PROPOSED ENERCON E-53 800 kW WIND TURBINE AT

24 Bell Street

Pepper Mill Barn

Old Salisbury Lane

Romsey

SO51 0GD

T: 01794 515999

F: 01794 515100

E: [email protected]

PROPOSED ENERCON E-53 800 kW WIND TURBINE AT

TOP FARM, FOSTON

NOISE IMPACT ASSESSMENT

Technical Report: R4694-1 Rev 1

Date: 12th July 2013

For: IEP Ltd

The Granary

Centre of Renewable Energy

East Drayton

Nottinghamshire

DN22 0LG

IEP Ltd

Technical Report: R4694-1 Rev 1 of 21

24 Acoustics Document Control Sheet Project Title: Proposed ENERCON E-53 800 kW Wind Turbine at Top Farm, Foston

Noise Impact Assessment Report Ref: R4694-1 Rev 1 Date: 12th July 2013

Name Position Signature Date

Prepared by

David Coles BEng PhD MIOA

Consultant

Approved by

Reuben Peckham BEng MPhil CEng MIOA

Principal Consultant

For and on behalf of 24 Acoustics Ltd

Document Status and Approval Schedule

Revision Description Prepared By Approved By

0 Approved for Issue David Coles Reuben Peckham

1 Revised following client comments

David Coles Reuben Peckham

DISCLAIMER This report was completed by 24 Acoustics Ltd on the basis of a defined programme of work and terms and

conditions agreed with the Client. The report has been prepared with all reasonable skill, care and diligence

within the terms of the Contract with the Client and taking into account the project objectives, the agreed

scope of works, prevailing site conditions and the degree of manpower and resources allocated to the project.

24 Acoustics Ltd accepts no responsibility whatsoever, following the issue of the report, for any matters arising

outside the agreed scope of the works.

This report is issued in confidence to the Client and 24 Acoustics Ltd has no responsibility of whatsoever nature

to third parties to whom this report or any part thereof is made known. Any such party relies upon the report

at their own risk.

Unless specifically assigned or transferred within the terms of the agreement, 24 Acoustics Ltd retains all

copyright and other intellectual property rights, on and over the report and its contents.

© 24 Acoustics Ltd 2013

IEP Ltd


EXECUTIVE SUMMARY

24 Acoustics Ltd has been retained by IEP Ltd to undertake a noise impact assessment of the

operation of an ENERCON E-53 800 kW wind turbine at Top Farm in Foston, Lincolnshire.

Calculations of the noise emission from the proposed turbine indicate that the operational noise

level will be no greater than 35 dB LA90 (the level below which the ETSU-R-97 simplified

methodology applies) at all receptors.

IEP Ltd


CONTENTS Page

1.0 INTRODUCTION 5

2.0 SITE DESCRIPTION AND BACKGROUND 5

3.0 ASSESSMENT CRITERIA 5

4.0 WIND TURBINE NOISE PREDICTIONS 7

5.0 CONCLUSIONS 9

REFERENCES 10

APPENDIX A – ACOUSTIC TERMINOLOGY 11

APPENDIX B – WARRANTY AND NOISE SOURCE DATA DOCUMENTS 16

IEP Ltd


1.0 INTRODUCTION

1.1 24 Acoustics Ltd has been retained by IEP Ltd to undertake an assessment of the potential

noise impact of an ENERCON E-53 wind turbine operating at Top Farm in Foston,

Lincolnshire.

1.2 All sound pressure levels quoted in this report are in dB relative to 20 µPa. All sound

power levels are quoted in dB relative to 10-12 Watts. A glossary of the acoustic

terminology used in this report is provided in Appendix A.

2.0 SITE DESCRIPTION AND BACKGROUND

2.1 Top Farm is located in the village of Foston, approximately 9 km north-west of Grantham,

Lincolnshire.

2.2 IEP Ltd intends to apply for planning permission to erect an ENERCON E-53 wind turbine

on the site. The turbine will have a hub height of 73 m and blade diameter of 52.9 m

giving a tip height of approximately 99.5 m. The grid references of the proposed turbine

and of the nearest receptors are shown in Table 1 below.

Location OS Coordinates Distance from Turbine

E-53 Wind Turbine SK 87032 42558 n/a

1. The Firs SK 86519 42151 662 m

2. Mill House SK 86006 42313 1053 m

3. 16 Chapel Lane SK 86055 42839 1005 m

Table 1: Turbine and Receptor Locations

3.0 ASSESSMENT CRITERIA

3.1 ETSU-R-97 ‘The Assessment and Rating of Noise from Wind Farms’ [Reference 1] is used

for the assessment of noise from wind turbines/wind farms in the UK. This document

defines a framework for the measurement of noise from wind turbines and suggests noise

limits for use in assessing the noise impact from wind turbines at the planning application

stage of a project.

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3.2 ETSU-R-97 requires the assessment of wind turbine noise to be considered at night

(between 23:00 and 07:00 hours) and during the ‘quiet daytime hours’ (evenings from

18:00 until 23:00, Saturday afternoons between 13:00 and 18:00 and Sundays from

07:00 until 18:00). For the daytime period a noise limit of 35-40 dB LA90 or 5 dBA above

the prevailing background noise level is set (whichever is the greater). The distinction

between the use of the absolute noise limit of 35 or 40 dBA is not explicitly stated,

however, it relates to the number of receptor properties, the effect of the noise limit on the

amount of electrical power generated and the duration of the level of exposure. At night

the noise limit is 43 dB LA90 or 5 dBA above the prevailing background noise level,

whichever is greater.

3.3 The noise limits apply across the turbine operational wind speeds (usually between 4 and

10 m/s) and it is necessary to quantify both the background noise level and the noise level

emitted by the turbine(s) as a function of wind speed. The background noise level is

measured simultaneously with wind speed (determined at a height of 10 m) and the

prevailing background noise level is set by calculation of a best fit curve through values of

background noise plotted against wind speed for both the quiet daytime and night-time

operational periods.

3.4 ETSU-R-97 provides a simplified methodology for smaller or more remote schemes. This

method is appropriate when it can be shown that, even with no increase in background

noise levels with wind speed (up to quite high wind speeds), noise conditions will be met

at the nearest noise sensitive properties. To quantify this, ETSU-R-97 states that this is

the case when the predicted noise level from the turbine does not exceed 35 dB LA90 at

wind speeds up to 10 m/s at 10 m height. The limit of 10 m/s for the wind speed is given

here as it is assumed that for wind speeds greater than 10 m/s additional background

noise will be generated, thus elevating the background noise levels at the noise sensitive

property.

3.5 ETSU-R-97 states that background noise surveys are not required when the criteria for the

simplified methodology are met.

3.6 In the past decade there have been many planning appeals and public inquiries relating to

proposed wind farm/wind turbine sites. There have been a number of technical disputes

between acoustic consultants working on behalf of the different parties. To minimise these

disputes an agreement between these groups was published by the Institute of Acoustics

in April 2009 [Reference 2] (known as the IoA Agreement).

IEP Ltd


3.7 Of relevance here, the IoA Agreement provides the following clarification:

• The prediction of wind turbine noise at receptor locations. It states that the

propagation methodology of ISO 9613 [Reference 3] be used with a ground effects

condition of G=0.5 along with a 4 m receptor height and the turbine vendor’s

warranted sound power level data or G=0 together with the measured noise

levels. No account should be taken of barrier attenuation caused by a landform

unless there is no line-of-sight between the receptor and the highest point of the

turbine rotor (in which case a barrier correction of 2 dBA can be justified).

4.0 WIND TURBINE NOISE PREDICTIONS & IMPACT ASSESSMENT

4.1 The noise source data for the ENERCON E-53 wind turbine have been provided by the

manufacturer [Reference 4] and are stated below. These data have been warranted by

ENERCON (evidence of the warranty can be found in Appendix B along with the noise

source data reports). A correction of +1 dB has been added for measurement uncertainty

(in accordance with current agreed best practice).

Wind Speed, m/s (at 10 m reference height, hub height 73 m) & LAeq Sound Power Levels, dB

4 5 6 7 8 9 10

Measured Sound Power Level (IEC 61400-11)

92.5 94.2 97.7 100.1 101.5 102.5 102.5

Warranted Sound Power Level (IEC 61400-11)

93.5 95.2 98.7 101.1 102.5 103.5 103.5

+1 dB Measurement Uncertainty

94.5 96.2 99.7 102.1 103.5 104.5 104.5

Table 2: ENERCON E-53 800 kW Wind Turbine LAeq Sound Power Levels

Sound Power Level, dB per Octave Band, Hz

63 125 250 500 1000 2000 4000 8000

84.4 91.2 93.2 95.2 97.6 96.1 89.5 79.6

Table 3: E-53 LAeq Sound Power Level Frequency Spectrum, 10 m/s Wind Speed

4.2 The noise source data report states that there are no tonal components in the noise

emission from the turbine which would warrant a correction, in accordance with the

requirements of ETSU-R-97. Therefore a tonal penalty has not been added to the source

spectrum. ENERCON should be asked to provide a warranty to this effect.

IEP Ltd


4.3 Predictions of the noise emission from the proposed wind turbine have been carried out

using IMMI 2011-1 noise mapping software. The propagation methodology of ISO 9613

has been used which takes into account the effects of geometric divergence, acoustic

screening and atmospheric and ground absorption.

4.4 The calculations have assumed an ambient temperature of 10°C and relative humidity of

70%. Downwind propagation conditions have been assumed throughout. The

calculations have determined the noise level from the turbine at a receptor height of 4 m

above local grade level and have assumed a ground absorption factor of G=0.5 (which

complies with current agreed understanding). No account has been taken of any acoustic

shielding that may be provided by the natural topography of the land at a given site. The

calculations therefore represent a worst-case assessment.

4.5 The turbine noise levels have been corrected from LAeq sound pressure levels to LA90 sound

pressure levels by subtracting 2 dBA in accordance with the ETSU-R-97 methodology.

Table 4 below presents the results of the calculations (at an operational wind speed of 10

m/s at 10 m height). Figure 2 shows the noise contour map associated with the

proposals.

Location Sound Pressure Level, dB LA90

1. The Firs 34.0

2. Mill House 29.0

3. 16 Chapel Lane 29.5

Table 4: Calculated Operational Noise Levels, 10 m/s wind speed at 10 m height

4.6 The calculations indicate that the operational noise level from the proposed turbine will be

no greater than 35 dB LA90 at all receptors. The requirements of ETSU-R-97 have therefore

been fulfilled in this assessment.

IEP Ltd


Cumulative Impact

4.7 A review of existing and planned turbines close to the turbine proposed here has been

undertaken. An application (reference S12/2411 - Yew Tree Farm) has been made for a

500 kW wind turbine at land off Green Lane. The proposed turbine, an ENERCON E48, is

to be located 1.6 km south-east of the Top Farm turbine at OS coordinates SK 88317

41578 and will operate at a hub height of 50 m. It should be noted that this application

has been refused. However, given the possibility of an appeal, it is considered that the

potential cumulative noise impact from this turbine should be assessed.

4.8 Source noise data are provided in the noise impact assessment submitted with the

application and these noise levels are used here in the cumulative assessment.

Receptor Predicted Sound Pressure Level, dB LA90

No. Name Top Farm Only Cumulative Impact

1 The Firs 34.0 34.2

2 Mill House 29.0 29.2

3 16 Chapel Lane 29.5 29.7

Table 5: Calculated Cumulative Noise Impact, 10 m/s wind speed at 10 m height

4.9 The cumulative assessment shows that, taking account of nearby proposed wind turbines,

the predicted turbine noise levels will still fall below 35 dB LA90 at all receptors and

therefore fulfil the requirements of the simplified methodology.

5.0 CONCLUSIONS

5.1 24 Acoustics Ltd has been retained by IEP Ltd to undertake a noise impact assessment of

the operation of an ENERCON E-53 800 kW wind turbine at Top Farm in Foston,

Lincolnshire.

5.2 Calculations of the noise emission from the proposed turbine indicate that the operational

noise level will be no greater than 35 dB LA90 (the level below which the ETSU-R-97

simplified methodology applies) at all receptors.

IEP Ltd


REFERENCES

1. ETSU-R-97, Assessment and Rating of Noise from Wind Farms, Department of Trade and

Industry, 1997.

2. Prediction and Assessment of Wind Turbine Noise, Institute of Acoustics, Acoustics Bulletin

March, April 2009.

3. ISO 9613, Acoustics- Attenuation of Sound During Propagation Outdoors, International

Standards Organisation, 1993.

4. Sound Power Level of the ENERCON E-53, Operational Mode I, ENERCON GmbH, 2012.

IEP Ltd


Scale: N.T.S. Rev: A

Job No: 4694-1

Drawn By: DC

Project: Top Farm, Foston

Description: Proposed Turbine and Receptor Locations

DWG No: Figure 1

Date: April 2013

1. The Firs

2. Mill House

3. 16 Chapel Lane

Turbine Location

IEP Ltd



Job No: 4694-1

Drawn By: DC


Description: Site Noise Contours

DWG No: Figure 2

Date: April 2013

IEP Ltd



Job No: 4694-1 Drawn By: DC


Title: Location of Cumulative Impact Wind Turbines

DWG No: Figure 3

Date: July 2013

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APPENDIX A – ACOUSTIC TERMINOLOGY

Noise is defined as unwanted sound. The range of audible sound is from 0 to 140 dB. The

frequency response of the ear is usually taken to be around 18 Hz (number of oscillations per

second) to 18000 Hz. The ear does not respond equally to different frequencies at the same level.

It is more sensitive in the mid-frequency range than the lower and higher frequencies and

because of this, the low and high frequency components of a sound are reduced in importance by

applying a weighting (filtering) circuit to the noise measuring instrument. The weighting which is

most widely used and which correlates best with subjective response to noise is the dBA

weighting. This is an internationally accepted standard for noise measurements.

For variable sources, such as traffic, a difference of 3 dBA is just distinguishable. In addition, a

doubling of traffic flow will increase the overall noise by 3 dBA. The ‘loudness’ of a noise is a

purely subjective parameter, but it is generally accepted that an increase/ decrease of 10 dBA

corresponds to a doubling/ halving in perceived loudness.

External noise levels are rarely steady, but rise and fall according to activities within an area. In

attempt to produce a figure that relates this variable noise level to subjective response, a number

of noise indices have been developed. These include:

i) The LAmax noise level

This is the maximum noise level recorded over the measurement period.

ii) The LAeq noise level

This is “equivalent continuous A-weighted sound pressure level, in decibels” and is defined in

British Standard BS 7445 [1] as the “ value of the A-weighted sound pressure level of a

continuous, steady sound that, within a specified time internal, T, has the same mean square

sound pressure as a sound under consideration whose level varies with time”.

It is a unit commonly used to describe construction noise and noise from industrial premises and is

the most suitable unit for the description of other forms of environmental noise. In more

straightforward terms, it is a measure of energy within the varying noise.

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iii) The LA10 noise level

This is the noise level that is exceeded for 10% of the measurement period and gives an indication

of the noisier levels. It is a unit that has been used over many years for the measurement and

assessment of road traffic noise.

iv) The LA90 noise level

This is the noise level that is exceeded for 90% of the measurement period and gives an indication

of the noise level during the quieter periods. It is often referred to as the background noise level

and is used in the assessment of disturbance from industrial noise.

IEP Ltd


APPENDIX B – WARRANTY AND NOISE SOURCE DATA DOCUMENTS

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PROPOSED ENERCON E-53 800 kW WIND TURBINE AT

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