w w w . h o a r e l e a . c o m

Wind Farm Noise Impact Assessment

SMALL WIND TURBINE DEVELOPMENTS

w w w . h o a r e l e a . c o m

Small developments – issues to consider

• Specific characteristics• Full ETSU-R-97 study?• Definitions of small/micro?• Good data is hard to find!• Noise limits and/or policy vary

w w w . h o a r e l e a . c o m

• 3-bladed… sometimes 2 (or one!)• Passive wind direction control• Downwind (thumping?)• Horizontal axis designs• Stall regulated, fixed speed

regulation, furling at high speed

• Higher rotational speed (60 to 200 or more RPMcompared to <20 RPM for larger Ts)

• Control of tonality?• Structure-borne noise when fixed

to buildings

• Test data? “quiet”, “61 dB”

A multitude of designs…Different characteristics

w w w . h o a r e l e a . c o m

Discussion: EPUK Scotland 2010 workshop: Full ETSU-R-97 survey not required Use of nominal (generic, typical) backgrounds? Need for simple and easy approach, set out in policy External limit best and absolute limit helpful? LAeq, 5minutes more suitable? 35dB LA90 already in ETSU-R-97, restrictive? 40dB LAeq at a set wind speed? Fixed distances?

Small turbines = small budgets! • Background survey costs may be disproportionate• 10m masts surveys ok in this context, and simple fixed wind

shear correction (1 to 2 m/s) may be applicable• Adoption of fixed limit simplifies assessment

Using ETSU-R-97 ?

w w w . h o a r e l e a . c o m

• Offshore: currently turbines up to 7.5MW• Onshore: 2-3 MW turbines now typical in the UK• Feed-in-Tariffs(FiT): bands 1.5, 15, 100, 500,1500 kW• “Small”?: Varies…

Renewable UK indicative guidance• Micro wind: <1.5 kW, <18m• Small wind: 1.5-15kW, <25m• Small-medium: 15-100kW, <50m

>2 turbines>15m hub height EIA (screening)

Typical Scales

“Small” turbines:Defined in IEC 61400-2 edition 3 as: Up to ≤200 m2 swept area (≤16 m rotor diameter)

The Town and Country Planning (Environmental Impact Assessment) Regulations 2011 – schedule 2

w w w . h o a r e l e a . c o m

• Rated / Reference power output of up to 50 kW at 11 m/s:• RenewableUK recommended 45 dB LAeq,5min…

• Permitted development limit (2011) of 42 dB LAeq,5min

• Simple calculation: typical wind speed, distance and noise label

• May be “permitted development” in England/Scotland (GPDO)

(swept area < 3.8 m2 or turbines up to 15 m tip height).

Microgeneration Certification Scheme

MCS 020 planning standardStatutory instrument 2011 No. 2056

MCS 006 certification standard

w w w . h o a r e l e a . c o m

• BWEA had dedicated document (UK, 2008) • References EC 61400-11 simplified test procedure • Applies to ≤200 m2 swept area (≤16 m rotor diameter)• Gives sound power + tonal penalty in standard label

>45 dB: unlikely to be acceptable <40dB: “generally acceptable” 40-45dB: depends on “national or local” policies

Small turbines: Sound power test standards

Replaced by new RUK doc

w w w . h o a r e l e a . c o m

Criteria and assessments - example

Cornwall standard policy (March 2012)• “Small” (200m2 definition)

• 35dB LAeq

• Larger: • 35dB LA90 for single turbines

• full ETSU-R-97 for wind farms• Guidance on data requirements,

conditions and financial involvement

w w w . h o a r e l e a . c o m

• Particular characteristics of small turbines may cause annoyance

• No clear definition of what is “small” but some consensus emerging

• Good emission data is hard to find but methods exist

• Full ETSU-R-97 study may not be suitable • Fixed limit can represent a practical and

suitable control• Local policies and specific criteria are also

emerging

Conclusions

w w w . h o a r e l e a . c o m

Thank you