Draft Wind Energy Guidelines address concerns of Local Communities but will reduce energy yield from sites

The government this week provided some details on a preferred draft approach for the updated Wind Energy Development Guidelines.  It will be early 2018 before the new guidelines are finalised and they will then replace the previous 2006 edition.

The key aspects have been well covered in the press and include:

• More stringent noise limit;
• New Visual Amenity Setback (4 times the turbine height with a minimum distance of 500 metres);
• ZERO shadow flicker; and
• New obligations in relation to engagement with local communities

The government press release provides some details and are analysed by Fehily Timoney experts below.

More Stringent Noise Limits

The 2006 Guidelines provided guidance on daytime and night-time noise limits, with separate noise limits for each period.   The proposed approach adopts more stringent noise limits: it provides for a relative rated noise limit of 5dB(A) above existing background noise within the range of 35 dB(A) to a maximum of 43dB(A). Noise limits will be applicable for both daytime and night-time periods. The noise limits are described as a ‘rated’ limit and they will take account of certain noise characteristics specific to wind turbines (e.g. tonal, low frequency and amplitude modulation). Where these characteristics are identified, the noise limit permitted will be further reduced to mitigate for these noise characteristics.

The noise limits derived using the proposed approach will be below the 2006 wind energy development guidelines and implementation of the proposed approach could result in reduced energy yield from a site. The reduced energy yield will result from either a reduced number of turbines and/or curtailment of some turbines to meet the more stringent noise limits.   An important detail to watch out for is the definition of the noise indicator e.g. L_A90 or L_Aeq.  This is particularly relevant information as for wind turbine noise, a noise limit of 43 dB L_Aeq is equivalent to a noise limit of 41 dB L_A90.

Visual Amenity Setback

The Wind Energy Development Guidelines (2006) did not indicate a specific setback distance but instead recommended that “sufficient distance should be maintained from farmsteads, houses and centres of population in order to ensure that wind energy developments do not visually dominate them.”   The proposed approach is to introduce a setback distance of 4 times the tip height, between a wind turbine and the curtilage of a residential property, subject to a mandatory minimum setback of 500 metres.  Although visual presence of a development is based on a number of aspects beyond simply scale in relation to distance, the recommended setback distance for visual amenity will need to be incorporated as a constraint on the design of the wind farm.  This will likely result in lower turbines (potentially just at the periphery of developments) or increased site curtailment.  The impact will be reduced energy yield from a site.

Zero Tolerance Policy on Shadow Flicker

Whereas the 2006 Guidelines recommended constraints on shadow flicker (max. 30 hours per year or 30 minutes per day at any dwelling/offices within 500m of turbines), the new guidelines are stricter.  The draft approach mandates that shadow flicker should be eliminated.  Under such a constraint, if shadow flicker conditions were to arise at any receptor, turbine control measures would need to be applied to shut down the turbine for the duration of the shadow flicker event. Such turbine shutdown would reduce the operating time of the affected turbines, decreasing the total power output of the wind farm.

If you would like more information on this and discuss the potential implications on your proposed development please contact FT Energy Planning Team.