www.hoarelea.com 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
www.hoarelea.com 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 RPM compared 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
www.hoarelea.com 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? L Aeq, 5minutes more suitable? 35dB L A90 already in ETSU-R-97, restrictive? 40dB L Aeq 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 ?
www.hoarelea.com 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
www.hoarelea.com Rated / Reference power output of up to 50 kW at 11 m/s: RenewableUK recommended 45 dB L Aeq,5min… Permitted development limit (2011) of 42 dB L Aeq,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 standard Statutory instrument 2011 No. 2056 MCS 006 certification standard
www.hoarelea.com BWEA had dedicated document (UK, 2008) References EC 61400-11 simplified test procedure Applies to 200 m 2 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
www.hoarelea.com Criteria and assessments - example Cornwall standard policy (March 2012) Small (200m 2 definition) 35dB L Aeq Larger: 35dB L A90 for single turbines full ETSU-R-97 for wind farms Guidance on data requirements, conditions and financial involvement
www.hoarelea.com 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