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Wind Farm Noise Impact Assessment Training Session 1: Introduction Different Types of Wind Turbine Planning Policy & ETSU-R-97

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

Wind Farm Noise Impact Assessment

INTRODUCTION AND OVERVIEW OF THE DAY

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

• Hoare Lea founded in 1862 • Extensive experience in wind farm noise assessments since the early 1990’s • Specialists in feasibility studies, noise impact assessments for planning, expert witness services, compliance monitoring, complaint investigation, detailed mitigation strategies and peer reviews • State-of-the-art research in the field of wind turbine noise • Members of DTI NWG (ETSU-R-97) committee • Members of IoA Good Practice Guide committee • Members of IEC61400-11 committee w w w . h o a r e l e a . c o m

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Introduction

About Hoare Lea Acoustics


Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

The options …. • Offshore large scale (>100kW) • Onshore large scale (>100kW)

• Onshore medium / small / micro scale • Building mounted / integrated medium / small / micro scale

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

Power in wind = 0.5 ρ A v3 ρ = air density A = swept area of rotor = π r2 v = wind speed Power increases with …. • cube of wind speed • square of rotor radius • height (increasing wind speed) … therefore locate large diameter rotors on high towers in areas of high wind speed

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Introduction

The economies of scale


Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

Onshore large scale turbines • Typical installed capacity 2MW to 3MW • Typical hub height 60m to 100m • Typical rotor diameter 60m to 90m • Typical height to blade tip 90m to 140m

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

• Demonstrate acceptable wind farm noise impact at the planning stage • Achieve this acceptable noise impact in practice • Balance local noise impact against wider benefits (generating capacity) w w w . h o a r e l e a . c o m

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Introduction

Wind Farm Noise - the basic aims ….


Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

Context of the need to attain this balance

• Diversity of energy supply is a necessity • Renewables must play a key role in this diversity • The UK has the best wind resource in Europe • Large scale onshore wind is the key contributor in the immediate term • There is a commitment to attain government targets w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

So where’s the problem?

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Introduction

Where is wind farm noise on the scale?


Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

Attitude and audibility are key … • Wind farm developments are often in quiet rural areas • Wind farms are designed to produce an ‘acceptable’ level of noise (in planning terms) • ‘Acceptable’ does not necessarily mean inaudible • Wind farm noise is likely to be audible at some neighbouring residences for at least some of the time • Audibility may be unacceptable to some individuals

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

When does sound become noise ?

Image courtesy Bruel & Kjaer

Depends on individual

Depends on activity of individual

Depends on attitude of individual

Depends on hearing acuity of individual

Depends on level of noise

Depends on character of noise w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

Noise – an all encompassing definition The World Health Organisation (WHO) provides the following definitions: Noise -

any sound that is damaging to health

Health - a complete state of mental, physical and social well- being and not merely the absence of disease or infirmity Hearing damage Sleep disturbance Activity interference

Stress

Annoyance Heart disease Gastric disorders Raised blood pressure w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

Very high noise level Physical damage to structures Direct physical damage to humans (e.g. irreversible hearing damage) Secondary adverse health effects (e.g. stress, increased blood pressure, etc.) Activity interference (e.g. speech, sleep, work, relaxation, etc.) Annoyance

Lower noise level w w w . h o a r e l e a . c o m

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Introduction

Potential adverse effects of noise ‌


Wind Farm Noise Assessment Training Introduction and Overview of the Day

Introduction

Assessment of ‘true’ impact •

Overall level - dB(A)

Additional noise characteristics - tones etc.

Time of exposure – day/evening/night

Actual duration of exposure to noise

Activity during exposure – work/home/sleep

Expectations of sound environment

Variability of noise – level/character

Masking effects of other sounds

Variability of masking sounds

Attitude towards the source of noise

Hearing acuity and general health

Non-acoustic influences w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Introduction and Overview of the Day

• • • • • • • • • • • • • • •

Infrasound Low frequency noise (LFN) Ground-borne vibration Direct adverse health effects (WTS) Vibro-acoustic disease (VAD) Indirect (secondary) adverse health effects Sleep disturbance Use of background noise measurements Cumulative effects Effects of wind shear Effects of increased turbine size Noise propagation effects External to internal noise transmission effects Amplitude modulation (AM) Conditions w w w . h o a r e l e a . c o m

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Introduction

Wind farms and current noise ‘issues’ ….


Wind Farm Noise Assessment Training Different Types of Wind Turbine

Wind Farm Noise Impact Assessment Source and Characteristics – Different types of wind turbine

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Wind Farm Noise Assessment Training Different Types of Wind Turbine

• Higher frequencies Swishing, lapping, hissing, whistling… • Mid frequencies Tones, whines, roar… • Lower frequencies Rumble, thumping…

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Source

Subjective noise from wind turbines


Wind Farm Noise Assessment Training Different Types of Wind Turbine

Source

Principal Sources of Noise Aerodynamic sources • Motion of air around the blades • Various sources, complex mechanisms Mechanical sources • Motion of mechanical & electrical components • Sources are more easily identified and controlled Aerodynamic sources affected by air inflow speed and turbulence All sources affected by rotor speed and loading

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Wind Farm Noise Assessment Training Different Types of Wind Turbine

Source

Aerodynamic sources (after Hayes, IOA 25-04-2006 and Lowson)

Turbulence ingestion

Separation (stall) noise

Tip noise

Dominant

Trailing edge noise

Boundary layer noise

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Wind Farm Noise Assessment Training Different Types of Wind Turbine

115 Two speed (stall regulated)

Sound power output level, dB(A)

Source

Comparison of sound power outputs of different wind turbines….

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105 Two speed (pitch regulated)

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95 Speed changeover region for two speed turbines

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Variable speed

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Wind speed at 10m height, ms

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Turbine sound output levels are wind speed dependent

Actual variation with wind speed is turbine specific

Common now for large turbines to be pitch-regulated variable speed w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Different Types of Wind Turbine

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Source

Evolution for a particular model


Wind Farm Noise Assessment Training Different Types of Wind Turbine

Source

Reduced noise modes Capacity of variable speed pitch-regulated turbines

Most turbines offer reduced noise mode operation

Speed restriction or pitch setting change

Cost is power generation loss but can be restricted to specific conditions w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Wind Farm Noise Impact Assessment

PLANNING POLICY & ETSU-R-97

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Planning system to deliver renewables ‌ Scotland

SPP Climate Change Act

BS 8233

Energy Act

PAN1/2011

www Onshore WTs

Renewable Development & Noise EU Directives

ETSU-R-97

BS 4142 COPA EPA

Kyoto Protocol

WHO

NSNA

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

The UK has the best wind resource in Europe w w w . h o a r e l e a . c o m

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Policy

The EU and UK wind resource


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Wind Farm Noise - the basic aims ….

• Demonstrate acceptable wind farm noise impact at the planning stage • Achieve this acceptable noise impact in practice • Balance local noise impact against wider benefits (generating capacity) w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Good acoustical design and siting of turbines is essential to minimise the potential to generate noise. Web based planning advice on renewable technologies for onshore wind turbines provides advice on ‘The Assessment and Rating of Noise from Wind Farms’ (ETSU-R-97) published by the former Department of Trade and Industry [DTI] ….

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Policy

Scottish Planning Policy – PAN1/2011


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Onshore Wind Turbines (as updated 17 July 2013) - Noise

PAN on Planning and Noise provides advice on the role of the planning system in helping to prevent and limit the adverse effects of noise. The associated Technical Advice Note provides guidance which may assist in the technical evaluation of noise assessment.

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

The report, "The Assessment and Rating of Noise from Wind Farms“ (ETSU-R-97) ….. should be followed by applicants and consultees, and used by planning authorities to assess and rate noise from wind energy developments, until such time as an update is available. This gives indicative noise levels thought to offer a reasonable degree of protection to wind farm neighbours, without placing unreasonable burdens on wind farm developers ….

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Policy

Onshore Wind Turbines (as updated 17 July 2013) - Noise


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Onshore Wind Turbines (as updated 17 July 2013) - Noise

A further report produced by Hayes McKenzie for DECC … “An Analysis of How Noise Impacts are Considered in the Determination of Wind Farm Planning Applications” suggested that best practice guidance is required to confirm and, where necessary, clarify and add to the way ETSU-R-97 should be implemented in practice ….

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

The Institute of Acoustics (IOA) has since published ‘Good Practice Guide to the Application of ETSU-R-97 for the Assessment and Rating of Wind Turbine Noise’. The document provides significant support on technical issues to all users of the ETSU-R-97 method for rating and assessing wind turbine noise, and should be used by all IOA members and those undertaking assessments to ETSU-R-97. The Scottish Government accepts that the guide represents current industry good practice.

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Policy

Onshore Wind Turbines (as updated 17 July 2013) - Noise


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Onshore Wind Turbines (as updated 17 July 2013) - Noise

Further research by AECOM entitled ‘NANR 277 Wind Farm Noise: Statutory Nuisance Complaints Methodology’ is aimed at helping Local Authorities deal with wind farm noise complaints, using statutory nuisance powers

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

What does ‘minimise increases in noise’ mean in the context of noise policies? ‘… taken in isolation and to a literal extreme, noise minimisation would mean no noise at all.’ ‘In reality, although it has not always been stated, the aim has tended to be to minimise noise as far as is reasonably practical’ ‘the application of the NPSE should enable noise to be considered alongside other relevant issues and not to be considered in isolation. In the past, the wider benefits of a particular policy, development or other activity may not have been given adequate weight when assessing the noise implications.’

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Policy

Noise Policy Statement for England


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Consider effect of 2 dB(A) reduction

Effect of 2dB(A) at all Baseline oneproperties property 45 MW 3627MW MW

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

The situation to be addressed ‌. Source

Propagation

Receiver

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Wind Farm Noise – setting acceptable limits

ETSU-R-97 w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Wind farms are likely to be developed in largely rural areas and not in the areas to which the BS4142 standard is principally addressed, namely mixed residential and industrial areas

The scope of BS 4142 specifically precludes situations where background noise levels lie below 30 dB(A) but such low levels can be encountered in rural areas

BS 4142 recommends that noise measurements should not be taken in extreme weather conditions such as high wind speeds greater than 5 metres per second average – just those conditions under which wind farms would be operating

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Policy

BS4142 was used as a helpful starting point but recognised as having a number of practical limitations …


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

… but it appears to have been accepted that the general principles of BS4142 should be retained … •

like should be compared with like

specific noise assessed against background noise under the same conditions

special consideration given to situations of low noise levels

time of day effects for background

mode and time of operation effects for specific noise

wind effects (direction and speed)

use of robust metrics LA90 versus LAeq (specific to wind farm noise)

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

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Policy

Use of the LAeq,T index for the measurement of specific noise levels in quiet rural areas is highly susceptible to corruption by natural sources of noise


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Both turbine noise and background noise are wind speed dependent

VH

VL

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

• Specify the location of wind turbines and a candidate type of turbine • Identify the locations of the nearest noise sensitive properties (or groups of properties) • Determine whether noise immission levels exceed 35dB(A) • Measure background noise levels as a function of site wind speed at nearest neighbours, or at least a representative sample of such • Determine the day-time and night-time noise limit curves from the measured background noise levels • Calculate the noise immission levels at the neighbouring properties • Compare calculated wind farm noise levels with derived noise limit curves to ensure ETSU noise limits will not be breached

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Policy

Steps for undertaking an ETSU-R-97 assessment


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Assessment Property Day-time Periods Assessment property-–Quiet ‘quiet daytime’ or night time 60 55 50 45

L90 dB(A)

Policy

Measure the existing (inherently variable) background noise level at selected locations as a function of site wind speed and time of day

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Wind Speed at 10m (m/s)

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

Calculate the ‘average’ background level by fitting a best fit curve to the measured noise data

Assessment Property property -–Quiet ‘quietDay-time daytime’Periods or night time 60 55 50

L90 dB(A)

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Wind Speed at 10m (m/s) w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Assessment property Property -–Quiet Assessment ‘quietDay-time daytime’Periods or night time 60 55 50

involved night

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L90 dB(A)

Policy

Set the ETSU-R-97 noise limit at 5dB(A) above the background noise curve but with an absolute lower limit

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day 35 30 25 20 15 10 0

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Wind Speed at 10m (m/s)

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Wind Turbine Sound Power Output Level 60 Tu rbine S ou nd P ow er Level, dB (A )

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Wind Speed at 10m (m/s)

Noise Propagation Calculation Algorithm

Assessment Property - Quiet Day-time Periods 60 55

ETSU-R-97 Noise Limit

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L90 dB(A)

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Wind Farm Noise Immission Level

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Wind Speed at 10m (m/s)

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Policy

Calculate wind farm noise immission levels at receptors and compare with ETSU noise limits


Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

Policy

The Institute of Acoustics ‘Good Practice Guide’ • Response to request to IoA from DECC • Follow up to HMP report • Applies to all turbines above 50kW • Formally endorsed in Scotland - consultation & engagement - background noise surveys - wind and rain measurements - data analysis and noise limit derivation - noise predictions - cumulative noise issues w w w . h o a r e l e a . c o m

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Wind Farm Noise Assessment Training Planning Policy and ETSU-R-97

• The majority of wind farms designed using ETSU-R-97 appear to be operating successfully without noise issues? • Site-specific noise issues have occurred that need to be better understood/managed • Operational noise management is possible with current technology wind turbines to mitigate noise effects • Amenity of neighbours and a proactive attitude towards noise concerns remains of paramount importance but • Inaudibility at all locations and at all times is not a realistic proposition • Fears of adverse noise effects may be causing undue stress even before wind farms are constructed w w w . h o a r e l e a . c o m

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Policy

Summary of current situation


Wind farm noise assessment training session 1