development, EIA and permitting • Ecology services • Construction and geotechnical services • Site management • Operational site analysis and optimisation • 360o Due-diligence

  5. Wind 101 – Overview • Wind: The Basics • Commercial Background • Site Selection • Wind data collection • Data analysis – Long-term prediction • Wind flow modelling • Turbine layout and selection • Energy yield modelling

  6. The Basics

  7. The Basics: Wind • All renewable energy (except tidal and geothermal power) ultimately comes from the sun. • Uneven heating of the earth’s surface causes differences in temperature throughout the atmosphere. • Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. • This movement of air is what makes the wind blow. 

  8. The Basics: Turbines Blades (35-55m length) Rotor (70-110m diameter) Nacelle Rotor Hub Tower (60-100m high) Transformer

  9. The Basics: Wind • Maximum theoretical power in a moving fluid is defined in Watts…For wind, the power in the area swept by the turbine rotor: • P = 0.5 x rho x A x V3 • Betz law: maximum of 59% of the power moving through the rotor can be captured.

  10. The Basics: Wind • The Watt is the SI unit of power - instantaneous • Energy in the context of electricity generation is the multiplication of power in Watts and time in hours. • E.g. a 1MW turbine producing at 100% for 1 hour will produce 1MWh of energy. • However, the wind never blows 100% of the time! • The term Capacity Factor (C.F.) is used to describe the actual energy produced vs the max rated production.

  11. The Basics: Commercial Background What are the commercial drivers in performing technical analyses?: • For a wind farm to receive financial backing, lenders and developers require a robust estimate of the lifetime energy yield (GWh) • To secure wind turbines, a developer needs to demonstrate that the site conditions do not exceed the design and operational limits of the turbines • The greater the uncertainty in the yield and design predictions, the greater the risk to the lender/developer

  12. The Basics: Process of Design & Analysis • Desk-based resource modelling • Short-term wind data collection • Long-term wind climate prediction • Wind flow modelling • Energy yield modelling • Uncertainty analysis

  13. Site Selection

  14. Site Selection: Desk Based Modelling • Used for initial site prospecting • Does not use any actual on-site wind data as an input • Instead uses a local correction model • Examples of regional mesoscale models are the Canadian Wind Atlas and the BC Wind Atlas, both are available online. • Typically of too coarse a resolution and accuracy to be applicable in absolute wind resource assessment for financing

  15. Site Selection: Desk Based Modelling

  16. Site Selection: Desk Based Modelling

  17. Site Selection: Desk Based Modelling

  18. Site Selection– Constraints Economic Considerations: • Distance to transmission • Transmission capacity • Site access • Constructability • Wind speed Technical constraints: • Forestry, topography, obstacles • Public rights of way, Parks • Microwaves/Telecommunication links, other Infrastructure (pipelines, etc.) • Ecology, Hydrology, Archaeology • Noise • Setbacks from other windfarms • Visual impact / Landscape / Shadow flicker

  19. Site Selection– Constraints

  20. Site Selection

  21. Wind data collection

  22. Wind Data Collection Why are on-site measurements required? • Provide an accurate representation of the wind regime of the site and its viability • Highlight localised wind flow issues • Reducing prediction uncertainty Measurement locations must be representative of turbine locations: • Topographically • Altitude • Exposure

  23. Wind Data Collection Duration and density of masts: • Ideally, a “known point “ within 2km of every prediction location (depends on size and topography of wind farm) • Particularly complex locations should be further investigated with additional monitoring/modelling • 12 month minimum campaign

  24. Wind Data Collection

  25. Wind Data Collection Prop Vane - (measures wind speed and direction) Wind vane (measures wind direction) Cup anemometer (measures wind speed)

  26. R r Wind Data Collection To achieve an industry best practice 0.5% deficit in wind speed or less: • Cylindrical mast: • For a mast with diameter, d, and boom with diameter, D: • r/d > 8.5 • R/D > 12 • Lattice mast • For a mast with face length, L, and low porosity: • r/L > 5.7 • R/D > 12

  27. Wind Data Collection • Masts • At least 2/3rds of hub height • Cup anemometers at 3 or 4 heights (for shear and turbulence profiles) • Collect 10 minute average speed, direction, SD, gusts, temperature, pressure, • Instruments • Vector, NRG, Thies, RM Young ... • Calibrated instruments (MEASNET wind tunnel) • Mounting adhering to best practice • Consider a mix of instruments

  28. Wind Data Collection

  29. Wind Data Collection Remote sensing is another option: • Ground based wind data collection • LIDAR and SODAR • Measure up to ~200m height • Very useful for wind characteristics (shear, Ti) and for additional known points in complex flow • Replacing masts in many applications • LIDAR data is validated for project finance use

  30. Wind Data Collection transmitted light LASER local oscillator (reference beam) scattered and received light (with Doppler frequency shift) DETECTOR TARGET

  31. Wind Data Collection

  32. Wind Data Review

  33. Wind Data Review – Review & Processing Perform quality checks on the data • Instrument continuity • Mast integrity (boom slippage) • Tower/instrument shadow • Shear profile • Turbulence • Icing affected data

  34. Wind Data Review – Review & Processing • Process and review the raw data recorded (Excel / Windographer / WAsP)

  35. Wind Data Review – Long Term Prediction • Site data collection will result in an onsite time series dataset of typically 1-2 years duration • However, the wind farm annual energy yield prediction must be valid for the long-term mean annual average • Wind farm life is 20-25 years • We must therefore adjust the short-term site data to make it representative of the long-term mean annual wind climate

  36. Wind Data Review – Long Term Prediction Main tool to achieve the long term correlation is MCP: • MEASURE wind speed and direction at the wind farm site • CORRELATE between the wind farm site data and wind data from a suitable long-term reference weather station (Environment Canada station) • PREDICT the long-term wind climate at the site The keys to MCP are: • Establishing good correlations • Consistency of measurement

  37. Wind Data Review – Reference Stations

  38. Wind flow modelling

  39. Wind Flow Modelling • The data analysis and MCP process results in a prediction of the long-term mean annual wind climate (frequency of speed and direction) • This data is valid only at the height and location of the principal site anemometer (s) dataset used in the analysis • The turbines in the wind farm will be situated across the project area • The wind climate will vary across the site with changes in exposure, topography, surface roughness • The wind climate must therefore be extrapolated horizontally and vertically to the hub-height of all turbines within in the wind farm

  40. Wind Flow Modelling • WAsP/Ms-Micro flow model • Simple, quick, easy to run • Assume flow is always attached (i.e. no turbulence) • This severely limits their use in complex flow environments (steep slopes/forests) – can lead to significant model errors • Simple flow models are being replaced by advanced 3D computational fluid dynamics (CFD) models (such as Ventos) • Designed to deal specifically with complex terrain and forestry • Complex, computationally demanding, require expert use • Applicable also in determining areas of flow disturbance – the wind quality – for turbine micro-siting

  41. Wind Flow ModelLing: Complex Flow What causes complex flow? • Forestry • Terrain • Obstacles Complex flow impacts wind flow quality Flow parameters that define the wind quality : • Wind shear • Turbulence • In-flow angle

  42. Wind Flow ModeLling: Complex Flow

  43. Wind Flow Modelling: Shear Shear : Variation of horizontal wind speed with height Characterised by log or power law profile Effects : Increased fatigue loading Reduced power output Values : Power law exponent ≤ 0.3

  44. Wind Flow Modelling: Turbulence Turbulence : The formation of eddies and vortices (transient) Characterised by turbulence intensity (TI%) Effects : Reduced power output Increased fatigue loading Values : IEC limit ≈ 12 – 16 % @15m/s (Class A/B/C)

  45. Wind Flow Modelling: Inflow Angle Inflow Angle : Deviation of the directional component of the wind velocity from the turbine rotor axis in the vertical plane. Effects: Reduced power output Increased fatigue loading Values: θ ≤ 8° (±) θ

  46. Wind Flow Modelling: Turbulence

  47. Wind Flow Modelling: Recirculation

  48. Wind Flow Modelling: Mitigation Forestry felling or management options • Scenario modelling with Ventos CFD flow model • Potential improvements in wind quality and resource Sector-wise curtailment • Preserve turbine integrity • Maximise availability/energy in “clean” sectors Maintenance and repair strategy • Target maintenance and repair by turbine and component

  49. Turbine Layout and Selection

  50. Turbine Selection and Layout Design Wind farm should be designed to meet physical and technical constraints whilst utilising the maximum potential from the wind Other optimisation criteria: • Inter-turbine spacing (4-8 rotor diameters / circular or elliptical). Much greater offshore • Hub height • Proximity to trees (> 50 x tree height) – optimal not always practical • Proximity to noise sensitive properties - allowable noise limit in BC - 40dBA at night • Maximise energy output

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